A method for calculating oil increment of full release of offshore liquid-limited oilfield productivity

Abstract

The application discloses a kind of offshore liquid limited oilfield capacity full release oil increment calculation method, method includes: determining the liquid production capacity of research object oil well;Determine the maximum daily liquid production and platform life under existing facilities to maintain normal production;Determine index prediction time step;Index prediction under unlimited liquid condition is carried out to research object using reservoir numerical simulation;The first time step under liquid limited condition is carried out to carry out numerical simulation control condition setting;Carry out numerical simulation prediction;The latest prediction step is carried out to carry out numerical simulation control condition resetting under liquid limited condition;The total oil production of each time step under liquid limited condition is calculated;Total oil increment of capacity full release is calculated and the like steps.The application considers the water cut of single well in each time step when calculating the oil increment of basic scheme, fully assigns liquid to the well with lower water cut, realizes the maximum use of liquid of existing facilities under liquid limited condition, and the calculated oil increment of capacity full release of liquid limited oilfield is more reasonable and reliable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas field exploration and development, and particularly relates to a method for calculating oil increment of offshore limited-liquid oilfield capacity full release. BACKGROUND

[0002] The liquid production of offshore oilfield needs to go through a series of processes such as treatment and external transportation, which is restricted by economic cost, and the reserved amount of the scheme design is limited. After the change of the geological reservoir understanding, the liquid treatment and transportation capacity are often limited, which restricts the release of oilfield capacity. It is necessary to transform the treatment and external transportation equipment to further release the capacity of production wells and improve the final economic benefit of the oilfield. Therefore, it is of great and practical significance to reasonably predict the oil increment under the capacity release.

[0003] At present, the basic scheme for capacity release generally limits the liquid according to the liquid production index in proportion, and the oil increment under the liquid release is determined on this basis. Since the specific liquid production index does not consider the daily oil production capacity of each production well, the oil production of the basic scheme is less, and there is a phenomenon that the oil increment under the liquid release is large.

[0004] Therefore, it is urgent to establish a method for calculating the oil increment under the full release of the capacity of offshore limited-liquid oilfield, so as to guide the compilation of the oil increment scheme under the full release of the capacity of offshore limited-liquid oilfield. SUMMARY

[0005] The application is proposed to solve the problems in the prior art, and aims to provide a method for calculating the oil increment under the full release of the capacity of offshore limited-liquid oilfield.

[0006] The application is realized by the following technical scheme:

[0007] A method for calculating the oil increment under the full release of the capacity of offshore limited-liquid oilfield, comprising:

[0008] (I) determining the liquid production capacity of the research object oil well at different water cut stages:

[0009] According to the determined oil-water relative permeability curve, the dimensionless liquid production index of the oilfield at different water cut stages is calculated, and the liquid production capacity of the research object oil well at different water cut stages is calculated in combination with the oil well capacity;

[0010] (i) determining the oil well capacity of the research object oil well

[0011] a. The capacity of the well put into production is accurate according to the actual capacity after being put into production;

[0012] b. The capacity of the well not put into production is determined by analogy:

[0013] Firstly, the analog oil well is determined; then, the oil well capacity of the research object oil well is determined by using the method of mobility correction,

[0014] (ii) determining the oil-water relative permeability curve of the research object oil well

[0015] a. using the measured curve when the oil-water relative permeability curve is measured;

[0016] b. determined by analogy when there is no measured oil-water relative permeability curve;

[0017] (ii) determining the maximum daily liquid production and platform life under the existing facilities to maintain normal production

[0018] The specific method is: systematically combing the liquid treatment capacity and flow direction of the oilfield, determining the maximum daily liquid production that can maintain normal production under the existing facilities; the platform life is determined according to the scheme design, and the platform life is used to determine the prediction period;

[0019] (iii) determining the index prediction time step according to the prediction accuracy and prediction complexity

[0020] When using numerical simulation method to calculate the oil increment, it is necessary to determine a reasonable time step, and the determination of the time step is affected by the prediction accuracy and the prediction complexity. The smaller the time step, the higher the calculation accuracy and the higher the calculation complexity. The larger the time step, the lower the calculation accuracy and the lower the calculation complexity;

