A method for converting and encrypting square and triangular water injection well patterns

Abstract

The present invention belongs to the field of oil reservoir development, and discloses a method for converting and densifying a square or triangular area water injection well network. The present invention provides a method for exploiting the remaining oil between wells in a water injection oil reservoir by densifying, adjusting, and converting the well network. According to the technical method of the present invention, on the one hand, the square well network can be adjusted to a triangular well network to adapt to the newly recognized geological features such as sedimentary microfacies, oil sand bodies, and flow units after water injection; on the other hand, it can also be a method for densifying and adjusting the well network to improve the oil production speed and recovery rate when the basic well network includes both a triangular well network and a square well network, that is, by converting the corner wells of the oil production wells in the anti-seven-point basic well network and the anti-nine-point basic well network into water injection wells, forming multiple and various new injection and production well groups.

Description

Technical Field

[0001] The invention belongs to the field of oil reservoir development, relates to an area water injection oil reservoir, and relates to a square and triangle area water injection well network conversion and encryption method; specifically, it relates to a square and triangle encryption adjustment method for an area water injection oil reservoir. Background Art

[0002] Water injection development practice and theoretical research have proved that for heterogeneous multi-layer oil reservoirs, area water injection is currently mostly used. Its characteristics are that water injection wells and production wells are arranged in the entire oil reservoir according to a certain geometric shape and density. In essence, the oil layer is divided into many smaller development units. One water injection well controls and affects multiple oil wells, and each oil well is affected by the water injection well in several directions at the same time. Its advantages are that the production wells are all located in the first line of water injection wells, which is conducive to the multi-directional effect of the oil wells; the water injection area is large and the effect is fast; the oil wells are supplied with water from multiple directions and the oil production rate is high. The layout of the basic well network with large well spacing in the early stage of development is convenient for later densification and adjustment. After years of water injection development, the reservoir heterogeneity and long-term water drive will cause uneven utilization of the oil layer, and the water flow advantage channel will gradually form between the injection and production wells. The water drive sweep coefficient will deteriorate, resulting in a decrease in the water storage rate of the oil reservoir or a slowdown in the growth rate, a decrease in the remaining oil saturation, a significant increase in the liquid production and water content of the oil wells, and a significant decrease in oil production. The remaining oil in the reservoir is in the form of highly dispersed "islands" and is difficult to mobilize. By using well network densification technology and deploying densified adjustment wells to exploit the remaining oil, the oil production rate and recovery rate will increase. However, the original injection and production well network can no longer meet production needs. The ratio of injection and production wells is unreasonable, the oil wells have insufficient fluid supply capacity, the liquid production is reduced, and the inefficient and ineffective water injection causes the water content of the oil wells to rise rapidly and the oil production to decrease, which seriously affects the development effect.

[0003] Therefore, for oil reservoirs in the middle and late stages of development, how to reasonably adjust and change the well network pattern, optimize the density adjustment method, optimize the water drive direction and liquid flow direction, fully utilize the remaining oil between wells, maximize the water drive swept volume, improve the development effect, and increase the recovery rate are issues that need to be urgently addressed in the actual production of oil fields. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art and solve the technical problems existing under the condition of densification of the basic well network in the middle and late stages of water injection oil reservoir development, the present invention provides a method for extracting the remaining oil between wells in water injection oil reservoirs by densifying, adjusting and converting the well network. According to the technical method of the present invention, on the one hand, the square well network can be adjusted to a triangular well network to adapt to the newly recognized geological features such as sedimentary microfacies, oil sand bodies, flow units, etc. after water injection; on the other hand, it can also be a method for densifying and adjusting the basic well network to improve the oil production speed and recovery rate when the basic well network includes both a triangular well network and a square well network, that is, by converting the oil production corner wells in the anti-seven-point basic well network and the anti-nine-point basic well network into water injection wells, forming multiple and various new injection and production well groups.

[0005] The above object of the present invention is achieved through the following technical solutions:

[0006] The first purpose of the present invention is to provide a method for adjusting the density of a square well pattern to a triangular well pattern, which is suitable for sedimentary phases such as belt-shaped oil sand bodies or river channels in a diagonal direction of 30°-60°.

