Deep-water multi-zone composite oil reservoir productivity evaluation method based on short-time DST test

Abstract

The invention relates to a short-time DST test-based deepwater multi-zone composite oil reservoir productivity evaluation method, which comprises the following steps of: collecting original DST test data of a deepwater multi-zone composite oil reservoir, and screening data segments with preset conditions for well test interpretation to obtain a well test interpretation result; according to the original DST test data, a selected number of production obtaining sections are extracted, and a DST test average specific oil recovery index is calculated based on each production obtaining section; calculating the equivalent permeability of the composite oil reservoir within the test time according to a well test interpretation result; calculating a test time correction coefficient according to the data of each production section and a well test interpretation result; calculating a physical property change correction coefficient of the deepwater multi-zone composite oil reservoir according to the equivalent permeability of the composite oil reservoir and a well test interpretation result; and calculating the specific oil production index during stable production according to the DST test average specific oil production index, the test time correction coefficient and the physical property change correction coefficient of the deepwater multi-zone composite oil reservoir. And based on the specific oil recovery index during stable production, the stable productivity is evaluated in combination with directional development well parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore oil and gas exploitation, and in particular to a method for evaluating the productivity of deepwater multi-zone composite oil reservoirs based on a short-time DST test (drill stem formation test, or drill stem test). Background Art

[0002] In the preparation stage of deepwater oilfield development plan, it is often necessary to evaluate or predict the capacity of the reservoir. Compared with exploration and evaluation wells in onshore and shallow offshore oilfields, the investment cost of deepwater oilfield exploration and development is high, there are fewer exploration and evaluation wells, fewer DST tests, and shorter DST test time, which brings great uncertainty to the evaluation of deepwater oilfield capacity.

[0003] With the deepening of offshore oilfield exploration and development, the number of newly discovered low-grade and small-scale reserves has increased, and the DST test interpretation of exploration wells and evaluation wells has shown more and more multi-zone composite reservoir characteristics. For deepwater multi-zone composite reservoirs, due to the obvious differences in physical properties between the inner and outer zones and the short DST test time, the conventional capacity evaluation method is very likely to over- or under-evaluate the capacity when predicting the stable capacity of development wells in deepwater multi-zone composite reservoirs, which affects the reasonable evaluation of the economic feasibility of deepwater oilfield development. Summary of the invention

[0004] The present invention provides a method for evaluating the productivity of deepwater multi-zone composite oil reservoirs based on short-time DST testing, which is suitable for evaluating the productivity of deepwater oil reservoirs in the deepwater oilfield development plan preparation stage, where the DST test interpretation results of exploration wells or evaluation wells are composite oil reservoirs and pressure-maintaining development.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present application provides a method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST testing, comprising:

[0007] S1, collect the original DST test data of deepwater multi-zone composite reservoirs, and screen the data segments with preset conditions for well test interpretation to obtain the well test interpretation results;

[0008] S2, extracting a selected number of production sections according to the original DST test data, and calculating the average specific oil recovery index of the DST test based on each production section;

[0009] S3, calculate the equivalent permeability within the test time according to the well test interpretation results;

[0010] S4, calculating the test time correction coefficient according to the data of each production section and the well test interpretation results;

[0011] S5, calculate the correction coefficient of physical property change of deepwater multi-zone composite reservoir based on the equivalent permeability of the composite reservoir and the well test interpretation results;

[0012] S6, calculating the specific oil production index during stable production according to the average specific oil production index of the DST test, the test time correction factor and the physical property change correction factor of the deepwater multi-zone composite oil reservoir. Based on the specific oil production index during stable production, the stable production capacity of the directional development well is evaluated in combination with the directional development well parameters.

[0013] In one implementation, in S1, the pressure recovery section with no abnormal fluctuation in bottom hole flow pressure and the longest shut-in time is selected for well test interpretation to obtain the original formation pressure p0 of the composite reservoir, the skin coefficient S of the well test interpretation, and the permeability k of each zone of the composite reservoir. i , radius of each zone of composite reservoir r i And the total number of partitions m of the composite partition.

[0014] In one implementation, in S2, the average specific oil recovery index of the DST test is calculated as follows:

[0015]

[0016] Where, J0 is the average specific oil recovery index of each production section tested by DST; q j is the average daily oil production of each production segment, m 3 / d;p wfj is the minimum bottom hole flowing pressure for each production section; h is the effective contribution thickness of the DST test; n is the number of production sections set.

