A method for evaluating productivity of deepwater multi-zone composite reservoirs based on short DST test

Abstract

The present application relates to a kind of deepwater multi-zone composite reservoir productivity evaluation method based on short DST test, comprising: collecting the original DST test data of deepwater multi-zone composite reservoir, and the data section of pre-set condition is screened to carry out well test interpretation, and the well test interpretation result is obtained;According to the original DST test data, the selected number of production section is extracted, and the average oil production index of DST test is calculated based on each production section;According to the well test interpretation result, the equivalent permeability of composite reservoir in test time is calculated;According to the data of each production section and the well test interpretation result, test time correction coefficient is calculated;According to the equivalent permeability of composite reservoir and the well test interpretation result, the physical property change correction coefficient of deepwater multi-zone composite reservoir is calculated;According to the average oil production index of DST test, test time correction coefficient and the physical property change correction coefficient of deepwater multi-zone composite reservoir, the oil production index when stable production is calculated.Based on the oil production index when stable production, the stable productivity is evaluated in combination with the parameter of directional development well.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of offshore oil and gas exploitation, and particularly relates to a deepwater multi-zone composite reservoir deliverability evaluation method based on short DST testing (drill pipe formation testing, or drill pipe testing). BACKGROUND

[0002] In the preparation stage of a deepwater oilfield development plan, the deliverability of a reservoir often needs to be evaluated or expected. Compared with onshore and shallow sea oilfield exploration and evaluation wells, deepwater oilfield exploration and development has high investment cost, fewer exploration and evaluation wells, fewer DST testing times, and shorter DST testing time, which brings great uncertainty to the deliverability evaluation of deepwater oilfields.

[0003] With the deepening of offshore oilfield exploration and development, the number of newly discovered reserves with low grade and small scale increases, and the phenomenon of multi-zone composite reservoir characteristics appears more and more in exploration and evaluation well DST testing well test interpretation. For deepwater multi-zone composite reservoirs, due to the obvious difference in physical properties between the inner and outer zones and the short DST testing time, it is very easy to overestimate or underestimate the stable deliverability of the development well of the deepwater multi-zone composite reservoir by using the conventional deliverability evaluation method, which affects the reasonable assessment of the economic efficiency of deepwater oilfield development. SUMMARY

[0004] The present application provides a deepwater multi-zone composite reservoir deliverability evaluation method based on short DST testing, which is suitable for deepwater reservoir deliverability evaluation at the preparation stage of a deepwater oilfield development plan, and the DST testing well test interpretation result of the exploration or evaluation well is a composite reservoir and the deepwater reservoir is developed by pressure maintenance.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a deepwater multi-zone composite reservoir deliverability evaluation method based on short DST testing, comprising:

[0007] S1, collecting original DST testing data of a deepwater multi-zone composite reservoir, and screening data segments of preset conditions for well test interpretation to obtain well test interpretation results;

[0008] S2, extracting a selected number of production segments from the original DST testing data, and calculating the average specific oil production index of DST testing based on each production segment;

[0009] S3, calculating the equivalent permeability in the testing time according to the well test interpretation results;

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

[0011] S5, according to the equivalent permeability of the composite reservoir and the well test interpretation result, calculating the physical property change correction coefficient of the deepwater multi-zone composite reservoir;

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

[0013] In an implementation manner, in S1, the pressure recovery section with the longest shut-in time and the bottom hole flowing pressure without abnormal fluctuation is selected to carry out well test interpretation, and the original pressure p0 of the composite reservoir formation, the well test interpretation skin factor S, the well test interpretation permeability k of each zone of the composite reservoir i , the radius r i of each zone of the composite reservoir and the total number of sub-zones m of the composite sub-zone are obtained.

[0014] In an implementation manner, in S2, the calculation method of the DST test average oil productivity index is:

[0015]

[0016] In the formula, J0 is the DST test average oil productivity index of each production section; q j is the average daily oil production of each production section, 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; and n is the number of set production sections.

[0017] In an implementation manner, in S3, the calculation method of the equivalent permeability of the composite reservoir in the test time is:

[0018]

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

[0020] wherein when i = m, r m is the detection radius of the DST test.

