Well drilling leakage crack width prediction and bridging plugging particle optimization method and system

Abstract

The invention discloses a well drilling leakage crack width prediction and bridging plugging particle optimization method and system. The method comprises the steps that reservoir leakage points are found through a logging tool, and the type of a leakage crack is recognized; the leakage crack type comprises a horizontal crack or a vertical crack; according to the reservoir leakage point, establishing a working fluid flowing mathematical model from the surface pipeline to the reservoir leakage point; according to the type of the leakage crack, constructing a leakage crack deformation mathematical model based on a displacement discontinuity theory; calculating the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; according to the fluid pressure and the leakage data, the leakage crack width distribution is predicted based on the leakage crack deformation mathematical model; and preferably selecting the particle size of the bridging plugging particles according to the width distribution of the leakage crack. The method overcomes the defects that a traditional well drilling plugging material is high in selection subjectivity and lacks theoretical support, and the effects of improving the success rate of well drilling plugging operation, guaranteeing well drilling safety and improving the oil and gas recovery rate are expected to be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas wells, and in particular to a method and system for predicting the width of drilling leakage cracks and optimizing bridging and plugging particles. Background Art

[0002] Drilling, a critical process in oil and gas field development, enables the efficient development of underground oil and gas resources by establishing high-speed flow channels between the reservoir and the surface. Ensuring drilling safety is crucial for improving oil and gas recovery, reducing development costs, and ensuring energy security. Influenced by a combination of factors, including reservoir geological characteristics, fracture development, drilling fluid rheological properties, and drilling parameters, fracture losses often occur during drilling, leading to the loss of large amounts of drilling fluid through these fractures into the formation. Drilling fluid losses can cause a drop in wellbore fluid pressure, impacting fluid circulation and cuttings-carrying capacity. They can also lead to complex downhole accidents such as wellbore instability and stuck pipe, increasing drilling risks. If drilling fluid leaks into oil and gas reservoirs, solid particles in the fluid can clog pores, contaminating the reservoir and compromising subsequent oil and gas field development. Therefore, effectively controlling fracture losses during drilling is crucial for ensuring drilling safety, reducing operating cycles, minimizing reservoir damage, and improving oil and gas recovery.

[0003] Currently, the main plugging technologies for drilling fracture leakage include physical plugging technology, chemical plugging technology, and mechanical plugging technology. The reaction speed and effect of chemical plugging agents are difficult to control, and plugging operations often fail due to the unstable effect of the formed plugging layer. The mechanical plugging process is relatively complex, which will increase the cost of drilling operations and the difficulty of subsequent construction. Physical plugging technology, which adds bridging particles and plugging agents to the drilling fluid to form a plugging layer at the leakage fracture, is widely used at drilling sites due to its low material cost and simple construction process. However, the implementation of physical plugging technology often relies on the experience of on-site engineers. The particle size of the plugging material is manually selected according to the amount of drilling fluid leakage. Factors such as the difficulty in determining the location of the reservoir leakage point and the mismatch between the leakage fracture width and the bridging particle size often lead to the failure of drilling plugging operations, greatly increasing the construction risk and drilling cycle.

[0004] Existing technical solutions for drilling fracture-induced lost fluids primarily focus on the design and optimization of plugging materials and operational processes, but lack attention to issues such as predicting lost fluid fracture width and optimizing the particle size of bridging plugging particles. Matching the particle size of the bridging plugging particles to the lost fluid fracture width ensures that the temporary plugging material can successfully enter the lost fluid fracture and sequentially complete bridging, filling, and sealing to form a reliable plugging layer. Therefore, rationally predicting the width of lost fluid fractures and selecting appropriate bridging plugging particles are key to improving the success rate of drilling plugging operations and reducing non-drilling operation cycles. Therefore, it is urgent to establish a technology for predicting the width of lost fluid fractures and optimizing the particle size of bridging plugging particles to address these limitations. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for predicting the width of drilling leakage cracks and optimizing bridging plugging particles. By judging the location of the reservoir leakage point and the type of leakage cracks, the leakage crack width is reasonably predicted according to the in-situ stress parameters and the fluid pressure of the leakage point during the operation, and the particle size of the bridging plugging particles is selected according to the leakage crack width. The defects of traditional drilling plugging material selection, which are highly subjective and lack theoretical support, are overcome, so as to achieve the effect of improving the success rate of drilling plugging operations, ensuring drilling safety and improving oil and gas recovery rate.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for predicting the width of drilling leakage cracks and optimizing the bridging plugging particles, the method comprising:

[0008] Use logging tools to find reservoir leaks and identify the types of leaking fractures; leaking fracture types include horizontal fractures or vertical fractures;

[0009] According to the reservoir leakage point, a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point is established;

[0010] According to the type of leakage fractures, a mathematical model of leakage fracture deformation is constructed based on the displacement discontinuity theory;

[0011] Calculate the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; predict the leakage fracture width distribution based on the fluid pressure and leakage data and the leakage fracture deformation mathematical model;

[0012] According to the width distribution of leakage cracks, the particle size of the bridging plugging particles is optimized.

