A method for evaluating and screening potential areas of oilfield adjustment wells

Abstract

The present invention provides a method for evaluating and screening potential areas of oilfield adjustment wells. Based on the evaluation of the implementation effect of oilfield development adjustment wells, the fuzzy evaluation and identification method is used to clarify the main controlling factors affecting the productivity of adjustment wells; the main controlling factors of productivity are comprehensively analyzed and judged, and the evaluation and screening indexes and their boundary values of risk areas and potential areas are optimized to establish the screening boundary conditions for potential areas; an evaluation index layer model is created in the three-dimensional geological model, and the evaluation and screening of potential areas of adjustment wells are quickly realized through the superposition of multiple layers and multiple attributes. In the development adjustment stage of oil and gas fields, the present invention evaluates and screens potential areas of adjustment wells based on the main controlling factors of productivity. The method is fast and effective, with high compliance and reliability, strong practicability and operability, effectively solves the timeliness problem of evaluating and screening potential areas of oil and gas field adjustment wells, and helps to improve the development speed of oil and gas fields.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and more specifically to a method for evaluating and screening potential areas of oilfield adjustment wells. Background Art

[0002] Development adjustment wells play an important role in increasing and stabilizing oil production in oilfields, and are crucial for improving the oilfield development effect, increasing the oil production rate, and enhancing the ultimate oil recovery rate of the oilfield. Adjustment wells are an important measure for adjustment and tapping potential during the development process of offshore oilfields. Continuously implementing adjustment well tapping potential according to local conditions is a necessary task for maintaining long-term stable production and increased production of oilfields. Conducting a full effect evaluation based on the implemented adjustment wells, deepening the re-understanding of geology and reservoir, and clarifying the adjustment potential areas are the basis for subsequent adjustment well strategy deployment and the guarantee for improving the success rate of adjustment well measures. The normal adjustment well tapping potential deployment work is based on fine reservoir description to clarify the remaining oil potential distribution, and then comprehensively study to determine the potential areas of adjustment wells. Relatively speaking, the research workload is large and the consumption cycle is long, and it is impossible to achieve rapid screening of potential areas. Summary of the Invention

[0003] The present invention overcomes the deficiencies in the prior art. There are certain timeliness problems in the evaluation and screening of potential areas of existing oil and gas field adjustment wells. A method for evaluating and screening potential areas of oilfield adjustment wells is provided. During the development and adjustment stage of oil and gas fields, the present invention evaluates and screens potential areas of adjustment wells based on the main factors controlling production capacity. The method is fast and effective, with high compliance and reliability, strong practicability and operability, and helps to improve the development speed of oil and gas fields.

[0004] The object of the present invention is achieved by the following technical solutions.

[0005] A method for evaluating and screening potential areas of oilfield adjustment wells is carried out according to the following steps:

[0006] Step 1, based on the production effect of development adjustment wells in oil and gas fields, comprehensively conduct statistical regression analysis from geological and development perspectives, and use fuzzy evaluation to identify the main factors controlling the production capacity of adjustment wells. For fault-block oil and gas reservoirs, structural factors, reservoir thickness, and waterflooded thickness are the main factors affecting the production capacity of adjustment wells;

[0007] Step 2, comprehensively analyze and evaluate the main factors controlling production capacity, optimize and determine the evaluation indexes of each factor, select the proportion of reservoir thickness, waterflooded proportion, and structural position as evaluation indexes, create an isogram of the proportion of reservoir thickness, an isogram of waterflooded proportion, and a structural isogram, and based on the statistical analysis of the production capacity of adjustment wells, determine the thickness proportion Y of potential areas and risk areas and the waterflooded proportion boundary value X;

[0008] Step 3: Based on the boundary values of evaluation indicators, comprehensively determine the screening criteria for potential areas, and establish the screening conditions for high-yield areas as follows: ① water flooding ratio < X; ② proportion of thick layer thickness ≥ Y; ③ high structural position; areas that do not meet these conditions are risk areas.

[0009] Step 4: Create an evaluation index layer model in the three-dimensional geological model. Based on the screening conditions, quickly realize the evaluation and screening of potential areas for adjustment wells through multi-layer and multi-attribute overlay. During actual adjustment and potential tapping, if the screening conditions are adjusted, the overlay area range will change, so that the corresponding potential areas can be quickly delineated.

[0010] Step 5: Use dynamic results to verify the reliability of the evaluation results. Overlay the potential areas with the current production status map, water flooding map, and oil reservoir pressure distribution map to verify the reliability of the potential areas, determine the potential degree and risk degree of the potential areas, and finally identify the favorable target areas for the deployment of adjustment wells.

