Evaluation method for inter-well communication mode of fault control type fracture-cavity oil reservoir

Abstract

The invention provides an evaluation method for a disconnection control type fracture-cavity oil reservoir inter-well communication mode, and relates to the technical field of oil and gas development engineering. The evaluation method comprises the following steps: calculating an oil well detection distance xinv of a plane linear flow according to data information of an interference well test; defining and calculating inter-well tortuosity tau well according to an oil well detection distance xinv; defining and calculating the critical tortuosity [tau] critical between wells according to the spatial characteristics of the wells; according to the inter-well tortuosity tau well and the critical tortuosity tau critical, the inter-well communication mode is judged, and direct communication or indirect communication is judged. And then the method is verified in combination with an oil reservoir numerical simulation method. According to the method, the direct connectivity and the indirect connectivity between the oil reservoir wells are accurately judged, and the problem that whether the connectivity between the fault control type fracture-cavity oil reservoir wells is direct connectivity or indirect connectivity cannot be judged in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas development engineering, and particularly relates to an evaluation method for the inter-well connection mode of a fault-controlled fracture-cavity reservoir. Background Technique

[0002] Inter-well connectivity is crucial for the inter-well sweep of water injection and gas injection in a reservoir. If the inter-well connectivity in a well group is poor, water injection and gas injection cannot sweep laterally between wells. Therefore, when the enhanced oil recovery effect of water injection and gas injection is not good, a well group with poor inter-well connectivity will not be selected as a well group for water injection and gas injection.

[0003] For a fault-controlled fracture-cavity reservoir, it has a large reserve and high production. For some fault-controlled fracture-cavity reservoirs, water injection and gas injection have been carried out in the middle stage of reservoir development to enhance oil recovery. At present, the evaluation of inter-well connectivity is mainly carried out through interference well testing and inter-well tracer methods. Although some research results of interference well testing and inter-well tracers show good inter-well connectivity, sometimes the dynamics of water injection and gas injection reflect a poor conclusion of inter-well connectivity. For the above phenomenon, researchers explained it through a grid model with a separated upper part and a connected lower part of the reservoir: the wells may be directly connected (upper part connected, suitable for water injection and gas injection), or indirectly connected (lower part connected, not suitable for water injection and gas injection), and the connection situation between each pair of wells is not the same. With the current technical means, it is impossible to accurately judge the specific connection situation between two wells.

[0004] Chinese Patent Application No. 201710512800.5 provides a method and device for determining the inter-well connectivity of a reservoir. The method includes: establishing geological stratifications of a first reservoir to be measured and a second reservoir to be measured; respectively obtaining the measurement point data at the positions where each measurement point is located in the first reservoir to be measured and the second reservoir to be measured; determining the remaining pressure at the position where the measurement point is located according to the measurement point data and the pressure of the piezometric datum plane of the reservoir to be measured; respectively determining the inter-well connectivity of the first reservoir to be measured and the second reservoir to be measured according to the relationship between the remaining pressure and the altitude of the first reservoir to be measured and the second reservoir to be measured. In the embodiment of the invention, the remaining pressure that can finely depict the change of pressure with altitude in the reservoir to be measured is used to judge the inter-well connectivity of the reservoir, improving the judgment accuracy of the inter-well connectivity of the reservoir.

[0005] The Chinese invention patent with the application number 202010278922.4 discloses a method, device, computing device and computer storage medium for discriminating the well - to - well connectivity relationship. Among them, the method includes: calculating the standard unit pressure - drop liquid production volume of a production well when there is no water injection in the injection wells within the reservoir area; obtaining the actual unit pressure - drop liquid production volume of the production well during the production period; determining whether the standard unit pressure - drop liquid production volume is less than the actual unit pressure - drop liquid production volume; if it is less, determining whether the number of injection wells injecting water within the reservoir area exceeds one; if it exceeds one, determining whether there is overflow during the water injection period of the injection wells; if there is overflow, obtaining the differential pressure change curve between the injection well with overflow and the production well during the water injection period; and determining the injection wells connected to the production well according to the differential pressure change curve and the energy change curve of the production well. Using this solution, the well - to - well connectivity relationship between injection wells and production wells can be identified.