[0013] The above technical solution, the present invention reasonably calculates the geometric parameters of the leakage cracks through the mathematical model of the working fluid flow from the ground to the reservoir leakage point and the mathematical model of the leakage crack deformation, and selects the appropriate bridging and plugging particle size based on the fracture temporary plugging and bridging theory and the leakage crack width distribution, so that the plugging material can successfully enter the leakage cracks and bridge and plug them, thereby effectively controlling the loss of drilling fluid.

[0014] Furthermore, logging tools are used to find reservoir leakage points and identify the types of leakage fractures, including:

[0015] By observing the change of drilling return mud volume in the mud tank, it can be judged whether the reservoir has fracture leakage;

[0016] After confirming that fracture leakage has occurred, a downhole logging tool is inserted from the surface to locate the reservoir leakage point;

[0017] According to the location of the reservoir leakage point, the logging data is obtained and analyzed, and combined with the reservoir stress characteristics, the type of leakage fracture is determined to be horizontal fracture or vertical fracture.

[0018] Furthermore, based on the reservoir leakage point, a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point is established, including:

[0019] Obtain basic parameters of the downhole drilling assembly, including drill pipe length and inner diameter, drill collar length and inner diameter, and drill bit hole number and diameter;

[0020] According to the basic data and reservoir leakage points, the drill bit is positioned near the reservoir leakage point to carry out the plugging work cycle, and a mathematical model of the working fluid flow at the reservoir leakage point under the corresponding working conditions is established.

[0021] Furthermore, the drill bit is positioned near the reservoir leak point to carry out a plugging work cycle, and a mathematical model of the working fluid flow at the reservoir leak point under the corresponding working conditions is established, including:

[0022] When the bridging plugging particles are added in a low-displacement circulation mode, the first fluid pressure calculation model at the reservoir leakage point is established by the surface mud pump inlet pressure, pipe flow friction, drill bit pressure loss and static liquid column pressure; the expression of the first fluid pressure calculation model is: p leak =p pump +p g -Δp f -Δp d -Δp l , p leak Indicates the fluid pressure near the reservoir leakage point; p pump Indicates the surface mud pump inlet pressure; p g Indicates the hydrostatic column pressure of the drilling string; Δp f Indicates the friction resistance along the drilling string; Δp d Indicates the drill hole friction; Δp l Indicates local pressure loss;

[0023] When the bridging plugging particles are added by surface squeezing, the second fluid pressure calculation model at the reservoir leakage point is established by the surface mud pump inlet pressure and the hydrostatic column pressure; the second fluid pressure calculation model expression is: leak =p pump +p g , p leak Indicates the fluid pressure near the leak point; p pump Indicates the surface mud pump inlet pressure; p g Indicates the hydrostatic pressure of the drilling string.

[0024] Furthermore, according to the type of lost-flow fractures, a mathematical model of lost-flow fracture deformation is constructed based on the displacement discontinuity theory, including:

[0025] According to the type of leaking fractures, the structured plane rectangular grid unit is used to discretize the leaking fractures and calculate the displacement of the leaking fractures.

[0026] According to the displacement of the lost fractures, the fracture unit displacement calculation matrix is ​​constructed based on the displacement discontinuity theory;

[0027] Based on the fracture unit displacement calculation matrix, the mathematical model of the lost fracture deformation is derived; the mathematical model of the lost fracture deformation is the relationship between the lost fracture width and the fluid pressure.

[0028] Furthermore, the mathematical model of leakage fracture deformation is expressed as follows:

[0029] B M w+σ M =p f ,w=D N

[0030]

[0031] In the above formula, D L 、D H 、D N represent the strike displacement matrix, dip displacement matrix and normal displacement matrix respectively; B represents the boundary influence coefficient matrix; B NL Represents the boundary influence coefficient matrix between normal and strike; B NH Represents the boundary influence coefficient matrix between normal and inclination; B NN Represents the boundary influence coefficient matrix between normal and normal directions; B HH Represents the boundary influence coefficient matrix between tendencies; B LH Represents the boundary influence coefficient matrix between strike and dip; B HL Represents the boundary influence coefficient matrix between dip and strike; B LN Represents the boundary influence coefficient matrix between the strike and normal directions; B HN Represents the boundary influence coefficient matrix between the inclination and the normal; B LL Represents the boundary influence coefficient matrix between strikes; The inverse matrix of the boundary influence coefficient matrix between tendencies; The inverse matrix of the boundary influence coefficient matrix between strikes; () -1 represents the inverse of the matrix; τ L , τ H , σ N They represent the strike stress matrix, dip stress matrix and normal stress matrix acting on the fracture unit respectively; B M represents the comprehensive coefficient matrix; σ M represents the comprehensive stress matrix; w represents the leakage crack width matrix; Pf represents the fluid pressure matrix; σ far represents the reservoir normal in-situ stress matrix.

