Method for adjusting oil reservoir seepage field through injection-production well conversion

Abstract

The invention belongs to the field of methods for adjusting an oil reservoir seepage field through injection and production well conversion, and discloses a method for adjusting an oil reservoir seepage field through injection and production well conversion. Comprising the steps of establishing a seepage field evaluation model, representing a current seepage field evaluation system, understanding a remaining oil distribution rule, expanding a displacement medium wave and volume, improving the overall oil displacement efficiency, measuring and calculating to improve the recovery ratio, and determining the optimal conversion opportunity. According to the method, a feature model conforming to the actual mine field is established, and flow field reconstruction research is conducted on bed series adjustment and injection-production well pattern conversion through a numerical simulation method. Through multiple times of numerical simulation, a flow field reconstruction scheme of the region is obtained.

Description

Technical Field

[0001] The invention belongs to the field of methods for adjusting the seepage field of an oil reservoir by switching between injection and production wells, and particularly relates to a method for adjusting the seepage field of an oil reservoir by switching between injection and production wells. Background Art

[0002] After long periods of exploitation, the vast majority of my country's mature oilfields have entered a period of high or even extremely high water cut. Statistics show that approximately 67% of residual oil in these mature oilfields remains buried underground, unable to be effectively displaced. This residual oil, in this high-water-cut period, is locally concentrated and generally scattered, making conventional development difficult to exploit. As water flooding continues, the reservoir flow field undergoes uneven changes. Injected water flows strongly into areas with low seepage resistance, creating a dominant flow field. In areas with high seepage resistance, injected water is less likely to reach the reservoir, creating a weak flow field. The extent of this water reach severely impacts oilfield development. Therefore, research is needed to adjust the reservoir flow field through injection-production well conversion to provide technical support for tapping the potential of residual oil. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a method for adjusting reservoir seepage fields by converting injection and production wells. Based on oilfield geology and development knowledge, this method clarifies the distribution characteristics of remaining oil in the reservoir and its development characteristics. Through multi-index analysis, key indicators for evaluating the underground seepage field are selected. Combined with oil saturation to characterize the seepage field, a flow field evaluation system is established, enabling the identification of dominant channels.

[0004] The above-mentioned object of the present invention is achieved through the following technical solution: A method for adjusting the seepage field of an oil reservoir by converting injection and production wells, comprising the following steps:

[0005] 1. Establish a seepage field evaluation model through understanding the oilfield geology and studying the distribution law of the seepage field;

[0006] 2. Based on step 1, further study the formations and well patterns of the oil field to characterize the current seepage field evaluation system;

[0007] 3. Based on step 2, use a detailed geological model and high-precision numerical simulation technology to understand the distribution pattern of remaining oil;

[0008] 4. Based on step 3, the reservoir seepage field is readjusted by converting the injection and production wells, thereby expanding the swept volume of the displacement medium and improving the overall oil recovery efficiency;

[0009] 5. Based on the results obtained in steps 2, 3, and 4, the injection and production wells in the oil field are switched at different water-cut periods, the recovery factor is calculated, and the optimal switching time is determined.

[0010] Furthermore, the step 1 is specifically as follows: through understanding the geology of the oil field and studying the distribution law of the seepage field, after changing the injection and production wells, the stable pressure system of high-pressure injection and low-pressure production in the original reservoir is broken, the seepage field is redistributed, new seepage channels are added, and the fluid in the low-permeability reservoir is effectively mobilized. According to the fluid force during the conversion of the injection and production wells, a seepage field evaluation model is established.

[0011] In a further preferred embodiment of the present invention, the fluid force in step 1 specifically includes displacement force, capillary force, viscous force, and fluid elastic force.

[0012] Furthermore, in step 2, the formations and well networks of the oil field are further studied in depth, specifically: based on the principles of ensuring the ability of injection and production coordination, sufficient flow field reconstruction, and optimal effect and benefit, the current diamond-shaped inverted nine-point well network injection capacity is not satisfied, and it is adjusted to an inverted seven-point well network through updating, densification, and injection transfer, and a high-efficiency injection and production system adapted to water drive is rebuilt. At the same time, combined with the injection transfer of old wells, variable flow line adjustment is implemented, the water injection development formations are subdivided, and multiple sets of formation reorganizations are carried out to further construct an efficient three-dimensional flow field. Based on resource reserves, the parameters of comprehensive well network density, economic benefits, and injection demand are determined.

