Green development technology method of water drive reservoirs with dynamic seepage interface reduction

Abstract

The present invention provides a green development technology method for water-driven oil reservoirs with dynamic seepage interface reduction, and the green development technology method for water-driven oil reservoirs with dynamic seepage interface reduction includes: step 1, establishing a numerical model of the oil reservoir in the study area and performing dynamic history fitting; step 2, performing dynamic seepage interface identification; step 3, performing flow unit division considering dynamic seepage interface and static barrier interface; step 4, performing flow unit reorganization optimization design based on dynamic seepage interface reduction. The green development technology method for water-driven oil reservoirs with dynamic seepage interface reduction is aimed at old oil fields with high water content developed by water drive, has a certain technical leading role, provides a decision-making basis for the application of technology to further improve recovery rate in the ultra-high water content period, and has broad prospects for promotion and application.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a green development technical method of a water-driven oil reservoir with dynamic seepage interface reduction. Background Art

[0002] Water flooding is the main development method for medium- and high-permeability sandstone reservoirs. The medium- and high-permeability sandstone reservoirs in eastern China are highly heterogeneous. After long-term water injection development, they have generally entered the stage of ultra-high water content development. The dynamic heterogeneity has intensified, the difference in oil-water flow has increased, and the injected water in the high-water flooding zone has inefficiently circulated, or even "only produced water, no oil". Ineffective water circulation, facing a severe situation of large production decline and difficult stable production. How to break through the dilemma of "high consumption and low efficiency" and further improve the recovery rate mainly faces two difficulties: First, the ineffective water circulation in local layers is difficult to control, the displacement pressure field and the seepage resistance field do not match during the high water content period, the seepage channel of the injected water is fixed, the water absorption difference is as high as more than 100 times, and the injected water in the high saturated water area is ineffectively circulated, which urgently needs "efficient water control" development; second, the remaining oil in the weak drive area is difficult to mobilize: in the high water content stage, affected by the complexity of static boundaries such as faults and physical properties and the segmentation of hydrodynamic dynamic boundaries, the injection and production streamlines are fixed, the remaining oil is differentially enriched, and the injected water is limited, which urgently needs "efficient oil flooding" development.

[0003] In view of the above problems, especially under the condition of low oil price, the traditional and extensive development mode based on the adjustment of the well pattern of the new wells is unsustainable due to the constraints of economic benefits. Therefore, the ultra-high water cut period requires fine development. Since the flow unit was proposed in the 1980s, it has been one of the focuses of oil and gas field developers. Many scholars at home and abroad have carried out many fruitful explorations and developments on the flow unit, providing a feasible technical direction for the fine development of the ultra-high water cut period. For example, in recent years, some scholars have proposed from a dynamic point of view that the flow unit can also be defined as a reservoir unit with similar seepage characteristics separated by the seepage barrier interface and the seepage difference interface inside the reservoir, and therefore has similar development dynamic characteristics (Dou Zhilin, "Reservoir Flow Unit Research", 2000; Wu Yuanyan et al., "Oil and Mineral Geology (Third Edition)", 2005), but the current methods and results of flow unit research are mainly used for the prediction of remaining oil or the study of physical parameters such as reservoir permeability, and the scope of application of the results is still relatively narrow.

[0004] In the Chinese patent application with application number 201410321227.6, a method for interpreting the formation pore structure based on flow units is involved. The evaluation block is divided into flow units with similar geological structures, and the porosity and permeability of each flow unit are analyzed. The patent method is still limited to the evaluation and application of flow units from the static parameter - geological structure similarity.

[0005] Application No. 201410853036.4 discloses a method for rapidly evaluating the production status of a single flow unit in a complex reservoir. According to the reservoir potential and development status, relevant indicators are selected to quantitatively evaluate the adjustment effect of a single flow unit and determine the sequence of the adjustment unit. This method is still based on the division of flow units based on static parameters, and lacks the dynamic understanding and description of the formation of dynamic seepage interface in the ultra-high water cut period and its effect on the division of flow units. Therefore, it is limited to a single flow unit, that is, the adjustment strategy research within the flow unit.

[0006] To this end, we have invented a new green development technology method for water-drive oil reservoirs with dynamic seepage interface reduction to solve the above technical problems. Summary of the invention

[0007] The purpose of the present invention is to provide a water-drive oil reservoir green development technology method with clear ideas and strong operability, which provides a practical and feasible dynamic seepage interface reduction for realizing green development of water-drive oil reservoirs in ultra-high water-cut period.

