Method for improving recovery efficiency by plugging dominant seepage channel through road passing well

Abstract

The invention relates to the technical field of improvement of recovery efficiency in a water flooding extra-high water cut period, in particular to a method for improving the recovery efficiency by blocking a dominant seepage channel through a road passing well, which comprises the following steps: carrying out a scouring capacity test experiment according to permeability and a gel system injection scheme, and if the experiment result does not meet a first requirement, determining that the permeability of the water flooding extra-high water cut period meets the first requirement; if yes, adjusting a gel system injection scheme to determine an optimal injection scheme; and a recovery ratio and remaining oil saturation test experiment is conducted according to the plugging position and the optimal injection scheme, if the experiment result does not meet the second requirement, the plugging position and / or the injection amount of the gel system in the optimal injection scheme are / is adjusted, and the final plugging position and / or the final injection scheme are / is determined. According to the method, the deep part of the high-permeability reservoir can be effectively blocked, so that the injected water is turned to displace the remaining oil of the low-permeability reservoir, and finally, the water drive recovery efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of improving oil recovery during water drive with extremely high water content, and in particular to a method for improving oil recovery by plugging a superior seepage channel with a passing well. Background Art

[0002] As my country's oil and gas resource exploration and development technology matures, many oil fields have entered the water-driven high water-cut period. At this stage, the high permeability layer has become the focus of attention due to its high water drive efficiency, while the low permeability layer needs special treatment to improve the recovery rate due to its low water drive efficiency. Profile control and water plugging technology is designed to plug the high permeability layer, allowing water to flow into the medium and low permeability layers and drive out the crude oil therein. Profile control and water plugging technology mainly includes two methods: chemical water plugging and mechanical water plugging. Chemical water plugging is divided into single liquid method and double liquid method. The single liquid method is to inject a liquid into the oil layer. After the liquid enters the oil layer, it forms a plugging material by its own reaction, thereby reducing the permeability of the high permeability layer. Commonly used single liquid plugging agents include lime milk, silica sol, chromium gel, sulfuric acid, water-in-water thick oil, etc. The double liquid method involves two working fluids, which react to form plugging materials when they meet in the formation. The commonly used plugging agents in the double liquid method mainly include precipitation type, gel type, gel type, colloidal dispersion type plugging agents, etc. However, whether it is profile control in water injection wells or water plugging in production wells, the effect of plugging high permeability layers is often not obvious. This is mainly because the plugging situation in the formation cannot be understood through profile control of water injection wells, and due to the limitations of test instruments and measurement accuracy, a single method cannot accurately give the specific location of the plugging agent in the formation and the plugging situation. Based on this, it is necessary to establish a new method to plug high permeability layers. Summary of the invention

[0003] The present invention proposes a method for improving the recovery rate by plugging the dominant seepage channel by using a passing well, so as to solve the problem that the existing profile adjustment and plugging method cannot understand the plugging situation in the formation, and there is water seepage in the dominant seepage channel, resulting in poor plugging effect and failure to further improve the recovery rate.

[0004] According to one aspect of the present invention, a method for improving oil recovery by plugging a dominant seepage channel using a passing well is provided, comprising:

[0005] Obtain the reservoir permeability of the target block, set the initial well plugging position and the gel system injection plan;

[0006] According to the permeability and the gel system injection scheme, a flushing capacity test experiment is carried out to obtain the experimental results of the breakthrough pressure gradient, gel plugging rate and effective plugging radius of the gel system. If the experimental results do not meet the first requirement, the gel system injection scheme is adjusted to determine that the corresponding gel system injection scheme is the optimal injection scheme when the experimental results meet the first requirement;

[0007] According to the plugging position and the optimal injection scheme, a recovery factor and remaining oil saturation test experiment is performed to obtain an oil saturation field distribution experimental result. If the experimental result does not meet the second requirement, the plugging position and / or the injection amount and concentration of the gel system in the optimal injection scheme are adjusted, and the corresponding adjusted plugging position and / or the injection scheme after adjusting the injection amount and concentration when the experimental result meets the second requirement are determined as the final plugging position and / or injection scheme.

[0008] Preferably, the method of conducting a flushing capacity test experiment according to the permeability and the gel system injection scheme to obtain the experimental results of the gel system breakthrough pressure gradient, gelation plugging rate and effective plugging radius includes:

[0009] Make a sand-filled pipe model of a predetermined length and a permeability that matches the reservoir permeability of the work area;

[0010] The sand-filled tube model is evacuated and saturated with water to determine the pore volume V of the sand-filled tube model. After the sand-filled tube model is placed in a constant temperature box at a predetermined temperature for the first predetermined hour, water is driven at a predetermined speed to measure the stable pressure P of the sand-filled tube model in the water-drive stage. w ;

[0011] According to the gel system injection plan, the gel system is injected at a predetermined speed until it becomes a static gel;

[0012] The sand-filled pipe model is water-flooded at a predetermined speed, and the pressure at each pressure measuring point is recorded to determine the maximum injection pressure and the subsequent stable pressure P of the water flooding stage. w ';

[0013] According to the maximum injection pressure, determining the corresponding maximum breakthrough pressure gradient of the gel system;

[0014] According to the stable pressure P in the water flooding stage w , and the subsequent water flooding stage steady-state pressure P w ', determine the gel plugging rate;

[0015] The effective plugging radius of the gel system is determined according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model.

[0016] Preferably, the water flooding stage steady stage pressure P w , and the subsequent water flooding stage steady-state pressure P w ', the method for determining the gel plugging rate includes:

[0017] The gel plugging rate is calculated using formula (1);

[0018]

[0019] Where: η is the plugging rate, %; K w is the permeability of the sand-filled pipe model in the water flooding stage, 10 -3 μm 2 ; K′ w is the permeability of the sand-filled pipe model in the subsequent water flooding stage, 10 -3 μm 2 ;P w is the steady-state pressure in the water flooding stage, MPa; P w ' is the stable section pressure in the subsequent water flooding stage, MPa.