[0011] In Step 1, for fault-block oil reservoirs, the oil-water distribution is mainly controlled by the structure. Based on the oil-water differentiation effect, the remaining oil is relatively enriched in the high structural position, followed by the middle part of the structure, and the worst is the bottom part of the structure; the reservoir thickness is proportional to the production capacity. The thicker the reservoir drilled, the better the reservoir development, the better the distribution, and the easier it is for oil wells to obtain high production capacity; the water flooding ratio, that is, the actual drilled water flooded thickness of the target layer divided by the actual drilled reservoir thickness of the target layer, generally shows an inverse relationship with the daily oil production. The smaller the drilled water flooded thickness and the water flooding ratio, the lower the recovery degree of the oil layer, and the easier it is for oil wells to obtain higher production capacity.

[0012] In Step 2, select the proportion of reservoir thickness, water flooding ratio, and structural position as the evaluation indicators for each factor, establish an evaluation index layer, and delineate the relevant boundary values of the evaluation indicators.

[0013] In Step 4, create an evaluation index layer model in the three-dimensional geological model, that is, the water flooding ratio layer Surface_FB, the proportion of thick layer thickness layer Surface_HB, and the contour map of the structural layer Surface_GZ. Based on the screening conditions, quickly realize the evaluation and screening of potential areas (Potential area) for adjustment wells through multi-layer and multi-attribute overlay. The potential area is expressed in the form of a set concept, that is: the potential area is the intersection area of the complement of the union of the water flooding ratio risk area and the proportion of thick layer thickness risk area and the high structural position area, and the expression is: Potential area = Cu((Surface_FB ≥ X) ∪ (Surface_HB < Y)) ∩ Surface_GZ_high. During actual adjustment and potential tapping, if the screening conditions are adjusted, the overlay area range will change, so that the corresponding potential areas can be quickly delineated.

[0014] In Step 5, use the dynamic results of the oil reservoir to verify the evaluation and screening results of the potential areas to improve the accuracy of determining the favorable target areas for the deployment of adjustment wells.

[0015] The beneficial effects of the present invention are as follows: During the development and adjustment stage of oil and gas fields, the potential areas of adjustment wells are evaluated and screened based on the main factors controlling production capacity. The method is fast and effective, with high compliance and reliability, strong practicability and operability, effectively solving the timeliness problem of evaluating and screening potential areas of adjustment wells in oil and gas fields, and helping to improve the development speed of oil and gas fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of screening potential areas in the F50 oil reservoir in Area A of a certain oilfield, where: 1 is the water flooding ratio level Surface_FB≥X, 2 is the proportion level of thick layer thickness Surface_HB<Y, 3 is the contour map of the structural level Surface_GZ, and 4 is the potential area (Potential area);

[0017] Figure 2 It is a schematic diagram of the superposition verification of the potential areas and the current production status map in the F50 oil reservoir in Area A of a certain oilfield; DETAILED DESCRIPTION OF THE INVENTION

[0018] The technical solutions of the present invention will be further described below through specific embodiments.

[0019] Taking the fault block reservoir of a certain oilfield in the Bohai Sea as an example, the specific implementation manner of the present invention will be further described in conjunction with the accompanying drawings.

[0020] Comprehensively statistically analyzing the production capacity of 14 adjustment wells in the main area of a certain oilfield in the Bohai Sea. Among them, 10 wells are located at the high or relatively high positions of the structure. The average daily oil production at the initial production stage is 88.8 m 3 / d. Excluding 2 wells with low production due to engineering reasons, the average daily oil production is 104.8 m 3 / d. There are 4 wells located at the middle position of the structure, and the average daily oil production at the initial production stage is 70 m 3 / d, indicating that the structural factor is closely related to the production capacity. Newly drilled adjustment wells at the high positions of the structure are more likely to obtain higher production capacity, which is consistent with the principles such as the oil-water differentiation effect and the effect of the structure on the oil-water distribution. The remaining oil is relatively enriched at the high positions of the structure, followed by the middle part of the structure, and the worst is the bottom part of the structure. Based on fuzzy evaluation and statistical analysis, it is considered that the drilled reservoir thickness and the water flooded thickness are two important factors affecting the production capacity of adjustment wells: ① The reservoir thickness is proportional to the production capacity. The thicker the drilled reservoir, the better the reservoir development, the better the distribution, and the easier it is for oil wells to obtain high production capacity. The larger the proportion of thick layers, the better the lateral extension and connectivity of the reservoir, and the greater the probability of high production for oil wells; ② The water flooding ratio is inversely proportional to the daily oil production. The smaller the drilled water flooded layer thickness and the smaller the water flooding ratio, the lower the exploitation degree of the reservoir, and the easier it is for oil wells to obtain higher production capacity. For example, the 4 wells with the highest production capacity at the initial production stage are Well A, Well B, Well C, and Well D, and the initial production capacities are 103 m 3 / d, 131 m 3 / d, 136m 3 / d, 150m 3 / d. The reservoir thicknesses drilled in the target interval are 78m, 103m, 77m, and 52m, and the water - flooded layer thicknesses drilled in the target interval are 17m, 40m, 3m, and 4m. The water - flooded ratios are 21.8%, 38.8%, 3.9%, and 7.7%. Among them, the reasons for the relatively high productivity of Well A, Well C, and Well D are that the drilled reservoir thickness is relatively large and the water - flooded layer thickness is small. The reason for the relatively high productivity of Well B is that the drilled reservoir thickness is relatively large, which is 103m, and the water - flooded layer thickness is medium. The main controlling factors affecting productivity are structural factors, reservoir thickness, and water - flooded thickness through comprehensive evaluation.