[0006] Although the current interference well test and inter - well tracer methods can determine whether wells are connected, they cannot accurately distinguish different situations of direct connection or indirect connection. To solve this problem and accurately select effective injection and gas - injection wells, there is an urgent need for a method that can specifically determine the well - to - well connectivity based on existing data, such as interference well test data, which has an important role in guiding petroleum exploration and improving exploration efficiency. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides an evaluation method for the well - to - well connectivity mode of a fault - controlled fracture - cave reservoir. The main technology is as follows: accurately determine direct connection or indirect connection through the size relationship between the well - to - well tortuosity and the critical tortuosity; then verify this method by combining the reservoir numerical simulation method. The evaluation method of the present invention can accurately determine the direct connectivity and indirect connectivity between wells in the reservoir based on interference well test data, and solves the problem that the prior art cannot determine whether the connectivity between wells in a fault - controlled fracture - cave reservoir is direct connection or indirect connection.

[0008] To achieve the above - mentioned purpose, the technical solution adopted by the present invention is as follows:

[0009] First of all, the present invention provides an evaluation method for the well - to - well connectivity mode of a fault - controlled fracture - cave reservoir, including the steps:

[0010] S1. Calculate the oil - well detection distance x of planar linear flow according to the data of the interference well test inv ;

[0011] S2. Define and calculate the well - to - well tortuosity τ according to the oil - well detection distance x inv ; well ;

[0012] S3. Define and calculate the critical well - to - well tortuosity τ according to the spatial characteristics of the wellscritical ;

[0013] S4. Determine the inter-well connection mode according to the inter-well tortuosity τ well and the critical tortuosity τ critical .

[0014] Preferably, in step S1, the data includes the distance between wells, the completion position, and the interference test result data.

[0015] Preferably, in step S1, the detection distance x inv of the oil well is calculated as follows:

[0016]

[0017] where t is the production time, ks; η is the pressure diffusion coefficient, m 2 / ks;

[0018] The calculation formula of η is as follows:

[0019]

[0020] where k is the formation permeability, D; μ is the viscosity of the formation fluid, mPa·s; φ is the porosity of the rock, dimensionless; c t is the total compressibility of the formation, MPa -1 .

[0021] Preferably, in step S2, the calculation formula of the inter-well tortuosity τ well is:

[0022]

[0023] where x horizon is the planar distance between two wells, m.

[0024] In step S3, the spatial characteristics of the well include the parameters: the critical distance of the well test, the planar distance of the well test, and the maximum elevation difference of the production section of the well test.

[0025] Preferably, in step S3, the calculation formula of the critical tortuosity τ critical is:

[0026]

[0027] where x critical is the critical distance between two wells, that is, the farthest distance between two wells in the longitudinal plane;

[0028] The critical distance x critical and the planar distance x horizon have the following relationship:

[0029]

[0030] In the formula, h is the maximum height difference between the production sections of the two wells, in m.

[0031] Preferably, in step S4, the criterion for judging the inter-well connection mode is: when τ well >τ critical , it is judged that the wells are in an indirect connection state; when τ well <τ critical , it is judged that the wells are in a direct connection state.

[0032] In the present invention, the indirect connection state means that there is no direct connection channel between the wells, and the connection is formed by other means such as bottom water. Such wells are not suitable for injecting fluid for displacement.

[0033] In the present invention, the direct connection state means that there is a connection channel between the wells, and such wells are suitable for injecting fluid for displacement.

[0034] Then, the present invention provides an expression for judging the relationship of inter-well connection degree, and the parameters of this expression are the tortuosity τ well and the critical tortuosity τ critical ;

[0035] In the formula, x horizon is the planar distance between the two wells, in m; x inv is the detection distance of the oil well;

[0036] In the formula, x critical is the critical distance between the two wells, that is, the farthest distance between the two wells in the longitudinal plane;

[0037] The critical distance x critical and the planar distance x horizon have the following relationship:

[0038]

[0039] In the formula, h is the maximum height difference between the production sections of the two wells, in m.

[0040] Finally, the present invention provides the application of the above relationship expression in judging the inter-well connection degree.

[0041] Preferably, in the above application, when τ well >τ critical , it is judged that the wells are in an indirect connection state; when τ well <τ critical , it is judged that the wells are in a direct connection state.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The evaluation method provided by the present invention can accurately judge the direct and indirect connectivity between wells in the reservoir based on interference test well data, solving the problem in the prior art that it is impossible to judge whether the connectivity between wells in a fracture-vug reservoir controlled by faults is direct or indirect.