[0020] Preferably, the method for determining the effective plugging radius of the gel system according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model comprises:

[0021] According to the designed injection volume of the gel system in the gel system injection plan and the pore volume of the sand-filled tube model, the dimensionless plugging radius of the gel system design is determined;

[0022] According to the dimensionless plugging radius, the length of the sand-filled tube model and the length of the sand-filled tube model corresponding to the half of the maximum breakthrough pressure gradient of the gel system, the effective plugging radius of the gel system is calculated using formula (2);

[0023]

[0024] Where: L′ is the effective plugging radius of the gel system, dimensionless; l′ is the length of the sand-filled tube model corresponding to 1 / 2 of the maximum breakthrough pressure gradient of the sand-filled tube model gel system, m; l is the length of the sand-filled tube model, m; L is the dimensionless plugging radius of the gel system design.

[0025] Preferably, the method for determining the dimensionless plugging radius of the gel system design according to the gel system design injection volume in the gel system injection scheme and the pore volume of the sand-filled tube model comprises:

[0026] The dimensionless plugging radius of the gel system design is calculated using formula (3);

[0027]

[0028] Where: L is the dimensionless plugging radius of the gel system design, dimensionless; V w is the designed injection volume of the gel system, ml; V is the pore volume of the sand-filled tube model, ml.

[0029] Preferably, the method for adjusting the gel system injection scheme comprises:

[0030] The polymer concentration in the gel system is increased to a first predetermined value, and / or the injection volume is increased to a second predetermined value, and a flushing capacity test experiment is performed using the gel system injection scheme after increasing the polymer concentration and / or injection volume, until the experimental results obtained meet the first requirement.

[0031] Preferably, the first requirement includes:

[0032] The gel plugging rate reaches or exceeds the predetermined plugging rate, the effective plugging radius is less than or equal to the predetermined range of the predetermined gel dam radius, and the breakthrough pressure gradient of the gel system is greater than the maximum pressure gradient actually measured in the target block reservoir;

[0033] and / or,

[0034] The pressure gradient is calculated using formula (4);

[0035]

[0036] Where: ΔP is the pressure difference between two adjacent pressure measuring points; L is the distance between two adjacent pressure measuring points.

[0037] Preferably, the method of performing recovery factor and remaining oil saturation test experiments according to the plugging position and the optimal injection scheme to obtain the oil saturation field distribution experimental results includes:

[0038] A microelectrode model was established based on the reservoir permeability of the target block, and a standard curve between resistance and oil saturation was established by testing the model resistance under different proportions of crude oil and water.

[0039] Create core models based on reservoir permeability and well locations in the target area;

[0040] saturating the core model with water and oil;

[0041] The core model is water-flooded at a predetermined displacement rate until the outlet water content is above the predetermined water content, and the water-flooding recovery factor is determined;

[0042] Injecting the gel system at a predetermined speed according to the gel system injection plan;

[0043] Close all injection wells and production wells in the core model, wait for the gel to form a static gel, and then open the water injection wells and production wells;

[0044] The core model is water-flooded at a predetermined displacement rate until the outlet water content is above the predetermined water content, and the water-flooding recovery factor is calculated;

[0045] Monitor the resistance values ​​of different test points during the displacement process, such as saturated oil, water drive and water drive after condensation;

[0046] According to the resistance value and the standard curve, the oil saturation value of each test point is determined, and the oil saturation field distribution result is obtained by using the oil saturation value of each test point.

[0047] Preferably, the method of saturating the core model with water and oil comprises:

[0048] The core model injection end starts to be vacuumed for a preset hour, and each pressure test point is vacuumed for a preset hour;

[0049] The core model is saturated with artificial synthetic brine and then placed in a thermostat at the target block reservoir temperature for more than a predetermined number of hours;

[0050] Crude oil is injected into the core model from the injection end of the core model until no water is produced, and the core model is placed in a constant temperature box for constant temperature maturation for more than a predetermined number of hours.

[0051] Preferably, the second requirement includes:

[0052] The seepage resistance of the water flow channel at the blocked passing well in the core model is increased, and the injected water forms a bypass flow after encountering the rubber dam of the passing well. The affected area near the production well is expanded, the injection pressure is increased, and the oil washing effect in the affected area of ​​the water drive is improved.

[0053] The present invention has at least the following beneficial effects:

[0054] The present invention proposes a method for improving the recovery rate by plugging the dominant seepage channel by using a passing well. The method uses a gel system injected into a passing well between injection and production wells to plug the high permeability layer, thereby preventing water from seeping through the dominant seepage channel, achieving effective plugging of the deep part of the high permeability reservoir, and allowing the injected water to be diverted to displace the remaining oil in the low permeability reservoir, ultimately achieving improved water drive recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present invention and, together with the specification, are used to explain the technical solutions of the present invention.

[0056] Figure 1 A flow chart showing a method for improving oil recovery by plugging a dominant seepage channel using a passing well according to an embodiment of the present invention;

[0057] Figure 2 A pressure gradient distribution diagram between injection and production wells in a target block according to an embodiment of the present invention is shown;

[0058] Figure 3 A pressure distribution diagram of the displacement stage according to an embodiment of the present invention is shown;

[0059] Figure 4A schematic diagram showing the breakthrough pressure gradient of the gel system according to an embodiment of the present invention is shown;

[0060] Figure 5 A schematic diagram of a core model according to an embodiment of the present invention is shown;

[0061] Figure 6 The recovery rate and water content variation curve according to the embodiment of the present invention are shown;

[0062] Figure 7 The pressure field distribution diagram according to the embodiment of the present invention is shown, wherein (a) is the pressure field distribution after water flooding, and (b) is the pressure field distribution after gel injection;

[0063] Figure 8 The oil saturation field distribution diagram according to an embodiment of the present invention is shown, wherein (a) is the oil saturation field distribution after the model is saturated with oil, (b) is the oil saturation field distribution after the model is water flooded, and (c) is the oil saturation field distribution after the model is injected with gel, flooded and subsequently water flooded. DETAILED DESCRIPTION

[0064] Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0065] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0066] The term "and / or" herein is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the term "at least one" herein represents any combination of at least two of any one or more of a plurality of. For example, including at least one of A, B, and C can represent including any one or more elements selected from the set consisting of A, B, and C.