[0021] (iv) using numerical simulation to predict the index under the condition of unlimited liquid for the research object

[0022] Specifically: carrying out numerical simulation calculation under the condition of unlimited liquid according to the liquid production capacity of the research object calculated in step (i), outputting the daily liquid production at any time step; comparing the daily liquid production of the oilfield with the maximum daily liquid production under the existing facilities to maintain normal production, selecting the first time step that exceeds the maximum daily liquid production under the existing facilities to maintain normal production as the first liquid-limited time step, outputting the oil production at any time step, and calculating the total oil production at each time step under the condition of unlimited liquid;

[0023] (v) setting the numerical simulation control conditions under the condition of liquid limitation for the first liquid-limited time step

[0024] Specifically, the total liquid release amount of the first liquid limiting time step is calculated, which is the difference between the maximum daily liquid production amount that can be maintained under the existing facilities and the daily liquid production amount of the previous time step. If the first liquid limiting time step is the first time step, i.e., there is no daily liquid production amount prediction result of the previous time step, the daily liquid production amount of the previous time step is treated as zero. Then, the oil wells are sorted in ascending order of water cut in the first liquid limiting time step, and the liquid release amount of each oil well in the first liquid limiting time step is calculated. The liquid release amount of each oil well in the first liquid limiting time step is the difference between the daily liquid production capacity of each oil well under the water cut in the first liquid limiting time step and the daily liquid production amount of the well in the previous time step. The releasable liquid amount is preferentially allocated to wells with low water cut until the total liquid release amount is distributed.

[0025] (VI) numerical simulation prediction is carried out on the step after setting the numerical simulation control conditions, and it is judged whether the prediction period is reached. If the prediction period is reached, step (VIII) is entered, and if the prediction period is not reached, the next time step numerical simulation prediction is carried out and step (VII) is entered.

[0026] (VII) re-setting the numerical simulation control conditions under the liquid limiting condition for the latest predicted step;

[0027] The specific method is as follows: after setting the numerical simulation control conditions, the daily liquid production amount of the next time step is judged to see if it reaches the maximum daily liquid production amount that can be maintained under the existing facilities. If it reaches the maximum daily liquid production amount that can be maintained under the existing facilities, the numerical simulation control conditions are kept unchanged and returned to step (VI). If it does not reach the maximum daily liquid production amount that can be maintained under the existing facilities, it is judged whether the daily liquid production amount of all wells reaches the maximum liquid production capacity. If the daily liquid production amount of all wells reaches the maximum liquid production capacity, the numerical simulation control conditions are kept unchanged and returned to step (VI). If the daily liquid production amount of some wells still does not reach the maximum liquid production capacity, the total liquid release amount of the time step is calculated, which is the difference between the maximum daily liquid production amount that can be maintained under the existing facilities and the daily liquid production amount of the oilfield in the time step. The oil wells are sorted in ascending order of water cut in the time step, and the liquid release amount of each oil well in the time step is calculated. The liquid release amount of each oil well in the time step is the difference between the daily liquid production capacity under the water cut in the time step and the daily liquid production amount of the well in the time step. The releasable liquid amount is preferentially allocated to wells with low water cut until the total liquid release amount is distributed, and step (VI) is entered.

[0028] (VIII) calculating the total oil production amount of each time step under the liquid limiting condition: the oil production amounts of all time steps under the liquid limiting condition are added up to obtain the total oil production amount of each time step under the liquid limiting condition;

[0029] (IX) Calculate the total incremental oil production of full capacity release

[0030] The total incremental oil production of full capacity release is equal to the total oil production of each time step under the unlimited liquid condition obtained in step (IV) minus the total oil production of each time step under the liquid limited condition obtained in step (VIII).