[0017] In one implementation, in S3, the equivalent permeability of the composite reservoir during the test time is calculated as follows:

[0018]

[0019] In the formula, k a is the equivalent permeability of deepwater multi-zone composite reservoir; r eDST Test detection radius for DST;

[0020] When i = m, r m The detection radius for the DST test.

[0021] In one implementation, in S4, the calculation method of the test time correction coefficient includes:

[0022]

[0023] Where D tj Test time correction factor for each production segment; t j Duration of each production segment; is the porosity; μ is the viscosity of the formation crude oil; C t is the comprehensive compression coefficient; r w is the radius of the DST test wellbore; r e is the oil leakage radius.

[0024] In one implementation, in S5, the calculation method of the physical property change correction coefficient includes:

[0025]

[0026] In one implementation, in S6, the calculation formula of the specific oil recovery index during stable production is:

[0027] J1=D t ×D k ×J0

[0028] In one implementation, in S6, the calculation formula for the stable production capacity of the directional development well is:

[0029]

[0030] Where, Δp is the designed production pressure difference of the directional development well; h dw Effective thickness of well control in well area for directional development; k dw The average permeability of well logging in the well area for directional development wells; μ dw The viscosity of the crude oil in the formation of the well area for directional development; k c S is the logging permeability of the test section of the DST test well; dw Predicting skin factors for directional development wells.

[0031] The technical solution of the present invention has the following advantages:

[0032] 1. For the first time, a capacity evaluation method for deepwater multi-zone composite reservoirs based on short-time DST test was proposed by comprehensively considering the short DST test time of deepwater oilfields and the changes in physical properties of the inner and outer zones of multi-zone composite reservoirs. This method can realize the capacity evaluation of composite reservoirs in the preparation stage of deepwater oilfield development plans, and improve the rationality and reliability of the capacity evaluation of composite reservoirs.

[0033] 2. The relevant parameters can be updated according to the actual DST test interpretation results of exploration wells and evaluation wells. The technical method is convenient, fast, highly applicable and reliable;

[0034] 3. It is not only applicable to deepwater composite oil reservoirs, but also can provide reference for the production capacity evaluation of other types of offshore oil reservoirs, such as offshore fault block reservoirs, offshore lithologic reservoirs, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1It is a schematic diagram of the division of the DST test section of the three-zone composite reservoir in one embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the fitting results of double logarithmic pressure and pressure derivative of a three-zone composite reservoir in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0038] In view of the defects and problems of the prior art, the present application provides a method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST testing, comprising:

[0039] S1, collect the original DST test data of deepwater multi-zone composite reservoirs, and screen the data segments with preset conditions for well test interpretation to obtain the well test interpretation results;

[0040] S2, extracting a selected number of production sections according to the original DST test data, and calculating the average specific oil recovery index of the DST test based on each production section;

[0041] S3, based on the well test interpretation results, calculate the equivalent permeability of the composite reservoir during the test time;

[0042] S4, calculating the test time correction coefficient according to the data of each production section and the well test interpretation results;

[0043] S5, calculate the correction coefficient of physical property change of deepwater multi-zone composite reservoir based on the equivalent permeability of the composite reservoir and the well test interpretation results;

[0044] S6, calculate the specific oil production index during stable production based on the average specific oil production index of the DST test, the test time correction factor and the physical property change correction factor of the deepwater multi-zone composite reservoir. Based on the specific oil production index during stable production, the stable production capacity of the directional development well is evaluated in combination with the parameters.

[0045] The above method is described below in a more detailed embodiment in conjunction with more drawings.

[0046] The present invention proposes a method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test, and the specific steps are as follows:

[0047] Collect the bottom hole pressure data, test geological daily report and test basic data of deepwater reservoir DST test, divide the DST test work system, select the pressure recovery section with no abnormal fluctuation of bottom hole flow pressure and the longest shut-in time to carry out well test interpretation, and obtain the original formation pressure p0 of composite reservoir, the skin coefficient S of well test interpretation, and the permeability k of each area of ​​composite reservoir i , radius of each zone of composite reservoir r i This step is a common method in the field of offshore oil and gas production technology and will not be described in detail in the present invention.