[0007] Newly drilled water injection wells are deployed at the edge of the required adjustment direction, with east-west intensification, suitable for belt-shaped oil sand bodies or phase belts with an azimuth of about 60° in the north, south, and west directions. If the oil sand bodies are distributed along an azimuth of about 30°, the north-south edge wells can be intensified, and the same applies to other wells.

[0008] The envelope lines with injection wells and oil production wells as endpoints are the outer interfaces of the main water drive lines corresponding to homogeneity, isotropy, water-oil mobility ratio of 1, and 50% water content in the oil wells, i.e., the plane affected area of ​​the main water injection line. The shaded area is the newly added affected area after the square well pattern is transformed into a triangular reverse seven-point well pattern ( Figure 1 ), it can be seen that there is a significant improvement. Specifically, the plane wave coefficient obtained from the two-dimensional plane physical model is calculated by the following formula:

[0009]

[0010] Where: Ep is the plane sweep coefficient, a decimal; M is the oil-water mobility ratio; f w is the water content, a decimal; a1, a2, a3, a4, a5, a6 are geological constants.

[0011] When the oil layers in the original well pattern are isotropic and have basically the same thickness, the present invention also adopts a five-point method to convert the central side wells into an inverse nine-point method well pattern, and the ratio of injection and production wells is reduced from 1:1 to 1:3. The advantage is that the remaining oil-rich area is directly used to ensure that the water content of the infilled wells is low in the initial production period. The disadvantage is that the ratio of injection and production wells is greatly reduced. In order to achieve this injection-production balance, it is necessary to increase the water injection intensity of the central well of the water injection well, which increases the risk of water channeling and flooding. Figure 2 The present invention also adopts another method of filling the middle water injection wells of the main line and filling the middle wells of the side line at the same time, and the original water injection wells are converted into oil production wells, and the ratio of injection and production wells is still maintained at 1:1, such as Figure 2 As shown in Figure b. The advantage is that the ratio of injection and production wells remains unchanged, water injection and oil production are strengthened, and it is helpful to improve the oil production rate and water drive sweep coefficient. The disadvantage is that there are production risks of water injection wells turning into oil production wells, and the large number of newly drilled wells and high oil production intensity lead to accelerated production decline in the later period, which has the economic risk of poor economic benefits.

[0012] Due to the above-mentioned shortcomings and problems in the technical solution provided by the present invention, the second purpose of the present invention is to specifically provide a method for adjusting the encryption of the combined well network of the anti-seven-point + anti-nine-point basic well network composed of the triangular well network and the square well network of the water injection oil reservoir, including a new anti-seven-point well network, an anti-four-point well network, a five-point well network, and a multi-point encrypted well network.

[0013] In order to avoid the main line of strong flooding, the reinforcement wells of the anti-seven-point large well network are deployed in the middle of the edge of the anti-seven-point well network. After reinforcement, two sets of well networks are formed: the new anti-seven-point well network and multiple adjacent anti-four-point well networks. Among them, the new anti-seven-point well network maintains a hexagonal shape, consisting of 6 oil production wells and 1 water injection well. The water injection wells of the anti-four-point well network are converted from the oil production wells of the anti-seven-point basic well network. The anti-four-point well network is a triangle, consisting of 3 oil production corner wells and 1 water injection well center well.

[0014] The five-point well network consists of 4 oil production wells and 1 water injection well; the multi-point encrypted well network is a polygonal well network, consisting of 12 oil production wells and 1 water injection well.

[0015] The central well of the water injection well in the five-point well pattern is transformed from the oil production well in the reverse nine-point basic well pattern.

[0016] The combined well network densification adjustment method of the inverse seven-point + inverse nine-point basic well network composed of the triangular well network and the square well network of the water injection reservoir includes the combined densification well network units of the inverse seven-point well network, the inverse four-point well network, the five-point well network, and the polygonal well network.