[0067] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0068] Figure 1 A flow chart showing a method for improving oil recovery by plugging a dominant seepage channel using a passing well according to an embodiment of the present invention; Figure 2 A pressure gradient distribution diagram between injection and production wells in a target block according to an embodiment of the present invention is shown; Figure 3 A pressure distribution diagram of the displacement stage according to an embodiment of the present invention is shown; Figure 4 A schematic diagram showing the breakthrough pressure gradient of the gel system according to an embodiment of the present invention is shown; Figure 5 A schematic diagram of a core model according to an embodiment of the present invention is shown; Figure 6 The recovery rate and water content variation curve according to the embodiment of the present invention are shown; Figure 7 The pressure field distribution diagram according to the embodiment of the present invention is shown, wherein (a) is the pressure field distribution after water flooding, and (b) is the pressure field distribution after gel injection; Figure 8 The oil saturation field distribution diagram according to the embodiment of the present invention is shown, wherein (a) is the oil saturation field distribution after the model is saturated with oil, (b) is the oil saturation field distribution after the model is water flooded, and (c) is the oil saturation field distribution after the model is injected with gel, adjusted and flooded, and subsequently water flooded. Figure 1-8 As shown, a method for improving the recovery rate by plugging the superior seepage channel by using a passing well comprises: step S01: obtaining the reservoir permeability of the target block, the set initial passing well plugging position and the gel system injection scheme; step S02: performing a flushing ability test experiment according to the permeability and the gel system injection scheme, obtaining the experimental results of the breakthrough pressure gradient of the gel system, the gel plugging rate and the effective plugging radius; if the experimental result does not meet the first requirement, adjusting the gel system injection scheme, and determining that the corresponding gel system injection scheme when the experimental result meets the first requirement is the optimal injection scheme; step S03: performing a recovery rate and residual oil saturation test experiment according to the plugging position and the optimal injection scheme, obtaining the experimental results of the oil saturation field distribution; if the experimental result does not meet the second requirement, adjusting the plugging position and / or the gel system injection amount in the optimal injection scheme, and determining that the corresponding adjusted plugging position and / or the injection scheme after adjusting the injection amount and concentration when the experimental result meets the second requirement are the final plugging position and / or injection scheme.

[0069] A method for improving oil recovery by plugging a superior seepage channel using a passing well provided in an embodiment of the present invention specifically comprises the following steps:

[0070] Step S01: Obtain the reservoir permeability of the target block, the set initial well plugging position and the gel system injection plan.

[0071] In the embodiment of the present invention, the plugging effect of the gel system in the reservoir has an important influence on improving the recovery rate. The purpose of the flushing capacity test is to determine the strength and range of the gelling of the gel system in the reservoir of the target block. In order to clarify the gelling strength and gelling distance of the gel system at different positions in the reservoir, it is necessary to carry out a dynamic gelling experiment of the gel system. During the experiment, it is necessary to obtain the average permeability of the reservoir to be plugged in the work area, and establish a 10m long sand filling pipe (including 17 pressure measuring points) model based on it. Using the sand filling pipe model, the flushing capacity test experiment is carried out using the initial set gel system injection scheme, and the pressure of different pressure measuring points during water drive, gel system injection and water drive after gelation is tested, so as to determine the optimal gel system injection scheme, and through the set initial pass well plugging position, the recovery rate and residual oil saturation test experiment are carried out, so as to determine the final plugging position and gel system injection scheme, and use the final plugging position and gel system injection scheme to effectively plug the target block.

[0072] Step S02: According to the permeability and the gel system injection scheme, a flushing capacity test experiment is performed to obtain the experimental results of the breakthrough pressure gradient of the gel system, the gelation plugging rate and the effective plugging radius. If the experimental results do not meet the first requirement, the gel system injection scheme is adjusted to determine that the corresponding gel system injection scheme is the optimal injection scheme when the experimental results meet the first requirement.

[0073] In the present invention, the method of conducting a flushing capacity test experiment according to the permeability and the gel system injection scheme to obtain the experimental results of the breakthrough pressure gradient, gel plugging rate and effective plugging radius of the gel system includes: making a sand-filled pipe model of a predetermined length and a permeability that meets the permeability of the reservoir in the work area; evacuating the sand-filled pipe model and saturating it with water to determine the pore volume V of the sand-filled pipe model, placing it in a thermostat at a predetermined temperature for the first predetermined hour, and then water-flooding at a predetermined speed to measure the steady-state pressure P of the sand-filled pipe model in the water-flooding stage. w ; According to the gel system injection plan, the gel system is injected at a predetermined speed, and the gel is gelled to a static state; the sand filling pipe model is water-flooded at a predetermined speed, and the pressure at each pressure measuring point is recorded to determine the maximum injection pressure and the subsequent water flooding stage stable section pressure P w '; According to the maximum injection pressure, determine the corresponding maximum breakthrough pressure gradient of the gel system; according to the stable pressure P of the water flooding stage w , and the subsequent water flooding stage steady-state pressure P w ', determine the gel plugging rate; according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model, determine the effective plugging radius of the gel system.

