A method of establishing an injection-production pattern between different sand body reservoirs

Abstract

The application provides a method for establishing injection-production well pattern between different sand body reservoirs, and belongs to the technical field of oilfield development. The method comprises the following steps: determining the positions of the sand body reservoirs according to the spatial distribution development conditions of the reservoirs, and setting a plurality of sand body reservoirs with overlapping parts in the longitudinal direction as target reservoirs; connecting the overlapping parts of the sand body reservoirs in the target reservoirs through an intermediate well, the two sand body reservoirs connected in the target reservoirs are a first reservoir and a second reservoir, and the intermediate well is an existing well or a newly drilled well in the overlapping part of the target reservoir in the longitudinal direction; plugging the intermediate well, the plugging position is located in the upper part of the sand body reservoir above the intermediate well connection, and the plugging is also set when the lower part of the sand body reservoir below the intermediate well connection is not the bottom of the well; taking the well far from one end of the first reservoir and the intermediate well as an injection well, and taking the well far from one end of the second reservoir and the intermediate well as a production well, and then water injection and oil displacement are carried out, so that the injection-production well pattern between different sand body reservoirs is established for development.

Description

Technical Field

[0001] This invention provides a method for establishing an injection-production well network between different sandstone reservoirs, belonging to the field of oilfield development technology. Background Technology

[0002] With the development of petroleum science and technology, in order to further improve reservoir recovery, oilfield development methods have successively included primary oil recovery, secondary oil recovery, and tertiary oil recovery. Primary oil recovery mainly utilizes the natural energy contained within the reservoir itself for extraction. Secondary oil recovery involves artificially supplementing formation energy, such as water injection and gas injection. Tertiary oil recovery employs various physical and chemical methods to alter the properties of crude oil and its adsorption to rocks, thereby further improving reservoir recovery. Generally speaking, the recovery rate of primary oil recovery is less than 15%, secondary oil recovery can reach 45% or even higher, and tertiary oil recovery can reach over 50%, even 90%. From a comprehensive benefit perspective, primary oil recovery requires the least investment but also has the lowest recovery rate. Tertiary oil recovery has the highest recovery rate but also requires the most investment. Secondary oil recovery, especially water injection to supplement formation energy, offers the best benefits due to the wide availability of water, ease of engineering construction, and good water drive effect. Water injection development has become the most widely used oil recovery method in the world. In the 1950s, my country began to extract oil through water injection. To date, water injection technology is used in about 95% of my country's oil reservoir development. Water injection has long been the main method of oil reservoir development in my country, and how to better develop and apply water injection technology has received widespread attention and importance.

[0003] Currently, research and application of water injection development technology mainly focus on aspects such as development layer division, injection-production well network deployment, water injection timing selection, injection-production intensity adjustment, and injection-production process matching. The key to further improving reservoir recovery lies in developing an efficient reservoir development adjustment plan. Before developing such a plan, it is essential to understand the spatial distribution patterns of reservoirs and their connectivity between oil and water wells. Based on interconnected reservoirs, a reasonable injection-production well network should be deployed. Water injection development can maximize water-driven reserve control and utilization, and optimize and implement effective remaining oil tapping measures. However, if the sandstone reservoirs are not identical and are not interconnected, it is impossible to establish an injection-production well network suitable for different sandstone reservoirs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for establishing an injection-production well network between different sandstone reservoirs, in order to solve the problem that existing technologies make it difficult to inject water into poorly developed or late-stage sandstone reservoirs or result in low water injection development efficiency.

[0005] To achieve the above objectives, the present invention provides a method for establishing an injection-production well network between different sandstone reservoirs, comprising the following steps: 1) determining the location of each sandstone reservoir based on the spatial distribution and development of the reservoir; designating two sandstone reservoirs with overlapping portions in the longitudinal direction as target reservoirs; 2) connecting the overlapping portions of the sandstone reservoirs in the target reservoirs through an intermediate well, wherein the two connected sandstone reservoirs are the first reservoir and the second reservoir, and the intermediate well is an existing well or a newly drilled well within the overlapping portion in the longitudinal direction of the target reservoir; 3) sealing the intermediate well, wherein the sealing position is located at the upper part of the sandstone reservoir connected to the intermediate well, and sealing is also performed when the lower part of the sandstone reservoir connected to the intermediate well is not the bottom of the well; 4) designating the well at the end of the first reservoir furthest from the intermediate well as a water injection well, and the well at the end of the second reservoir furthest from the intermediate well as an oil production well, for water injection and oil displacement.