[0031] The beneficial effects of the present application are:

[0032] The present application provides a method for calculating the incremental oil production of full capacity release of offshore liquid-limited oilfields. In the calculation of the incremental oil production of the basic scheme, the water cut of each well in each time step is considered, and the liquid volume is fully assigned to the wells with lower water cut, thereby realizing the maximum utilization of the liquid volume of the existing facilities under the liquid-limited condition. The incremental oil production of full capacity release of the liquid-limited oilfield calculated is more reasonable and reliable, which can effectively guide the facility modification of the liquid-limited oilfield. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The flowchart of the method for calculating the incremental oil production of full capacity release of offshore liquid-limited oilfields.

[0034] For those skilled in the art, other related drawings can be obtained according to the above drawings without creative labor. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be further described below in combination with the drawings of the specification and through specific embodiments.

[0036] Example 1

[0037] According to the flowchart shown in Figure 1 , the method for calculating the incremental oil production of full capacity release of offshore liquid-limited oilfields is used to calculate the incremental oil production of Bohai X oilfield, which specifically includes the following steps:

[0038] (I) Calculate the dimensionless liquid production index of the oilfield at different water cut stages according to the determined oil-water relative permeability curve of the research object, and calculate the liquid production capacity of the oil well of the research object at different water cut stages in combination with the oil well productivity of the research object:

[0039] Bohai X oilfield was put into production in 2022, a total of 8 oil wells were implemented, among which 4 oil wells H1, H3, H4 and H7 were put into production in 2022, and the other 4 oil wells H2, H5, H6 and H8 were put into production in 2023. The daily oil production capacity of H1, H2, H3, H4, H5, H6, H7 and H8 in the first year of production is 90, 102, 90, 100, 137, 110, 94 and 105 respectively. Bohai X oilfield has 5 measured oil-water relative permeability curves. According to the normalization results of the 5 measured oil-water relative permeability curves and the oil well productivity, the maximum daily liquid production capacity of H1, H2, H3, H4, H5, H6, H7 and H8 is 620, 589, 502, 622, 658, 651, 600 and 651 respectively.

[0040] (II) Determine the maximum daily liquid production capacity to maintain normal production under existing facilities and platform life:

[0041] The maximum liquid treatment capacity of Bohai X oilfield is 4500 m3 / d, and the maximum export capacity is 4000 m3 / d, so the maximum daily liquid production capacity that Bohai X oilfield can maintain normal production is 4000 m3 / d, and the designed platform life is 15 years.

[0042] (III) Determine the index prediction time step based on the prediction accuracy and prediction complexity:

[0043] The index prediction time step of Bohai X oilfield is determined to be 1 year based on the prediction accuracy and prediction complexity.

[0044] (IV) Use numerical simulation of the research object to predict the index under unlimited liquid conditions:

[0045] The development index prediction results of Bohai X oilfield under unlimited liquid conditions are shown in Table 1. Comparing the daily liquid production of Bohai X oilfield with the maximum daily liquid production that can maintain normal production under existing facilities, the daily liquid production of the oilfield in 2026 is 4419 m3 / d, which exceeds the maximum daily liquid production that Bohai X oilfield can maintain normal production of 4000 m3 / d. Therefore, 2026 is the first time step for liquid limitation, and the total oil production of Bohai X oilfield under unlimited liquid conditions is 185.68 million m3 through the summation of annual oil production.

[0046] (V) Set the numerical simulation control conditions under liquid limitation for the first time step of liquid limitation

[0047] Table 1 Development index prediction results of Bohai X oilfield under unlimited liquid conditions

[0048]

[0049]

[0050] From table 1, the daily liquid production of the last time step 2025 of the first time step of liquid limiting in Bohai X oilfield is 3709 cubic meters, the total liquid release of the first time step of liquid limiting in 2026 is 291 cubic meters, the water cut of H1, H2, H3, H4, H5, H6, H7 and H8 in the first time step of liquid limiting in 2026 is 94.2%, 87.8%, 87.4%, 92.6%, 91.3%, 86.7%, 83.1% and 86.7% respectively, according to the order of low to high priority liquid release, it is H7, H6, H8, H2, H3, H5, H4 and H1, the liquid release of H7, H6, H8, H2, H3, H5, H4 and H1 in the first time step of liquid limiting is 89 cubic meters, 120 cubic meters, 120 cubic meters, 129 cubic meters, 52 cubic meters, 118 cubic meters, 82 cubic meters and 0 cubic meters respectively, the releasable liquid of 291 cubic meters is preferentially allocated to H7, H6 and H8, and the liquid allocated to H7, H6 and H8 is 89 cubic meters, 120 cubic meters and 82 cubic meters respectively.