[0013] Furthermore, the distribution pattern of the remaining oil in step 3 is specifically as follows: the remaining oil is mainly distributed in the near-well area of ​​the oil well end that has not been displaced.

[0014] Furthermore, in step 4, the displacement medium volume is expanded by more than 8%.

[0015] Furthermore, the overall oil displacement efficiency is increased by more than 3% in step 4.

[0016] Furthermore, the step 5 is specifically as follows: based on the injection and production well types and well network adjustment principles, combined with the formation adjustment plan, a variety of well layout plans are proposed, numerical simulation is used for prediction, and the optimal plan is obtained in combination with the final recovery rate and workload, laying the foundation for formulating development and adjustment technical policies for various high-water-content oil reservoirs.

[0017] The beneficial effects of the present invention compared with the prior art are:

[0018] Based on the geology and development knowledge of the main oilfield blocks, this paper defines the distribution characteristics of remaining oil in the reservoir and its development characteristics. Through multi-index analysis, key indicators for evaluating the underground seepage field are screened. Combined with oil saturation to characterize the seepage flow field, a flow field evaluation system is established, enabling the identification of dominant channels. A characteristic model that conforms to the actual mine site is established, and numerical simulation methods are used to conduct flow field reconstruction research on stratum adjustment and injection-production well pattern conversion. Through multiple numerical simulations, a flow field reconstruction scheme for the region is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 Schematic diagram of the steps of the method of the present invention;

[0021] Figure 2 This is a schematic diagram of establishing a microscopic displacement model in the present invention - changing the displacement path and activating the dead and live zones;

[0022] Figure 3 This is a schematic diagram of establishing a macro displacement model - improving single sand body injection and production, and changing the water flooding direction;

[0023] Figure 4 It is a prediction chart of the production increase amplitude by implementing well-specific direction reversal at different stages. DETAILED DESCRIPTION

[0024] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0025] Example 1

[0026] As shown in Figure 1, a method for adjusting the reservoir seepage field by converting injection and production wells includes the following steps:

[0027] (1) Establish a seepage field evaluation model through understanding the oilfield geology and studying the distribution law of the seepage field;

[0028] (2) Based on step (1), further study the formations and well patterns of the oil field to characterize the current seepage field evaluation system;

[0029] (3) Based on step (2), using a fine geological model and high-precision numerical simulation technology, understand the distribution pattern of remaining oil;

[0030] (4) Based on step (3), the reservoir seepage field is readjusted by converting the injection and production wells, thereby expanding the swept volume of the displacement medium and improving the overall oil recovery efficiency;

[0031] (5) Based on the results obtained in steps (2), (3), and (4), the injection and production wells in the oil field are switched at different water content periods, the recovery rate is calculated, and the optimal switching time is determined.

[0032] The step (1) comprises:

[0033] Based on the current development characteristics, establish a reservoir seepage field model that reflects the current reservoir characteristics. Establish a current reservoir seepage field evaluation system by analyzing and evaluating the main geological characteristics, well pattern characteristics, production characteristics, and seepage characteristics of the reservoir;

[0034] The step (2) comprises:

[0035] Using the results of step (1), based on the seepage field system evaluation, the reservoir seepage field is quantitatively characterized, and the reservoir seepage field quantitative characterization refers to the ability to reflect the remaining resources and seepage characteristics of the main strata of the reservoir;

[0036] The step (3) comprises:

[0037] Using the results of step (2), using a fine geological model and high-precision numerical simulation technology, based on historical matching, accurately understand the distribution pattern of remaining oil;

[0038] The step (4) comprises:

[0039] By utilizing the results of step (3), the reservoir seepage field is readjusted by switching the injection and production wells during the high water cut period, thereby alleviating interlayer conflicts, expanding the swept volume of the displacement medium, improving the overall oil recovery efficiency, effectively improving the well pattern control degree, and improving the streamline distribution;

[0040] The step (5) comprises:

[0041] According to the conclusions obtained from step (2), step (3) and step (4),

[0042] Based on the principles of injection and production well classification and well pattern adjustment, combined with the formation adjustment plan, a variety of well layout plans are proposed, and numerical simulation is used for prediction. The optimal plan is obtained based on the final recovery rate and workload, laying the foundation for the formulation of development and adjustment technical policies for various high-water-content oil reservoirs.