[0006] For poorly developed sandstone reservoirs, there are no locations required to simultaneously establish water injection wells and production wells, making water injection development difficult. For individual sandstone reservoirs in the later stages of development, existing water injection and production wells are ineffective for water displacement. This invention addresses this by jointly developing poorly developed and late-stage oil-producing sandstone reservoirs, aiming to further tap into the remaining oil in the reservoirs. It establishes a network of water injection wells between relatively small or late-stage unconnected sandstone reservoirs, significantly improving reservoir recovery.

[0007] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, the connectivity between sandstone reservoirs is determined based on the spatial distribution and development of the reservoirs, and connected sandstone reservoirs are regarded as a single sandstone reservoir.

[0008] Furthermore, in the above method for establishing an injection-production well network among different sandstone reservoirs, the development range of the multiple sandstone reservoirs mentioned in step 1) cannot simultaneously meet the conditions for establishing an injection-production well network of water injection wells and oil production wells.

[0009] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, the plugging method in step 3) includes cement plugging and drop-out tool method.

[0010] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, when using the cement plug method, the length L of the cement plug should be greater than a set value, wherein the set value L is:

[0011] L=P / (π·τ·D)

[0012] Where P is the reservoir pressure borne by the cement plug, π is pi, τ is the bonding strength between the cement plug and the casing, and D is the inner diameter of the casing.

[0013] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, if there is no sandstone reservoir above the cement plug that is connected to the intermediate well, the reservoir pressure borne by the cement plug is the reservoir pressure below the cement plug; if there is a sandstone reservoir above the cement plug that is connected to the intermediate well, the reservoir pressure borne by the cement plug is the pressure difference between the reservoir pressure above the cement plug and the reservoir pressure below the cement plug.

[0014] This invention uses cement plugging to seal intermediate wells, giving full play to the multiple functions of intermediate wells. While providing a water injection channel for oil displacement, intermediate wells can also continue to act as water injection wells to inject water into other sandstone reservoirs or as production wells to continue to extract the remaining oil from other sandstone reservoirs, thus avoiding the cost of additional drilling.

[0015] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, when the intermediate well is an existing well, the different sandstone reservoirs are opened by perforation or hydraulic jetting based on the location information of the different sandstone reservoirs in each well.

[0016] Furthermore, in the above method for establishing an injection-production well network between different sandstone reservoirs, the location information of the well development is determined based on well logging curve analysis. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the process of establishing an injection-production well network between different sandstone reservoirs according to the present invention.

[0018] Figure 2 This is a schematic diagram illustrating the forces acting on the cement plug of the present invention within a wellbore.

[0019] Figure 3 This is a schematic diagram of the injection-production well network established between different sandstone reservoirs in Embodiment 1 of the method of the present invention;

[0020] Figure 4 This is a schematic diagram of the injection-production well network established between different sandstone reservoirs in Embodiment 2 of the method of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] This invention mainly provides a method for establishing an injection-production well network between different sandstone reservoirs, such as... Figure 1 As shown, the specific steps include the following:

[0023] 1) Obtain the spatial distribution and development of reservoirs, clarify the development status of each sand body reservoir and the connectivity between reservoirs in the well area, determine the relative positions of oil production wells and water injection wells in the well area, and set multiple sand body reservoirs with overlapping parts in the vertical direction as target reservoirs.

[0024] 2) Connect the target reservoir with water injection wells and the target reservoir with oil production wells through an intermediate well, wherein the intermediate well is an existing well or a newly drilled well located in the overlapping part of the target reservoir in the longitudinal direction.

[0025] 3) The intermediate well is plugged, and the plugging location is located in the upper part of the intermediate well connecting to the upper sand body reservoir and / or the lower part of the intermediate well connecting to the lower sand body reservoir.