[0008] The purpose of the present invention can be achieved through the following technical measures: a green development technical method for water-drive oil reservoirs with dynamic seepage interface reduction, which comprises: step 1, establishing a numerical model of the oil reservoir in the study area and performing dynamic history fitting; step 2, identifying the dynamic seepage interface; step 3, dividing the flow unit considering the dynamic seepage interface and the static barrier interface; step 4, performing flow unit reorganization optimization design based on dynamic seepage interface reduction.

[0009] The purpose of the present invention can also be achieved by the following technical measures:

[0010] In step 1, a numerical reservoir model is established based on the detailed stratigraphic comparison and structural interpretation results of the research target unit and the collation and analysis of production performance data.

[0011] In step 1, production dynamic history matching is carried out to further modify the reservoir model and obtain the reservoir fluid saturation and pressure field distribution.

[0012] In step 2, the distribution of fluid seepage velocity field of each grid at any time step is calculated, and then the relative velocity difference of adjacent grids and the derivative of the relative velocity difference with respect to time are obtained. The dynamic seepage interface is judged to be a dynamic seepage interface based on its characteristic of large and stable relative flow velocity difference on both sides of the interface. Combined with the control effects of the main controlling factors of the dynamic seepage interface such as reservoir heterogeneity and the size and direction of the driving force, the dynamic seepage boundary and distribution are continuously tracked.

[0013] In step 3, the flow units are divided according to the distribution of dynamic seepage boundaries and the static barrier interface divisions such as faults, lithological boundaries, interlayers, and lateral accumulation layers in the study area, effectively distinguishing between two types of inefficient driving systems: high-speed ineffective flow units and low-speed inefficient flow units.

[0014] In step 4, the flow unit is taken as the research object, and inefficient and invalid flow units are given equal importance as efficient flow units. The existing well network conditions are comprehensively considered, and technical measures for changing the direction and size of the driving force are optimized and designed to minimize the relatively stable dynamic seepage interface between flow units such as high-speed invalid flow units and low-speed and inefficient flow units. By reorganizing the flow units, an efficient driving system is recreated to achieve efficient development of water control and oil displacement in old oil fields with high water content.

[0015] In step 4, the technical measures for optimizing the design to change the direction and magnitude of the driving force include well pattern conversion, well pattern densification or thinning, and injection and production volume control.

[0016] The technical method for green development of water-driven oil reservoirs with dynamic seepage interface reduction in the present invention particularly relates to a green development method for the ultra-high water-cut development stage of medium-high permeability sandstone oil reservoirs, which is based on the reorganization of flow units based on the reduction of dynamic seepage interfaces and the reconstruction of an efficient development system. Specifically, in the ultra-high water-cut development stage of medium-high permeability sandstone oil reservoirs, there are problems such as long-term water injection development, fixed seepage channels of injected water, coexistence of inefficient and ineffective water circulation and difficulty in sweeping residual oil in weak drive parts, and inefficient operation of the development system. By regulating the driving force, reducing the dynamic seepage interface, realizing the reorganization of flow units, rebuilding an efficient development system, and improving the utilization rate of water injection, the technical method provides a decision-making basis and technical support for further improving the recovery rate and green development of water-driven oil reservoirs in the ultra-high water-cut period.

[0017] The present invention solves the problems of inefficient and ineffective water circulation of injected water and difficulty in spreading residual oil in weak drive parts, and inefficient operation of the development system, which are common in the development stage of medium-high permeability sandstone reservoirs with extremely high water content, and provides a green development technology method for water-drive reservoirs based on dynamic seepage interface reduction to achieve reconstruction of an efficient development system. The core is to effectively identify the distribution of dynamic seepage interfaces based on the formation and evolution mechanism of dynamic seepage interfaces in water-drive reservoirs with extremely high water content, and divide and classify flow units by comprehensively considering static barrier interfaces and dynamic seepage interfaces, analyze and clarify the main development contradictions faced by different flow units, propose targeted technical countermeasures for reducing dynamic seepage interfaces and reorganizing flow units, carry out optimization design of flow unit reorganization based on dynamic seepage interface reduction, and compile adjustment implementation plans to guide old oil fields to rebuild efficient development systems and further improve water drive recovery rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A flowchart of a specific embodiment of the water-drive reservoir green development technology method for dynamic seepage interface reduction of the present invention;

[0019] Figure 2 A permeability distribution diagram of a well group reservoir numerical model in a specific embodiment of the present invention;

[0020] Figure 3 A dynamic seepage interface distribution diagram of a well group in a high water cut period in a specific embodiment of the present invention;

[0021] Figure 4 It is a schematic diagram of the dynamic seepage interface distribution and flow unit division of a well group in the ultra-high water cut period in a specific embodiment of the present invention;

[0022] Figure 5 A schematic diagram of a reorganized flow unit development for reducing a dynamic seepage interface by converting a well pattern in a specific embodiment of the present invention;

[0023] Figure 6 This is a design diagram for optimizing the direction and magnitude of the driving force for the reorganization flow unit development in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings.