[0074] In the embodiment of the present invention, the predetermined length is 10 meters. The method for making a sand-filled pipe model of a predetermined length and a permeability equal to the permeability of the reservoir in the work area comprises: using a 10-meter-long sand-filled pipe to carry out a gel system displacement experiment, screening the sand to prevent the sand from migrating during the injection process, resulting in a decrease in the local permeability of the sand-filled pipe, and only selecting two types of sand for sand filling, and using a hammer to knock on the pipe wall to vibrate the sand during the sand filling process. The specific sand filling steps are as follows:

[0075] 1.1. Screen the sand, use sieves of different mesh sizes to screen 30-50 mesh and 80-90 mesh sand;

[0076] 1.2. Make a model based on the permeability of the target block and the filling method of the sand filling pipe model; if the permeability of the sand filling model is higher than the permeability K of the target block, increase the proportion of 100-110 mesh sand; conversely, if the permeability of the sand filling model is lower than the permeability of the target block, increase the proportion of 20-30 mesh sand; adjust the proportion of sand with different meshes until the permeability K of the sand filling model is achieved. w The difference between the permeability K of the reservoir in the dominant seepage channel of the target block and that in the target block is ±5%, that is, the model permeability is consistent with the reservoir permeability in the work area.

[0077] 1.3. Fill two straight pipes and one curved pipe as a group with sand, fill 30ml of sand each time, and knock on the pipe wall for 1 minute to ensure that the sand is in stable contact and no longer settles;

[0078] 1.4. Connect the two sets of sand filling pipes with a bend pipe at the top, pour sand into the sampling port of the upper bend pipe to fill the sand until the sand stops settling;

[0079] 1.5. Tighten the plugs at both ends of the connection between the elbow and the straight pipe.

[0080] The specific steps of the gel system flushing ability test experiment include:

[0081] 2.1. The sand-filled tube model is evacuated and saturated with water to calculate the pore volume V of the model. The model is placed in a thermostat at the target block reservoir temperature for the first predetermined hour (24 hours) and then water is driven at a predetermined speed (0.1 ml / min) to measure the steady pressure P of the sand-filled tube model during the water drive stage. w , calculate the water phase permeability K w ;

[0082] 2.2. Inject the gel system into the sand-filled pipe model after water flooding at a predetermined speed (0.1 ml / min) to the designed amount V in the injection plan. w , and record the pressure at each pressure measuring point; gel to parallel sample static gelation in a glass container;

[0083] 2.3. Carry out water flooding on the gelled sand-filled pipe model at a predetermined speed (0.1 ml / min), and record the pressure at each pressure measuring point, the maximum injection pressure, and the subsequent pressure stability value.

[0084] The initial gel system injection scheme used in the experiment is shown in Table 1 below.

[0085] Table 1: Gel system injection scheme

[0086]

[0087] In the embodiment of the present invention, to determine the gelation radius, the maximum breakthrough pressure gradient of the sand-filled tube model gel system must first be determined, such as Figure 3 As shown in the displacement stage pressure distribution diagram, it can be seen that with the increase of gel injection amount, the pressure distribution along the sand-filled tube gradually increases, and the pressure gradient decreases greatly near the inlet. According to the pressure value of the measuring point corresponding to the maximum injection pressure measured in the experiment and the pressure difference ΔP between the adjacent measuring points and the distance L, the maximum breakthrough pressure gradient of the gel system corresponding to the sand-filled tube model is calculated using formula (4).

[0088] In the present invention, the water flooding stage steady stage pressure P w , and the subsequent water flooding stage steady-state pressure P w ', a method for determining the gel plugging rate, comprising: using formula (1) to calculate the gel plugging rate;

[0089]

[0090] Where: η is the plugging rate, %; K w is the permeability of the sand-filled pipe model in the water flooding stage (water phase permeability), 10 -3 μm 2 ; K′ w is the permeability of the sand-filled pipe model in the subsequent water flooding stage, 10 -3 μm 2 ;P w is the steady-state pressure in the water flooding stage, MPa; P w ' is the stable section pressure in the subsequent water flooding stage, MPa.

[0091] In the embodiment of the present invention, the gelation plugging rate η of the gel system in the reservoir can directly reflect the plugging effect of the gel system after the gelation water flooding breakthrough under the dynamic conditions of the reservoir. Therefore, the gelation plugging rate of the gel system in the reservoir is used as a gelation characteristic parameter to evaluate the gelation plugging effect under the dynamic conditions of the reservoir after a certain amount of gel system is injected. The calculation formula of the gelation plugging rate is shown in formula (1).

[0092] Based on the water flooding and subsequent water flooding pressure of the sand-filled tube model, the steady pressure P of the water flooding stage obtained by the gel system flushing capacity test experimentw And the subsequent pressure plateau value P w Substitute '(the pressure of the stable section in the subsequent water flooding stage) into formula (1) to calculate the corresponding gel plugging rate.

[0093] The gel plugging rate results calculated in the embodiment of the present invention are shown in Table 2 below.

[0094] Table 2: Calculation results of gel blocking rate of gel system

[0095]

[0096] In the present invention, the method for determining the effective plugging radius of the gel system according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model comprises: determining the designed dimensionless plugging radius of the gel system according to the designed injection amount of the gel system in the gel system injection scheme and the pore volume of the sand-filled tube model; calculating the effective plugging radius of the gel system according to the dimensionless plugging radius, the length of the sand-filled tube model and the length of the sand-filled tube model corresponding to 1 / 2 of the maximum breakthrough pressure gradient of the gel system using formula (2);

[0097]

[0098] Where: L′ is the effective plugging radius of the gel system, dimensionless; l′ is the length of the sand-filled tube model corresponding to 1 / 2 of the maximum breakthrough pressure gradient of the sand-filled tube model gel system, m; l is the length of the sand-filled tube model, m; L is the dimensionless plugging radius of the gel system design.