[0026] The sealing methods in this step mainly include cement plug injection or drop-out tools. The principle is to ensure that the force between the plug and the casing exceeds the pressure of the target reservoir to achieve a sealing effect. If cement plug injection is used, the length of the cement plug must meet minimum requirements to ensure its strength meets safety standards. Figure 2 As shown, according to the principle of force balance, for the cement plug to remain stable, the reservoir pressure P borne by the cement plug must be equal to the cementing force F it experiences. Therefore, the mechanical equilibrium equation can be established:

[0027] F = P (1)

[0028] in:

[0029] F=τ·S (2)

[0030] S=π·D·L (3)

[0031] The length L of the cement plug can be calculated by combining formulas (1), (2), and (3):

[0032] L=P / (π·τ·D) (4)

[0033] In the formula, F represents the bonding force between the cement plug and the casing, in N; P represents the reservoir pressure borne by the cement plug, in MPa; and τ represents the bonding strength between the cement plug and the casing, in MPa / m. 2 S—Contact area between the cement plug and the casing, m² 2 π—pi; D—inner diameter of the sleeve, m; L—length of the cement plug, m.

[0034] 4) Water injection wells are used for water injection, and oil production wells are used for oil production. The process of water injection wells injecting water is the process of water-driven oil recovery. After the injected water reaches a certain volume, the injected water will be transported sequentially to the reservoir connected to the water injection well, the intermediate well passage, and the reservoir connected to the oil production well. The oil production well will measure the water-driven oil recovery effect, increase oil well production, and establish an injection-production well network between different sandstone reservoirs, thereby achieving the goal of improving reservoir recovery through water injection development.

[0035] Method Example 1:

[0036] 1) such as Figure 3 As shown, there are two oil production wells and one water injection well in this well area. The oil production well A1 is located at the north end, the oil production well B1 is in the middle, and the water injection well C1 is located at the south end. The three wells are arranged in an approximately straight line. The distance between oil production wells A1 and B1 is 125 meters, the distance between oil production well B1 and water injection well C1 is 90 meters, and the distance between oil production well A1 and water injection well C1 is 195 meters. After water injection to drive oil production in the connected sandstone reservoir, it has been flooded to a high degree, and the development of the well group is no longer economically viable. Currently, water injection well C1 has been shut down and injection has stopped. Oil production well A1 is in normal production (low daily fluid production), and oil production well B1 is in normal production (high water content in the produced fluid).

[0037] Within the target formation, production well A1 encountered one sand body reservoir 11, production well B1 encountered three sand body reservoirs, namely sand body reservoirs 11, 12, and 13, and injection well C1 encountered one sand body reservoir 12. Sand body reservoirs 11 and 12 within this well area are designated as target reservoirs, and an injection-production well network is established.

[0038] 2) Using the logging curve interpretation results, determine the depths of sand body reservoir 11 and sand body reservoir 12 at production well A1, production well B1 and water injection well C1. Use production well B1 as an intermediate well, and connect sand body reservoir 11 and sand body reservoir 12 in intermediate well B1 by implementing oil and water well measures and using perforation.

[0039] 3) A cement plug is injected into the wellbore of the intermediate well, i.e., production well B1. The cement plug is located above sand body reservoir 12. Since the lower part of sand body reservoir 11 is the bottom of the well, no plugging is required. In addition, fluid migration must be ensured in the area between the cement plug and the bottom of the wellbore in production well B1, i.e., between sand body reservoir 11 and sand body reservoir 12.

[0040] The length of the cement plug is determined using formula (4).

[0041] L=P / (π·τ·D) (4)

[0042] The reservoir pressure P below the cement plug in the intermediate well is 33.6 MPa, and the bonding strength τ between the cement plug and the casing is 1.52 MPa / m. 2The value of π is taken as 3.14, and the inner diameter D of the intermediate well casing is 0.11862m. The calculated cementing length L is 59.35m, but for safety reasons, the actual cement plug length during on-site construction is 75.8m.