[0044] 2. The evaluation method of the present invention has a high processing efficiency, can quickly and accurately judge the connectivity mode between wells, whether it is direct or indirect; has a large operation flexibility and accurate results; moreover, this method has good economy, based on the existing interference test well data, without the need for new on-site tests.

[0045] 3. The present invention aims at the actual production situation of fracture-vug reservoirs, solving the problem that interference test wells cannot accurately judge the connectivity degree between wells; the present invention can obtain an accurate expression of the relationship of the connectivity degree between wells in fracture-vug reservoirs; the present invention is widely applicable to production diagnosis and prediction in the actual production process of fracture-vug reservoirs, as well as dynamic data inversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic diagram of the inter-well planar distance and critical distance of the present invention.

[0047] Figure 2 is a flowchart of the evaluation method for the inter-well connectivity mode of a fault-controlled fracture-vug reservoir of the present invention.

[0048] Figure 3 is a numerical model diagram for verifying the inter-well connectivity judgment of the present invention.

[0049] Figure 4 is a schematic diagram of the stimulation production and bottom-hole flowing pressure conditions of the pressure stimulation well of the present invention.

[0050] Figure 5 is a diagram of the bottom-hole flowing pressure fluctuation of the pressure observation well of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] The following non-limiting embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is only an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and it should also fall within the scope claimed by the present invention. When the embodiments give numerical ranges, it should be understood that unless otherwise specified by the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The present invention will be further described below by way of specific embodiments.

[0052] Example 1

[0053] The present invention provides an evaluation method for the inter-well connectivity mode of a fault-controlled fracture-vug reservoir, which is applicable to the evaluation of inter-well connectivity in a fault-controlled fracture-vug reservoir.

[0054] S1. Calculate the detection distance x of the oil well in planar linear flow according to the data of the interference well test. inv .

[0055] The reservoir space of the fault-controlled reservoir is mainly composed of fractures. The analytical formula for pressure propagation in fractures is as follows:

[0056]

[0057] In formula (1), x is the linear coordinate, m; t is the production time, ks; p is the formation pressure, MPa; p wf is the bottom-hole flowing pressure, MPa; p i is the original formation pressure, MPa; η is the pressure conductivity coefficient, m 2 / ks;

[0058] The calculation formula for η is as follows:

[0059]

[0060] In formula (2), k is the formation permeability, D; μ is the viscosity of the formation fluid, mPa·s; φ is the porosity of the rock, dimensionless; c t is the total compressibility of the formation, MPa -1 ;

[0061] Let Then the detection distance x can be obtained from formula (1) inv The calculation formula for is:

[0062]

[0063] In formula (3), t is the production time, ks; η is the pressure conductivity coefficient, m 2 / ks.

[0064] Formula (3) is the calculation formula for the detection distance of the oil well in planar linear flow. The formula (3) of the present invention is determined by solving the gradient of the formation pressure, while the traditional methods are all determined by solving the change rate of the pressure. It can be seen from formula (3) that the detection distance is related to the production time. The longer the production time, the larger the detection distance; the detection distance is also related to the pressure conductivity coefficient. The larger the pressure conductivity coefficient, the larger the detection distance. The detection distance is independent of the production rate of the oil well and the production mode of the oil well.

[0065] S2. Define and according to the detection distance x of the oil well invCalculate the tortuosity τ between wells well 。

[0066] The tortuosity between wells is where x horizon is the horizontal distance between two wells, in m.

[0067] As Figure 1 shown, x horizon is the distance between the target point coordinates of the two wells on the horizontal plane.

[0068] Define the maximum distance between two wells in the longitudinal plane as the critical distance x critical , and the schematic diagram of the horizontal distance and the critical distance between wells is as Figure 1 shown.

[0069] The relationship between the critical distance and the horizontal distance is:

[0070] where h is the maximum height difference between the production sections of the two wells, in m.

[0071] S3. Define and calculate the critical tortuosity τ between wells according to the spatial characteristics of the wells critical 。

[0072] The critical tortuosity between wells is:

[0073]

[0074] Calculate the tortuosity and the critical tortuosity between wells according to the above formula.