[0017] The straight-line distance between the injection wells and the oil production wells in the inverted four-point well network is the injection-production well spacing; the injection-production well spacing between the injection wells and the oil production wells in the inverted four-point well network is 1 / 2 of the injection-production well spacing of the inverted seven-point basic well network, that is, 200m.

[0018] The injection and production well spacing of the reverse seven-point well network is equal to the injection and production well spacing of the reverse seven-point basic well network. times, that is 346m.

[0019] The injection and production well spacing of the reverse five-point well network is 1 / 2 of the injection and production well spacing of the reverse nine-point basic well network, that is, 200m. The injection and production well spacing of the multi-point well network is 400m (the distance between the injection well and the oil well side well) to 560m of the injection and production well spacing of the reverse nine-point basic well network.

[0020] (distance between water injection well and oil well corner well) times, that is, 400m~447m.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] The technical solution of the present invention solves the problems of unreasonable ratio of injection and production wells in oil reservoirs, insufficient fluid supply capacity of oil wells, insufficient water injection and water drive direction, inefficient and ineffective circulation of injected water, poor water injection effect, and difficulty in using the remaining oil between wells. It is of great significance to improve the utilization of reserves in such oil reservoirs, improve the water drive effect, and optimize the final recovery rate of oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the specification of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 It is a schematic diagram of the transformation of a square well network into a triangular (seven oblique and inverted points) well network.

[0025] Figure 2 The diagram is a schematic diagram of the transformation of a square well pattern into an inverted nine-point pattern and a small five-point pattern. Figure (a) is a schematic diagram of the transformation of a square well pattern into an inverted nine-point pattern. Figure (b) is a schematic diagram of the transformation of a square well pattern into a small five-point pattern.

[0026] Figure 3 It is a schematic diagram of the encryption adjustment method of reverse four points + reverse seven points and reverse five points + multi-point combination.

[0027] Figure 4 This is a comparison chart of recovery factors under different well pattern conditions.

[0028] In the figure: 1 oil production wells, 2 water injection wells, 3 water injection well infill wells, 4 original well network mainstream line envelope, 5 infill adjustment new well network mainstream line envelope A, 6 infill adjustment new well network mainstream line envelope B, 7 original well network edge line, 8 new well network edge line, 9 newly added affected area, 10 streamline schematic line, 11 oil production well infill wells, 12 five-point well network water injection well infill wells, 13 inverted four-point well network, 14 inverted seven-point well network, 15 five-point well network, 16 polygonal well network, 17 inverted seven-point basic well network, 18 inverted nine-point basic well network, 19 oil production wells, 20 water injection well center well, 21 oil production well infill wells, 22 oil wells converted to water injection wells. DETAILED DESCRIPTION

[0029] The present invention is described in detail below by specific embodiments, but the protection scope of the present invention is not limited. Unless otherwise specified, the methods adopted by the present invention are all conventional methods. It should be noted that, in the case of no conflict, the features in the embodiments and the embodiments in this application can be combined with each other. The present invention is described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0030] Example 1

[0031] Example 1 is implemented by taking the triangle reverse seven-point + square reverse nine-point combined well pattern as an example. All implementations are carried out on the basis of this design. Figure 3 .

[0032] Figure 3 In the figure, the black solid lines represent the inverse seven-point basic well network and the inverse nine-point basic well network. The regular hexagon represents the inverse seven-point basic well network, the well in the center is a water injection well, and the solid circles at the six corners represent the six oil production wells. The distance between the two oil production wells is 400m, the distance between the injection and production wells is also 400m, and the ratio of the number of injection and production wells is 1:2. The square adjacent to the regular hexagon represents the inverse nine-point basic well network, the well in the center is a water injection well, and the solid circles at the four corners represent the four corner wells of the oil production wells. The four solid circles located at the edge and evenly distributed represent the four side wells of the oil production wells. The distance between the two oil production wells is 400m, the distance between the water injection well and the side well of the oil production well is 400m, the distance between the water injection well and the corner well of the oil production well is 560m, and the ratio of the number of injection and production wells is 1:3.