[0051] (VI) numerical simulation prediction is carried out on the step after setting the numerical simulation control condition, whether the prediction period is reached is judged, if the prediction period is reached, step (VIII) is entered, if the prediction period is not reached, the next time step numerical simulation prediction is carried out, step (VII) is entered;

[0052] (VI) numerical simulation prediction is carried out on the step after setting the numerical simulation control condition, whether the prediction period is reached is judged, if the prediction period is reached, step (VIII) is entered, if the prediction period is not reached, the next time step numerical simulation prediction is carried out, step (VII) is entered;

[0053] (VII) numerical simulation control condition is re-set under the condition of liquid limiting for the latest prediction step;

[0054] After setting the numerical simulation control conditions for the liquid-limited time step in 2026, numerical simulation prediction was carried out for 2026, which is the 5th year of the prediction scheme. Since the prediction period has not been reached, numerical simulation prediction for 2027 was carried out, entering step (VII). After setting the numerical simulation control conditions, the next time step of daily liquid production was judged to see if it reached the maximum daily liquid production that could be maintained under existing facilities. The daily liquid production of Bohai X Oilfield in 2027 was 4000 m3 / d, reaching the maximum daily liquid production that could be maintained under normal production. The numerical simulation control conditions were kept unchanged, and step (VI) was returned to. In 2027, the 6th year of the prediction scheme, the prediction period has not been reached, and numerical simulation prediction for 2028 was carried out, entering step (VII). The daily liquid production of Bohai X Oilfield in 2028 was 4000 m3 / d, reaching the maximum daily liquid production that could be maintained under normal production. The numerical simulation control conditions were kept unchanged, and step (VI) was returned to. In 2028, the 7th year of the prediction scheme, the prediction period has not been reached, and numerical simulation prediction for 2029 was carried out, entering step (VII). The daily liquid production of Bohai X Oilfield in 2029 was 4000 m3 / d, reaching the maximum daily liquid production that could be maintained under normal production. The numerical simulation control conditions were kept unchanged, and step (VI) was returned to. In 2029, the 8th year of the prediction scheme, the prediction period has not been reached, and numerical simulation prediction for 2030 was carried out, entering step (VII). The daily liquid production of Bohai X Oilfield in 2030 was 4000 m3 / d, reaching the maximum daily liquid production that could be maintained under normal production. The numerical simulation control conditions were kept unchanged, and step (VI) was returned to. In 2030, the 9th year of the prediction scheme, the prediction period has not been reached, and numerical simulation prediction for 2031 was carried out, entering step (VII). The daily liquid production of Bohai X Oilfield in 2031 was 4000 m3 / d, reaching the maximum daily liquid production that could be maintained under normal production. The numerical simulation control conditions were kept unchanged, and step (VI) was returned to. In 2031, the 10th year of the prediction scheme, the prediction period has not been reached, and numerical simulation prediction for 2032 was carried out, entering step (VII). The daily liquid production of Bohai X Oilfield in 2032 was 3380 m3 / d, which did not reach the maximum daily liquid production that could be maintained under existing facilities. The main reason is that H1 reached the shut-in condition and was shut in. The daily liquid production of H2, H3, H4, H5, H6, H7 and H8 did not reach the maximum liquid production capacity. The total liquid release amount calculated for this time step was 620 m3 / d. The water cut of H2, H3, H4, H5, H6, H7 and H8 in 2032 was 93.5%, 93.3%, 97.9%, 93.9%, 95.9%, 93.4% and 92.9%, the order of priority release liquid volume from low to high is H8, H3, H7, H2, H5, H6 and H4, the liquid volume required to be released in 2032 for H8, H3, H7, H2, H5, H6 and H4 is 149 m3 / day, 52 m3 / day, 192 m3 / day, 129 m3 / day, 118 m3 / day, 171 m3 / day and 82 m3 / day respectively, the releasable liquid volume of 620 m3 / day is preferentially allocated to H8, H3, H7, H2 and H5, the allocated liquid volume of H8, H3, H7, H2 and H5 is 149 m3 / day, 52 m3 / day, 192 m3 / day, 129 m3 / day and 98 m3 / day respectively.