[0075] S4. Judge the connection mode between wells according to the tortuosity τ well between wells and the critical tortuosity τ critical between wells.

[0076] The judgment criterion for the connection mode between wells is:

[0077] When τ well > τ critical , the wells are in an indirect connection state, that is, there is no direct connection channel between the wells, and the connection is formed by other means such as bottom water. Such wells are not suitable for injecting fluids for displacement;

[0078] When τ well < τ critical , the wells are in a direct connection state, that is, there is a connection channel between the wells. Such wells are suitable for injecting fluids for displacement.

[0079] The flow chart of the evaluation method for the connection mode between wells in the fault-controlled fracture-vug reservoir of the present invention is shown in Figure 2 。

[0080] The summary of the evaluation method process is:

[0081] Collect the well spacing (the planar distance between two wells), completion positions, and interference test result data between wells;

[0082] Calculate the tortuosity between wells according to the interference test results and the method proposed by the present invention;

[0083] Calculate the critical tortuosity between wells according to the spatial characteristics of the wells and the method proposed by the present invention;

[0084] Judge the connection mode between wells (direct connection or indirect connection) according to the magnitude relationship between the tortuosity between wells and the critical tortuosity;

[0085] Application Example 1

[0086] The evaluation method of the present invention is verified below in combination with the reservoir numerical simulation method.

[0087] Using the numerical simulation method, a numerical model for verifying the well connection judgment is established (see Figure 3 ), and the basic parameters of the numerical model are set as shown in Table 1 to verify the technical effect of the evaluation method of the present invention.

[0088] Table 1

[0089] Variables and Units Value Variables and Units Value Grid Size / m×m×m 50×50×3 Oil Saturation / % 90 Porosity / % 5 Maximum Elevation Difference between Two Wells 140 Average Permeability / mD 12.25 Number of Stimulation Wells 1 Initial Pressure / MPa 87 Number of Observation Wells 3

[0090] The research is based on the numerical simulation method. The numerical simulation grid and the well positions are as shown in Figure 3 . The evaluation method of the present invention is verified by using the numerical interference test method. One pressure pulse well (PULSER) and three pressure observation wells (OBSERVER: OBSERVER1, OBSERVER2, OBSERVER3) are used to analyze the pressure pulse situation and state.

[0091] Through the process of production - shutdown - production of the PULSER (pressure pulse well), a pressure pulse is generated. The production rate and bottom hole flowing pressure situation (pressure pulse state) of the pressure pulse well are as shown in Figure 4 .

[0092] The fluctuation changes of the bottom hole flowing pressure of the three pressure observation wells (OBSERVER) are as shown in Figure 5 .

[0093] In the model, there is no connection between the two observation wells and the pressure pulse well, belonging to an indirect connection relationship, and the connection position is at the bottom of the reservoir; the pressure fluctuation data of the pressure pulse well and the pressure observation wells are extracted in Table 2.

[0094] Table 2

[0095]

[0096]

[0097] According to the difference in the peak time, the inter-well detection distance is calculated through the detection distance formula, the inter-well tortuosity is obtained, and the critical value of the inter-well tortuosity is determined for comparison. The calculation and analysis results of the inter-well tortuosity are shown in Table 3.

[0098] Table 3

[0099]

[0100] The comparison results show that the calculated tortuosity is significantly greater than the critical tortuosity, indicating that the wells are indirectly connected and it is not suitable for water injection or gas injection between the wells. Therefore, the evaluation method of the present invention can accurately judge the connectivity category between wells in a fault-controlled fracture-vug reservoir.

[0101] Application Example 2

[0102] During the initial production stage in the first area of Shunbei, a large number of interference well tests were carried out, and the propagation speed of the pressure impulse between the wells in the interference well test was calculated. Theoretically, the propagation interference speed of the pressure impulse is closely related to the permeability between the wells.

[0103] This application example uses the evaluation method described in Example 1 of the present invention to evaluate and study the connectivity between wells in a fault-controlled fracture-vug reservoir. The evaluation method of the present invention can accurately describe the relationship between wells, and the obtained relationship is verified in the actual production dynamics.