[0033] After long-term water injection development, the first-line effective wells have changed from waterless production to high water content. The water drive on the main injection and production line is relatively sufficient, and the water flow advantage channel has been formed. However, in the area between the two oil production wells, the injected water is difficult to reach, and most of the remaining oil in the reservoir is retained between the wells. Using the infill well technology between these oil production wells can scientifically and rationally mobilize the remaining reserves and tap the remaining oil.

[0034] exist Figure 3 In the figure, the dotted line represents the infill well network line, and the small solid circle is the infill well. The double empty circle with arrows is the oil well converted into water injection well. In the early stage of infill well production, the number of oil production wells in the injection-production well group increased, while the number of water injection wells remained unchanged. The well group has a significant oil increase effect, and the water cut has dropped significantly.

[0035] As the infill wells are continuously mined, the ratio of injection wells to production wells is lower than the theoretical value due to the mismatch between the number of water injection wells and oil production wells, which cannot meet the needs of oil well discharge and the formation energy is difficult to maintain a high level. Increasing the amount of water injection can only make the flooding of high water content areas more serious, and the water drive effect of medium and low water content areas has not improved, and the remaining reserves cannot be reasonably used.

[0036] By applying the technical solution of the present invention, it is possible to effectively solve the contradictions of unreasonable ratio of injection and production wells in a well group, insufficient fluid supply capacity of oil wells, insufficient water drive direction, inefficient and ineffective circulation of injected water, and difficulty in mobilizing residual oil between wells, thereby tapping the residual oil between wells, increasing oil well production, and improving water drive effect.

[0037] exist Figure 3 In the reverse seven-point basic well pattern, the six oil-producing corner wells in the well pattern are transferred to injection after reaching high water cut, thus forming a combination of six or five reverse four-point infilled well patterns consisting of three oil-producing wells and one water injection well + one reverse seven-point infilled well pattern consisting of six oil-producing wells and one water injection well. These two well patterns are adjacent in plane, and the reverse seven-point infilled well pattern is located inside, while the small reverse four-point well pattern is evenly located outside.

[0038] Furthermore, the reverse seven-point infill well network is located inside the reverse seven-point basic well network, and consists of 6 oil production wells and a water injection well center well, which is at an angle of 30° to the reverse seven-point basic well network. The injection and production well spacing is 1 / 2 of the reverse seven-point basic well network spacing. The reverse four-point infill well network partially overlaps with the reverse seven-point basic well network. The injection wells of the reverse seven-point basic well network serve as the injection well center wells of the reverse four-point infill well network, and the production wells of the reverse four-point infill well network are shared with the production wells of the reverse seven-point infill well network. The ratio of injection and production wells is 1:3 to 1:2.

[0039] exist Figure 3 In the reverse nine-point basic well pattern, the four oil-producing corner wells in the well pattern were converted to water injection after reaching high water cut, thus forming a reverse five-point infill well pattern consisting of four oil-producing wells and one water injection well + a multi-point infill well pattern consisting of 12 oil-producing wells and one water injection well. The two well patterns are adjacent in plane, with the multi-point infill well pattern located inside and the small reverse five-point well pattern evenly located outside.

[0040] Furthermore, the multi-point infill well network is located inside the inverted nine-point basic well network, consisting of 12 oil production wells and a central water injection well. The injection and production well spacing is 1 / 2 of the inverted nine-point basic well network spacing. times. The reverse five-point infill well network partially overlaps with the reverse nine-point basic well network. The injection wells of the reverse nine-point basic well network serve as the injection well center wells of the reverse five-point infill well network, and the production wells of the reverse five-point infill well network are shared with the production wells of the multi-point infill well network. The ratio of injection and production wells is 1:4 to 1:1.