[0043] 4) Water injection was implemented in injection well C1, and oil production was implemented in production well A1. Through strengthening the daily management and effect tracking analysis of this injection-production well group, it was found that after three months of water injection for oil displacement, production well A1 showed the effect of water injection, with an initial daily oil increase of 4.8 tons. At the same time, the water cut of the intermediate well, i.e., production well B1, decreased by 1.9 tons per day, indicating that the invention has achieved results.

[0044] Method Example 2:

[0045] 1) such as Figure 4 As shown, there are 2 oil production wells and 2 water injection wells in this well area. The northern end is oil production well A2. Oil production well B2 is 120 meters south-southwest of oil production well A2. Water injection well C2 is 110 meters south-east of oil production well B2. Water injection well D2 is 110 meters south-southwest of water injection well C2. Oil production well A2 and water injection well C2 are 205 meters apart, and oil production well A2 and water injection well D2 are 300 meters apart.

[0046] Within the target formation, production well A2 encountered two sandstone reservoirs: sandstone reservoir 21 and sandstone reservoir 23; production well B2 encountered four sandstone reservoirs: sandstone reservoir 21, sandstone reservoir 23, sandstone reservoir 24, and sandstone reservoir 25; water injection well C2 encountered three sandstone reservoirs: sandstone reservoir 21, sandstone reservoir 22, and sandstone reservoir 24; and water injection well D encountered one sandstone reservoir 22. Sandstone reservoirs with the same designation are considered the same type of reservoir, and vice versa. Development experience shows that the sandstone reservoirs in this reservoir can be developed with water injection. Therefore, sandstone reservoirs 21, 22, 23, and 24 within this well area are designated as target reservoirs, and an injection-production well network is established.

[0047] 2) Using the logging curve interpretation results, determine the depths of sand body reservoirs 21, 22, 23, and 24 at production wells A2, B2, C2, and D2, respectively; designate water injection well C2 as the intermediate well for sand body reservoirs 21 and 22, and production well B2 as the intermediate well for sand body reservoirs 23 and 24; implement oil-water well measures and use perforation to connect sand body reservoirs 21 and 22 in water injection well C2, and connect sand body reservoirs 23 and 24 in production well B2.

[0048] 3) Cement plugs are injected into the wellbores of oil production well B2 and water injection well C2. Two cement plugs are injected into oil production well B2, labeled ① and ②, and one cement plug is injected into water injection well C2, labeled ③. Cement plug ① is located between sand body reservoirs 21 and 23; cement plug ② is located between sand body reservoirs 24 and 25; and cement plug ③ is located between sand body reservoirs 22 and 24. Simultaneously, sand body reservoir 21 is used for bottom sealing at the lower parts of oil production wells A2, B2, and C2, and at the lower part of water injection well D2. In the oil well B2 wellbore, between cement plugs ① and ②, and in the water injection well C2 wellbore between the cement plug and the bottom of the well, i.e. between sand body reservoirs 23 and 24, and between sand body reservoirs 21 and 22, fluid migration must be ensured.

[0049] The length of the cement plug is determined using formula (4).

[0050] L=P / (π·τ·D) (4)

[0051] The reservoir pressure below cement plug ① is 30.2 MPa, the reservoir pressure between cement plug ① and cement plug ② is 28.5 MPa, the reservoir pressure below cement plug ③ is 34.8 MPa, the reservoir pressure above cement plug ③ is 32.6 MPa, the bonding strength between cement plug and casing is 1.52 MPa / m2, the value of pi is 3.14, and the inner diameter of the casing in the intermediate well is 0.11862 m. Calculations show that cement plug #1 can withstand a reservoir pressure difference of 1.7 MPa, and cement plug #3 can withstand a reservoir pressure difference of 2.2 MPa. In practical applications, considering that injection wells C2 and D2 are affected by various factors and simultaneous water injection cannot be guaranteed, the pressure difference across the cement plugs will vary significantly. For safety reasons, the length of the cement plugs is calculated based on the maximum possible reservoir pressure they can withstand. That is, the maximum possible pressure that cement plug #1 can withstand is 30.2 MPa, and its length is 53.3 m; the maximum possible pressure that cement plug #2 can withstand is 28.5 MPa, and its length is 50.3 m; and the maximum possible pressure that cement plug #3 can withstand is 34.8 MPa, and its length is 61.5 m. For safety reasons, the actual cement plug lengths used in the field construction are 58.7 m for cement plug #1, 62.6 m for cement plug #2, and 77.1 m for cement plug #3.

