Leaking stoppage method and leaking stoppage control system for improving pressure bearing capacity of fractured formation

Abstract

The invention provides a leaking stoppage method and a leaking stoppage control system for improving the pressure bearing capacity of a fractured stratum. Under the condition that it is determined that the leakage crack of the target leakage layer of the target leakage well is a pressure sensitive crack, a dynamic distribution model of the crack width based on the shaft pressure in the plugging slurry pump replacement-squeezing process is constructed; determining dynamic crack width distribution under different wellbore pressures in the plugging slurry pumping-squeezing process by utilizing a dynamic distribution model of crack width according to the wellbore pressure and the bearing target pressure; according to the dynamic crack width distribution, matched preparation parameters of the multi-stage plugging slurry are determined to prepare the corresponding plugging slurry of each stage; and then according to a preset pump injection rule, the multi-stage leaking stoppage slurry is injected into the leakage crack stage by stage in sequence for leaking stoppage. Therefore, leaking stoppage can be achieved scientifically, finely and safely, a good leaking stoppage effect is achieved, and the problems that due to poor pressure bearing stability, shaft pressure relief leaking stoppage slurry is prone to reverse spitting, and shaft pressurization is prone to re-leakage are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling engineering, and in particular to a plugging method and a plugging control system for improving the pressure bearing capacity of fractured formations. Background Art

[0002] Lost circulation often occurs during overbalanced drilling operations. Lost circulation is a phenomenon in which working fluid (including drilling fluid, cement slurry, completion fluid and other fluids) leaks into the formation under the action of positive pressure difference during downhole operations such as drilling, cementing, testing, completion or repair. Lost circulation not only causes huge economic and production time losses, but also affects the normal construction of downhole operations. Severe lost circulation causes the pressure in the well to drop, affecting normal drilling, causing the well wall to become unstable, and then inducing formation fluid to flow into the wellbore, and even causing safety accidents such as blowouts, endangering drilling and personal safety.

[0003] The existing plugging methods are mainly designed based on the leakage rate and the experience of the operators to design the plugging formula and prepare the plugging slurry, and then all the plugging slurry is injected into the leaking well section at one time, and then squeezed into the leaking channel through the squeeze process to plug the leak. The above method is highly empirical, blind and trial-and-error when implemented, resulting in a low plugging success rate of the existing plugging methods. For fractured formations, the strong stress-sensitive nature of induced fractures and naturally extended fractures further exacerbates the above problems and reduces the plugging success rate.

[0004] To address the above problems, no effective solution has been proposed yet. Summary of the invention

[0005] This manual provides a plugging method and a plugging control system for improving the pressure bearing capacity of fractured formations, which can implement plugging operations in a more scientific, precise and safe manner, achieve better plugging effects, reduce the problems of conventional bridging plugging that are prone to door sealing, direct leakage, frequent blockage of drilling tools, easy backflow during pressure relief, and easy re-leakage during pressurization, and improve the success rate and safety of plugging.

[0006] This specification provides a plugging method for improving the pressure bearing capacity of fractured formations, including:

[0007] Detect whether the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks;

[0008] When the target leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed;

[0009] Using the dynamic distribution model of crack width, according to the wellbore pressure and the pressure-bearing target pressure, the dynamic crack width distribution under different wellbore pressures of the plugging slurry pump replacement-squeezing process is determined;

[0010] According to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined to prepare the corresponding plugging slurries at each stage;

[0011] According to the preset pumping rules, the multi-stage plugging slurry is injected into the leakage fractures step by step in sequence to plug the leakage.

[0012] In one embodiment, detecting whether a leakage crack of a target leakage layer of a target leakage well is a pressure sensitive crack includes:

[0013] Obtaining leakage background information about leakage fractures in the target leakage layer where the target leakage well is located;

[0014] Based on the leakage background data, whether there is any operation that causes the wellbore pressure to increase during the leakage detection; and / or whether there is a backflow phenomenon when the wellbore pressure decreases after the leakage detection, and obtain corresponding detection results;

[0015] According to the detection results, when it is determined that there is an operation that causes the wellbore pressure to increase; and / or when there is a backflow phenomenon when the wellbore pressure decreases after the leakage, the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks.

[0016] In one embodiment, a dynamic distribution model of fracture width based on wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed, including:

[0017] Acquire mechanical property parameters of the leaky layer related to the target leaky layer; wherein the mechanical property parameters of the leaky layer include at least: Young's modulus of the leaky layer rock, Poisson's ratio of the leaky layer rock, and ground stress of the leaky layer;

[0018] Obtain the wellbore radius of the target lost-flow well and the length of the lost-flow fracture;

[0019] According to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed.

[0020] In one embodiment, according to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed, including:

[0021] According to the following formula, a dynamic distribution model of fracture width based on wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed:

[0022]

[0023] Where x is the distance between a point in the leaking fracture and the wellbore wall of the target leaking well along the long axis of the fracture, W(x) is the fracture width at a point in the leaking fracture at a distance x from the wellbore wall along the long axis of the fracture, υ is the Poisson's ratio of the leaking layer rock, E is the Young's modulus of the leaking layer rock, S H is the maximum horizontal principal stress of the target leaky layer, S h is the minimum horizontal principal stress of the target leaky layer, S V is the vertical principal stress of the target leaky layer, P w is the wellbore pressure during the plugging slurry pump displacement-squeezing process, R is the wellbore radius of the target lost circulation well, L is the fracture length of the lost circulation fracture, and c is the stress anisotropy factor.

[0024] In one embodiment, the dynamic distribution model of crack width is used to determine the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure, including:

[0025] Determining a first dynamic fracture width distribution under the wellbore pressure during a first pumping process according to the wellbore pressure using the dynamic distribution model of the fracture width;

[0026] Determining a second dynamic crack width distribution under the wellbore pressure during a second pumping process by using the dynamic distribution model of the crack width and according to an average value of the wellbore pressure and the pressure-bearing target pressure;

[0027] The dynamic distribution model of the crack width is used to determine a third dynamic crack width distribution based on the wellbore pressure of the third squeezing process according to the pressure target pressure.

[0028] In one embodiment, according to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined, including:

[0029] According to the first dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching first-level plugging slurry;

[0030] According to the second dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching second-level plugging slurry;

[0031] According to the third dynamic crack width distribution, the preset reference formulation table is queried to determine the formulation parameters of the matching third-level plugging slurry.

[0032] In one embodiment, the formulation parameters include at least: plugging material combination, particle size, and gradation.

[0033] In one embodiment, the plugging material combination includes at least: sheet-like rigid plugging material, granular elastic plugging material, granular rigid plugging material, and fiber plugging material.

[0034] In one embodiment, according to a preset pumping rule, the multi-stage plugging slurry is sequentially injected into the leakage fractures step by step to plug the leakage, including:

[0035] Obtaining drilling tool parameters of the plugging drilling tool assembly; wherein the drilling tool parameters at least include: the number of variable diameter positions and inlet and outlet diameters of the plugging drilling tool;

[0036] According to the preparation parameters of the multi-stage plugging slurry, the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are determined;

[0037] According to the preset pumping rules, the drilling tool parameters of the plugging drilling tool assembly, as well as the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are used to determine the safe displacement and pumping strategy for each level of the plugging slurry in the multi-stage plugging slurry;

[0038] Based on the corresponding safe displacement and pumping strategy, the multi-stage plugging slurry is injected into the leakage fractures step by step in sequence to plug the leakage.

[0039] In one embodiment, after determining the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution, the method further includes:

[0040] According to the preparation parameters of the first-stage plugging slurry, the first-stage plugging slurry is prepared;

[0041] Based on the safe displacement and pumping strategy of the first-stage plugging slurry, a first volume of the first-stage plugging slurry is pumped into the wellbore leaking layer position of the target leaking well;

[0042] According to the preparation parameters of the second-stage plugging slurry, the remaining plugging slurry of the first-stage plugging slurry is used to prepare the second-stage plugging slurry;

[0043] Based on the safe displacement and pumping strategy of the second-stage plugging slurry, a second volume of the second-stage plugging slurry is pumped into the wellbore leaking zone of the target leaking well;

[0044] According to the preparation parameters of the third-level plugging slurry, the remaining plugging slurry of the second-level plugging slurry is used to prepare the third-level plugging slurry;

[0045] Based on the safe displacement and pumping strategy of the third-level plugging slurry, pump the third-level plugging slurry into the wellbore leaking layer position of the target leaking well;

[0046] The first-stage plugging slurry, the second-stage plugging slurry and the third-stage plugging slurry in the wellbore of the target leakage well are squeezed into the leakage cracks.

[0047] In one embodiment, after the multi-stage plugging slurry is injected into the leakage fractures in sequence step by step to plug the leakage, the method further comprises:

[0048] According to the preset static pressure leak detection rule, a first leak detection is performed on the target leaking well to obtain a corresponding first leak detection result;

[0049] According to the first leak detection result, when it is determined that the target leaking well has passed the first leak detection, a second leak detection is performed on the target leaking well according to a preset dynamic pressure leak detection rule to obtain a corresponding second leak detection result;

[0050] According to the second leak detection result, when it is determined that the target leaking well has passed the second leak detection, it is determined that the target leaking well has passed the leak detection.

[0051] This specification also provides a plugging device for improving the pressure bearing capacity of fractured formations, comprising:

[0052] A detection module, used to detect whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks;

[0053] A construction module is used to construct a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process when the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks;

[0054] The first determination module is used to determine the dynamic crack width distribution under different wellbore pressures of the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure by using the dynamic distribution model of the crack width;

[0055] The second determination module is used to determine the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution, so as to prepare the corresponding plugging slurry at each stage;

[0056] The pumping module is used to inject the multi-stage plugging slurry into the leakage cracks in sequence according to the preset pumping rules to plug the leakage.

[0057] The present specification also provides a computer storage medium on which computer instructions are stored. When the instructions are executed by a processor, the relevant steps of the plugging method for improving the pressure bearing capacity of fractured formations are implemented.

[0058] The present specification also provides a plugging control system for improving the pressure bearing capacity of fractured formations, comprising a processor and a memory for storing processor executable instructions, wherein the processor implements the following steps when executing the instructions: detecting whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; in the case where the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks, constructing a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process; using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, determining the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process; according to the dynamic crack width distribution, controlling and determining the preparation parameters of matching multi-stage plugging slurries to prepare corresponding plugging slurries of each stage; according to a preset pumping rule, controlling the multi-stage plugging slurries to be injected into the leakage cracks in sequence and stage by stage for plugging.