[0048] Taking a deepwater oil field at sea as an example, two main production sections and one pressure recovery section are divided according to the DST test bottom hole pressure data and the test geological daily report. Figure 1 The three-zone composite reservoir model was used for interpretation through well test interpretation, and the pressure and pressure derivative fitting effect was good, such as Figure 2 The original formation pressure was 24.42MPa through well test interpretation, the skin coefficient was 0.314, the permeability of each zone from the inner zone to the outer zone was k1=3400mD, k2=1500mD, k3=650mD, the radius of the inner zone 1 and the inner zone 2 were r1=68m and r2=208m, respectively, and the detection radius r eDST =446m, specific parameters are shown in Appendix 1.

[0049]

[0050] Table 1

[0051] According to the daily geological test report, the production sections 1 to 3 with a long well opening time and no abnormal fluctuation in bottom hole pressure were selected, and the average specific oil recovery index J0 of the DST test of each production section was calculated.

[0052] The specific calculation method is:

[0053]

[0054] Where, J0 is the average specific oil recovery index of each production section tested by DST, m 3 / (d·m·MPa);q j is the average daily oil production of each production segment, m 3 / d; p0 is the original formation pressure interpreted in the test well in step 1), MPa; p wfj The minimum bottom hole flowing pressure for each production section, MPa; h is the effective contribution thickness of the DST test, m; n is the number of selected production sections, n = 1, 2, 3.

[0055] Taking a deepwater oil field at sea as an example, two main production sections are divided according to the DST test bottom hole pressure data and the test geological daily report. Combined with the well test interpretation results, the parameters of each production section are shown in Appendix 2.

[0056]

[0057] Table 2

[0058] Based on the data in Appendix 2, the average specific oil recovery index J0 of the DST test for each production section is calculated:

[0059]

[0060] Calculation of equivalent permeability k of composite reservoirs during well testing time based on well testing interpretation parameters a .

[0061] The specific calculation method is:

[0062]

[0063] In the formula, k a is the equivalent permeability of the composite reservoir, mD; k i The permeability of each zone in the composite reservoir is interpreted by well test, mD; r eDST is the detection radius of the DST test, m; r i is the radius of each zone of the composite reservoir interpreted by the pilot well, where when i = m, r m is the detection radius of the DST test, m; m is the total number of composite reservoir partitions interpreted from the pilot well, m=1,2,3,….

[0064] Taking a deepwater oil field at sea as an example, according to the well test interpretation parameter table 1, the equivalent permeability k of the three-zone composite reservoir during the well test time is calculated. a :

[0065]

[0066] Calculate the test time correction coefficient D according to the test time of each production section, test basic parameters, and well test interpretation parameters. t .

[0067] The specific calculation method is:

[0068]

[0069]

[0070] Where D tj k is the test time correction factor for each production segment, dimensionless; a is the equivalent permeability of the composite reservoir, mD; t j Duration of each production segment, hr; is the porosity, %; μ is the formation crude oil viscosity, mPa·s; C t is the comprehensive compression coefficient, MPa -1; r w is the radius of the DST test wellbore, m; S is the skin coefficient interpreted from the pilot well, decimal; r e is the oil leakage radius, m; n is the number of selected production sections, n=1,2,3,…

[0071] Taking a deepwater oil field at sea as an example, according to the well test interpretation parameter table 1 and the production section parameter table 2, the test time correction coefficient D is calculated. t :

[0072]

[0073] Calculate the correction coefficient D of composite reservoir physical property change based on well test interpretation parameters and test basic parameters k .

[0074] The specific calculation method is:

[0075]

[0076] In the formula, k m is the permeability of the outermost area of ​​the composite reservoir interpreted by well testing, mD.

[0077] Taking a deepwater oil field at sea as an example, according to the well test interpretation parameter table 1 and the equivalent permeability k of the composite reservoir exploration well test time a , calculate the correction coefficient D of composite reservoir physical property change k :

[0078]

[0079] Correction factor D according to test time t , correction coefficient D for changes in composite reservoir physical properties k Calculate the specific oil production index J1 during stable production.

[0080] The specific calculation method is:

[0081] J1=D t ×D k ×J0

[0082] Taking a deepwater oil field at sea as an example, according to the test time correction coefficient D t , correction coefficient D for changes in composite reservoir physical properties k Calculate the specific oil production index J1 during stable production:

[0083] J1=D t ×D k ×J0=0.645×0.298×39.8=7.6m 3 / (d·m·MPa)

[0084] According to the effective well control thickness, average permeability, crude oil viscosity, predicted skin factor and designed production pressure difference of the directional development well layout area, the stable production capacity q when deploying directional wells in the composite reservoir is calculated. o .