[0032] Furthermore, based on the fluid pressure and leakage data and the mathematical model of leakage fracture deformation, the leakage fracture width distribution is predicted, including:

[0033] Step A: Obtain the morphology of the leakage fracture based on the well logging data analysis, and preset the initial plane leakage fracture at the leakage point of the reservoir, wherein the horizontal fracture adopts the coin-shaped fracture assumption and the vertical fracture adopts the rectangular fracture assumption;

[0034] Step B, calculating a stress matrix acting on the initial plane leaking fractures using reservoir in-situ stress parameters based on the spatial position relationship of the initial plane leaking fractures; the stress matrix includes a strike stress matrix, a dip stress matrix, and a normal stress matrix;

[0035] Step C, calculating the geometric parameters of the lost fracture based on the stress matrix and the fluid pressure and the lost fracture deformation mathematical model; the geometric parameters of the lost fracture include the fracture width and the fracture volume;

[0036] In step D, the lost-flow fracture volume estimated by wellhead monitoring data is compared with the fracture volume calculated in step C, and the lost-flow fracture front is iteratively corrected to finally obtain a reasonable lost-flow fracture width distribution.

[0037] Furthermore, based on the width distribution of leakage cracks, the preferred particle size of the bridging plugging particles includes:

[0038] Based on the distribution of lost-circulation fracture widths and the crack bridging and plugging patterns, the average width of lost-circulation fractures within a preset range from the wellbore axis is used as the critical fracture width. Based on the critical fracture width, the bridging particle size range is determined. The bridging particle size range is the reasonable bridging particle size range that can enter the lost-circulation fracture and successfully bridge it.

[0039] The amount of bridging particles is reasonably designed according to the volume of the leakage cracks, and the leakage cracks can be sealed according to the amount of bridging particles and the particle size range of the bridging particles.

[0040] In a second aspect, the present invention provides a system for predicting the width of lost circulation cracks in drilling and optimizing the bridging and plugging particles, the system comprising:

[0041] The leakage point and fracture type identification unit is used to find the reservoir leakage point and identify the leakage fracture type through the logging tool; the leakage fracture type includes horizontal fracture or vertical fracture;

[0042] The first model building unit is used to establish a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point according to the reservoir leakage point;

[0043] The second model building unit is used to build a mathematical model of the leakage fracture deformation based on the displacement discontinuity theory according to the leakage fracture type;

[0044] The leakage crack width prediction unit is used to calculate the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; based on the fluid pressure and leakage data and the leakage crack deformation mathematical model, the leakage crack width distribution is predicted;

[0045] The particle size optimization unit is used to optimize the particle size of bridging plugging particles according to the width distribution of leakage cracks.

[0046] In a third aspect, the present invention further provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned method for predicting the width of drilling leakage cracks and optimizing the bridging plugging particles.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] The present invention provides a method and system for predicting the width of drilling lost cracks and optimizing bridging plugging particles. The invention uses a mathematical model of working fluid flow from the ground to the reservoir leakage point and a mathematical model of lost crack deformation to reasonably calculate the geometric parameters of the lost cracks. Based on the crack temporary plugging and bridging theory and the lost crack width distribution, the invention optimizes the appropriate bridging plugging particle size, so that the plugging material can successfully enter the lost cracks and bridge and plug them, thereby effectively controlling the loss of drilling fluid. Specifically, (1) based on the reservoir leakage point positioning, lost crack identification and actual lost parameters, the present invention achieves quantitative prediction of the geometric parameters of the lost cracks by establishing a reasonable fluid pressure calculation model (i.e., a working fluid flow mathematical model) and a lost crack deformation model; (2) The present invention provides a method and system for predicting the width of drilling lost cracks and optimizing bridging plugging particles. Through the lost crack width and the shielding temporary plugging and bridging principle, the invention selectively selects bridging plugging particles of appropriate particle size, thereby overcoming the limitations of the traditional empirical plugging material selection method and providing a reference for the design of on-site drilling plugging solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0050] Figure 1 This is a flow chart of the method for predicting the width of drilling leakage cracks and optimizing the bridging and plugging particles of the present invention;

[0051] Figure 2 This is a schematic diagram of a curve showing changes in mud temperature versus formation depth obtained by well logging according to the present invention;

[0052] Figure 3Schematic diagram of the drilling lost circulation fracture and discrete fracture unit of the present invention;

[0053] Figure 4 The calculation results of the leakage crack profile and width distribution of the present invention are as follows;

[0054] Figure 5 This is a structural block diagram of the drilling leakage crack width prediction and bridging plugging particle optimization system of the present invention. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0056] Example 1

[0057] like Figure 1 As shown, the method for predicting the width of drilling leakage cracks and optimizing the bridging and plugging particles of the present invention comprises:

[0058] S01. Use logging tools to find reservoir leakage points and identify the types of leakage fractures. The leakage fracture types include horizontal fractures or vertical fractures.