[0059] Based on the plugging method and plugging control system for improving the pressure bearing capacity of fractured formations provided in the present specification, when it is determined that the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is first constructed; then, using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process is determined; and according to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined to prepare the corresponding plugging slurries at each level; and then, according to the preset pumping rules, the multi-stage plugging slurries are sequentially injected into the leakage cracks step by step to plug the leaks. By fully considering the pressure sensitivity of the leaking cracks during the plugging slurry pump replacement-squeezing process, the corresponding dynamic distribution model of crack width is constructed and used to predict the dynamic change trend of the crack width of the leaking cracks under the action of wellbore pressure in different plugging slurry pump replacement-squeezing processes; then according to the above dynamic change trend of the crack width, a multi-level plugging slurry matching the dynamic change trend of the crack width of the leaking cracks during the plugging slurry pump replacement-squeezing process is prepared, and the multi-level plugging slurry is injected into the leaking cracks in sequence. In this way, the plugging operation can be achieved more scientifically, finely and safely, and a better plugging effect can be obtained, the pressure bearing capacity of the fractured formation can be improved, and the problems of easy sealing, easy direct leakage, frequent blockage of drilling tools, easy backflow during pressure relief, and easy re-leakage during pressurization can be reduced, and the one-time success rate and safety of plugging can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the embodiments of this specification, the drawings required for use in the embodiments will be briefly introduced below. The drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 It is a flow chart of a plugging method for improving the pressure bearing capacity of fractured formations provided by an embodiment of the present specification;

[0062] Figure 2 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0063] Figure 3 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0064] Figure 4 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0065] Figure 5 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0066] Figure 6 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0067] Figure 7 is a schematic diagram of the structure of a computer device provided by an embodiment of this specification;

[0068] Figure 8 It is a schematic diagram of the structural composition of a plugging device for improving the pressure bearing capacity of a fractured formation provided by an embodiment of the present specification;

[0069] Fig. 9 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0070] Fig.10 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0071] Fig.11 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification in a scenario example;

[0072] Fig.12 It is a schematic diagram of an embodiment of a plugging method for improving the pressure bearing capacity of a fractured formation provided by an embodiment of this specification, in a scenario example. DETAILED DESCRIPTION

[0073] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0074] Considering that in actual construction, for fractured formations, the wellbore pressure will change during the process of waiting for plugging operations, pulling out the drill bit assembly, and plugging the leaking fractures with pumping-squeezing plugging slurry, which will cause the crack width of the leaking fracture to change accordingly. For example, while waiting for plugging operations and pulling out the drill bit assembly, the crack will close as the wellbore pressure decreases; during the pumping-squeezing process, the crack will open and even expand as the wellbore pressure increases. The above situation is more obvious for pressure-sensitive fractures.

[0075] However, based on the existing plugging methods, the width change of the leakage cracks caused by the change of wellbore pressure during the plugging process is often ignored. The plugging slurry used has a low matching degree with the actual cracks, which leads to the plugging slurry being sealed during the injection process due to crack closure or leaking due to crack expansion. In addition, the precise control of the pressure in the plugging process is not considered, resulting in cracks that are either closed or unstably extended, thereby increasing the difficulty of matching the plugging materials with the cracks. The permeability of the plugging slurry drilling tools is also not considered, resulting in improper setting of the plugging formula and construction parameters. In addition, the plugging materials selected by the existing plugging methods when configuring the plugging slurry are mostly rigid and plastic particles. The plugging slurry is configured based on the above plugging materials for plugging. The resulting plugging layer has poor stability against pressure fluctuations, and there are problems such as easy backspitting of the plugging slurry during wellbore pressure relief and easy re-leakage during wellbore pressurization.

[0076] In view of the root cause of the above-mentioned problems, this specification considers that when it is determined that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process can be constructed according to the specific characteristics of the target leakage layer, the target leakage well, and the leakage cracks; then, using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, different wellbore pressure conditions of the plugging slurry pump replacement-squeezing process can be distinguished, and the dynamic crack width distribution under different wellbore pressures of the plugging slurry pump replacement-squeezing process can be determined; and then, according to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry can be determined to prepare the corresponding plugging slurries at each level; finally, according to the preset pumping rules, the multi-stage plugging slurry can be injected into the leakage cracks in sequence step by step to plug the leaks. By fully considering the pressure sensitivity of the lost cracks during the plugging slurry pump replacement-squeezing process, a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed and used to predict the dynamic change trend of the crack width of the lost cracks under different wellbore pressures during the plugging slurry pump replacement-squeezing process; then according to the dynamic change trend of the crack width, a multi-stage plugging slurry matching the dynamic change of the crack width of the lost cracks during the plugging slurry pump replacement-squeezing process is prepared, and the multi-stage plugging slurry is injected into the lost cracks in sequence. In this way, the plugging operation can be achieved in a more scientific, precise and safe manner, and a better plugging effect can be obtained, reducing the problems of easy sealing of the conventional bridge plugging, easy direct leakage, frequent blockage of drilling tools, easy backflow of pressure relief, and easy re-leakage during pressurization, thereby improving the one-time plugging success rate and safety.

[0077] See also Figure 1 As shown, the embodiment of this specification provides a plugging method for improving the pressure bearing capacity of fractured formations. In specific implementation, the method may include the following contents:

[0078] S101: Detect whether the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks;

[0079] S102: when it is determined that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed;

[0080] S103: using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, determining the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process;

[0081] S104: determining matching preparation parameters of multi-stage plugging slurry according to the dynamic crack width distribution, so as to prepare corresponding plugging slurries of each stage;

[0082] S105: According to a preset pumping rule, the multi-stage plugging slurry is injected into the leakage fractures step by step in sequence to plug the leakage.

[0083] Based on the above embodiment, by fully considering the pressure sensitivity of the lost cracks during the plugging slurry pump replacement-squeezing process, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed and used, and the dynamic change trend of the crack width of the lost cracks under different wellbore pressures during the plugging slurry pump replacement-squeezing process is predicted; then according to the dynamic change trend of the crack width, a multi-stage plugging slurry matching the dynamic change of the crack width of the lost cracks during the plugging slurry pump replacement-squeezing process is prepared, and the multi-stage plugging slurry is sequentially injected into the lost cracks step by step. In this way, the plugging operation can be realized more scientifically, precisely and safely, a better plugging effect can be obtained, the pressure bearing capacity of the fractured formation can be improved, and the problems of easy sealing of the conventional bridge plugging, easy direct leakage, frequent blockage of drilling tools, easy backflow of pressure relief, and easy re-leakage of pressurization can be reduced, and the success rate and safety of plugging can be improved.

[0084] In some embodiments, the target leakage well can be specifically understood as a well that is experiencing leakage and needs to be plugged. The target leakage layer can be specifically understood as a stratum where the leakage crack is located. The pressure-sensitive crack can be specifically understood as a crack that is easily affected by pressure, and the width and / or length of the crack is easily changed accordingly with the change of pressure.

[0085] In some embodiments, see Figure 2 As shown, detecting whether the leakage cracks of the target leakage layer of the target leakage well are pressure sensitive cracks includes:

[0086] S1: Obtaining leakage background information about the leakage fractures of the target leakage layer where the target leakage well is located;

[0087] S2: Based on the leakage background data, whether there is any operation that causes the wellbore pressure to increase during the leakage; and / or whether there is a backflow phenomenon when the wellbore pressure decreases after the leakage, and obtain corresponding detection results;

[0088] S3: According to the detection results, when it is determined that there is an operation that causes the wellbore pressure to increase; and / or when there is a backflow phenomenon when the wellbore pressure decreases after the leakage, determine that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks.

[0089] Based on the above embodiments, it is possible to accurately detect and determine whether the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks.

[0090] In some embodiments, during specific implementation, the above leakage background information can be obtained by querying the construction operation records of the target leakage well.

[0091] When it is determined that the missed cracks in the target leaking layer of the target leaking well are non-pressure sensitive cracks, the crack size parameters (for example, crack width, etc.) of the current leaking cracks can be estimated based on the leaking velocity data to determine the matching plugging slurry; and the plugging slurry is pumped all at once to the leaking layer position, and 1 / 2 to 2 / 3 of the volume of the pumped plugging slurry is squeezed into the leaking cracks to achieve plugging.

[0092] In some embodiments, see Figure 3 As shown, the above-mentioned construction of a dynamic distribution model of crack width based on wellbore pressure during the plugging slurry pump replacement-squeezing process may include the following contents during specific implementation:

[0093] S1: Acquire mechanical property parameters of the leaky layer related to the target leaky layer; wherein the mechanical property parameters of the leaky layer at least include: Young's modulus of the leaky layer rock, Poisson's ratio of the leaky layer rock, and ground stress of the leaky layer;

[0094] S2: Obtain the wellbore radius of the target lost-flow well and the fracture length of the lost-flow fracture;

[0095] S3: According to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed.

[0096] Among them, the above-mentioned dynamic distribution model of crack width can more accurately predict the crack width at different positions along the long axis of the crack under the action of different wellbore pressures during the plugging slurry pump replacement-squeezing process.

[0097] Based on the above embodiments, a dynamic distribution model of crack width with high matching performance with the leakage cracks in the target leakage layer and good effect can be constructed.

[0098] In some embodiments, during specific implementation, the required mechanical property parameters of the target leaky layer, the wellbore radius of the target leaky well, and the crack length of the leaky crack can be obtained by acquiring and based on the data of the target leaky well, such as the drilling data, logging data, measurement while drilling records, logging records, and ground breaking test results of the target leaky well.

[0099] In specific implementation, when the data of the target leaking well is missing, the data of the neighboring wells or reference wells of the target leaking well can also be obtained, and the mechanical property parameters of the leaking layer and other data can be estimated based on the above data. The above reference well can be specifically understood as a well with complete data in the same or similar block, the same or similar structure, and the same or similar formation as the target leaking well.

[0100] In specific implementation, after obtaining the wellbore radius of the target lost circulation well, the wellbore expansion rate of the target lost circulation well can be obtained and used to perform targeted correction on the wellbore radius.