[0041] The numerical modeling method was used to compare the injection-production well pattern. In the late stage of water injection reservoir development, the mainstream injection-production line area has been strongly flooded. Inter-well infill wells were deployed in the basic well pattern to predict the ultimate recovery rate of the reservoir when the water cut of the oil wells reached more than 98%. Four schemes were compared: the inverted four-point + inverted seven-point combined infill well pattern, the inverted seven-point simple infill well pattern, the inverted five-point + multi-point combined infill well pattern (polygonal well pattern), and the inverted nine-point simple infill well pattern. The prediction results show that the inverted five-point + multi-point combined infill well pattern (polygonal well pattern) has the highest recovery rate, followed by the inverted four-point and inverted seven-point combined infill well pattern, and the inverted seven-point simple infill well pattern has the lowest recovery rate of 6.0%, and the inverted nine-point simple infill well pattern has a recovery rate of 6.8%. The inverted four-point and inverted seven-point combined infill well pattern has a recovery rate that is 1.7% higher than that of the inverted seven-point simple infill well pattern, and the inverted five-point + multi-point combined infill well pattern (polygonal well pattern) has a recovery rate that is 1.5% higher than that of the inverted nine-point simple infill well pattern. Although the number of oil-producing wells in the combined infill well network is less than that in the simple infill well network, the water drive effect is high and the displacement is more sufficient, resulting in a large amount of oil produced, a high final recovery rate and good economic benefits.

[0042] Industrial Applicability:

[0043] The application of the inverse four-point + inverse seven-point and five-point + multi-point combined encryption adjustment method can effectively improve the water drive degree and oil reservoir recovery rate.

[0044] K oilfield has been developed with water injection for many years and has entered the stage of extremely high water content, with a comprehensive water content of 91.3%. In the early stage, the anti-seven-point and anti-nine-point basic well pattern combination structures were adopted, such as Figure 3 As shown, it includes three groups of reverse seven-point and reverse nine-point basic well network structures arranged continuously. Each reverse seven-point basic well network includes a central water injection well and six oil production wells. The distance between oil production wells and between injection and production wells is 400m, and the ratio of injection and production wells is 1:2; each adjacent reverse nine-point basic well network includes a central water injection well, 4 oil production corner wells and 4 oil production side wells. The distance between two oil production wells is 400m, the distance between the water injection well and the oil production side well is 400m, and the distance between the water injection well and the oil production corner well is 560m, and the ratio of injection and production wells is 1:3.

[0045] After the comprehensive water content reaches 90%, comprehensive adjustments are implemented and intensified adjustment wells are deployed, forming the anti-seven-point intensified well network and the anti-nine-point intensified adjustment method. Figure 3 As shown. Since 2014, the infill wells have been implemented. The infill wells are located between adjacent oil wells with a well spacing of 200m. After the infill wells were put into production, the well group had a significant increase in production. The average daily oil production was more than twice that of the old wells, and the water content dropped by more than 20% on average. With the further development of water injection, the water content of the oil wells in the basic well network gradually increased to 95%, and some even reached 98%. There was no need to continue to produce oil, and they needed to be converted into water injection wells to displace the remaining oil between wells. As a result, the oil field was converted from the combination of the anti-seven-point basic well network and the anti-nine-point basic well network to the combination of anti-four-point + anti-seven-point and anti-five-point + multi-point four-point well networks. One set of well networks consists of an anti-seven-point large well network and 6 (or 5) anti-four-point small well networks, and the other set of well networks consists of a multi-point infill large well network and 4 anti-five-point small well networks.

[0046] In the in-depth well network of the combination of reverse four points and reverse seven points, the injection and production well spacing of the reverse four-point well network is 200m, and the injection and production well spacing of the reverse seven-point well network is 346m. In the in-depth well network of the combination of reverse five points and multiple points (polygonal well network), the injection and production well spacing of the reverse five-point well network is 200m, and the injection and production well spacing of the multiple-point in-depth well network is 400m to 447m.

[0047] After the full implementation of the conversion to water injection wells, the anti-four-point + anti-seven-point combination encrypted well network unit includes 7 injection and production well groups, namely 1 anti-seven-point large well group and 6 anti-four-point small well groups, including 12 oil production wells and 7 water injection wells. The daily oil production increased by 147.2t and the water cut decreased by 15.1%.