[0059] S02. Based on the reservoir leakage point, a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point is established;

[0060] S03. According to the type of leakage cracks, a mathematical model of leakage crack deformation is constructed based on the displacement discontinuity theory;

[0061] S04. Calculate the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; predict the leakage fracture width distribution based on the fluid pressure and leakage data and the leakage fracture deformation mathematical model;

[0062] S05. Based on the width distribution of leakage cracks, the particle size of the bridging plugging particles is optimized.

[0063] The above technical solution, the present invention reasonably calculates the geometric parameters of the leakage cracks through the mathematical model of the working fluid flow from the ground to the reservoir leakage point and the mathematical model of the leakage crack deformation, and selects the appropriate bridging and plugging particle size based on the fracture temporary plugging and bridging theory and the leakage crack width distribution, so that the plugging material can successfully enter the leakage cracks and bridge and plug them, thereby effectively controlling the loss of drilling fluid.

[0064] Specifically, step S01 includes:

[0065] S011, judging whether the reservoir has fracture leakage by the change of drilling return mud volume in the mud tank;

[0066] S012: After confirming the occurrence of fracture leakage, a downhole logging tool is inserted from the surface to locate the reservoir leakage point;

[0067] S013, based on the location of the reservoir leakage point, obtain and analyze the logging data, and determine whether the leakage fracture type is a horizontal fracture or a vertical fracture in combination with the reservoir ground stress characteristics.

[0068] In this embodiment, the vertical well A in the X oil field is taken as the target. The designed depth of well A is 3450m. The wellbore structure of four openings is adopted. The drilling strata include the leakage risk strata with developed fractures. During the three-opening drilling process of well A, the surface mud tank liquid level dropped abnormally and the mud pump pressure decreased. Combined with the characteristics of the fracture development of the drilled reservoir, it was judged that fracture leakage occurred in the well. In response to the drilling leakage, the drill was started to raise the drill bit height. During the process, mud was replenished from the mud supply tank every time a column was pulled out. After reaching a certain depth, the displacement was circulated at 1100L / min. The leakage rate was measured to be 25.0m 3 / h, the total leakage during the cycle is 8.5m 3 After drilling, the mud was added to the wellbore. The loss rate in the static state was 0.8m 3 / h, the leakage during the static period is 8.5m 3 Since the reservoir leakage point during drilling cannot be determined, the well is first drilled through, and then low-displacement pumping of mud is performed for circulation. Subsequently, the well is pulled out of the wellbore and downhole logging tools are run to measure the mud temperature profile in the wellbore. By analyzing the mud well temperature profile characteristics of the open hole section, the location of the drilling leakage point is determined. Figure 2 The inflection point in the formation depth and mud temperature zoning curve is the leak point location. The type of leaking fracture is further determined by the range of temperature fluctuations within the inflection point area. If the temperature fluctuation range is small, the formation leak entrance is small and is considered a horizontal fracture with the fracture surface perpendicular to the wellbore axis. If the temperature fluctuation range is large, the formation leak entrance is large and is considered a vertical fracture with the fracture surface parallel to the wellbore axis. In this example, the analysis shows that the leak point of Well A is located at 2620m, and the leaking fracture type is a horizontal fracture.

[0069] Specifically, step S02 includes:

[0070] S021, obtaining basic parameters of the downhole drilling assembly, including drill pipe length and inner diameter, drill collar length and inner diameter, and drill bit hole number and diameter;

[0071] S022: Based on the basic data and the reservoir leakage point, the drill bit is positioned near the reservoir leakage point during the plugging cycle. The bridging plugging particle addition methods include low-displacement circulation and surface injection. A mathematical model of the working fluid flow at the reservoir leakage point under the corresponding working conditions is established. Specifically:

[0072] (1) Use low-displacement circulation to add bridging plugging particles:

[0073] Under low-displacement circulation conditions, the first fluid pressure calculation model at the reservoir leakage point can be established through the surface mud pump inlet pressure, pipe flow friction, drill bit pressure loss and static liquid column pressure;

[0074] The calculation formula for the friction resistance of fluid flow along the drilling string is:

[0075]

[0076] In the above formula, f represents the friction coefficient; L represents the length of the pipeline; D represents the inner diameter of the pipe string; ρ represents the density of the drilling fluid; v represents the average flow velocity of the fluid in the pipeline;