[0101] During specific implementation, the ground stress of the leaky layer may specifically include: the maximum horizontal principal stress of the target leaky layer, the minimum horizontal principal stress of the target leaky layer, the vertical principal stress of the target leaky layer, etc.

[0102] In some embodiments, the above-mentioned dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed according to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length. When implemented specifically, it may include:

[0103] According to the following formula, a dynamic distribution model of fracture width based on wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed:

[0104]

[0105] Where x is the distance between a point in the leaking fracture and the wellbore wall of the target leaking well along the long axis of the fracture, W(x) is the fracture width at a point in the leaking fracture at a distance x from the wellbore wall along the long axis of the fracture, υ is the Poisson's ratio of the leaking layer rock, E is the Young's modulus of the leaking layer rock, S H is the maximum horizontal principal stress of the target leaky layer, S h is the minimum horizontal principal stress of the target leaky layer, S V is the vertical principal stress of the target leaky layer, P w is the wellbore pressure during the plugging slurry pump displacement-squeezing process, R is the wellbore radius of the target lost circulation well, L is the fracture length of the lost circulation fracture, and c is the stress anisotropy factor.

[0106] In specific implementation, based on the above formula, it is possible to more comprehensively and accurately predict the changes in crack width caused by changes in wellbore pressure during the replacement and squeezing process of the plugging slurry pump at each position between the position farthest from the wellbore wall along the long axis direction of the leakage crack and the position closest to the wellbore wall.

[0107] The wellbore pressure during the plugging slurry pumping-squeezing process may specifically refer to the wellbore pressure that changes from time to time during the plugging process by pumping-squeezing the plugging slurry.

[0108] In some embodiments, see Figure 4 As shown, the above-mentioned dynamic distribution model of crack width is used to determine the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure. When implemented specifically, the following contents may be included:

[0109] S1: using the dynamic distribution model of the fracture width and according to the pumping wellbore pressure, determining a first dynamic fracture width distribution under the wellbore pressure of the first pumping process;

[0110] S2: using the dynamic distribution model of the fracture width, according to the average value of the pumping wellbore pressure and the pressure target pressure, determining a second dynamic fracture width distribution under the wellbore pressure of the second pumping process;

[0111] S3: using the dynamic distribution model of the crack width and according to the pressure-bearing target pressure, determining a third dynamic crack width distribution under the wellbore pressure of the third squeezing process.

[0112] The wellbore pressure may specifically be the sum of the static liquid column pressure and the annular circulation pressure loss at the target leaking layer position at different stages during the plugging slurry pump replacement-squeezing process.

[0113] The above-mentioned pressure bearing target pressure (or pressure bearing plugging target) can specifically be the pressure bearing capacity of the formation required by the next step of higher density drilling fluid, cement slurry or higher displacement operation. For example, the current formation pressure bearing capacity is 50MPa, and the next step needs to increase the drilling fluid density or displacement, and the formation pressure bearing capacity needs to reach 60MPa. Then, through pressure bearing plugging, the formation pressure bearing capacity needs to be increased to 60MPa, and this value is the pressure bearing target pressure. By introducing the pressure bearing target pressure, the pressure bearing requirements of the next step of the operation to be carried out can be effectively taken into account in each plugging process, and the pressure bearing capacity of the formation can be improved, thereby ensuring that the subsequent drilling process can be relatively more stable and reliable.

[0114] In some cases, the measured wellbore pressure can also be directly used as the wellbore pressure in the pumping-squeezing process and substituted into the dynamic distribution model of the fracture width to calculate the corresponding dynamic fracture width distribution.

[0115] In specific implementation, in the first stage of the plugging slurry pump replacement-squeezing process, the wellbore pressure of the first pump replacement process can be obtained and determined based on the wellbore pressure; and the wellbore pressure of the first pump replacement process is substituted into the dynamic distribution model of the crack width to calculate the corresponding first dynamic crack width distribution. In the second stage of the plugging slurry pump replacement-squeezing process, the wellbore pressure of the second pump replacement process can be obtained and determined based on the average value of the wellbore pressure and the pressure-bearing target pressure; and the wellbore pressure of the second pump replacement process is substituted into the dynamic distribution model of the crack width to calculate the corresponding second dynamic crack width distribution. In the third stage of the plugging slurry pump replacement-squeezing process, the wellbore pressure of the third squeezing process can be obtained and determined based on the pressure-bearing target pressure; and the wellbore pressure of the third squeezing process is substituted into the dynamic distribution model of the crack width to calculate the corresponding third dynamic crack width distribution.

[0116] Based on the above embodiments, the crack characteristics of pressure-sensitive cracks can be fully considered. By estimating the wellbore pressure of the plugging slurry pump replacement-squeezing process at different stages, and then using the dynamic distribution model of crack width based on the wellbore pressure of the plugging slurry pump replacement-squeezing process, the dynamic distribution of crack width under different wellbore pressures of the plugging slurry pump replacement-squeezing process can be accurately predicted, so that the dynamic distribution of crack width can be used to accurately determine the plugging slurry suitable for cracks at different stages.

[0117] In some embodiments, the above-mentioned determination of the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution may include the following contents during specific implementation:

[0118] S1: According to the first dynamic crack width distribution, query the preset reference formulation table to determine the formulation parameters of the matching first-level plugging slurry;

[0119] S2: According to the second dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching second-level plugging slurry;

[0120] S3: According to the third dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching third-level plugging slurry.

[0121] Correspondingly, the multi-stage plugging slurry may include three-stage plugging slurry (including at least two-stage plugging slurry), namely: first-stage plugging slurry, second-stage plugging slurry and third-stage plugging slurry.

[0122] Among them, the first-level plugging slurry can be specifically understood as the plugging slurry that is pumped into the wellbore first; the second-level plugging slurry can be specifically understood as the plugging slurry that is pumped into the wellbore immediately after the first-level plugging slurry; the third-level plugging slurry can be specifically understood as the plugging slurry that is pumped into the wellbore last.

[0123] In some embodiments, the above-mentioned preparation parameters may specifically include: parameters such as the combination of plugging materials, particle size, gradation, etc. Among them, the above-mentioned particle size and gradation may specifically refer to the particle size and gradation of the plugging materials.

[0124] Among them, the above-mentioned plugging material combination includes at least: sheet-like rigid plugging material, granular elastic plugging material, granular rigid plugging material (for example, natural minerals with corresponding structural shapes or products with equivalent properties, etc.), fiber plugging material (for example, short fiber plugging material, etc.), etc.

[0125] By introducing and using in combination a variety of different types of plugging materials such as rigid plugging materials, elastic plugging materials, fiber plugging materials, etc., it is possible to effectively solve the problems of limited contact between plugging materials, small friction resistance between plugging materials and between plugging materials and crack walls, and weak adaptability of the plugging layer to changes in wellbore pressure, which makes it easy for the overall structure to be destroyed or squeezed out of the cracks to cause backflow, or even plugging failure, during the opening and closing of the cracks. This can improve the stability of the plugging layer and achieve better plugging effects.

[0126] The above-mentioned preparation parameters may further include the particle size of the plugging material.

[0127] The above-mentioned particle size may specifically refer to the particle size distribution of the plugging material in the plugging slurry, for example, the particle size distribution characteristic value D90. The above-mentioned gradation may specifically refer to the content (concentration) of different particle sizes of various types of plugging materials contained in the plugging slurry.

[0128] Furthermore, for different plugging materials, different numerical ranges of particle sizes can be provided. For example, for sheet-like rigid plugging materials, the particle size ranges can include: 1-3 mm, 3-5 mm, 5-8 mm, etc. For another example, for granular elastic plugging materials, the particle size ranges can include: 100 μm, 400 μm, 1000 μm, etc.

[0129] Specifically, according to the dynamic crack width distribution, suitable plugging materials with matching particle sizes can be selected and combined in a certain proportion and concentration to obtain multi-stage plugging slurry that matches the dynamic change trend of crack width at different stages.

[0130] In specific implementation, the plugging material, base slurry, and weighting material (e.g., barite or similar products, etc.) can be combined to prepare the corresponding plugging slurry. The base slurry can be a well site drilling fluid, specifically, a water-based drilling fluid, an oil-based drilling fluid, or a synthetic-based drilling fluid.

[0131] By introducing weighting materials, the density of the plugging slurry can be effectively adjusted. Specifically, the density of the plugging slurry can be made consistent with the downhole drilling fluid based on the calculated amount of weighting materials added to reduce the impact of the slurry mixing on the plugging effect.

[0132] Specifically, the above-mentioned preset reference configuration table may specifically include a plurality of groups of preset configuration parameters; wherein each group of configuration parameters corresponds to a numerical range of a dynamic crack width distribution.

[0133] Before specific implementation, a preset reference formulation table can be constructed in the following manner: obtain a large number of historical plugging records, and screen out historical plugging records with better plugging effects from the historical plugging records, and use a high-temperature and high-pressure crack automatic adjustment plugging tester (or a similar product with the function of simulating pressure-sensitive cracks and automatically adjusting the width as the pressure in the crack changes) to conduct historical plugging record review and optimization experiments, and use the plugging records after review and optimization as sample plugging records; extract the corresponding crack width and formulation parameters of the plugging slurry from the sample plugging records, and establish corresponding sample plugging reference data; cluster the sample plugging reference data to obtain multiple clusters; wherein each cluster corresponds to a group of formulation parameters of the plugging slurry; calculate and obtain the numerical distribution interval of the dynamic crack width distribution corresponding to the formulation parameters of the plugging slurry of the cluster based on the central value of the crack width contained in each cluster, thereby obtaining a preset reference formulation table.

[0134] In some embodiments, according to the preset pumping rules, the multi-stage plugging slurry is injected into the leakage fractures in sequence step by step to plug the leakage. The specific implementation may include the following contents:

[0135] S1: Obtaining drilling tool parameters of the plugging drilling tool assembly; wherein the drilling tool parameters at least include: the number of variable diameter positions and inlet and outlet diameters of the plugging drilling tool;

[0136] S2: According to the preparation parameters of the multi-stage plugging slurry, the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are determined;

[0137] S3: According to the preset pumping rules, the drilling tool parameters of the plugging drilling tool assembly, the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are used to determine the safe displacement and pumping strategy for each level of the plugging slurry in the multi-stage plugging slurry;

[0138] S4: Based on the corresponding safe displacement and pumping strategy, the multi-stage plugging slurry is injected into the leakage fractures in sequence step by step to plug the leakage.