[0055] After setting the numerical simulation control conditions of the liquid-limited time step in Bohai X Oilfield in 2032, numerical simulation prediction was carried out, 2032 was the 11th year of the scheme prediction, and the prediction period was not reached, numerical simulation prediction in 2033 was carried out, and step (VII) was entered, the daily liquid production of Bohai X Oilfield in 2033 was 3460 m3 / day, which did not reach the maximum daily liquid production that could be maintained under the existing facilities, the main reason was that H4 reached the shut-in condition and shut-in was carried out, the daily liquid production of H5 and H6 did not reach the maximum liquid production capacity, the total releasable liquid volume in this time step was calculated to be 540 m3 / day, the water cut of H2, H3, H5, H6, H7 and H8 in 2033 was 94.4%, 93.8%, 94.2%, 96.6%, 93.3% and 94.0% respectively, the order of priority release liquid volume from low to high was H7, H3, H8, H5, H2 and H6, the liquid volume required to be released in 2033 for H7, H3, H8, H5, H2 and H6 was 0 m3 / day, 0 m3 / day, 0 m3 / day, 20 m3 / day, 0 m3 / day and 171 m3 / day respectively, the releasable liquid volume of 620 m3 / day was preferentially allocated to H5 and H6, the allocated liquid volume of H5 and H6 was 20 m3 / day and 171 m3 / day respectively, by which all single wells had reached the maximum daily liquid production, the numerical simulation control conditions were unchanged and numerical simulation research was carried out until the prediction period was reached;

[0056] (VIII) Calculate the total oil production of each time step under the liquid-limited condition;

[0057] The total oil production of each time step under the liquid-limited condition was obtained by adding up the oil production of all time steps under the liquid-limited condition, and the total oil production of each time step under the liquid-limited condition of Bohai X Oilfield was obtained by adding up the oil production of all time steps of Bohai X Oilfield, which was 1.795 million m3;

[0058] (IX) Calculate the total incremental oil production of full capacity release.

[0059] The total oil production of each time step of Bohai X Oilfield under the non-liquid-limited condition was obtained by calculating step (IV), which was 1.8567 million m3, the total oil production of each time step under the liquid-limited condition was obtained by subtracting step (VIII), and the total incremental oil production of full capacity release was 60.7 thousand m3.

[0060] The method of the present application calculates the oil increment of the base scheme by time step numerical simulation condition control, and distributes the releasable liquid volume according to the water cut and the liquid production capacity of the single well, so that the maximum utilization of the facility liquid volume under the liquid limiting condition is realized, and the calculation result is more real and reliable. In the existing methods, the consideration of liquid distribution according to the oil production and liquid production capacity of the single well is rarely seen, and the evaluation result of the present application is more reasonable and reliable.