[0099] In the present invention, the method for determining the dimensionless plugging radius of the gel system design according to the gel system design injection volume in the gel system injection scheme and the pore volume of the sand filling pipe model comprises: using formula (3) to calculate the dimensionless plugging radius of the gel system design;

[0100]

[0101] Where: L is the dimensionless plugging radius of the gel system design, dimensionless; V w is the designed injection volume of the gel system, ml; V is the pore volume of the sand-filled tube model, ml.

[0102] In the embodiment of the present invention, the effective plugging radius of the gel system in the reservoir can directly reflect the gelation radius under dynamic conditions after a certain amount of the gel system is injected into the reservoir. Therefore, the effective plugging radius of the gel system in the reservoir is used as a gelation characteristic parameter to evaluate the gelation radius under dynamic conditions of the reservoir after a certain amount of the gel system is injected.

[0103] According to the pore volume of the sand-filled tube model and the total designed injection volume of the injection scheme, the corresponding dimensionless plugging radius L of the gel system is calculated by substituting into formula (3). The dimensionless plugging radius results calculated in the embodiment of the present invention are shown in Table 3 below.

[0104] Table 3: Calculation results of dimensionless plugging radius of gel system

[0105]

[0106] like Figure 4 The pressure gradient curves of each test sample point at each stage of the sand-filled tube model scouring capacity experiment are shown. The length corresponding to the maximum breakthrough pressure gradient of 1 / 2 is defined as the effective plugging radius. According to the length of the sand-filled tube model corresponding to the maximum breakthrough pressure gradient of 1 / 2, the dimensionless plugging radius and the length of the sand-filled tube model l obtained by the above calculation, they are substituted into formula (2) to calculate the corresponding effective plugging radius L' of the gel system.

[0107] In the present invention, the first requirement includes: the gel plugging rate reaches above the predetermined plugging rate, the effective plugging radius is less than the predetermined range of the predetermined gel dam radius, and the breakthrough pressure gradient of the gel system is greater than the maximum pressure gradient actually measured in the target block reservoir.

[0108] and / or,

[0109] The pressure gradient is calculated using formula (4);

[0110]

[0111] Where: ΔP is the pressure difference between two adjacent pressure measuring points; L is the distance between two adjacent pressure measuring points.

[0112] In the present invention, the method for adjusting the injection scheme of the gel system includes: increasing the polymer concentration in the gel system to a first predetermined value, and / or increasing the injection volume to a second predetermined value, and performing a flushing capacity test experiment using the gel system injection scheme after increasing the polymer concentration and / or injection volume, until the experimental results obtained meet the first requirement.

[0113] In the embodiment of the present invention, the predetermined plugging rate is 98%. As shown in Table 2, the plugging rate of the gel system obtained through the experiment can reach more than 98% in the target reservoir. The higher the permeability of the target layer, the better the plugging effect of the gel system. If the plugging rate does not reach more than 98%, the gel viscosity of the system is increased by increasing the polymer concentration in the gel system. After increasing the polymer viscosity of the gel system in the injection scheme, repeat the above-mentioned flushing capacity test experiment, and use formula (1) again to calculate the corresponding plugging rate according to the experimental results until the plugging rate reaches more than 98%.

[0114] The predetermined range is 50%. If the effective plugging radius of the gel system calculated according to the experimental results is less than the expected gel radius (predetermined gel dam radius) by 50%, it is necessary to increase the injection amount of the gel system, increase the polymer viscosity of the gel system in the injection scheme, repeat the above flushing capacity test experiment, and calculate the corresponding effective plugging radius again using formula (2) according to the experimental results, until the effective plugging radius is less than the expected gel radius by 50%.

[0115] The measured maximum pressure gradient of the target block reservoir is calculated based on the pressure distribution data between the injection well and the production well in the target block using formula (4). In the embodiment of the present invention, the pressure gradient of the target block is 2.47MPa / m, and the pressure gradients at different positions are obtained by analogy. The obtained pressure gradient distribution diagram is shown in the attached figure. Figure 2 shown.

[0116] The calculated breakthrough pressure and gradient of the gel system in the sand-filled tube model are compared with the actual injection pressure difference and pressure gradient curve between the injection well and the production well in the target block to evaluate the anti-scouring ability of the gel system. Figure 4 As shown in the figure, the gel system erosion breakthrough pressure gradient is much greater than the maximum pressure gradient of the gel well in the target block reservoir. The higher the permeability of the target layer, the higher the gel system erosion breakthrough pressure and breakthrough pressure gradient.

[0117] When the plugging rate of the gel system in the target reservoir reaches more than 98%, the effective plugging radius is less than 50% of the expected gel radius, and the maximum pressure gradient of the gel system is greater than the maximum measured pressure gradient of the target block reservoir, the corresponding gel system injection plan (including the adjusted polymer viscosity and gel system injection amount) is the optimal injection plan.

[0118] Step S03: According to the plugging position and the optimal injection scheme, a recovery factor and remaining oil saturation test experiment is performed to obtain an oil saturation field distribution experimental result. If the experimental result does not meet the second requirement, the plugging position and / or the injection amount of the gel system in the optimal injection scheme are adjusted, and the corresponding adjusted plugging position and / or the injection scheme after adjusting the injection amount and concentration when the experimental result meets the second requirement are determined as the final plugging position and / or injection scheme.

[0119] In the embodiment of the present invention, in order to clarify the ability of deep liquid flow diversion of the gel system injected into the well between the injection and production wells and the development effect after improving the reservoir, the well selection location of the well, the injection amount of the gel system and the formula of the gel system are optimized. By calibrating the resistance and oil saturation, a set of standard curves of resistance and oil saturation suitable for the model used in the present invention is established. By monitoring the resistance of the embedded electrode core model, the change of oil saturation before and after the injection of the gel system in the well is calculated, and the saturation field distribution cloud map is drawn to evaluate the effect of liquid flow diversion and improved recovery rate injected with the gel system.