[0139] The plugging drilling tool assembly may include one or more plugging drilling tools, which may specifically include: a drill bit, a downhole power drilling tool, and the like.

[0140] In specific implementation, the safe displacement (or safe construction displacement) of each level of plugging slurry for each plugging drill tool can be calculated based on the drill tool parameters of each plugging drill tool, as well as the base slurry density and apparent viscosity of each level of plugging slurry in the multi-level plugging slurry; and then the safe displacement with the smallest value for the same level of plugging slurry is screened out as the safe displacement of the drill tool combination for the same level of plugging slurry.

[0141] In specific implementation, the characteristic particle size value of the plugging material of the multi-level plugging slurry can be measured by sieving method. Specifically, it can include: preparing and weighing a certain amount (for example, 500 grams) of plugging material sample; then selecting a set of standard sieves with continuous mesh numbers according to the size of the plugging material, for example, about 10, and combining them from top to bottom according to the mesh number from small to large, wherein the top layer is a vibrating screen and the bottom layer is a bottom tray; then placing the plugging material sample on the top layer of the vibrating screen, covering it with a lid and placing it on a vibrating machine, vibrating it for a certain period of time, and weighing the mass of the plugging material on each sieve; then drawing and using the mass change curve of the plugging material according to the mass of the plugging material on each sieve to determine the characteristic particle size value of the plugging material.

[0142] In specific implementation, the safe displacement of the plugging slurry at the current level for any drill bit in the drill bit assembly can be determined according to the following formula:

[0143]

[0144]

[0145] Among them, Q c For safe displacement, is the average particle (plugging material particle) concentration at the outlet of the variable diameter position, is the average particle velocity at the outlet of the variable diameter position, d o is the outlet diameter at the variable diameter position, d p is the particle diameter (characteristic particle size value of plugging material), C LCM is the volume concentration of the plugging material flowing into the variable diameter position, d i V is the inlet diameter at the variable diameter position, in is the particle velocity at the inlet of the variable diameter position, C D is the drag force coefficient.

[0146] In specific implementation, the above-mentioned pumping strategy may correspond to one of the multi-stage plugging slurries, including relevant parameters such as the pumping amount, pumping method, and pumping speed of the plugging slurry.

[0147] In some embodiments, see Figure 5 As shown, after determining the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution, the method may further include the following contents when implemented:

[0148] S1: preparing the first-stage plugging slurry according to the preparation parameters of the first-stage plugging slurry;

[0149] S2: based on the safe displacement and pumping strategy for the first-stage plugging slurry, pump a first volume of the first-stage plugging slurry into the wellbore leaking layer position of the target leaking well;

[0150] S3: According to the preparation parameters of the second-stage plugging slurry, the remaining plugging slurry of the first-stage plugging slurry is used to prepare the second-stage plugging slurry;

[0151] S4: based on the safe displacement and pumping strategy for the second-stage plugging slurry, pump a second volume of the second-stage plugging slurry into the wellbore leaking layer position of the target leaking well;

[0152] S5: According to the preparation parameters of the third-level plugging slurry, the remaining plugging slurry of the second-level plugging slurry is used to prepare the third-level plugging slurry;

[0153] S6: based on the safe displacement and pumping strategy of the third-level plugging slurry, pumping the third-level plugging slurry into the wellbore leaking layer position of the target leaking well;

[0154] S7: squeeze the first-stage plugging slurry, the second-stage plugging slurry and the third-stage plugging slurry in the wellbore of the target leakage well into the leakage fracture.

[0155] The position of the leaking layer in the wellbore of the target leaking well may be specifically understood as a position in the wellbore of the target leaking well that is on the same horizontal plane as the leaking fracture.

[0156] In specific implementation, after the first-level plugging slurry, the second-level plugging slurry, and the third-level plugging slurry are pumped into the leaking layer position of the wellbore of the target leaking well in sequence, the following three plugging slurry sections will be formed from bottom to top at the leaking layer position of the wellbore of the target leaking well: the first-level plugging slurry section, the second-level plugging slurry section, and the third-level plugging slurry section. In the process of pumping the plugging slurry, the bottommost part of the plugging slurry in the above-mentioned continuous plugging slurry sections will enter the leaking cracks. Further, by squeezing the first-level plugging slurry, the second-level plugging slurry, and the third-level plugging slurry in the wellbore of the target leaking well into the leaking cracks, the first-level plugging slurry, the second-level plugging slurry, and the third-level plugging slurry at the wellbore position can be injected into the leaking cracks in sequence and step by step to form a long wedge-shaped plugging layer to plug the leak.

[0157] Based on the above embodiment, according to the matching preparation parameters of the multi-stage plugging slurry, at the construction site of the target leaking well, the plugging slurry can be prepared step by step and injected into the leaking cracks step by step in sequence to obtain a relatively good plugging effect.

[0158] In specific implementation, according to the preparation parameters of the first-level plugging slurry, a variety of plugging materials with corresponding particle sizes and gradations can be added in sequence in the order of fiber plugging material, granular elastic plugging material, flaky rigid plugging material, and granular rigid plugging material to prepare a first-level plugging slurry, and continue to stir; after the first volume of the first-level plugging slurry is pumped into the leaking layer position of the wellbore, according to the preparation parameters of the second-level plugging slurry, plugging materials with corresponding particle sizes and gradations in the second-level plugging slurry can be continued to be added to the remaining first-level plugging slurry according to the preparation parameters of the second-level plugging slurry to prepare a second-level plugging slurry; after the second volume of the second-level plugging slurry is pumped into the leaking layer position of the wellbore, according to the preparation parameters of the third-level plugging slurry, plugging materials with corresponding particle sizes and gradations in the third-level plugging slurry can be continued to be added to the remaining second-level plugging slurry according to the preparation parameters of the third-level plugging slurry to prepare a third-level plugging slurry; and then the third-level plugging slurry is pumped into the leaking layer position of the wellbore to achieve the plugging operation.

[0159] Among them, based on the preparation parameters of the second-level plugging slurry, when preparing the second-level plugging slurry, plugging materials with the same size or larger particle size relative to the first-level plugging slurry can be added to the first-level plugging slurry; similarly, based on the preparation parameters of the third-level plugging slurry, when preparing the third-level plugging slurry, plugging materials with the same size or larger particle size relative to the second-level plugging slurry can be further added to the second-level plugging slurry.

[0160] Specifically, when preparing the second-level plugging slurry, the plugging material further added on the basis of the first-level plugging slurry may include at least one of flaky rigid plugging material and granular elastic material, and the particle size thereof is not lower than the particle size of the plugging material in the first-level plugging slurry; when preparing the third-level plugging slurry, the plugging material further added on the basis of the second-level plugging slurry may include at least one of flaky rigid plugging material and granular elastic material, and the particle size thereof is not lower than the particle size of the plugging material in the second-level plugging slurry.

[0161] During specific implementation, when the first-level plugging slurry is pumped into the leaking layer position of the wellbore, the first-level plugging slurry can be pumped into the leaking layer position of the wellbore according to the safe displacement and pumping strategy corresponding to the first-level plugging slurry; when the second-level plugging slurry is pumped into the leaking layer position of the wellbore, the second-level plugging slurry can be pumped into the leaking layer position of the wellbore according to the safe displacement and pumping strategy corresponding to the second-level plugging slurry; when the third-level plugging slurry is pumped into the leaking layer position of the wellbore, the third-level plugging slurry can be pumped into the leaking layer position of the wellbore according to the safe displacement and pumping strategy corresponding to the third-level plugging slurry.

[0162] Specifically, for example, the amount of the first-stage plugging slurry pumped in can be 40% (corresponding to the first volume) of the total amount of the initially prepared plugging slurry, the amount of the second-stage plugging slurry pumped in can be 30% (corresponding to the second volume) of the total amount of the initially prepared plugging slurry, and the amount of the third-stage plugging slurry pumped in can be 30% of the initially prepared plugging slurry.

[0163] The specific process of injecting the multi-stage plugging slurry into the leakage cracks step by step in sequence can be found in Figure 6 shown.

[0164] Specifically, when different multi-stage plugging slurries are pumped step by step according to different safe displacements and pumping strategies, they can be processed step by step: after the first volume of the first-stage plugging slurry is completely injected into the leaking fracture, when the second-stage plugging slurry is pumped in, if the wellhead pressure rises significantly, the displacement can be reduced and the pumping can be continued. After a certain amount of the second-stage plugging slurry is pumped into the leaking layer (5 to 6 cubic meters), the remaining plugging slurry can be completely replaced with the drill bit, and then the drill can be pulled up to a position 50 meters above the theoretical plugging slurry return height position for squeezing and injection; if the first-stage plugging slurry enters the leaking fracture, the wellhead pressure will rise significantly, and the wellhead pressure will rise significantly. When a certain amount of the second-stage plugging slurry is pumped into the leaking layer, or a small amount of the second-stage plugging slurry (≤5 cubic meters) enters the leaking layer, and the wellhead pressure gradually reaches the target pressure, the remaining plugging slurry can be completely replaced by the drill bit, and then the drill is pulled up to a position 50m above the theoretical plugging slurry return height position for squeezing injection; when the first-stage plugging slurry of the first volume and the second-stage plugging slurry of the second volume have all entered the leaking layer, if there is no obvious pressure increase at the wellhead during the process of replacing the plugging slurry, the drill bit is lifted up by more than 100m to the water hole position of the drill bit, and it is kept still for plugging for a period of time before squeezing injection.

[0165] Furthermore, the operation mode of intermittent squeezing with holding pressure can be adopted to squeeze the multi-stage plugging slurry into the leakage fracture step by step. Specifically, for example, the plugging slurry can be squeezed at a uniform speed of 1.5-2.5L / s (generally not higher than 3L / s), and when the wellbore pressure gradually reaches the pressure target (i.e., the pressure target pressure), and the pressure drop does not exceed 0.5MPa in 15 minutes, the pressure can be held and plugging can be performed.

[0166] During this period, if the wellhead pressure rises slowly or cannot be maintained, the plugging slurry can be squeezed in small amounts multiple times, and each squeeze can be separated by a period of time (about 30 minutes) to gradually reach the pressure target. Usually, when the initial squeeze volume is high and it is still difficult to start the pressure, you can squeeze in a proper amount of plugging slurry and wait for a period of time before squeezing it again. During the static period, you can maintain a sufficient stable pressure time so that the plugging slurry can fully lose water and form a plugging layer.