[0061] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for calculating the increase in oil production from fully released offshore liquid-limiting oilfields, characterized in that: Includes the following steps: (I) Determine the production capacity of the oil wells of the research object: Calculate the dimensionless production index of the oil field at different water cut stages based on the oil-water relative permeability curve of the research object, and calculate the production capacity of the oil wells of the research object at different water cut stages in combination with the production capacity of the oil wells of the research object. (II) Determine the maximum daily liquid production and platform life for maintaining normal production under existing facilities; (III) Determine the forecast time step for the indicators by comprehensively considering the forecast accuracy and forecast complexity; (IV) Predict the indicators of the research object under unlimited liquid conditions using reservoir numerical simulation; (V) Set the control conditions for numerical simulation under the liquid-limiting condition at the first time step of the liquid-limiting process; The specific method for step (V) is as follows: (i) Calculate the total amount of liquid that can be released at the first time step of the liquid limiting process compared to the previous time step; (ii) Sort the oil wells according to the water cut of the single wells from low to high within the first time step of the liquid limit, and calculate the amount of liquid that each oil well needs to release in the first time step of the liquid limit; (iii) Prioritize allocating the releaseable fluid volume to wells with low water cut until the total releaseable fluid volume has been allocated; (VI) Perform numerical simulation prediction on the step size after setting the numerical simulation control conditions, and determine whether the prediction period has been reached. If the prediction period has been reached, proceed to step (VIII); if the prediction period has not been reached, proceed to step (VII). (VII) Reset the control conditions for numerical simulation under limited liquid conditions for the latest predicted step size; The specific method for resetting step (VII) is as follows: Determine whether the daily fluid production at the next time step after setting the numerical simulation control conditions reaches the maximum daily fluid production for maintaining normal production under the existing facilities. If it does, keep the numerical simulation control conditions unchanged and return to step (VI). If it does not, determine whether the daily fluid production of all wells has reached the maximum production capacity. If it has reached the maximum production capacity, keep the numerical simulation control conditions unchanged and return to step (VI). If there are wells that have not reached the maximum production capacity, calculate the total fluid volume that can be released at that time step. The total release volume is the difference between the maximum daily production volume that can maintain normal production under existing facilities and the daily production volume of the oilfield at this time step. The oil wells are sorted from low to high water cut within this time step. The volume of fluid to be released by each oil well at this time step is calculated. The volume of fluid to be released by each oil well at this time step is the difference between the daily production capacity under water cut at this time step and the daily production volume of the well at this time step. The release volume is preferentially allocated to wells with low water cut until the total release volume is allocated, and then proceed to step (VI). (VIII) Calculate the total oil production at each time step under the limited liquid condition; (IX) Calculate the total increase in oil production when production capacity is fully released.

2. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: When the research object is a well that has been put into production, the oil well production capacity in step (I) shall be based on the actual production capacity after production; when the research object is a well that has not been put into production, the oil well production capacity in step (I) shall be determined by analogy based on the actual production capacity after production.

3. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: For research objects with measured oil-water relative permeability curves, the measured curves shall be used in step (I); for research objects without measured oil-water relative permeability curves, the oil-water relative permeability curves shall be determined by analogy in step (I).

4. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: The determination of the maximum daily liquid production in step (II) is obtained by systematically analyzing the oilfield's liquid processing capacity and logistics flow; the platform lifespan is determined according to the scheme design.

5. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: The specific method of step (IV) is as follows: based on the fluid production capacity of the research object oil well calculated in step (I), conduct numerical simulation calculations under unlimited fluid conditions, and output the daily fluid production at any time step; compare the daily fluid production of the oil field with the maximum daily fluid production under existing facilities to maintain normal production, select the first time step that exceeds the maximum daily fluid production under existing facilities as the first time step of fluid limitation, output the oil production at any time step, and calculate the total oil production at each time step under unlimited fluid conditions.

6. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: The total amount of liquid that can be released in the first time step of the liquid restriction compared to the previous time step is the difference between the maximum daily liquid production that can maintain normal production under existing facilities and the daily liquid production of the oilfield in the previous time step. If the first time step of the liquid restriction is the first time step, then the daily liquid production of the oil well in the previous time step is treated as zero. The amount of liquid that each oil well needs to release in the first time step of the liquid restriction is the difference between the daily liquid production capacity of each oil well under water cut in the first time step of the liquid restriction and the daily liquid production of that well in the previous time step.

7. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: The total oil production at each time step under the liquid-limited condition in step (VIII) is obtained by summing up the oil production at all time steps under the liquid-limited condition.

8. The method for calculating the increased oil production from fully released offshore liquid-limited oilfields according to claim 1, characterized in that: In step (IX), the total increase in oil production due to full capacity release is equal to the total oil production at each time step under the unrestricted liquid condition obtained in step (IV) minus the total oil production at each time step under the restricted liquid condition obtained in step (VIII).

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