[0077] Under low-displacement pumping conditions, the fluid flow in the pipeline is approximately laminar flow, and the friction coefficient calculation formula is:

[0078]

[0079] In the above formula, Re represents the Reynolds number; μ represents the viscosity of the drilling fluid;

[0080] The calculation formula for the friction generated by the drilling fluid passing through the drill bit hole is:

[0081]

[0082] In the above formula, q represents the drilling fluid displacement; C represents the hole flow coefficient; n represents the number of holes in the drill bit; d represents the hole diameter of the drill bit;

[0083] The calculation formula for the static liquid column pressure of the drilling string is:

[0084] p g =ρgΔh

[0085] In the above formula, g represents the acceleration due to gravity; Δh represents the height of the static liquid column in the drilling string;

[0086] The fluid pressure near the reservoir leak point during plugging operation is calculated, that is, the expression of the first fluid pressure calculation model is:

[0087] p leak =p pump +p g -Δp f -Δp d -Δp l

[0088] In the above formula, p leak Indicates the fluid pressure near the reservoir leakage point; p pump Indicates the surface mud pump inlet pressure; p gIndicates the hydrostatic column pressure of the drilling string; Δp f Indicates the friction resistance along the drilling string; Δp d Indicates the friction resistance of the drill hole; Δp l Indicates local pressure loss;

[0089] (2) Add bridging plugging particles by ground extrusion:

[0090] Under surface squeeze conditions, the fluid velocity in the drill string is extremely small. The second fluid pressure calculation model at the reservoir leakage point can be established by using the surface mud pump inlet pressure and the hydrostatic column pressure. The second fluid pressure calculation model expression is:

[0091] p leak =p pump +p g

[0092] In the above formula, p leak Indicates the fluid pressure near the leak point; p pump Indicates the surface mud pump inlet pressure; p g Indicates the hydrostatic pressure of the drilling string.

[0093] In this example, bridging plugging particles were first mixed with mud, and a low-volume circulation method was used to perform an initial plugging operation on Well A. The basic parameters of the main downhole drill assembly from the surface to the leak point included: a total drill pipe length of 2221 meters and an inner diameter of 108.62 mm; a total weighted drill pipe length of 285 meters and an inner diameter of 76.2 mm; a total drill collar length of 114 meters and an inner diameter of 71.4 mm; and a PDC drill bit with 5 nozzles and an aperture of 18 mm. Furthermore, the mud density was 1.45 g / cm³, the viscosity was 18 mPa·s, the pumping rate was 350 L / min, the average surface pump pressure was 400 psi, and the local pressure loss was approximately 150 psi. Without considering the effect of the bridging plugging particles on the mud rheological parameters, the fluid pressure at the reservoir leak point calculated using a model for calculating fluid pressure under low-volume circulation was approximately 38.7 MPa, indicating that the on-site plugging operation failed to seal the leaking fracture. Subsequently, the leak plugging operation was carried out by squeezing. The drill bit was raised to the distance of a column, and then mud containing bridging plugging particles was squeezed in. Within 15 minutes, the ground pump pressure decayed from 500psi to 110psi. The calculated fluid pressure range at the leak point was 38.0~40.7MPa.

[0094] Specifically, step S03 includes:

[0095] S031: Based on the type of leaking cracks, the structured plane rectangular grid units are used to discretize the leaking cracks and calculate the displacement of the leaking cracks. The calculation formula for the displacement of the leaking cracks is:

[0096]

[0097] In the above formula, the subscripts (x`, y`, z`) represent the local coordinate system; the superscripts + and - represent the overlapping crack surfaces of the crack units; the subscripts L, H, and N represent the strike direction, dip direction, and normal direction along the crack, respectively; u represents the displacement of the crack unit; D L 、D H 、D N They represent the displacement of the strike, dip and normal of the fracture unit, respectively, where the displacement is the fracture width;

[0098] S032, based on the displacement of the missing fractures, the fracture unit displacement calculation matrix is ​​constructed based on the displacement discontinuity theory, and the expression is:

[0099]

[0100] In the above formula, D L 、D H 、D N represent the strike displacement matrix, dip displacement matrix and normal displacement matrix respectively; B represents the boundary influence coefficient matrix; B NL Represents the boundary influence coefficient matrix between normal and strike; B NH Represents the boundary influence coefficient matrix between normal and inclination; B NN Represents the boundary influence coefficient matrix between normal and normal directions; B HH Represents the boundary influence coefficient matrix between tendencies; B LH Represents the boundary influence coefficient matrix between strike and dip; B HL Represents the boundary influence coefficient matrix between dip and strike; B LN Represents the boundary influence coefficient matrix between the strike and normal directions; B HN Represents the boundary influence coefficient matrix between the inclination and the normal; B LL represents the boundary influence coefficient matrix between strikes; τ L , τ H , σ N They represent the strike stress matrix, dip stress matrix and normal stress matrix acting on the fracture unit respectively;