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

[0022]

[0023] In the formula, D tj is the test time correction coefficient of each production section; t j is the duration of each production section; is the porosity; μ is the formation crude oil viscosity; C t is the overall compressibility; r w is the DST test well bore radius; r e is the drainage radius.

[0024] In an implementation manner, in the S5, the calculation manner of the physical property change correction coefficient comprises:

[0025]

[0026] In an implementation manner, in the S6, the calculation formula of the specific oil production index in the stable production is:

[0027] J1=D t ×D k ×J0

[0028] In an implementation manner, in the S6, the calculation formula of the stable productivity of the directional development well is:

[0029]

[0030] In the formula, Δp is the design production pressure difference of the directional development well; h dw is the well control effective thickness of the well distribution area of the directional development well; k dw is the average permeability of the well distribution area of the directional development well; μ dw is the formation crude oil viscosity of the well distribution area of the directional development well; k c is the DST test well test section logging permeability; S dw is the predicted skin factor of the directional development well.

[0031] The technical scheme of the present application has the following advantages:

[0032] 1. A deepwater multi-zone composite reservoir productivity evaluation method based on short DST testing is proposed by comprehensively considering the short DST testing time and the physical property change of the inner and outer zones of the multi-zone composite reservoir for the first time, which can realize the productivity evaluation of the composite reservoir in the development plan preparation stage of the deepwater oilfield, and improves the rationality and reliability of the productivity evaluation of the composite reservoir.

[0033] 2. The related parameters can be updated according to the actual DST testing well test interpretation results of the exploration well and the evaluation well, and the technical method is convenient, fast, strong in applicability and high in reliability.

[0034] 3. The method is not only suitable for deepwater composite reservoirs, but also can provide reference for productivity evaluation of other types of offshore reservoirs, such as offshore fault block reservoirs and offshore lithologic reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1is a schematic diagram of division of a DST test section of a three-zone composite reservoir in an embodiment of the present application.

[0036] Figure 2 is a schematic diagram of double logarithmic pressure and pressure derivative fitting results of a three-zone composite reservoir in an embodiment of the present application. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

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

[0039] S1, collecting original DST test data of a deepwater multi-zone composite reservoir, and screening data segments of preset conditions for well test interpretation to obtain well test interpretation results;

[0040] S2, extracting a selected number of production segments from the original DST test data, and calculating a DST test average oil productivity index based on each production segment;

[0041] S3, calculating an equivalent permeability of the composite reservoir in the test time according to the well test interpretation results;

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

[0043] S5, calculating a physical property change correction coefficient of the deepwater multi-zone composite reservoir according to the equivalent permeability of the composite reservoir and the well test interpretation results;

[0044] S6, calculating an oil productivity index during stable production according to the DST test average oil productivity index, the test time correction coefficient, and the physical property change correction coefficient of the deepwater multi-zone composite reservoir. Based on the oil productivity index during stable production, the stable productivity of a directional development well is evaluated in combination with the parameters of the directional development well.

[0045] The above method will be described in a more detailed embodiment in connection with more drawings.

[0046] The present application provides a deepwater multi-zone composite reservoir productivity evaluation method based on short DST testing, and the specific steps are as follows:

[0047] Collecting deep water reservoir DST test well bottom pressure data, test geology daily report, test basic data, dividing DST test work system, selecting the pressure recovery section with the longest shut-in time and the bottom hole flowing pressure without abnormal fluctuation to carry out well test interpretation, obtaining the composite reservoir formation original pressure p0, well test interpretation skin factor S, well test interpretation permeability k of each area of the composite reservoir i , radius r of each area of the composite reservoir i . This step is a common method in the field of offshore oil and gas production technology, which will not be repeated in the present application.

[0048] Taking a certain deep water oilfield at sea as an example, according to the DST test well bottom pressure data and test geology daily report, two main production sections and one pressure recovery section are divided, such as Figure 1 . Through well test interpretation, the three-zone composite reservoir model is used for interpretation, and the fitting effect of pressure and pressure derivative is good, such as Figure 2 . Through well test interpretation, the original formation pressure is 24.42 MPa, the well test interpretation skin factor is 0.314, and the well test interpretation permeability of each area from the inner area to the outer area is k1=3400 mD, k2=1500 mD, k3=650 mD, and the radii of the inner 1 area and the inner 2 area are r1=68 m and r2=208 m respectively, and the detection radius r eDST =446 m, and the specific parameters are shown in Table 1.