[0052] 4) Water injection was implemented in injection wells C2 and D2, and oil production was carried out in production well A2. Through enhanced daily management and effect tracking analysis of this injection-production well network, it was found that after 4 and 6 months of water injection for oil displacement, production well A2 successively achieved the water injection effects of injection wells C2 and D2, with initial daily oil increases of 5.5 tons and 6.8 tons respectively, indicating that the invention was effective.

[0053] This invention presents a method for establishing injection-production well networks among different sandstone reservoirs. Aimed at tapping into the remaining oil in reservoirs, it establishes a water injection development well network between relatively small, unconnected sandstone reservoirs, significantly improving reservoir recovery. Simultaneously, it leverages the dual function of intermediate wells, allowing them to provide water injection channels for oil displacement while also functioning as water wells to inject water into other sandstone reservoirs or as oil wells to continue extracting remaining oil from other sandstone reservoirs. This method was invented to further improve reservoir recovery in oil reservoir development. It effectively solves the challenge of establishing injection-production well networks between different sandstone reservoirs for water injection-driven oil displacement development, demonstrating strong practicality and universality. It provides a new method for establishing injection-production relationships and improving recovery rates in oil reservoir development, particularly for water injection development of reservoirs with relatively small development areas.

Claims

1. A method of establishing an injection-production pattern between different sand body reservoirs, characterized in that, The method comprises the following steps: 1) determining the position of each sand reservoir according to the development condition of reservoir space distribution; setting two sand reservoirs with overlapping parts in the longitudinal direction as target reservoirs; the development range of the sand reservoirs cannot simultaneously meet the conditions of water injection well and oil production well required for establishing injection-production well pattern; 2) connecting the overlapping parts of the sand reservoirs in the target reservoirs through an intermediate well, the two sand reservoirs connected are a first reservoir and a second reservoir, and the intermediate well is an existing well or a newly drilled well in the overlapping part in the longitudinal direction of the target reservoir; 3) performing plugging in the intermediate well, and the plugging position is located in the upper part of the sand reservoir above the intermediate well connection; when the lower part of the sand reservoir below the intermediate well connection is not the bottom of the well, plugging is also set; 4) taking the well at one end of the first reservoir away from the intermediate well as a water injection well, and taking the well at one end of the second reservoir away from the intermediate well as an oil production well, and then performing water injection for oil displacement.

2. The method of establishing an injection-production pattern between different sand body reservoirs of claim 1, wherein, The connection relationship between the sand reservoirs is also determined according to the development condition of reservoir space distribution, and the sand reservoirs connected are regarded as one sand reservoir.

3. The method of establishing an injection-production pattern between different sand body reservoirs of claim 1, wherein, The plugging method in step 3) comprises a cement plug injection method and a lost tool dropping method.

4. The method of establishing an injection-production pattern between different sand body reservoirs of claim 3, wherein, When the cement plug injection method is used, the length L of the cement plug should be greater than a set value, and the set value L is: wherein P is the reservoir pressure borne by the cement plug, π is the circular constant, τ is the cementing strength between the cement plug and the casing, and D is the inner diameter of the casing.

5. The method of establishing an injection-production pattern between different sand body reservoirs of claim 4, wherein, If there is no sand reservoir connected with the intermediate well above the cement plug, the reservoir pressure borne by the cement plug is the reservoir pressure below the cement plug; if there is a sand reservoir connected with the intermediate well above the cement plug, the reservoir pressure borne by the cement plug is the pressure difference between the reservoir pressure above the cement plug and the reservoir pressure below the cement plug.

6. The method of establishing an injection-production pattern between different sand body reservoirs of claim 5, wherein, When the intermediate well is an existing well, different sand reservoirs are opened through perforation or hydraulic jetting according to the position information of the development of different sand reservoirs in each well.

7. The method of establishing an injection-production pattern between different sand body reservoirs of claim 6, wherein, The position information of the development in the well is determined according to logging curve analysis.

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