[0101] S033, based on the fracture unit displacement calculation matrix, derive the mathematical model of the lost fracture deformation; the lost fracture deformation mathematical model is the relationship between the lost fracture width and the fluid pressure. The expression of the lost fracture deformation mathematical model is:

[0102] B M w+σ M =p f ,w=D N

[0103]

[0104]

[0105] In the above formula, The inverse matrix of the boundary influence coefficient matrix between tendencies; The inverse matrix of the boundary influence coefficient matrix between strikes; () -1 represents the inverse of the matrix; B M represents the comprehensive coefficient matrix; σ M represents the comprehensive stress matrix; w represents the leakage crack width matrix; P f represents the fluid pressure matrix; σ far represents the reservoir normal in-situ stress matrix.

[0106] In this example, based on downhole logging results, the leaking fractures were identified as horizontal fractures. The reservoir in-situ stress and rock mechanics parameters near the leak point included: Young's modulus of 24.5 GPa, Poisson's ratio of 0.23, and vertical stress of 36.1 MPa. These parameters, combined with the mathematical model for leaking fracture deformation, were used to calculate a comprehensive coefficient matrix and a comprehensive stress matrix. Combined with the fluid pressure near the leak point, the leaking fracture width was then predicted.

[0107] Specifically, in step S04, the loss crack width distribution is predicted based on the fluid pressure and loss data and the loss crack deformation mathematical model, including:

[0108] Step A: Obtain the morphology of the leakage fracture based on the well logging data analysis, and preset the initial plane leakage fracture at the leakage point of the reservoir, wherein the horizontal fracture adopts the coin-shaped fracture assumption and the vertical fracture adopts the rectangular fracture assumption;

[0109] Step B, calculating a stress matrix acting on the initial plane leaking fractures using reservoir in-situ stress parameters based on the spatial position relationship of the initial plane leaking fractures; the stress matrix includes a strike stress matrix, a dip stress matrix, and a normal stress matrix;

[0110] Step C, calculating the geometric parameters of the lost fracture based on the stress matrix and the fluid pressure and the lost fracture deformation mathematical model; the geometric parameters of the lost fracture include the fracture width and the fracture volume;

[0111] In step D, the lost-flow fracture volume estimated by wellhead monitoring data is compared with the fracture volume calculated in step C, and the lost-flow fracture front is iteratively corrected to finally obtain a reasonable lost-flow fracture width distribution.

[0112] In this embodiment, the drilling loss fracture is a horizontal fracture, and the initial loss fracture is assumed to be a coin-shaped fracture. The fracture surface is perpendicular to the axial direction of the vertical wellbore. Figure 3The lost fractures are discretized by using a square structured two-dimensional grid. Since the horizontal fractures are perpendicular to the vertical stress direction, the shear stress of the reservoir stress acting on the direction and dip of the lost fractures can be ignored, and the normal stress acting on the lost fractures is the vertical stress. According to the surface shut-in mud injection volume of 1.40m 3 , Surface well return slurry volume 0.74m 3 and mud loss rate of 2.2m 3 / h, the whole process lasted 15 minutes, the surface pump pressure decreased from 550psi to 190psi, and the estimated volume of the leakage crack was 0.11m 3 The fluid pressure at the leak point varies from 38.5 to 41.1 MPa. The maximum radius of the leak fracture obtained by iterative calculation is about 4.7 m. The width distribution of the leak fracture is shown in Figure 2. Figure 4 .

[0113] Specifically, step S05 includes:

[0114] S051: Based on the distribution of lost-circulation fracture widths and the crack bridging and plugging patterns, the average width of lost-circulation fractures within 0.5 m from the wellbore axis is used as the critical fracture width. Based on this critical fracture width, the bridging particle size range is determined. The bridging particle size range is the reasonable size range for entering lost-circulation fractures and successfully bridging them.

[0115] 0.9×w c ≤d≤1.0×w c

[0116] In the above formula, d represents the particle size of the bridging particles; w c Indicates the critical gap width value;

[0117] S052, reasonably design the amount of bridging particles according to the volume of the leakage cracks, and select medium and small particle size plugging agents for filling and sealing on the basis of successful bridging, gradually establish a stable sealing zone and complete the plugging of the leakage cracks.

[0118] In this embodiment, the critical width value is calculated to be 2.0 mm based on the width distribution of the leakage cracks. Therefore, the reasonable bridging particle size range is 1.80 to 2.00 mm. On this basis, the amount of bridging particles is designed, and appropriate medium and small particle size plugging agents are selected for filling and sealing to achieve effective plugging of the leakage cracks.