[0021] According to the statistical analysis of reservoir thickness and productivity, the isopach maps of the sand layer thickness ratio <2m and >5m in the target oil group are respectively drawn. The results show that the wells with unmet expected productivity are all located in the high - value area of the sand layer thickness ratio <2m and the low - value area of the sand layer thickness ratio >5m. This indicates that the greater the proportion of thin - layer thickness in the drilled reservoir, the smaller the possibility of a newly drilled well obtaining high production, while the greater the proportion of thick - layer thickness, the greater the possibility of a newly drilled well obtaining high production. Through comprehensive statistics, it is determined that the area with a thin - layer thickness ratio ≥30% and a thick - layer thickness ratio <30% is the risk area, and the area with a thick - layer thickness ratio ≥30% is the potential area. The isopach map of the water - flooded ratio in the target oil group is drawn, showing that the distribution of the water - flooded ratio on the plane is quite different. The wells with unmet expected productivity are located in the high - value area of the water - flooded ratio, indicating that the greater the water - flooded ratio, the smaller the possibility of a newly drilled well obtaining high production, and vice versa. Through comprehensive research, it is determined that the area with a low water - flooded layer ratio (water - flooded ratio <10%) is the potential area, and the area with a high water - flooded layer ratio (water - flooded ratio ≥20%) is the risk area.

[0022] Based on the evaluation indexes of reservoir thickness ratio and water - flooded ratio, combined with the structural position, the screening conditions for high - production areas are established: ① water - flooded ratio <10%, ② thick - layer thickness ratio ≥30%, ③ high - structural position. Then the screening conditions for risk areas are: ① water - flooded ratio ≥10%, ② thick - layer thickness ratio <30%, ③ low - structural position.

[0023] In the three - dimensional geological model, an evaluation index layer model (water - flooded ratio layer Surface_FB, thick - layer thickness ratio layer Surface_HB, structural layer isopach map Surface_GZ) is created. According to the screening conditions for high - production areas, after the superposition of the evaluation index layer models, the northeastern, central, and southern near - fault areas of the F50 oil group in Area A are selected as high - production potential areas.

[0024] Based on the superposition of dynamic results such as the exploitation status map, water flooding map, and oil reservoir pressure distribution map with potential areas, the reliability of potential areas is verified, the potential degree and risk degree of potential areas are clarified, so as to implement favorable target areas for the deployment of adjustment wells. The verification results of the exploitation status map show that: ① There are relatively few producing wells in the potential area in the northeast, and the well pattern can be further densified; ② Among the producing wells in the potential area in the middle, the production is mainly from the F80 and F100 oil groups, and relatively few other oil groups are perforated, leaving room for further potential tapping; ③ The producing wells in the potential area near the faults in the south generally have a high water cut, presenting certain risks. The superposition verification of the water flooding map shows that the water flooding degree of the main layers in the potential area in the northeast of Area A is relatively weak, the remaining oil is relatively enriched, and the potential for new wells to obtain high yields is relatively large. The verification of the reliability of the pressure situation shows that there is overpressure in the upper section of the main layers in the potential areas in the middle and south of Area A, indicating sufficient formation energy and strong liquid supply capacity, and a high probability of high yields for adjustment wells. However, there is a certain pressure deficit in the lower section of the main layers, indicating certain leakage risks during the drilling process. The verification of the reliability of the evaluation results by dynamic results shows that the three potential areas in the northeast, middle, and near the faults in the south of Area A have high potential for tapping and can be used as target areas for adjustment wells.

[0025] Based on the selected target areas for adjustment wells, the actually drilled adjustment wells all obtained relatively high production capacities, thus verifying the effectiveness of this method. Overall, the main factors controlling production capacity in this method are selected favorably, the guiding role of the evaluation indicators for potential areas of adjustment wells is obvious, the evaluation and screening method is fast and effective, and it has strong practicability and operability.