[0043] Example 2

[0044] The method for adjusting the reservoir seepage field by converting injection and production wells is the same as that in Example 1.

[0045] Aiming at the poor recovery effect of long-term water flooding in the main block of X Oilfield, the present invention establishes a flow field evaluation system and applies numerical simulation methods to evaluate and predict the development effect of the target block, realizes the research of seepage field reconstruction technology, and uses the technology formed above to evaluate the method of adjusting the seepage field by converting injection and production wells.

[0046] First, based on geological understanding and the original high-precision geological model, a seepage field evaluation system was established and model characterization was carried out. Reservoir numerical simulation software was used to perform detailed historical fitting of the main blocks. The fitting accuracy of the main wells reached over 85%, and the fitting error of the entire area was within 5%.

[0047] Secondly, the seepage field and remaining oil distribution of the target block were studied, and it was found that the remaining oil was mainly distributed in the low-permeability reservoir near the oil well;

[0048] Finally, based on the principle of injection-production well conversion and reconstruction, a new well network was deployed and multiple schemes were simulated, which increased the recovery rate by 3.2% compared with the current well network method.

[0049] The X Oilfield began applying injection-production well conversion between 1996 and 2000, with large-scale implementation from 2001 to 2005. It was further applied from 2006 to 2010. A total of 186 water wells were converted into oil wells, with a cumulative oil production of 383,000 tons. The current annual production capacity is 17,000 tons, and the cumulative increased geological reserves are 5.77 million tons. The decline method is used to calculate the increase in recoverable reserves by 1.44 million tons. The average annual reduction in natural decline was 3.85% from 2016 to 2020.

[0050] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for adjusting the seepage field of an oil reservoir by converting injection and production wells, characterized in that: Here are the steps: S1. Establish a seepage field evaluation model through understanding the oilfield geology and studying the distribution law of the seepage field; S2. Based on the step S1, further study the oilfield strata and well patterns to characterize the current seepage field evaluation system; S3. Based on the step S2, the use of fine geological models and high-precision numerical simulation technology to understand the distribution of remaining oil; S4. Based on the step S3, the injection and production wells are converted to readjust the reservoir seepage field, expand the displacement medium swept volume, and improve the overall oil recovery efficiency; S5. Based on the results obtained in steps S2, S3, and S4, the injection and production wells in the oil field are switched at different water-cut periods, the recovery rate is calculated, and the optimal switching time is determined.

2. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: The step S1 is specifically as follows: through understanding the geology of the oil field and studying the distribution law of the seepage field, after changing the injection and production wells, the stable pressure system of high-pressure injection and low-pressure production in the original reservoir is broken, the seepage field is redistributed, new seepage channels are added, and the fluid in the low-permeability reservoir is effectively mobilized. According to the fluid force during the injection and production well conversion process, a seepage field evaluation model is established.

3. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 2, characterized in that: The fluid force in step S1 specifically includes displacement force, capillary force, viscous force, and fluid elastic force.

4. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: In step S2, the strata and well patterns of the oil field are further studied in depth. Specifically, based on the principles of ensuring injection-production coordination, sufficient flow field reconstruction, and optimal effect and benefit, the current diamond-shaped inverted nine-point well pattern is adjusted to an inverted seven-point well pattern through updating, densification, and injection conversion, and a high-efficiency injection-production system adapted to water flooding is rebuilt. At the same time, combined with the conversion of old wells, variable flow line adjustment is implemented, the water injection development strata are subdivided, and multiple strata are reorganized to further build an efficient three-dimensional flow field. Based on resource reserves, the parameters of comprehensive well pattern density, economic benefits, and injection demand are determined.

5. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: The distribution pattern of the residual oil in step S3 is specifically as follows: the residual oil is mainly distributed in the near-well area where the oil well end has not been displaced.

6. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: In step S4, the displacement medium volume is expanded by more than 8%.

7. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: In step S4, the overall oil displacement efficiency is increased by more than 3%.

8. The method for adjusting reservoir seepage field by converting injection and production wells according to claim 1, characterized in that: The step S5 specifically includes: based on the injection and production well types and well pattern adjustment principles, combined with the formation adjustment plan, proposing multiple well layout plans, using numerical simulation to make predictions, and combining the final recovery rate and workload to obtain the optimal plan, laying the foundation for formulating development and adjustment technical policies for various high-water-cut oil reservoirs.

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