[0119] Example 2

[0120] like Figure 5As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a system for predicting the width of drilling lost circulation cracks and optimizing the bridging plugging particles. This system corresponds one-to-one with the method for predicting the width of drilling lost circulation cracks and optimizing the bridging plugging particles in embodiment 1. The system includes:

[0121] The leakage point and fracture type identification unit is used to find the reservoir leakage point and identify the leakage fracture type through the logging tool; the leakage fracture type includes horizontal fracture or vertical fracture;

[0122] The first model building unit is used to establish a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point according to the reservoir leakage point;

[0123] The second model building unit is used to build a mathematical model of the leakage fracture deformation based on the displacement discontinuity theory according to the leakage fracture type;

[0124] The leakage crack width prediction unit is used to calculate the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; based on the fluid pressure and leakage data and the leakage crack deformation mathematical model, the leakage crack width distribution is predicted;

[0125] The particle size optimization unit is used to optimize the particle size of bridging plugging particles according to the width distribution of leakage cracks.

[0126] The execution process of each unit can be performed according to the process steps of the method for predicting the width of drilling leakage cracks and optimizing the bridging and plugging particles in Example 1, and will not be described in detail in this embodiment.

[0127] At the same time, the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the above-mentioned method for predicting the width of drilling leakage cracks and optimizing the bridging plugging particles is implemented.

[0128] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0129] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0130] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0131] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0132] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting the width of drilling leakage cracks and optimizing the bridging and plugging particles, characterized in that: The method includes: Finding reservoir leakage points and identifying leakage fracture types using logging tools; the leakage fracture types include horizontal fractures or vertical fractures; According to the reservoir leakage point, a mathematical model of working fluid flow from the surface pipeline to the reservoir leakage point is established; According to the type of the leakage fracture, a mathematical model of the leakage fracture deformation is constructed based on the displacement discontinuity theory; Calculating the fluid pressure at the reservoir leakage point based on the working fluid flow mathematical model; predicting the leakage fracture width distribution based on the leakage fracture deformation mathematical model according to the fluid pressure and leakage data; According to the width distribution of leakage cracks, the particle size of the bridging plugging particles is optimized.

2. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging plugging particles according to claim 1, wherein: Logging tools are used to find reservoir leaks and identify leakage fracture types, including: By observing the change of drilling return mud volume in the mud tank, it can be judged whether the reservoir has fracture leakage; After confirming that fracture leakage has occurred, a downhole logging tool is inserted from the surface to locate the reservoir leakage point; According to the location of the reservoir leakage point, the logging data is obtained and analyzed, and combined with the reservoir stress characteristics, the type of leakage fracture is determined to be horizontal fracture or vertical fracture.

3. The method for predicting the width of drilling leakage cracks and optimizing the bridging and plugging particles according to claim 1, wherein: According to the reservoir leakage point, a mathematical model of the working fluid flow from the surface pipeline to the reservoir leakage point is established, including: Obtaining basic parameters of the downhole drilling assembly, including drill pipe length and inner diameter, drill collar length and inner diameter, and drill bit hole number and diameter; According to the basic data and the reservoir leakage point, the drill bit is positioned near the reservoir leakage point to carry out a plugging work cycle, and a mathematical model of the working fluid flow at the reservoir leakage point under the corresponding working conditions is established.

4. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging plugging particles according to claim 3, wherein: The drill bit is positioned near the reservoir leak point to carry out a plugging work cycle, and a mathematical model of the working fluid flow at the reservoir leak point under the corresponding working conditions is established, including: When the bridging plugging particles are added in a low-displacement circulation mode, the first fluid pressure calculation model at the reservoir leakage point is established by the surface mud pump inlet pressure, pipe flow friction, drill bit pressure loss and static liquid column pressure; the expression of the first fluid pressure calculation model is: p leak =p pump +p g -Δp f -Δp d -Δp l , p leak Indicates the fluid pressure near the reservoir leakage point; p pump Indicates the surface mud pump inlet pressure; p g Indicates the hydrostatic column pressure of the drilling string; Δp f Indicates the friction resistance along the drilling string; Δp d Indicates the friction resistance of the drill hole; Δp l Indicates local pressure loss; When the bridging plugging particles are added by surface squeezing, the second fluid pressure calculation model at the reservoir leak point is established by the surface mud pump inlet pressure and the hydrostatic column pressure. The expression of the second fluid pressure calculation model is: p leak =p pump +p g , p leak Indicates the fluid pressure near the leak point; p pump Indicates the surface mud pump inlet pressure; p g Indicates the hydrostatic pressure of the drilling string.

5. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging and plugging particles according to claim 1, wherein: According to the type of leakage fractures, a mathematical model of leakage fracture deformation is constructed based on the displacement discontinuity theory, including: According to the type of the leakage crack, the leakage crack is discretized using structured plane rectangular grid units to calculate the displacement of the leakage crack; According to the missing fracture displacement, a fracture unit displacement calculation matrix is ​​constructed based on displacement discontinuity theory; Based on the fracture unit displacement calculation matrix, a lost fracture deformation mathematical model is derived; the lost fracture deformation mathematical model is a relationship between the lost fracture width and the fluid pressure.

6. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging and plugging particles according to claim 5, wherein: The mathematical model of the leakage crack deformation is expressed as follows: B M w+σ M =p f ,w=D N In the above formula, D L 、D H 、D N represent the strike displacement matrix, dip displacement matrix and normal displacement matrix respectively; B represents the boundary influence coefficient matrix; B NL Represents the boundary influence coefficient matrix between normal and strike; B NH Represents the boundary influence coefficient matrix between normal and inclination; B NN Represents the boundary influence coefficient matrix between normal and normal directions; B HH Represents the boundary influence coefficient matrix between tendencies; B LH Represents the boundary influence coefficient matrix between strike and dip; B HL Represents the boundary influence coefficient matrix between dip and strike; B LN Represents the boundary influence coefficient matrix between the strike and normal directions; B HN Represents the boundary influence coefficient matrix between the inclination and the normal; B LL Represents the boundary influence coefficient matrix between strikes; The inverse matrix of the boundary influence coefficient matrix between tendencies; The inverse matrix of the boundary influence coefficient matrix between strikes; () -1 represents the inverse of the matrix; τ L , τ H , σ N They represent the strike stress matrix, dip stress matrix and normal stress matrix acting on the fracture unit respectively; B M represents the comprehensive coefficient matrix; σ M represents the comprehensive stress matrix; w represents the leakage crack width matrix; P f represents the fluid pressure matrix; σ far represents the reservoir normal in-situ stress matrix.

7. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging and plugging particles according to claim 1, wherein: According to the fluid pressure and leakage data, based on the leakage fracture deformation mathematical model, the leakage fracture width distribution is predicted, including: Step A: Obtain the morphology of the leakage fracture based on the well logging data analysis, and preset the initial plane leakage fracture at the leakage point of the reservoir, wherein the horizontal fracture adopts the coin-shaped fracture assumption and the vertical fracture adopts the rectangular fracture assumption; Step B, calculating a stress matrix acting on the initial plane leakage fractures using reservoir in-situ stress parameters based on the spatial position relationship of the initial plane leakage fractures; the stress matrix includes a strike stress matrix, a dip stress matrix, and a normal stress matrix; Step C, calculating geometric parameters of the lost fracture based on the stress matrix and fluid pressure and based on a lost fracture deformation mathematical model; the geometric parameters of the lost fracture include fracture width and fracture volume; In step D, the lost fracture volume estimated by the wellhead monitoring data is compared with the fracture volume calculated in step C, and the lost fracture front is iteratively corrected to finally obtain the lost fracture width distribution.

8. The method for predicting the width of drilling lost circulation cracks and optimizing the bridging and plugging particles according to claim 1, wherein: Based on the width distribution of leakage cracks, the optimal particle size for bridging and plugging includes: Based on the distribution of lost-flow crack widths and crack bridging and plugging rules, the average width of lost-flow cracks within a preset range from the wellbore axis is used as the critical crack width; based on the critical crack width, the particle size range of the bridging particles is determined; the particle size range of the bridging particles is the particle size range of the bridging particles that can enter the lost-flow cracks and successfully bridge them; The amount of bridging particles is designed according to the volume of the leaking cracks, and the leaking cracks are sealed according to the amount of bridging particles and the particle size range of the bridging particles.

9. A drilling leakage crack width prediction and bridging plugging particle optimization system, characterized by: The system includes: A leakage point and fracture type identification unit is used to find the reservoir leakage point and identify the leakage fracture type through the logging tool; the leakage fracture type includes horizontal fracture or vertical fracture; A first model building unit is used to establish a mathematical model of working fluid flow from a surface pipeline to the reservoir leakage point according to the reservoir leakage point; The second model building unit is used to build a mathematical model of the leakage fracture deformation based on the displacement discontinuity theory according to the leakage fracture type; A leakage crack width prediction unit is used to calculate the fluid pressure at the leakage point of the reservoir based on the working fluid flow mathematical model; and predict the leakage crack width distribution based on the fluid pressure and leakage data and the leakage crack deformation mathematical model; The particle size optimization unit is used to optimize the particle size of bridging plugging particles according to the width distribution of leakage cracks.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for predicting the width of drilling lost circulation cracks and optimizing the bridging plugging particles according to any one of claims 1 to 8 is implemented.

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