[0049]

[0050] Table 1

[0051] According to the test geology daily report, the production sections 1-3 with longer open well time and bottom hole flowing pressure without abnormal fluctuation are selected, and the DST test average specific oil production index J0 of each production section is calculated.

[0052] The specific calculation method is as follows:

[0053]

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

[0055] Taking a certain deep water oilfield at sea as an example, according to the DST test well bottom pressure data and test geology daily report, two main production sections are divided, and the parameters of each production section are combined with the well test interpretation results as shown in Table 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 was calculated:

[0059]

[0060] The equivalent permeability k during the well test time of the composite reservoir was calculated based on the well test interpretation parameters. a .

[0061] The specific calculation method is as follows:

[0062]

[0063] In the formula, k a For the equivalent permeability of the composite reservoir, mD; k i To interpret the permeability (mD) and r of each zone of the composite reservoir through well testing. eDST The DST test detection radius is in meters (m); r i Let r be the radius of each zone in the composite reservoir as interpreted from the pilot well, where r is the radius when i = m. m denoted as the detection radius of the DST test, in meters; m is the total number of composite reservoir zones interpreted from the pilot well, where m = 1, 2, 3, ...

[0064] Taking a deep-water oilfield at sea as an example, based on the well test interpretation parameters in Table 1, the equivalent permeability k of the three-zone composite reservoir exploration well during the test period is calculated. a :

[0065]

[0066] The test time correction coefficient D is calculated based on the test time, test baseline parameters, and well test interpretation parameters for each production section. t .

[0067] The specific calculation method is as follows:

[0068]

[0069]

[0070] In the formula, D tj A dimensionless correction factor for the test time of each production segment; k a For the equivalent permeability of the composite reservoir, mD; t j Duration of each production segment, in hr; Porosity (%); μ is the viscosity of the formation crude oil (mPa·s); C t The overall compressibility factor is expressed in MPa. -1; r w r is the DST test wellbore radius, m; S is the skin factor interpreted from the pilot well, decimal; r e is the drainage radius, m; n is the selected number of production intervals, n = 1, 2, 3,....

[0071] Taking a certain deepwater oilfield as an example, according to the well test interpretation parameter table 1 and the parameter table 2 of each production interval, the test time correction coefficient D t is calculated.

[0072]

[0073] According to the well test interpretation parameters and the test basic parameters, the composite reservoir physical property change correction coefficient D k is calculated.

[0074] The specific calculation method is:

[0075]

[0076] In the formula, k m is the outermost zone permeability of the composite reservoir interpreted from the well test, mD.

[0077] Taking a certain deepwater oilfield as an example, according to the well test interpretation parameter table 1 and the equivalent permeability k a of the pilot well in the test time of the composite reservoir, the composite reservoir physical property change correction coefficient D k is calculated.

[0078]

[0079] According to the test time correction coefficient D t and the composite reservoir physical property change correction coefficient D k , the specific oil recovery index J1 during stable production is calculated.

[0080] The specific calculation method is:

[0081] J1 = D t × D k × J0

[0082] Taking a certain deepwater oilfield as an example, according to the test time correction coefficient D t and the composite reservoir physical property change correction coefficient D k , the specific oil recovery index J1 during stable production is calculated.

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

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

[0085] The specific calculation method is:

[0086]

[0087] In the formula, Δp is the designed production pressure difference of the directional well, MPa; h dw is the well control effective thickness of the well arrangement area of the directional well, m; k dw is the average logging permeability of the well arrangement area of the directional well, mD; μ dw is the crude oil viscosity of the well arrangement area of the directional well, mPa·s; k c is the logging permeability of the tested section of the DST tested well, mD; S dw is the predicted skin factor of the directional well, mD.