[0167] When the pressure-holding intermittent squeezing reaches the pressure target, you can first hold the pressure and wait for plugging for 4 to 8 hours, then release the pressure and open the well, and then wait for plugging for 8 to 12 hours.

[0168] By pumping in multi-stage plugging slurry in the above manner, each level of plugging slurry can be accurately and effectively squeezed into the cracks step by step during the pressure plugging and pressurizing process; and the cracks can be gradually opened in a stable and controllable manner for plugging and supporting, that is, opening a section, plugging a section, and supporting a section. Through the above operation method, the risk of serious leakage caused by sudden leakage of the formation due to pressure plugging can be further effectively reduced in conventional plugging methods.

[0169] In specific implementation, at the construction site of the target leaking well, in the first stage of the plugging process, during the process of pumping the first-level plugging slurry into the leaking layer position of the wellbore, the actual value of the wellbore pressure at the site can be collected in real time; then, based on the actual value of the wellbore pressure and the dynamic distribution model of the crack width, the actual dynamic crack width distribution can be accurately determined; then, based on the actual dynamic crack width distribution, the preparation parameters of the second-level plugging slurry can be adjusted or reset, and then based on the adjusted or reset preparation parameters of the second-level plugging slurry, a better second-level plugging slurry can be prepared on the basis of the remaining first-level plugging slurry, and the second-level plugging slurry can be injected into the leaking cracks to enter the second stage of the plugging process. Similarly, in the second stage of the plugging process, when the second-level plugging slurry is pumped into the wellbore leaking layer, the actual value of the wellbore pressure on site can be collected in real time; then, based on the actual value of the wellbore pressure and the dynamic distribution model of the crack width, the actual dynamic crack width distribution can be accurately determined; then, according to the actual dynamic crack width distribution, the preparation parameters of the third-level plugging slurry can be adjusted or reset, and then based on the adjusted or reset third-level plugging slurry preparation parameters, a better third-level plugging slurry is prepared on the basis of the remaining second-level plugging slurry, and the third-level plugging slurry is injected into the leaking cracks to enter the third stage of the plugging process. This can better achieve plugging and obtain a relatively better and more stable plugging effect.

[0170] In some embodiments, after the multi-stage plugging slurry is sequentially injected into the leaking fractures step by step to plug the leaks, the method may further include the following when implemented:

[0171] S1: According to a preset static pressure leak detection rule, a first leak detection is performed on the target leaking well to obtain a corresponding first leak detection result;

[0172] S2: Based on the first leak detection result, when it is determined that the target leaking well has passed the first leak detection, a second leak detection is performed on the target leaking well according to a preset dynamic pressure leak detection rule to obtain a corresponding second leak detection result;

[0173] S3: According to the second leak detection result, when it is determined that the target leaking well has passed the second leak detection, it is determined that the target leaking well has passed the leak detection.

[0174] Based on the above embodiments, it is possible to accurately determine whether the plugging effect of the target leaking well meets the requirements by combining static pressure-bearing and dynamic pressure-bearing leak detection.

[0175] In specific implementation, when it is determined that the first leak test has not passed according to the first leak test result, or when it is determined that the second leak test has not passed according to the second leak test result, it can be determined that the target leak test has not passed. At this time, the current actual wellbore pressure can be collected and obtained; and the current actual wellbore pressure, the dynamic distribution model of the crack width, and the preset reference formulation table can be used to determine the formulation parameters of the matching supplementary plugging slurry; then, supplementary plugging slurry is formulated according to the formulation parameters of the supplementary plugging slurry, and the supplementary plugging slurry is pumped into the wellbore leaking layer position to perform supplementary repairs based on the current plugging results.

[0176] After the supplementary plugging slurry is pumped in as described above, the target leaking well may be subjected to the first leak detection and the second leak detection to determine whether the target leaking well has passed the leak detection. If the target leaking well still fails the leak detection, it is necessary to trigger the re-plugging of the target leaking well.

[0177] As can be seen from the above, based on the plugging method for improving the pressure-bearing capacity of fractured formations provided in the embodiments of this specification, when it is determined that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pumping-squeezing process is first constructed; then, using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, the dynamic crack width distribution under different wellbore pressures during the plugging slurry pumping-squeezing process is determined; and according to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined to prepare the corresponding plugging slurries at each level; and then, according to the preset pumping rules, the multi-stage plugging slurries are injected into the leakage cracks in sequence step by step to plug the leaks. By fully considering the pressure sensitivity of the lost cracks during pumping, a dynamic distribution model of crack width is constructed and used to predict the dynamic change trend of the crack width of the lost cracks under different wellbore pressures during the plugging slurry pumping-squeezing process; then according to the dynamic change trend of the crack width, a multi-stage plugging slurry is prepared to match the dynamic change of the crack width of the lost cracks during the pumping process, and the multi-stage plugging slurry is injected into the lost cracks in sequence. In this way, plugging can be achieved in a more scientific, precise and safe manner, and a better plugging effect can be obtained, reducing problems such as easy spitting of plugging slurry due to wellbore pressure relief and easy re-leakage due to wellbore pressurization caused by poor pressure-bearing stability.

[0178] The present specification also provides a plugging control system for improving the pressure bearing capacity of fractured formations, comprising a processor and a memory for storing processor executable instructions, wherein the processor implements the following steps when executing the instructions: detecting whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; in the case where the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks, constructing a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process; using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, determining the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process; according to the dynamic crack width distribution, controlling and determining the preparation parameters of matching multi-stage plugging slurries to prepare corresponding plugging slurries of each stage; according to a preset pumping rule, controlling the multi-stage plugging slurries to be injected into the leakage cracks in sequence and stage by stage for plugging.

[0179] The present specification also provides a computer device, which can be referred to as Figure 7 The computer device includes a network communication port 701, a processor 702 and a memory 703, and the above structures are connected through internal cables so that each structure can perform specific data interaction.

[0180] The network communication port 701 may be used to receive a leakage plugging trigger instruction;

[0181] The processor 702 can be specifically used to respond to the plugging trigger instruction and detect whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; when it is determined that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed; using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, the dynamic crack width distribution under the wellbore pressure of different plugging slurry pump replacement-squeezing processes is determined; according to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined to prepare the corresponding plugging slurries at each level; according to the preset pumping rules, the multi-stage plugging slurries are sequentially injected into the leakage cracks step by step to plug the leaks;

[0182] The memory 703 may be specifically used to store corresponding instruction programs.

[0183] In this embodiment, the network communication port 701 can be a virtual port that is bound to different communication protocols so that different data can be sent or received. For example, the network communication port can be a port responsible for web data communication, a port responsible for FTP data communication, or a port responsible for email data communication. In addition, the network communication port can also be a physical communication interface or communication chip. For example, it can be a wireless mobile network communication chip, such as GSM, CDMA, etc.; it can also be a Wifi chip; it can also be a Bluetooth chip.

[0184] In this embodiment, the processor 702 may be implemented in any appropriate manner. For example, the processor may take the form of a microprocessor or processor and a computer-readable medium storing a computer-readable program code (such as software or firmware) executable by the (micro)processor, a logic gate, a switch, an application specific integrated circuit (ASIC), a programmable logic controller, and an embedded microcontroller, etc. This specification does not limit this.

[0185] In this embodiment, the memory 703 may include multiple levels. In a digital system, anything that can store binary data can be a memory; in an integrated circuit, a circuit with a storage function that has no physical form is also called a memory, such as RAM, FIFO, etc.; in a system, a storage device with a physical form is also called a memory, such as a memory stick, TF card, etc.

[0186] The embodiment of the present specification also provides a computer storage medium based on the above-mentioned plugging method for improving the pressure bearing capacity of fractured formations, wherein the computer storage medium stores computer program instructions, and when the computer program instructions are executed, the following steps are implemented: detecting whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; in the case where the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks, constructing a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pumping-squeezing process; using the dynamic distribution model of the crack width, according to the wellbore pressure and the pressure-bearing target pressure, determining the dynamic crack width distribution under different wellbore pressures during the plugging slurry pumping-squeezing process; according to the dynamic crack width distribution, determining the preparation parameters of the matching multi-stage plugging slurry to prepare the corresponding plugging slurries at each stage; according to the preset pumping rules, injecting the multi-stage plugging slurries into the leakage cracks in sequence and stage by stage for plugging.

[0187] In this embodiment, the storage medium includes, but is not limited to, a random access memory (RAM), a read-only memory (ROM), a cache, a hard disk (HDD), or a memory card. The memory may be used to store computer program instructions. The network communication unit may be an interface for network connection communication set in accordance with the standard specified by the communication protocol.

[0188] In this embodiment, the functions and effects specifically implemented by the program instructions stored in the computer storage medium can be explained in comparison with other implementations and will not be described in detail here.

[0189] See also Figure 8 As shown, at the software level, the embodiment of this specification also provides a plugging device for improving the pressure bearing capacity of fractured formations, and the device may specifically include the following structural modules:

[0190] The detection module 801 may be specifically used to detect whether the leakage cracks of the target leakage layer of the target leakage well are pressure sensitive cracks;

[0191] The construction module 802 may be specifically used to construct a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process when the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks;

[0192] The first determination module 803 may be specifically used to determine the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure by using the dynamic distribution model of the crack width;

[0193] The second determination module 804 may be specifically used to determine the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution, so as to prepare the corresponding plugging slurry at each stage;

[0194] The pumping module 805 can be specifically used to inject the multi-stage plugging slurry into the leakage fractures in sequence according to a preset pumping rule to plug the leakage.

[0195] In some embodiments, when the above-mentioned detection module 801 is specifically implemented, it can be detected in the following manner whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks: obtain leakage background information about the leakage cracks of the target leakage layer where the target leakage well is located; based on the leakage background information, detect whether there is an operation that causes the wellbore pressure to increase at the time of leakage; and / or, detect whether there is a backflow phenomenon when the wellbore pressure is reduced after the leakage, and obtain corresponding detection results; based on the detection results, when it is determined that there is an operation that causes the wellbore pressure to increase at the time of leakage; and / or, when there is a backflow phenomenon when the wellbore pressure is reduced after the leakage, determine that the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks.