[0104] Similarly, based on the inter-well permeability obtained from the well test, after calculations such as harmonic average and arithmetic average, the calculated well spacing (the detection distance x of the oil well for calculating planar linear flow inv ) of the interference well test in the first area of Shunbei, the inter-well tortuosity, and the critical tortuosity were studied and calculated, as shown in Table 4.

[0105] Table 4

[0106]

[0107]

[0108] According to Table 4, the difference between the calculated well spacing and the actual well spacing of some wells is extremely small (<20%), indicating good connectivity between the wells. For example, 1-10H and 1-6H, and the water injection effect is rapid and obvious. However, the difference of some wells is large, indicating that although the wells are connected, they are connected through the bottom water. For example, SHB5-3 and SHB5-11H, although the tracer breakthrough occurs, the water injection effect is not obvious. Using the traditional evaluation method cannot accurately judge whether it is directly connected or indirectly connected.

[0109] Traditional methods can only determine whether there is connectivity, but cannot determine whether it is indirect connectivity or direct connectivity. The connectivity methods (direct and indirect) are unique to the fault-controlled reservoir bodies and are of great significance for later water injection and gas injection development. The calculation of the present invention needs to be based on the well test data of interference well tests. If interference well tests have not been carried out on two wells, the algorithm of the present invention cannot be used to determine the connectivity relationship.

[0110] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than limiting the protection scope of the present invention. Simple modifications or equivalent replacements made by those of ordinary skill in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An evaluation method for the inter-well connectivity mode of a fracture-cavity reservoir with disconnection control, characterized in that Including the steps: S1. Calculate the detection distance x of the oil well in the planar linear flow according to the data of the interference test well inv ; S2. Define and calculate the tortuosity τ between wells based on the detection distance x of the oil well inv well ;​ S3. Define and calculate the critical tortuosity τ between wells based on the spatial characteristics of the wells critical ; S4. Determine the inter-well connection mode according to the inter-well tortuosity τ well and the critical tortuosity τ critical ​ 2. The evaluation method according to claim 1, wherein In step S1, the data includes the distance between wells, the completion position, and the interference test result data.

3. The evaluation method according to claim 1, wherein In step S1, the detection distance x of the oil well inv is calculated as follows: where t is the production time, in ks; η is the pressure conductivity, in m 2 / ks; The calculation formula of η is as follows: where k is the formation permeability, D; μ is the formation fluid viscosity, mPa·s; φ is the rock porosity, dimensionless; c t is the total formation compressibility, MPa -1 .

4. The evaluation method according to claim 1, characterized in that In step S2, the inter-well tortuosity τ well is calculated by the formula: where x horizon Horizontal distance between two wells, m.

5. The evaluation method according to claim 1, characterized in that In step S3, the spatial characteristics of the well include the parameters: the critical distance of the well test, the planar distance of the well test, and the maximum elevation difference of the production section of the well test.

6. The evaluation method according to claim 1, wherein In step S3, the critical tortuosity τ critical has the following calculation formula: where x critical is the critical distance between two wells, i.e., the maximum distance between two wells in the longitudinal plane; Critical distance x critical Distance x from the plane horizon The relationship is as follows: In the formula, h is the maximum elevation difference of the production sections of two wells, in m.

7. The evaluation method according to claim 1, characterized in that In step S4, the judgment criterion for judging the inter-well connection mode is: when τ well >τ critical , it is judged that the wells are in an indirect connection state; when τ well <τ critical , it is judged that the wells are in a direct connection state.

8. A judgment expression of the well - to - well connectivity degree obtained by the evaluation method according to any one of claims 1 - 7, characterized in that, The parameters of the expression are tortuosity τ well and critical tortuosity τ critical ; where x horizon is the horizontal distance between two wells, m; x inv is the detection distance of the oil well; where x critical is the critical distance between two wells, i.e., the maximum distance between two wells in the longitudinal plane; Critical distance X critical Distance x from the plane horizon The relationship is as follows: In the formula, h is the maximum elevation difference of the production sections of two wells, in m.

9. Application of the relational expression according to claim 8 in judging the connectivity between wells.

10. The application according to claim 9, characterized in that, When the relational expression is used to judge the degree of inter-well connectivity, when τ well > τ critical , it is judged that the wells are in an indirectly connected state; when τ well < τ critical , it is judged that the wells are in a directly connected state.

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