[0025] like Figure 1 As shown, Figure 1 The present invention is a flow chart of the green development technology method of water drive oil reservoirs with dynamic seepage interface reduction.

[0026] Step 101, establish a numerical model of the reservoir in the study area and perform dynamic history matching. Based on the detailed stratigraphic comparison and structural interpretation results of the target unit, and collate and analyze the production dynamic data, establish a numerical model of the reservoir, perform production dynamic history matching, further modify the reservoir model, and obtain the reservoir fluid saturation and pressure field distribution.

[0027] Step 102, dynamic seepage interface identification. The seepage velocity field distribution of each grid fluid at any time step is calculated, and then the relative velocity difference of adjacent grids and the derivative of the relative velocity difference with respect to time can be obtained. The dynamic seepage interface is identified based on the characteristics that the relative flow velocity difference on both sides of the interface is large and relatively stable. Combined with the control of the main control factors of the dynamic seepage interface such as reservoir heterogeneity and the size and direction of the driving force, the dynamic seepage boundary and distribution are continuously tracked.

[0028] Step 103, consider the division of flow units based on dynamic seepage interface and static barrier interface. The flow units are divided based on the distribution of dynamic seepage boundaries and the division of static barrier interfaces such as faults, lithologic boundaries, interlayers, and lateral accumulation layers in the study area. This can effectively distinguish two types of inefficient drive systems: high-speed invalid flow units (injected water invalid water circulation zones) and low-speed and inefficient flow units (weak drive remaining oil enrichment zones).

[0029] Step 104, based on the optimization design of flow unit reorganization for dynamic seepage interface reduction. Based on the understanding of the flow unit evolution law that "variable driving force conditions (direction, size) can reduce the dynamic seepage interface and merge flow units", flow units are taken as the research object, inefficient and invalid flow units and efficient flow units are given equal importance, and the existing well network conditions are comprehensively considered to optimize the design of technical measures for changing the direction and size of driving forces, such as well network conversion, well network densification or thinning, injection and production volume control, etc., to minimize the relatively stable dynamic seepage interface of high-speed invalid flow units and low-speed and inefficient flow units, and reconstruct the efficient driving system through flow unit reorganization to achieve efficient development of water control and oil displacement in old oil fields with high water content.

[0030] The present invention further studies and clarifies that reservoir heterogeneity and displacement power are the main controlling factors of the dynamic seepage interface, clarifies the formation and evolution mechanism of the dynamic seepage interface of "differential physical property segmentation, same-direction power solidification, and variable-direction power reduction", and invents a flow unit reorganization and development technical method based on dynamic seepage interface reduction. By targetedly changing the direction and size of the driving force, the dynamic seepage interface is reduced or reconstructed, high- and low-speed inefficient flow units are reorganized, the flow field adaptation is improved, and an efficient driving system is rebuilt. Relevant development technology policies are formed to achieve green development of water control and oil displacement in old oil fields, and provide technical support for further improving the water drive recovery rate of high-permeability sandstone reservoirs in the ultra-high water cut period.

[0031] The following is a specific embodiment of the present invention, which includes the following steps:

[0032] In step 1, the target area is a two-injection and two-production well group, and a reservoir numerical simulation model is established. A low-permeability zone is developed in the middle of the reservoir plane, with a permeability of 100mD, and the permeability of other parts is 3000mD. Well1 and well3 are injection wells, and well2 and well4 are production wells. Figure 2 According to the dynamics of injection and production of oil and water wells, fitting is performed to obtain the corrected reservoir numerical simulation model and the oil and water saturation and pressure field distribution at any calculation time step, and the process enters step 102.

[0033] In step 2, the fluid seepage velocity field distribution of each grid at any time step is calculated according to the Darcy formula, and then the relative velocity difference of adjacent grids and the derivative of the relative velocity difference with respect to time are obtained. The dynamic seepage interface is judged to be a dynamic seepage interface according to the characteristics that the relative flow velocity difference on both sides of the interface is large and relatively stable. Combined with the control of the main control factors of the dynamic seepage interface such as reservoir heterogeneity and the size and direction of the driving force, the dynamic seepage boundary and distribution are continuously tracked to obtain the dynamic seepage interface distribution, such as Figure 3 , Figure 4 As shown, they are schematic diagrams of dynamic seepage interface distribution when the water content of the oil well is 60% and 90%, respectively. The process enters step 103.