[0088] Taking a deepwater oilfield at sea as an example, according to the well control effective thickness h dw of the well arrangement area of the directional development well determined by the geological professional research, the average logging permeability k dw is 400 mD, the crude oil viscosity μ dw is 2.584 mPa·s. According to the designed production pressure difference Δp of 2.0 MPa and the predicted skin factor S of 5 of the similar oilfield, the stable production capacity q of the directional well arranged in the complex reservoir is calculated based on the above parameters, the basic parameters of the DST test and the specific oil production index J1 in the stable production: o :

[0089]

[0090] In several embodiments provided by the present application, it should be understood that the disclosed method can be implemented by other ways. For example, the above-described device embodiments are only schematic, and for example, the division of the above units is only a logical function division, and there can be another division way in actual implementation, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0091] The above are only preferred embodiments of the present application, and are not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing, characterized in that, include: S1. Collect raw DST test data of deep-water multi-zone composite reservoirs, and select data segments with preset conditions for well test interpretation to obtain well test interpretation results; S2, based on the original DST test data, extract a selected number of production-producing sections, and calculate the average DST test specific oil recovery index based on each production-producing section; S3, Calculate the equivalent permeability of the composite reservoir during the test period based on the well test interpretation results; S4. Calculate the test time correction coefficient based on the data of each production section and the well test interpretation results; S5. Based on the equivalent permeability of the composite reservoir and the well test interpretation results, calculate the correction coefficient for the physical property changes of the deep-water multi-zone composite reservoir. S6. Calculate the specific oil recovery index during stable production based on the average specific oil recovery index of the DST test, the test time correction coefficient, and the property change correction coefficient of the deep-water multi-zone composite reservoir; evaluate the stable production capacity of the directional development well based on the specific oil recovery index during stable production and in conjunction with the parameters of the directional development well. In S6, the formula for calculating the stable production capacity of directional development wells is: In the formula, Δp Design production pressure differential for directional development wells; h dw To determine the effective thickness of well control in the well area for targeted development; k dw Average permeability of well logging in the well layout area for targeted development wells; dw To determine the viscosity of crude oil in the formation of the well area for targeted development; k c The well logging permeability of the test section of the DST test well; The specific oil recovery index is used to stabilize production. S To interpret the skin coefficient for well testing; r w The radius of the DST test wellbore; r e The oil drain radius; The viscosity of the formation crude oil; S dw Predicting the skin coefficient for directional wells.

2. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 1, characterized in that, In step S1, well testing interpretation is conducted on the pressure recovery section where there are no abnormal fluctuations in bottom hole flowing pressure and the longest shut-in time, to obtain the original pressure of the composite reservoir formation. p 0. Skin coefficient in well test interpretation S Interpretation of permeability from well tests in various zones of the complex reservoir k i Radius of each zone in the composite reservoir r i and the total number of partitions in a composite partition. m .

3. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 2, characterized in that, In S2, based on the daily geological test report, n production sections with longer well opening times and no abnormal fluctuations in bottom hole flowing pressure were selected, and the average specific oil recovery index of the DST test was calculated: In the formula, J 0 represents the average specific oil recovery index from DST tests in each production section; q j For each production segment, calculate the average daily oil production, m 3 / d; p wfj Minimum bottomhole flowing pressure for each production section; h Effectively contributes thickness to DST testing; n The total number of production segments selected is n, where n ranges from 1 to 3.

4. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 3, characterized in that, In S3, the equivalent permeability of the composite reservoir during the test period is calculated as follows: In the formula, Equivalent permeability for deep-water multi-zone composite reservoirs; r eDST is the DST test detection radius; ki is the well test interpretation permeability of each zone in the composite reservoir, where when i =m r m This represents the detection radius of the DST test.

5. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 4, characterized in that, In S4, the calculation method for the test time correction coefficient includes: In the formula, D tj Correction coefficients for the test time of each production segment; t j Duration of each production segment; Porosity; The viscosity of the formation crude oil; C t The overall compression coefficient; r w The radius of the DST test wellbore; r e The radius of the oil drain is denoted as .

6. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 5, characterized in that, The calculation method for the property change correction coefficient in S5 includes: 。 7. The method for evaluating the productivity of deep-water multi-zone composite reservoirs based on short-time DST testing according to claim 5, characterized in that, In S6, the formula for calculating the specific oil recovery index during stable production is as follows: 。

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