[0048] The anti-five-point + multi-point combined encrypted well network (polygonal well network) unit includes 5 injection and production well groups, namely 1 multi-point encrypted large well group and 4 anti-five-point small well groups, including 20 oil production wells and 5 water injection wells. The daily oil production increased by 186.0t and the water cut decreased by 17.2%.

[0049] The present invention provides a method for adjusting the densification of square well patterns, triangular well patterns and their combined well patterns for area water injection oil reservoirs, which solves the contradictions of unreasonable ratio of injection and production wells, insufficient fluid supply capacity of oil wells, insufficient water drive direction, inefficient and ineffective circulation of injected water, and difficulty in mobilizing residual oil between wells under the current basic well pattern densification conditions. The method is of great significance for realizing the improvement of reserve utilization, water drive effect, and crude oil production speed and recovery rate of such oil reservoirs.

[0050] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for adjusting the density of a combined well pattern of an inverse seven-point + inverse nine-point basic well pattern composed of a triangular well pattern and a square well pattern in a water injection reservoir, characterized in that: Including the new reverse seven-point well network, reverse four-point well network, five-point well network, and multi-point intensified well network; In order to avoid the main line of strong flooding, the oil production wells of the anti-seven-point basic well pattern are deployed in the middle of the anti-seven-point well pattern edge line. After the intensification, two sets of well patterns are formed: the new anti-seven-point well pattern and the adjacent anti-four-point well patterns. The new reverse seven-spot well pattern maintains a hexagonal shape and consists of six infill wells for oil production and one water injection well; The water injection wells of the reverse four-point well pattern are converted from the oil production wells of the reverse seven-point basic well pattern; The reverse four-point well pattern is triangular, consisting of three corner wells for oil production and one center well for water injection; The infill wells of the reverse nine-point basic well pattern are deployed at the midpoint of the line connecting two oil wells of the reverse nine-point basic well pattern; after infilling, two sets of well patterns are formed: a new multi-point infill well pattern and multiple adjacent five-point well patterns; The five-point well pattern consists of 4 oil production wells and 1 water injection well; the multi-point infill well pattern is a polygonal well pattern, consisting of 8 oil production infill wells, 4 reverse nine-point basic well pattern oil production well side wells and 1 water injection well; The center well of the water injection well in the five-point well pattern is transformed from the corner wells of the oil production wells in the reverse nine-point basic well pattern; The method for adjusting the combined well network densification of the inverse seven-point + inverse nine-point basic well network composed of the triangular well network and the square well network of the water injection reservoir includes a new inverse seven-point well network, an inverse four-point well network, a five-point well network, and a polygonal well network, and the intensified well network unit formed by the combination of the above well networks.

2. The method for adjusting the combined well pattern of the reverse seven-point + reverse nine-point basic well pattern composed of the triangular well pattern and the square well pattern of the water injection reservoir according to claim 1, characterized in that the reverse The straight-line distance between the injection wells and the oil production wells in the four-point well network is the injection-production well spacing; the injection-production well spacing between the injection wells and the oil production wells in the reverse four-point well network is 1 / 2 of the injection-production well spacing of the reverse seven-point basic well network, that is, 200m.

3. The method for adjusting the combined well pattern of the reverse seven-point + reverse nine-point basic well pattern composed of the triangular well pattern and the square well pattern of the water injection reservoir according to claim 2, characterized in that the reverse The injection and production well spacing of the seven-point well pattern is the reverse of the injection and production well spacing of the seven-point basic well pattern. times, that is 346m.

4. The method for adjusting the combined well pattern of the reverse seven-point + reverse nine-point basic well pattern composed of the triangular well pattern and the square well pattern of the water injection reservoir as claimed in claim 3, characterized in that the reverse The injection and production well spacing of the five-point well network is 1 / 2 of the injection and production well spacing of the reverse nine-point basic well network, that is, 200m. The injection and production well spacing of the multi-point well network is 1 / 2 of the injection and production well spacing of the reverse nine-point basic well network, that is, 400m. times, that is, 400m~447m.

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