[0196] In some embodiments, when the above-mentioned construction module 802 is implemented, a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process can be constructed in the following manner: obtain the mechanical property parameters of the leaking layer related to the target leaking layer; wherein the mechanical property parameters of the leaking layer at least include: Young's modulus of the leaking layer rock, Poisson's ratio of the leaking layer rock, and the leaking layer ground stress; obtain the wellbore radius of the target leaking well, and the crack length of the leaking crack; according to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, construct a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process.

[0197] In some embodiments, when the construction module 802 is implemented, a dynamic distribution model of crack width based on wellbore pressure during the plugging slurry pump replacement-squeezing process can be constructed according to the following formula:

[0198]

[0199] Where x is the distance between a point in the leaking fracture and the wellbore wall of the target leaking well along the long axis of the fracture, W(x) is the fracture width at a point in the leaking fracture at a distance x from the wellbore wall along the long axis of the fracture, is the Poisson's ratio of the leaking layer rock, E is the Young's modulus of the leaking layer rock, S H is the maximum horizontal principal stress of the target leaky layer, S h is the minimum horizontal principal stress of the target leaky layer, S V is the vertical principal stress of the target leaky layer, P w is the wellbore pressure during the plugging slurry pump displacement-squeezing process, R is the wellbore radius of the target lost circulation well, L is the fracture length of the lost circulation fracture, and c is the stress anisotropy factor.

[0200] In some embodiments, when the above-mentioned first determination module 803 is implemented, the dynamic distribution model of the crack width can be used in the following manner to determine the dynamic crack width distribution under the wellbore pressure of different plugging slurry pumping-squeezing processes according to the wellbore pressure and the pressure-bearing target pressure: using the dynamic distribution model of the crack width, according to the wellbore pressure, determine the first dynamic crack width distribution based on the wellbore pressure of the first pumping process; using the dynamic distribution model of the crack width, according to the average value of the wellbore pressure and the pressure-bearing target pressure, determine the second dynamic crack width distribution based on the wellbore pressure of the second pumping process; using the dynamic distribution model of the crack width, according to the pressure-bearing target pressure, determine the third dynamic crack width distribution based on the wellbore pressure of the third squeezing process.

[0201] In some embodiments, when the above-mentioned second determination module 804 is implemented, the preparation parameters of the matching multi-level plugging slurry can be determined according to the dynamic crack width distribution in the following manner: according to the first dynamic crack width distribution, query the preset reference preparation table to determine the preparation parameters of the matching first-level plugging slurry; according to the second dynamic crack width distribution, query the preset reference preparation table to determine the preparation parameters of the matching second-level plugging slurry; according to the third dynamic crack width distribution, query the preset reference preparation table to determine the preparation parameters of the matching third-level plugging slurry.

[0202] In some embodiments, the formulation parameters may at least include: plugging material combination, particle size, grading, etc.

[0203] In some embodiments, the plugging material combination may include at least: sheet-like rigid plugging material, granular elastic plugging material, granular rigid plugging material, fiber plugging material, etc.

[0204] In some embodiments, when the above-mentioned pumping module 805 is implemented, the multi-stage plugging slurry can be injected into the leaking fractures in sequence and step by step according to the preset pumping rules in the following manner: the drilling tool parameters of the plugging drill tool combination are obtained; wherein the drilling tool parameters include at least: the number of variable diameter positions and the inlet and outlet diameters of the plugging drill tool; according to the preparation parameters of the multi-stage plugging slurry, the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are determined; according to the preset pumping rules, the drilling tool parameters of the plugging drill tool combination, as well as the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are used to determine the safe displacement and pumping strategy for each level of the plugging slurry in the multi-stage plugging slurry; based on the corresponding safe displacement and pumping strategy, the multi-stage plugging slurry is injected into the leaking fractures in sequence and step by step for plugging.

[0205] In some embodiments, after determining the preparation parameters of matching multi-stage plugging slurries according to the dynamic crack width distribution, the device can also be used when it is implemented to: prepare a first-stage plugging slurry according to the preparation parameters of the first-stage plugging slurry; pump a first volume of the first-stage plugging slurry into the leaking layer position in the wellbore based on the safe displacement and pumping strategy for the first-stage plugging slurry; prepare a second-stage plugging slurry according to the preparation parameters of the second-stage plugging slurry using the remaining plugging slurry of the first-stage plugging slurry; pump a second volume of the second-stage plugging slurry into the leaking layer position in the wellbore based on the safe displacement and pumping strategy for the second-stage plugging slurry; prepare a third-stage plugging slurry according to the preparation parameters of the third-stage plugging slurry using the remaining plugging slurry of the second-stage plugging slurry; and pump the third-stage plugging slurry into the leaking layer position in the wellbore based on the safe displacement and pumping strategy for the third-stage plugging slurry.

[0206] In some embodiments, after the multi-stage plugging slurry is injected into the leaking fractures in sequence and step by step to plug the leaks, the device can also be used when it is implemented: according to a preset static pressure leak detection rule, a first leak detection is performed on the target leaking well to obtain a corresponding first leak detection result; according to the first leak detection result, when it is determined that the target leaking well has passed the first leak detection, according to the preset dynamic pressure leak detection rule, a second leak detection is performed on the target leaking well to obtain a corresponding second leak detection result; according to the second leak detection result, when it is determined that the target leaking well has passed the second leak detection, it is determined that the leak detection of the target leaking well has passed.

[0207] It should be noted that the units, devices or modules described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described separately by functions divided into various modules. Of course, when implementing this specification, the functions of each module can be implemented in the same or more software and / or hardware, or the modules that implement the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0208] As can be seen from the above, the plugging device for improving the pressure bearing capacity of fractured formations provided by the embodiments of this specification fully considers the pressure sensitivity of the lost fracture pumping process, builds and uses a dynamic distribution model of the fracture width, and predicts the dynamic change trend of the fracture width of the lost fracture under different wellbore pressures during the plugging slurry pumping-squeezing process; then, according to the dynamic change trend of the fracture width, a multi-stage plugging slurry is prepared to match the dynamic change of the fracture width of the lost fracture during the pumping-squeezing process, and the multi-stage plugging slurry is sequentially injected into the lost fracture step by step. In this way, plugging can be achieved in a more scientific, precise and safe manner, and a better plugging effect can be obtained, reducing problems such as easy backspitting of the plugging slurry due to wellbore pressure relief and easy re-leakage due to wellbore pressurization caused by poor pressure bearing stability.

[0209] In a specific scenario example, the plugging method for improving the pressure bearing capacity of fractured formations provided in this specification can be used to implement plugging operations to improve the pressure bearing capacity of pressure-sensitive fractured formations. Fig. 9 As shown, the following steps are included.

[0210] S00, judging whether it is a pressure sensitive crack according to the missing data (for example, the missing background data);

[0211] S10, collecting and arranging basic parameters required for crack width calculation (for example, mechanical property parameters of leaky layer, wellbore radius, crack length of leaky crack, etc.);

[0212] S20, calculating the width of the leakage crack under different wellbore pressures (i.e., constructing a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pumping-squeezing process, and using the model to determine the dynamic crack width distribution under different wellbore pressures during the pumping-squeezing process);

[0213] S30, determining the particle size, gradation and concentration of the plugging slurry according to the pressure plugging target and the calculated crack width (i.e., determining the preparation parameters of the matching multi-level plugging slurry according to the dynamic crack width distribution);

[0214] S40, determining a safe construction displacement (eg, a safe displacement) according to the plugging drilling tool assembly and the plugging slurry;

[0215] S50, preparing plugging slurry on site (for example, multi-stage plugging slurry);

[0216] S60, pump the plugging slurry to the leaking layer step by step;

[0217] S70, hold the pressure and intermittently squeeze the plugging slurry into the leaking layer;

[0218] S80. Hold the pressure and wait for plugging, release the pressure to open the well, keep it still and wait for plugging, then pull out the drill to check for leaks.

[0219] The following mainly takes a certain well in a certain oil field as an example to specifically illustrate the above steps.

[0220] Specifically, the well (for example, the target leakage well) can be a vertical well. The well leakage returns to 3097.86m after three drillings. The leakage layer is a pressure-sensitive fractured formation. The well leakage stops when the static waiting measures are taken. The well leakage occurs when drilling down or increasing the displacement cycle, and pressure-bearing plugging treatment is required.

[0221] In specific implementation, the above-mentioned collection and collation of basic parameters required for crack width calculation may include: according to the data of drilling, logging, measurement while drilling, logging, ground breaking test, etc., determining the wellbore size (for example, wellbore radius) as 166.7 mm, the Young's modulus of the leaking layer rock as 50000 MPa, the Poisson's ratio as 0.20, and the ground stress of the leaking layer as S H =96MPa, S h =64MPa,S V =73MPa, leaking layer pressure P p =65MPa.

[0222] In specific implementation, the above calculation of the leakage crack width under different wellbore pressures may include: according to equations (1) to (2) (corresponding to the dynamic distribution model of crack width), calculating the crack width under different wellbore pressures (for example, the dynamic crack width distribution under different wellbore pressures during the pumping-squeezing process), and drawing a curve chart of the crack width changing with the distance from the wellbore. Then substituting the wellbore pressure of 67MPa during the pumping process, we get Fig.10 Crack width graph shown.

[0223]

[0224]

[0225] In formula (1), x is the distance between a position point in the leaking fracture and the wellbore wall of the target leaking well along the long axis of the fracture, m; W(x) is the fracture width of the position point in the leaking fracture at a distance x from the wellbore wall along the long axis of the fracture, m; υ is the Poisson's ratio of the leaking layer rock, dimensionless; E is the Young's modulus of the leaking layer rock, MPa; S H is the maximum horizontal principal stress of the target leaky layer, S h is the minimum horizontal principal stress of the target leaky layer, S V is the vertical principal stress of the target leaking layer, MPa; P w is the wellbore pressure during the plugging slurry pump displacement-squeezing process, MPa; R is the wellbore radius of the target lost circulation well, m; L is the fracture length of the lost circulation fracture, m; c is the stress anisotropy factor, dimensionless.

[0226] In specific implementation, according to equations (1) to (2), the wellbore pressure during the pumping process and the average wellbore pressure of the pressure target, 70 MPa, can be substituted to obtain Fig.11 Crack width graph shown.

[0227] In specific implementation, according to equations (1) to (2), the borehole pressure corresponding to the pressure target, 73 MPa, can be substituted to obtain Fig.12 Crack width graph shown.