[0026] The above makes an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent replacement that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A method for evaluating and screening potential areas of oilfield adjustment wells, characterized in that: Proceed as follows: Step 1: Based on the production performance of the development adjustment wells in the oil and gas field, comprehensively conduct statistical regression analysis from multiple geological and development perspectives, and use fuzzy evaluation to identify the main controlling factors affecting the productivity of the adjustment wells. For fault-block oil and gas reservoirs, structural factors, reservoir thickness, and water-flooded thickness are the main factors affecting the productivity of the adjustment wells; Among them, in Step 1, for fault-block oil reservoirs, the oil-water distribution is mainly controlled by the structure. Based on the oil-water differentiation effect, the remaining oil is relatively enriched in the high part of the structure, followed by the middle part of the structure, and the worst in the bottom part of the structure; the reservoir thickness is proportional to the productivity. The thicker the reservoir drilled, the better the reservoir development, the better the distribution, and the easier it is for oil wells to obtain high productivity. That is, the area where the thin-layer thickness ratio ≥ 30% and the thick-layer thickness ratio < 30% is the risk area, and the area where the thick-layer thickness ratio ≥ 30% is the potential area; the water-flooded ratio, that is, the actual drilled water-flooded thickness of the target layer divided by the actual drilled reservoir thickness of the target layer, is generally inversely proportional to the daily oil production. The smaller the drilled water-flooded thickness and the smaller the water-flooded ratio, the lower the recovery degree of the oil layer, and the easier it is for oil wells to obtain higher productivity. That is, the area with a low water-flooded layer ratio where the water-flooded ratio < 10% is the potential area, and the area with a high water-flooded layer ratio where the water-flooded ratio ≥ 20% is the risk area; Step 2: Comprehensively analyze and evaluate the main controlling factors of productivity, optimize and determine the evaluation indicators for each factor, select the reservoir thickness ratio, water-flooded ratio, and structural position as the evaluation indicators, create an isoline map of the reservoir thickness ratio, an isoline map of the water-flooded ratio, and a structural isoline map, and based on the statistical analysis of the productivity of the adjustment wells, determine the thickness ratio Y and the water-flooded ratio limit value X of the potential area and the risk area; Among them, in Step 2, select the reservoir thickness ratio, water-flooded ratio, and structural position as the evaluation indicators for each factor, and establish an evaluation index layer to delineate the relevant limit values of the evaluation indicators; Step 3: Based on the limit values of the evaluation indicators, comprehensively determine the screening criteria for the potential area, and establish the screening conditions for the high-yield area as follows: ① The water-flooded ratio < X; ② The thick-layer thickness ratio ≥ Y; ③ The high part of the structure; Those that do not meet this condition are the risk areas; Based on the evaluation indicators of the reservoir thickness ratio and the water-flooded ratio, combined with the structural position, establish the screening conditions for the high-yield area: ① The water-flooded ratio < 10%, ② The thick-layer thickness ratio ≥ 30%, ③ The high part of the structure; Then the screening conditions for the risk area are: ① The water-flooded ratio ≥ 10%, ② The thick-layer thickness ratio < 30%, ③ The low part of the structure; Step 4: Create an evaluation index layer model in the 3D geological model, and quickly realize the evaluation and screening of the potential area of the adjustment wells through multi-layer and multi-attribute overlay based on the screening conditions. If the screening conditions are adjusted during actual adjustment and potential tapping, the overlay area range will change, so that the corresponding potential area can be quickly delineated; Among them, in step 4, an evaluation index layer model is created in the three-dimensional geological model, namely, the water flooding ratio layer Surface_FB, the thick layer thickness ratio layer Surface_HB, and the structural layer contour map Surface_GZ. Based on the screening conditions, the evaluation and screening of the potential area of the adjustment well are quickly realized by the superposition of multiple layers and multiple attributes. The potential area is expressed in the form of a set concept, that is: the potential area is the intersection area of the complement of the union of the water flooding ratio risk area and the thick layer thickness ratio risk area and the high structural area, and the expression is: Potential area = Cu((Surface_FB≥X)∪(Surface_HB<Y))∩Surface_GZ_high. In actual adjustment and potential tapping, if the screening conditions are adjusted, the range of the superposition area will change, so that the corresponding potential area can be quickly delineated; Step 5, use the dynamic results to verify the reliability of the evaluation results. Superimpose the potential area with the current production map, the water flooding map, and the oil reservoir pressure distribution map to verify the reliability of the potential area, determine the potential degree and risk degree of the potential area, and finally implement the favorable target area for the deployment of adjustment wells; Among them, in step 5, the dynamic results of the oil reservoir are used to verify the evaluation and screening results of the potential area to improve the determination accuracy of the favorable target area for the deployment of adjustment wells.

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