[0034] In step 3, the study area can be divided into three flow units based on the static barrier interface (model boundary) and dynamic seepage boundary distribution of the study area, such as Figure 4 As shown, ① and ③ are type I high-speed ineffective flow units, and ② is type II low-speed inefficient flow unit

[0035] In step 4, considering the low abundance of remaining recoverable reserves and relatively complete well network in the study area, it is clear that the direction and magnitude of the driving force can be changed through well network conversion and injection and production intensity regulation, the dynamic interface can be reduced, and the combined flow unit development can be carried out, such as Figure 5 As shown in the figure, by converting well2 into an injection well and well3 into an oil well, the driving force direction can be turned 90° from horizontal to vertical. The numerical simulation shows that the original stable seepage interface is broken, continuously reduced, and finally disappears. The original type I high-speed ineffective flow unit and type II low-speed and inefficient flow unit in the study area are combined into high-speed and efficient flow units. The well network conversion angle can be optimized through numerical simulation ( Figure 6 ) and the injection-production intensity to achieve the optimal development effect of the combined flow unit.

[0036] The present invention aims at the problem of "difficulty in controlling local development of invalid water circulation and difficulty in using residual oil in weak drive parts" in the ultra-high water-cut period of water-drive oil reservoirs. Taking flow units as the research object, based on the formation and evolution mechanism of dynamic seepage interface, the present invention proposes for the first time a technical method for reorganizing flow unit development based on dynamic seepage interface reduction, changing the traditional method of avoiding local potential tapping of invalid water circulation belts to comprehensive utilization of invalid water circulation belts for precise regulation, regulating the pressure field across flow units to adapt the residual oil saturation field, recreating an efficient driving system, and realizing efficient development of old oil fields by controlling water and driving oil. This technical method, especially for old oil fields with high water content developed by water drive, has a certain technical leading role, and provides a decision-making basis for the application of further technology to improve recovery rate in the ultra-high water-cut period, and its promotion and application prospects are broad.

Claims

1. A green development technology method for water-flooding oil reservoirs with dynamic seepage interface reduction, characterized in that: The green development technology method of water drive reservoir with dynamic seepage interface reduction includes: Step 1: Establish a numerical model of the reservoir in the study area and perform dynamic history fitting; Step 2, dynamic seepage interface identification; Step 3, dividing the flow unit considering the dynamic seepage interface and the static barrier interface; Step 4, performing flow unit reorganization optimization design based on dynamic seepage interface reduction; In step 4, the flow unit is taken as the research object, and inefficient and invalid flow units are given equal importance as efficient flow units. Based on the existing well network conditions, the technical measures for changing the direction and size of the driving force are optimized and designed to minimize the relatively stable dynamic seepage interface between the high-speed invalid flow units and the low-speed and inefficient flow units. By reorganizing the flow units, an efficient driving system is recreated to achieve efficient development of water control and oil displacement in old oil fields with high water content.

2. The green development technology method of water-flooding oil reservoirs with dynamic seepage interface reduction according to claim 1 is characterized in that: In step 1, a numerical reservoir model is established based on the detailed stratigraphic comparison and structural interpretation results of the research target unit and the analysis of production performance data.

3. The green development technology method of water-flooding oil reservoirs with dynamic seepage interface reduction according to claim 1 is characterized in that: In step 1, production dynamic history matching is carried out to further modify the reservoir model and obtain the reservoir fluid saturation and pressure field distribution.

4. The green development technology method of water-flooding oil reservoirs with dynamic seepage interface reduction according to claim 1 is characterized in that: In step 2, the distribution of fluid seepage velocity field of each grid at any time step is calculated, and then the relative velocity difference of adjacent grids and the derivative of the relative velocity difference with respect to time are obtained. The dynamic seepage interface is judged to be a dynamic seepage interface based on its characteristic of large and stable relative flow velocity difference on both sides of the interface. Combined with the control effects of the main controlling factors of the dynamic seepage interface such as reservoir heterogeneity and the size and direction of the driving force, the dynamic seepage boundary and distribution are continuously tracked.

5. The green development technology method of water-flooding oil reservoirs with dynamic seepage interface reduction according to claim 1 is characterized in that: In step 3, the flow units are divided according to the distribution of dynamic seepage boundaries and the static barrier interface divisions such as faults, lithological boundaries, interlayers, and lateral accumulation layers in the study area, effectively distinguishing between two types of inefficient driving systems: high-speed ineffective flow units and low-speed inefficient flow units.

6. The green development technology method of water-flooding oil reservoirs with dynamic seepage interface reduction according to claim 1 is characterized in that: In step 4, the technical measures for optimizing the design to change the direction and magnitude of the driving force include well pattern conversion, well pattern densification or thinning, and injection and production volume control.

Images