[0228] In specific implementation, the particle size and gradation of the first-stage plugging slurry can be determined according to the wellbore pressure during the pumping process and the corresponding crack width. Fig.10 It can be seen that at a distance of 0.5m from the wellbore, the crack width reaches a maximum value of about 2.8mm, and at a distance of 15m from the wellbore, the crack width drops below 1.8mm. In order to allow the plugging slurry to effectively enter the cracks and form bridges, the bridging material of the first-level plugging slurry should be between 1.8 and 2.8mm, so 1-3mm sheet rigid plugging material is selected as the first-level plugging slurry bridging material.

[0229] In specific implementation, based on the average value of the wellbore pressure and the pressure target during the pumping process, the particle size and grading of the second-stage plugging slurry can be determined according to the corresponding crack width. Fig.11 It can be seen that at a distance of 0.5m from the wellbore, the crack width reaches a maximum value of about 5.4mm, and at a distance of 15m from the wellbore, the crack width drops below 3.5mm. In order to support the cracks behind the first-level plugging layer, the bridging material of the second-level plugging slurry should be between 3.5 and 5.4mm, so 3-5mm sheet rigid plugging material is selected as the second-level plugging slurry bridging material.

[0230] In specific implementation, the particle size and gradation of the third-level plugging slurry are determined according to the pressure bearing target and the corresponding crack width. Fig.12 It can be seen that at a distance of 0.5m from the wellbore, the crack width reaches a maximum value of about 8.1mm, and at a distance of 15m from the wellbore, the crack width drops below 5.3mm. In order to support the cracks behind the second-level plugging layer, the bridging material of the third-level plugging slurry should be between 5.3 and 8.1mm, so 5-8mm sheet rigid plugging material is selected as the third-level plugging slurry bridging material.

[0231] In this embodiment, refer to Figure 6As shown, a step-by-step plugging method can be used, that is, first, a plugging slurry with a smaller particle size and a lower concentration is prepared (i.e., the first-stage plugging slurry) to plug a crack with a smaller width opened at a lower wellbore pressure; then a plugging slurry with a medium particle size and a medium concentration is prepared (i.e., the second-stage plugging slurry) to plug a crack with a medium width opened at a medium wellbore pressure; finally, a plugging slurry with a larger particle size and a higher concentration is prepared (i.e., the third-stage plugging slurry) to plug a crack with a larger width opened at a target wellbore pressure. The specific preparation process is shown below.

[0232] For the first-level plugging slurry: Considering that the maximum crack width is about 5.4mm when the wellbore pressure is about 67MPa during the pumping process, 1-3mm sheet rigid plugging materials, 400μm granular elastic plugging materials, granular rigid plugging materials, and fiber plugging materials can be selected to prepare a plugging slurry with a total mass concentration of 15%. Among them, the base slurry is water-based drilling fluid.

[0233] For the second-level plugging slurry: Considering that the maximum crack width is about 5.4mm when the average value of the wellbore pressure and the pressure target is about 70MPa during the pumping process, 3-5mm flaky rigid plugging materials and 1000μm granular elastic plugging materials can be added to the first-level plugging slurry to prepare a plugging slurry with a total mass concentration of 20%. Among them, the base slurry is water-based drilling fluid.

[0234] For the third-level plugging slurry: considering that the maximum crack width is about 8.1mm based on the pressure target of 73MPa, 5-8mm sheet-shaped rigid plugging materials and 1000μm granular elastic plugging materials are added to the second-level plugging slurry to prepare a plugging slurry with a total mass concentration of 25%. Among them, the base slurry is water-based drilling fluid.

[0235] When determining the safe construction displacement based on the plugging drill tool combination and plugging slurry, it is considered that the plugging drill tool is a 139.7mm bare drill rod with an inner diameter of about 60mm. There is no obvious diameter change position in the plugging combination, and the inner diameter is much larger than the maximum particle size of the plugging material. Therefore, the safe construction displacement is the displacement when acceptable leakage occurs, that is, 12-20L / s.

[0236] When preparing the plugging slurry on site, the plugging slurry can be prepared on site according to the particle size, gradation and concentration of the plugging slurry determined in the above steps, and the following steps can be followed:

[0237] S1. Add plugging materials in the order of fiber, granular elastic, sheet rigid, and granular rigid to prepare the first-level plugging slurry for 30 minutes. 3. In this embodiment, the formula of the first-level plugging slurry is: water-based drilling fluid + 1-3 mm flaky rigid plugging material + 400 μm granular elastic plugging material + granular rigid plugging material + fiber plugging material (total mass concentration 15%). The preparation method is: first add the water-based drilling fluid into the mixing tank and stir evenly, then gradually add the fiber plugging material, 400 μm granular elastic plugging material, 1-3 mm flaky rigid plugging material, and granular rigid plugging material, while adding and stirring until the required concentration is reached.

[0238] S2. After pumping in the first-stage plugging slurry, add 3-5mm flaky rigid plugging material and 1000μm granular elastic plugging material to the remaining first-stage plugging slurry to prepare the second-stage plugging slurry. In this embodiment, the formula of the second-stage plugging slurry is: first-stage plugging slurry + 3-5mm flaky rigid plugging material + 1000μm granular elastic plugging material (total mass concentration 20%). The preparation method is: after pumping in the first-stage plugging slurry, gradually add 1000μm granular elastic plugging material and 3-5mm flaky rigid plugging material, stirring while adding until the required concentration is reached.

[0239] S3. After pumping in the second-stage plugging slurry, add 5-8mm flaky rigid plugging material and 1000μm granular elastic plugging material to the remaining first-stage plugging slurry to prepare the third-stage plugging slurry. In this embodiment, the formula of the third-stage plugging slurry is: second-stage plugging slurry + 5-8mm flaky rigid plugging material + 1000μm granular elastic plugging material (total mass concentration 25%). The preparation method is: after pumping in the first-stage plugging slurry, gradually add 1000μm granular elastic plugging material and 5-8mm flaky rigid plugging material, stirring while adding until the required concentration is reached.

[0240] When pumping the plugging slurry to the leaking layer step by step, the following principles can be followed: the amount of the first-stage plugging slurry pumped in is 40% of the total amount of the initially prepared plugging slurry, which is about 12m3. 3 The amount of the second-stage plugging slurry pumped in is 30% of the total amount of the initially prepared plugging slurry, which is about 9m 3 The amount of the third-stage plugging slurry pumped in at the end is 30% of the initial plugging slurry, which is about 9m 3 .

[0241] During the pump replacement process, a safe construction displacement of 12-20L / s can be used, while monitoring the wellhead pressure and the properties of the discharged liquid to ensure that the plugging slurry enters the leaking layer smoothly.

[0242] Specifically, when holding pressure and intermittently squeezing the plugging slurry into the leaking layer, after the pump replacement is completed, hold pressure and intermittently squeeze according to the following steps: squeeze the plugging slurry at a uniform speed according to the displacement of 2L / s. If the wellhead pressure control quickly reaches the pressure target value and the pressure drop does not exceed 0.5MPa in 15 minutes, hold the pressure and wait for plugging; if the wellhead pressure control rises slowly or cannot be built up, squeeze the plugging slurry in small amounts and multiple times, with an interval of about 30 minutes between each squeezing, and gradually reach the pressure target; during the process of holding pressure and intermittent squeezing, pay attention to the changes in wellhead pressure to prevent excessive squeezing from causing formation rupture or other adverse consequences.

[0243] Specifically, the process is to hold pressure and wait for plugging, release pressure to open the well, wait for plugging in a static state, and pull out the drill for leak testing. After the pressure target is reached by intermittent squeezing during the holding pressure, hold pressure and wait for plugging for 6 hours, then release pressure to open the well, and wait for plugging in a static state for 8 hours. During the static waiting for plugging period, check whether there is backflow at the wellhead. If there is backflow, it means that the plugging effect is not ideal and the plugging process needs to be repeated; if there is no backflow, it means that the plugging effect is good and the leak testing operation can be carried out. The leak testing methods include static pressure bearing and dynamic pressure bearing. Static pressure bearing is pressurization at the wellhead, and dynamic pressure bearing is pressurization by increasing the circulating displacement. The leak testing process adopts the order of static first and dynamic later.

[0244] In this embodiment, after completing the above steps, experience has shown that the leakage of the well has been effectively controlled, achieving the expected pressure-bearing plugging effect.

[0245] Through the above scenario examples, the plugging method for improving the pressure bearing capacity of fractured formations provided in this specification is verified. By using the dynamic crack width distribution calculation model (i.e., the dynamic distribution model of crack width), the distribution trend of the leakage crack width during the rising wellbore pressure during the plugging process is estimated, and the prediction of the width of induced cracks and extended cracks in pressure-sensitive fractured formations is achieved, thereby providing a basis for the grading and concentration design of the plugging slurry. By designing multi-stage plugging slurry according to the dynamic width of the cracks, and using the drifting characteristics of the sheet-like rigid plugging material under stable flow conditions and the flipping bridging characteristics under unstable flow conditions, as well as the elastic deformation properties of the granular elastic plugging material, the problem of matching the size of the plugging material with the crack width can be effectively solved. By using multi-stage plugging slurry, during the pressure plugging process, it is squeezed into the cracks step by step, and the cracks are gradually opened in a stable and controllable manner for plugging and supporting. One section is opened, one section is plugged, and one section is supported, which effectively reduces the risk of serious leakage caused by sudden pressure leakage of the formation under pressure plugging by conventional plugging methods. By utilizing the high friction properties of flaky rigid plugging materials and granular elastic plugging materials, the compressive resilience properties of granular elastic plugging materials, and the tensioning properties of fiber materials, the friction resistance of the plugging materials inside the plugging layer and between the plugging layer and the crack surface is increased, thereby increasing the compressive elastic deformation capacity of the plugging layer and improving the overall structural stability of the plugging layer during the opening and closing of the cracks. This can effectively solve the problems of easy backspitting of plugging slurry during wellbore pressure relief and easy re-leakage during wellbore pressurization in conventional plugging processes.