[0085] The specific calculation method is:

[0086]

[0087] Where, Δp is the designed production pressure difference of the directional well, MPa; h dw is the effective thickness of well control in the directional well layout area, m; k dw is the average logging permeability of the directional well layout area, mD; μ dw is the formation crude oil viscosity in the directional well layout area, mPa·s; k c is the logging permeability of the test section of the DST test well, mD; S dw Predict the skin factor, mD, for directional wells.

[0088] Taking a deepwater oil field at sea as an example, according to the geological professional research, the effective thickness of well control in the well area of ​​directional development wells is h. dw is 30m, and the average logging permeability k dw is 400mD, the formation crude oil viscosity μ dw The production pressure difference Δp is designed to be 2.0 MPa according to the analogy of similar oil fields, and the skin factor S is predicted to be 5. The stable production capacity q when deploying directional wells in composite reservoirs is calculated based on the above parameters, the basic parameters of DST test and the specific oil production index J1 during stable production. o :

[0089]

[0090] In the several embodiments provided by the present invention, it should be understood that the disclosed method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the above units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the productivity of deepwater multi-zone composite reservoirs based on DST testing, characterized in that: include: S1, collect the original DST test data of deepwater multi-zone composite reservoirs, and screen the data segments with preset conditions for well test interpretation to obtain the well test interpretation results; S2, extracting a selected number of production sections according to the original DST test data, and calculating the average specific oil recovery index of the DST test based on each production section; S3, based on the well test interpretation results, calculate the equivalent permeability of the composite reservoir during the test time; S4, calculating the test time correction coefficient according to the data of each production section and the well test interpretation results; S5, calculate the correction coefficient of physical property change of deepwater multi-zone composite reservoir based on the equivalent permeability of the composite reservoir and the well test interpretation results; S6, calculate the specific oil production index during stable production according to the average specific oil production index of the DST test, the test time correction factor and the physical property change correction factor of the deepwater multi-zone composite oil reservoir; based on the specific oil production index during stable production, the stable production capacity of the directional development well is evaluated in combination with the directional development well parameters.

2. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 1 is characterized in that: In S1, the pressure recovery section with no abnormal fluctuation of bottom hole flowing pressure and the longest shut-in time is selected for well test interpretation to obtain the original formation pressure p0 of the composite reservoir, the skin coefficient S of the well test interpretation, and the permeability k of each zone of the composite reservoir. i , radius of each zone of composite reservoir r i And the total number of partitions m of the composite partition.

3. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 2 is characterized in that: In S2, according to the daily geological report of the test, the production section n with a long well opening time and no abnormal fluctuation of bottom hole pressure is selected to calculate the average specific oil production index of the DST test: Where, J0 is the average specific oil recovery index of each production section tested by DST; q j is the average daily oil production of each production segment, m 3 / d;p wfj is the minimum bottom hole flowing pressure of each production section; h is the effective contribution thickness of the DST test; n is the total number of the selected production sections, and n is 1-3.

4. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 3 is characterized in that: In S3, the equivalent permeability of the composite reservoir during the test time is calculated as follows: In the formula, k a is the equivalent permeability of deepwater multi-zone composite reservoir; r eDST Test detection radius for DST; When i = m, r m The detection radius for the DST test.

5. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 4 is characterized in that: In S4, the calculation method of the test time correction coefficient includes: Where D tj Test time correction factor for each production segment; t j Duration of each production segment; is the porosity; μ is the viscosity of the formation crude oil; C t is the comprehensive compression coefficient; r w is the radius of the DST test wellbore; r e is the oil leakage radius.

6. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 5 is characterized in that: In S5, the calculation method of the physical property change correction coefficient includes:

7. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 5, characterized in that: In S6, the calculation formula of the specific oil recovery index during stable production is: J1=D t ×D k ×J0.

8. The method for evaluating the productivity of deepwater multi-zone composite reservoirs based on short-time DST test according to claim 7, characterized in that: In S6, the calculation formula for the stable production capacity of directional development wells is: Where, Δp is the designed production pressure difference of the directional development well; h dw Effective thickness of well control in well area for directional development; k dw The average permeability of well logging in the well area for directional development wells; μ dw The viscosity of the crude oil in the formation of the well area for directional development; k c S is the logging permeability of the test section of the DST test well; dw Predicting skin factor for directional development wells.

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