[0120] In the present invention, the method for performing recovery rate and remaining oil saturation test experiments according to the plugging position and the optimal injection scheme to obtain the oil saturation field distribution experimental results includes: establishing a microelectrode model according to the reservoir permeability of the target block, and establishing a standard curve of resistance and oil saturation by testing the model resistance under different proportions of crude oil and water; making a core model according to the reservoir permeability and well location of the target block; saturating the core model with water and saturating with oil; water-flooding the core model at a predetermined displacement speed until the outlet water content is above the predetermined water content, and determining the water flooding rate. Recovery rate; injecting the gel system at a predetermined speed according to the gel system injection plan; closing all injection wells and production wells of the core model, waiting for solidification to form static gel, and opening the water injection well and production well; water-flooding the core model at a predetermined displacement speed until the outlet water content is above the predetermined water content, and calculating the water-flooding recovery rate; monitoring the resistance values ​​of different test points during the displacement process when saturated with oil, water-flooding, and water-flooding after solidification; determining the oil saturation value of each test point according to the resistance value and the standard curve, and obtaining the oil saturation field distribution result using the oil saturation values ​​of each test point.

[0121] In an embodiment of the present invention, a standard curve of rock-electricity relationship is established: a microelectrode model with a size of 4.5×4.5×4.5 cm is established, and the resistance of the microelectrode model under different proportions of crude oil and water (oil saturations are 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 44%, 48%, 52%, 56%, 60%, 65%, 70%, and 75%, respectively) is tested to establish a standard curve of resistance and oil saturation.

[0122] In the present invention, the method for saturating the core model with water and oil comprises: starting from the injection end of the core model, vacuuming for a predetermined hour, and vacuuming each pressure test point for a predetermined hour; saturating the core model with artificial synthetic brine, and then placing it in a constant temperature box of the target block oil reservoir for more than a predetermined hour; injecting crude oil into the core model from the injection end of the core model, displacing until no water is produced, and placing the core model in a constant temperature box for constant temperature maturation for more than a predetermined hour.

[0123] In the embodiment of the present invention, Figure 5 The figure shows the established core model, and the model parameters are: model size 30×30×4.5cm, permeability 826mD, rubber dam well location: 1 / 2, well-to-well connectivity: 4-way connectivity, porosity 26.0%, oil saturation: 70.1%. The water saturation and oil saturation process is:

[0124] 3.1. Check the air tightness of the core model: put a core with a size of 30×30×4.5cm into water, pass gas at a flow rate of 0.5ml / min, and check whether the model is leaking;

[0125] 3.2. Vacuuming: Start vacuuming from the injection end of the core model for 6 hours, and vacuumize the remaining 8 pressure test points for 1 hour each, for a total of 14 hours;

[0126] 3.3. Saturated water: Saturate artificial synthetic brine, measure the saturated water volume, calculate the pore volume (pore volume is used to determine the gel injection plan), and then place the core model in a thermostat at the target block reservoir temperature for a preset hour (72 hours) or more;

[0127] 3.4. Model saturated with oil: Inject crude oil from the center of the core model as the injection end to the four corners of the core until no water is produced; then inject crude oil into the core model from the four injection ends surrounding the center of the core model until no water is produced; finally, push crude oil into the core model from the four injection ends at the outermost periphery until no water is produced in the core model. Measure the cumulative produced water volume, calculate the original oil saturation, and place the core model in a constant temperature box again for constant temperature maturation for more than 72 hours.

[0128] The process of saturating the core model with water and oil is as follows:

[0129] 3.5. Water flooding: Flood the core model with water at a predetermined displacement rate (1 ml / min) until the outlet water content is above 98%, and calculate the water flooding recovery factor;

[0130] 3.6. Injection of gel system: Inject the gel system to the designed volume V at a predetermined speed (1 ml / min). w ;

[0131] 3.7 Waiting for setting: Close all injection wells and production wells in the model, wait for setting for 72 hours until the parallel samples are statically gelled, then open the injection wells and production wells;

[0132] 3.8. Subsequent water flooding: water flooding at a predetermined rate (1 ml / min) until the water content at the core model outlet is above 98%, and the subsequent water flooding recovery factor is calculated;

[0133] 3.9, Saturation field and pressure field monitoring: During the displacement process, the resistance and pressure values ​​of different test points are monitored once each during the saturated oil, water drive and secondary water drive after the gel system solidifies. Table 4 shows the experimental plan for the recovery factor and remaining oil saturation test.

[0134] Table 4: Experimental plan for recovery factor and remaining oil saturation test

[0135]

[0136] The recovery rate and water content change curves drawn based on the recovery rate and remaining oil saturation test results are shown in the figure below: Figure 6 As shown, the pressure field distribution is Figure 7 Figure (a) shows the pressure field distribution after water flooding, and Figure (b) shows the pressure field distribution after gel injection. Figure 6 and 7 It can be seen that the pressure field is unevenly distributed and gradually increases from the injection well to the production well. After gel transfer + waiting for gelation + subsequent water flooding, the pressure gradient gradually becomes uniform after gelation.

[0137] The resistance of each test point in the core model at different displacement stages was measured by the electrode method. The saturation value of each test point was calculated based on the standard curve between resistance and oil saturation. The SUFER software was used to form the model oil saturation distribution cloud map, as shown in the figure. Figure 8 As shown, (a) shows the oil saturation field distribution after the model is saturated with oil, (b) shows the oil saturation field distribution after the model is water flooded, and (c) shows the oil saturation field distribution after the model is injected with gel, flooded and subsequently water flooded.