[0246] This effectively solves the following problems existing in the existing methods: 1) The induced cracks or extended cracks are highly pressure sensitive. During the plugging process, the cracks close due to the decrease in wellbore pressure. During the plugging process, the cracks open or even extend due to the increase in wellbore pressure. The crack width changes dynamically with the change in wellbore pressure, while the conventional static crack width determined by leakage rate or logging does not take this property into account; 2) The pressure sensitivity of the cracks further increases the difficulty of matching the size of the plugging material with the crack width. At the same time, the permeability of the plugging material from the wellbore into the crack and the plugging performance after entering the crack are contradictory, and the plugging slurry is easy to seal or cannot be retained; 3) Improper pressure control during the plugging squeezing and pressurizing process can easily lead to unstable expansion and extension of the cracks, resulting in gradually increasing plugging difficulty; 4) The plugging layer is formed by extrusion and accumulation of rigid or plastic materials. It has poor adaptive deformation ability and poor pressure-bearing stability during the change of wellbore pressure after plugging. The plugging slurry is easy to spit out during wellbore pressure relief and easy to leak again during wellbore pressurization.

[0247] Although the present specification provides method operation steps as described in the embodiments or flow charts, more or less operation steps may be included based on conventional or non-creative means. The order of steps listed in the embodiments is only one way of executing the order of many steps, and does not represent a unique execution order. When the device or client product in practice is executed, it can be executed in sequence or in parallel according to the method shown in the embodiments or the drawings (for example, a parallel processor or a multi-threaded processing environment, or even a distributed data processing environment). The term "include", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, product or device including a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such a process, method, product or device. In the absence of more restrictions, it is not excluded that there are other identical or equivalent elements in the process, method, product or device including the elements. The first, second, etc. words are used to represent the name, and do not represent any particular order.

[0248] Those skilled in the art also know that, in addition to implementing the controller in a purely computer-readable program code, the controller can be made to implement the same function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, such a controller can be considered as a hardware component, and the devices for implementing various functions included therein can also be considered as structures within the hardware component. Or even, the devices for implementing various functions can be considered as both software modules for implementing the method and structures within the hardware component.

[0249] This specification may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, classes, etc. that perform specific tasks or implement specific abstract data types. This specification may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media including storage devices.

[0250] Although the present specification is described through embodiments, those skilled in the art will appreciate that there are many modifications and changes to the present specification without departing from the spirit of the present specification, and it is intended that the appended claims include these modifications and changes without departing from the spirit of the present specification.

Claims

1. A plugging method for improving the pressure bearing capacity of fractured formations, characterized in that: include: Detect whether the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks; When the target leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed; Using the dynamic distribution model of crack width, according to the wellbore pressure and the pressure-bearing target pressure, the dynamic crack width distribution under different wellbore pressures of the plugging slurry pump replacement-squeezing process is determined; According to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined to prepare the corresponding plugging slurries at each stage; According to the preset pumping rules, the multi-stage plugging slurry is injected into the leakage fractures step by step in sequence to plug the leakage.

2. The method according to claim 1, characterized in that Detect whether the leakage cracks in the target leakage layer of the target leakage well are pressure-sensitive cracks, including: Obtaining leakage background information about leakage fractures in the target leakage layer where the target leakage well is located; Based on the leakage background data, whether there is any operation that causes the wellbore pressure to increase during the leakage detection; and / or whether there is a backflow phenomenon when the wellbore pressure decreases after the leakage detection, and obtain corresponding detection results; According to the detection results, when it is determined that there is an operation that causes the wellbore pressure to increase; and / or when there is a backflow phenomenon when the wellbore pressure decreases after the leakage, the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks.

3. The method according to claim 1, characterized in that A dynamic distribution model of fracture width based on wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed, including: Acquire mechanical property parameters of the leaky layer related to the target leaky layer; wherein the mechanical property parameters of the leaky layer at least include: Young's modulus of the leaky layer rock, Poisson's ratio of the leaky layer rock, and ground stress of the leaky layer; Obtain the wellbore radius of the target lost-flow well and the fracture length of the lost-flow fracture; According to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed.

4. The method according to claim 3, characterized in that According to the mechanical property parameters of the leaking layer, the wellbore radius and the crack length, a dynamic distribution model of the crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed, including: According to the following formula, a dynamic distribution model of fracture width based on wellbore pressure during the plugging slurry pump replacement-squeezing process is constructed: Where x is the distance between a point in the leaking fracture and the wellbore wall of the target leaking well along the long axis of the fracture, W(x) is the fracture width at a point in the leaking fracture at a distance x from the wellbore wall along the long axis of the fracture, υ is the Poisson's ratio of the leaking layer rock, E is the Young's modulus of the leaking layer rock, S H is the maximum horizontal principal stress of the target leaky layer, S h is the minimum horizontal principal stress of the target leaky layer, S V is the vertical principal stress of the target leaky layer, P w is the wellbore pressure during the plugging slurry pump displacement-squeezing process, R is the wellbore radius of the target lost circulation well, L is the fracture length of the lost circulation fracture, and c is the stress anisotropy factor.

5. The method according to claim 1, characterized in that The dynamic distribution model of crack width is used to determine the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure, including: Determining a first dynamic fracture width distribution under the wellbore pressure during a first pumping process using the dynamic distribution model of fracture width according to the wellbore pressure; Determining a second dynamic crack width distribution under the wellbore pressure during a second pumping process by using the dynamic distribution model of the crack width and according to an average value of the wellbore pressure and the pressure-bearing target pressure; The dynamic distribution model of the crack width is used to determine a third dynamic crack width distribution based on the wellbore pressure of the third squeezing process according to the pressure target pressure.

6. The method according to claim 5, characterized in that According to the dynamic crack width distribution, the preparation parameters of the matching multi-stage plugging slurry are determined, including: According to the first dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching first-level plugging slurry; According to the second dynamic crack width distribution, a preset reference formulation table is queried to determine the formulation parameters of the matching second-level plugging slurry; According to the third dynamic crack width distribution, the preset reference formulation table is queried to determine the formulation parameters of the matching third-level plugging slurry.

7. The method according to claim 6, characterized in that The preparation parameters at least include: plugging material combination, particle size, and gradation.

8. The method according to claim 7, characterized in that The plugging material combination at least includes: sheet-like rigid plugging material, granular elastic plugging material, granular rigid plugging material, and fiber plugging material.

9. The method according to claim 7, characterized in that: According to the preset pumping rules, the multi-stage plugging slurry is injected into the leakage fractures in sequence step by step to plug the leakage, including: Obtaining drilling tool parameters of the plugging drilling tool assembly; wherein the drilling tool parameters at least include: the number of variable diameter positions and inlet and outlet diameters of the plugging drilling tool; According to the preparation parameters of the multi-stage plugging slurry, the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are determined; According to the preset pumping rules, the drilling tool parameters of the plugging drilling tool assembly, as well as the characteristic particle size value, base slurry density and apparent viscosity of the plugging material of the multi-stage plugging slurry are used to determine the safe displacement and pumping strategy for each level of the plugging slurry in the multi-stage plugging slurry; Based on the corresponding safe displacement and pumping strategy, the multi-stage plugging slurry is injected into the leakage fractures step by step in sequence to plug the leakage.

10. The method according to claim 7, characterized in that After determining the matching preparation parameters of the multi-stage plugging slurry according to the dynamic crack width distribution, the method further includes: According to the preparation parameters of the first-stage plugging slurry, the first-stage plugging slurry is prepared; Based on the safe displacement and pumping strategy of the first-stage plugging slurry, a first volume of the first-stage plugging slurry is pumped into the wellbore leaking layer position of the target leaking well; According to the preparation parameters of the second-stage plugging slurry, the remaining plugging slurry of the first-stage plugging slurry is used to prepare the second-stage plugging slurry; Based on the safe displacement and pumping strategy of the second-stage plugging slurry, a second volume of the second-stage plugging slurry is pumped into the wellbore leaking zone of the target leaking well; According to the preparation parameters of the third-level plugging slurry, the remaining plugging slurry of the second-level plugging slurry is used to prepare the third-level plugging slurry; Based on the safe displacement and pumping strategy of the third-level plugging slurry, pump the third-level plugging slurry into the wellbore leaking layer position of the target leaking well; The first-stage plugging slurry, the second-stage plugging slurry and the third-stage plugging slurry in the wellbore of the target leakage well are squeezed into the leakage cracks.

11. The method according to claim 10, characterized in that After the multi-stage plugging slurry is injected into the leakage fractures in sequence and stage by stage for plugging, the method further comprises: According to the preset static pressure leak detection rule, a first leak detection is performed on the target leaking well to obtain a corresponding first leak detection result; According to the first leak detection result, when it is determined that the target leaking well has passed the first leak detection, a second leak detection is performed on the target leaking well according to a preset dynamic pressure leak detection rule to obtain a corresponding second leak detection result; According to the second leak detection result, when it is determined that the target leaking well has passed the second leak detection, it is determined that the target leaking well has passed the leak detection.

12. A plugging device for improving the pressure bearing capacity of fractured formations, characterized in that: include: A detection module, used to detect whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; A construction module is used to construct a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process when the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks; The first determination module is used to determine the dynamic crack width distribution under different wellbore pressures of the plugging slurry pump replacement-squeezing process according to the wellbore pressure and the pressure-bearing target pressure by using the dynamic distribution model of the crack width; The second determination module is used to determine the preparation parameters of the matching multi-stage plugging slurry according to the dynamic crack width distribution, so as to prepare the corresponding plugging slurry at each stage; The pumping module is used to inject the multi-stage plugging slurry into the leakage cracks in sequence according to the preset pumping rules to plug the leakage.

13. A computer storage medium, characterized in that: Computer instructions are stored thereon, and when the instructions are executed by a processor, the steps of the method according to any one of claims 1 to 11 are implemented.

14. A plugging control system for improving the pressure bearing capacity of fractured formations, characterized in that: The invention comprises a processor and a memory for storing instructions executable by the processor, wherein the processor implements the following steps when executing the instructions: detecting whether the leakage cracks of the target leakage layer of the target leakage well are pressure-sensitive cracks; constructing a dynamic distribution model of crack width based on the wellbore pressure during the plugging slurry pump replacement-squeezing process when the leakage cracks of the target leakage layer of the target leakage well are determined to be pressure-sensitive cracks; using the dynamic distribution model of crack width, according to the wellbore pressure and the pressure-bearing target pressure, determining the dynamic crack width distribution under different wellbore pressures during the plugging slurry pump replacement-squeezing process; according to the dynamic crack width distribution, controlling and determining the preparation parameters of the matching multi-stage plugging slurry to prepare the corresponding plugging slurries of each stage; and according to the preset pumping rules, controlling the multi-stage plugging slurries to be injected into the leakage cracks in sequence and stage by stage for plugging.

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