[0138] In the present invention, the second requirement includes: the seepage resistance of the water flow channel at the blocked passing well in the core model is increased, the injected water forms a bypass flow after encountering the rubber dam of the passing well, the affected area near the production well is expanded, the injection pressure is increased, and the oil washing effect in the affected area of ​​the water drive is improved.

[0139] In the embodiment of the present invention, according to the finally obtained oil inclusion density field distribution result, it is determined whether the reservoir fluid flow direction in the core model has changed, whether the water injection swept area, injection pressure and oil washing effect have improved compared with before the gel system was injected, so as to judge whether the final development effect has been improved.

[0140] If the test results of the recovery factor and the remaining oil saturation do not meet the second requirement, the plugging position and / or the injection amount and concentration of the gel system in the optimal injection scheme are adjusted. For example, if the gel system cannot achieve the change of the flow direction, or the affected area near the production well, the injection pressure, and the oil washing effect of the water drive affected area remain unchanged or decrease, the adjustment can be made by changing the plugging position (including well position, number, and layer) of the gel well (passing well), and / or increasing the injection amount of the gel system in the optimal injection scheme and increasing the concentration of the gel system components. After adjusting the passing well position and / or the concentration of the gel system components, repeat the above recovery factor and the remaining oil saturation test experiment, and determine again whether the second requirement is met based on the experimental results. If it is met, the corresponding adjusted passing well plugging position and the optimal injection scheme after adjusting the injection amount of the gel system and increasing the concentration of the gel system components are the final plugging position and injection scheme. According to the final plugging position and injection scheme obtained, the dominant seepage channel of the passing well is plugged in the target block to achieve the improvement of the block recovery factor.

[0141] The test results of the remaining oil in the water flooding stage show that the injected water forms a dominant water flow channel along the injection well to the production well. The water flow channel at the bottom of the injection well is significantly wider than that at the bottom of the production well, indicating that the area near the injection well is more fully affected, while the degree of deep-reservoir impact needs to be further improved.

[0142] The test results of residual oil in the gel injection + subsequent water flooding stage show that the gel well increases the seepage resistance of the water flow channel, and the injected water forms a bypass flow after encountering the gel, which expands the affected area near the production well; and the increase in injection pressure improves the oil washing effect in the water flooding affected area.

[0143] It can be understood that the above-mentioned various method embodiments mentioned in the present invention can be combined with each other to form a combined embodiment without violating the principle logic. Due to space limitations, the present invention will not go into details.

[0144] Those skilled in the art will appreciate that, in the above method of specific implementation, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of the steps should be determined by their functions and possible internal logic.

[0145] The present invention establishes a method for improving the recovery rate by plugging the high permeability layer by injecting a gel system into a passing well between the injection and production wells, aiming to better plug the high permeability layer to improve the recovery rate and solve the problem of water seepage in the dominant seepage channel. As an abandoned passing well between the production well and the water injection well, the high permeability layer is plugged by injecting a gel system. Compared with the traditional profile adjustment and water plugging method, the present invention has a more significant plugging effect on high permeability reservoirs. Traditional profile adjustment and water plugging technology mainly plugs injection wells. However, the present invention combines the profile adjustment of water injection wells with the method of injecting gel into overwells, which can more effectively plug the high permeability layer and improve the recovery rate. By conducting flushing capacity test experiments and recovery rate and remaining oil saturation test experiments, the injection position and amount of plugging agents can be controlled more accurately, thereby improving the plugging effect; by calculating the actual effective plugging distance and determining the plugging rate based on the change in the pressure gradient between the wells, the plugging ability of the gel system can be evaluated; by comparing the pressure gradient, the gel groups of the production wells and the water injection wells can be prevented from being broken due to the large pressure gradient between the water injection wells and the production wells, and the pressure gradient of the passing wells between the actual production wells and the water injection wells can be ensured to be less than the maximum breakthrough pressure gradient during the experiment, so that the gel group plugging effect is more stable. The gel has the ability to be difficult to be broken, and the plugging time effect is good, so it significantly improves the recovery rate. In practical applications, by combining the profile adjustment in the water injection well and the over-injection gel system, deep plugging of high permeability reservoirs can be achieved, and the injected water can be diverted to displace the remaining oil in the low permeability reservoir, thereby improving the water drive recovery rate.

[0146] In summary, the present invention blocks the high permeability layer by injecting a gel system into an abandoned passing well between injection and production wells, which not only improves the blocking effect, but also significantly increases the recovery rate, and has broad prospects for promotion and application.

[0147] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for improving oil recovery by plugging the dominant seepage channel using a passing well, characterized in that: include: Obtain the reservoir permeability of the target block, set the initial well plugging position and the gel system injection plan; According to the permeability and the gel system injection scheme, a flushing capacity test experiment is carried out to obtain the experimental results of the breakthrough pressure gradient, gel plugging rate and effective plugging radius of the gel system. If the experimental results do not meet the first requirement, the gel system injection scheme is adjusted to determine that the corresponding gel system injection scheme is the optimal injection scheme when the experimental results meet the first requirement; According to the plugging position and the optimal injection scheme, a recovery factor and remaining oil saturation test experiment is performed to obtain an oil saturation field distribution experimental result. If the experimental result does not meet the second requirement, the plugging position and / or the injection amount and concentration of the gel system in the optimal injection scheme are adjusted, and the corresponding adjusted plugging position and / or the injection scheme after adjusting the injection amount and concentration when the experimental result meets the second requirement are determined as the final plugging position and / or injection scheme.

2. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 1, characterized in that: The method of conducting a flushing capacity test experiment according to the permeability and the gel system injection scheme to obtain the experimental results of the gel system breakthrough pressure gradient, gel plugging rate and effective plugging radius includes: Make a sand-filled pipe model of a predetermined length and a permeability that matches the reservoir permeability of the work area; The sand-filled tube model is evacuated and saturated with water to determine the pore volume V of the sand-filled tube model. After the sand-filled tube model is placed in a constant temperature box at a predetermined temperature for the first predetermined hour, water is driven at a predetermined speed to measure the stable pressure P of the sand-filled tube model in the water-drive stage. w ; According to the gel system injection plan, the gel system is injected at a predetermined speed until it becomes a static gel; The sand-filled pipe model is water-flooded at a predetermined speed, and the pressure at each pressure measuring point is recorded to determine the maximum injection pressure and the subsequent stable pressure P of the water flooding stage. w '; According to the maximum injection pressure, determining the corresponding maximum breakthrough pressure gradient of the gel system; According to the stable pressure P in the water flooding stage w , and the subsequent water flooding stage steady-state pressure P w ', determine the gel plugging rate; The effective plugging radius of the gel system is determined according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model.

3. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 2, characterized in that: According to the stable pressure P of the water flooding stage w , and the subsequent water flooding stage steady-state pressure P w ', the method for determining the gel plugging rate includes: The gel plugging rate is calculated using formula (1); Where: η is the plugging rate, %; K w is the permeability of the sand-filled pipe model in the water flooding stage, 10 -3 μm 2 ; K w ′ is the permeability of the sand-filled pipe model in the subsequent water flooding stage, 10 -3 μm 2 ;P w is the steady-state pressure in the water flooding stage, MPa; P w ' is the stable section pressure in the subsequent water flooding stage, MPa.

4. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 2, characterized in that: The method for determining the effective plugging radius of the gel system according to the gel system injection scheme, the pore volume of the sand-filled tube model, the maximum breakthrough pressure gradient of the gel system and the length of the sand-filled tube model comprises: According to the designed injection volume of the gel system in the gel system injection plan and the pore volume of the sand-filled tube model, the dimensionless plugging radius of the gel system design is determined; According to the dimensionless plugging radius, the length of the sand-filled tube model and the length of the sand-filled tube model corresponding to the half of the maximum breakthrough pressure gradient of the gel system, the effective plugging radius of the gel system is calculated using formula (2); Where: L′ is the effective plugging radius of the gel system, dimensionless; l′ is the length of the sand-filled tube model corresponding to 1 / 2 of the maximum breakthrough pressure gradient of the sand-filled tube model gel system, m; l is the length of the sand-filled tube model, m; L is the dimensionless plugging radius of the gel system design.

5. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 4, characterized in that: The method for determining the dimensionless plugging radius of the gel system design according to the gel system design injection volume in the gel system injection scheme and the pore volume of the sand filling pipe model comprises: The dimensionless plugging radius of the gel system design is calculated using formula (3); Where: L is the dimensionless plugging radius of the gel system design, dimensionless; V w is the designed injection volume of the gel system, ml; V is the pore volume of the sand-filled tube model, ml.

6. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 1, characterized in that: The method for adjusting the gel system injection scheme comprises: The polymer concentration in the gel system is increased to a first predetermined value, and / or the injection volume is increased to a second predetermined value, and a flushing capacity test experiment is performed using the gel system injection scheme after increasing the polymer concentration and / or injection volume, until the experimental results obtained meet the first requirement.

7. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 1, characterized in that: The first requirement includes: The gel plugging rate reaches or exceeds the predetermined plugging rate, the effective plugging radius is less than or equal to the predetermined range of the predetermined gel dam radius, and the breakthrough pressure gradient of the gel system is greater than the maximum pressure gradient actually measured in the target block reservoir; and / or, The pressure gradient is calculated using formula (4); Where: ΔP is the pressure difference between two adjacent pressure measuring points; L is the distance between two adjacent pressure measuring points.

8. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 1, characterized in that: The method of performing recovery factor and remaining oil saturation test experiments according to the plugging position and the optimal injection scheme to obtain oil saturation field distribution experimental results includes: A microelectrode model was established based on the reservoir permeability of the target block, and a standard curve between resistance and oil saturation was established by testing the model resistance under different proportions of crude oil and water. Create core models based on reservoir permeability and well locations in the target area; saturating the core model with water and oil; The core model is water-flooded at a predetermined displacement rate until the outlet water content is above the predetermined water content, and the water-flooding recovery factor is determined; Injecting the gel system at a predetermined speed according to the gel system injection plan; Close all injection wells and production wells in the core model, wait for the gel to form a static gel, and then open the water injection wells and production wells; The core model is water-flooded at a predetermined displacement rate until the outlet water content is above the predetermined water content, and the water-flooding recovery factor is calculated; Monitor the resistance values ​​of different test points during the displacement process of saturated oil, water drive and water drive after condensation; According to the resistance value and the standard curve, the oil saturation value of each test point is determined, and the oil saturation field distribution result is obtained by using the oil saturation value of each test point.

9. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to claim 8, characterized in that: The method for saturating the core model with water and oil comprises: The core model injection end starts to be vacuumed for a preset hour, and each pressure test point is vacuumed for a preset hour; The core model is saturated with artificial synthetic brine and then placed in a thermostat at the target block reservoir temperature for more than a predetermined number of hours; Crude oil is injected into the core model from the injection end of the core model until no water is produced, and the core model is placed in a constant temperature box for constant temperature maturation for more than a predetermined number of hours.

10. The method for improving oil recovery by blocking the dominant seepage channel by using a passing well according to any one of claims 1 to 9, characterized in that: The second requirement includes: The seepage resistance of the water flow channel at the blocked passing well in the core model is increased, and the injected water forms a bypass flow after encountering the rubber dam of the passing well. The affected area near the production well is expanded, the injection pressure is increased, and the oil washing effect in the affected area of ​​the water drive is improved.

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