A method for increasing the single-well production of fault-block reservoirs

Abstract

The present invention discloses a method for increasing the single-well production of fault-block reservoirs, comprising: screening eligible reservoirs; determining the remaining oil reserves and remaining oil positions in the eligible reservoirs; increasing the dialysis replacement area at the remaining oil positions in the reservoirs so as to increase the single-well increment; and increasing the validity period of the single-well increment. The present invention not only greatly increases the single-well production of the reservoir, but also greatly increases the oil production rate of the reservoir, thereby improving the oil recovery factor of the reservoir.

Description

Technical Field

[0001] The present invention belongs to the technical field of tertiary oil recovery, and particularly relates to a method for increasing the single-well production of a fault-block reservoir. Background Art

[0002] Due to the structural fragmentation and the development of fracture systems in the Triassic fault-block reservoir, there are obvious differences in the degree of fragmentation of different small fault blocks. Moreover, there are differences in the sedimentary environment, reservoir development degree, hydrocarbon enrichment degree, reservoir type, and fluid properties between different fault blocks or different horizons of the same fault block, and the oil-water interface is different between different fault blocks.

[0003] Adopting the conventional reservoir development method has the following disadvantages: (1) Conventional stimulation technology: the sand addition amount ≤ 35 m 3 , the displacement ≤ 2.0 m 3 / min, and the preflush fluid volume ≤ 130 m 3 . It is mainly a simple fracture network, with a single fracture orientation, unable to effectively stimulate the fracture network, a small area of oil-water imbibition displacement, and the single-well production cannot be fully exerted. (2) The adaptability of the injection-production well pattern becomes poor, it is difficult to establish a water flooding system, an effective injection-production displacement system cannot be established, and the single-well production continuously decreases.

[0004] The above methods have a low level of reservoir development, low recovery degree and oil production rate. How to increase the single-well production has become a major problem that hinders the efficient development of fault-block reservoirs and improves the recovery rate. It is imperative to study a new method and technology for increasing the single-well production of fault-block reservoirs. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a method for increasing the single-well production of a fault-block reservoir, which not only greatly increases the single-well production of the reservoir, but also greatly increases the oil production rate of the reservoir, thereby improving the recovery rate of the reservoir.

[0006] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0007] A method for increasing the single-well production of a fault-block reservoir, comprising:

[0008] Step 1: Screening eligible reservoirs;

[0009] Step 2: Determining the remaining oil reserves and remaining oil positions in the eligible reservoirs;

[0010] Step 3: Increasing the dialysis displacement area at the remaining oil positions in the reservoir to increase the single-well increment;

[0011] Step 4: Increasing the validity period of the single-well increment.

[0012] Further, in Step 1, the reservoir shall meet the following conditions: 1.0 mD < reservoir permeability < 10.0 mD, effective reservoir thickness ≥ 13.0 m, injection-production correspondence rate < 50%, oil production rate < 0.5%, and recovery factor < 5.0%.

[0013] Further, in Step 2, the specific method for determining the remaining oil reserves in the qualified reservoir is as follows: taking different fault blocks as units, calculating the reserves of each fault block by the volume method, and then determining the remaining oil reserves in the reservoir.

[0014] Further, the calculation formula of the volume method is as follows:

[0015] N = 100 × A × φ × H × S oi × ρ o / B oi

[0016] Wherein: A is the oil-bearing area of the reservoir, ρ o is the crude oil density, φ is the porosity, B oi is the original formation volume factor, S oi is the average oil saturation of the original formation oil, H is the average effective thickness of the formation, and N is the geological reserves.

[0017] Further, in Step 2, the remaining oil position in the qualified reservoir is determined by establishing a three-dimensional three-phase numerical simulation model.

[0018] Further, the method for establishing the three-dimensional three-phase numerical simulation model is as follows: first, establish a three-dimensional geological model, establish a numerical simulation model according to the three-dimensional geological model, then establish an oil reservoir numerical simulation fitting model according to the numerical simulation model, and finally obtain the three-dimensional three-phase numerical simulation model.

[0019] Further, in Step 3, the dialysis displacement area of the remaining oil position in the reservoir is increased by overall increasing the pore pressure and matrix permeability. The specific implementation parameters are: energy storage fracturing sand addition volume in the reservoir ≥ 70 m 3 、displacement ≥ 5.0 m 3 / min, preflush fluid volume ≥ 1100 m 3 and shut-in time after fracturing < 15 days.

[0020] Further, in Step 4, the specific method for increasing the validity period of the single-well increment is as follows: based on the dynamic evaluation of flowing bottomhole pressure, pressure maintenance level, oil production rate, and monthly decline, clarify the injection conversion location and well number, and convert and improve the well pattern.

[0021] Further, it also includes:

[0022] Step 5: On-site test and effect evaluation. The specific method is as follows: Judge whether the daily oil increment per well, oil production rate, natural decline, and pressure maintenance level reach the expectations.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects: Through the screening of oil reservoirs, for low-permeability fault-block oil reservoirs, the present invention creates a method for improving the single-well production of oil reservoirs. By establishing a three-dimensional three-phase numerical simulation model, the present invention clarifies the remaining oil reserves and distribution positions of different fault blocks in the oil reservoir. By adopting overall energy storage fracturing to transform the oil reservoir and taking different types of differential transformations for oil wells in different fault blocks, the present invention reconstructs the complex fracture network, effectively increases the oil-water seepage displacement area, improves the degree of remaining oil utilization, and effectively solves the problem of full utilization of remaining oil in fault-block oil reservoirs. On the basis of reconstructing the fracture network, the present invention combines technical policy evaluation, redefines the injection-production corresponding system for each small layer in each fault block, realizes the reconstruction of the injection-production system in the fault-block oil reservoir, effectively solves the problem during the oil increment period after the single-well production is improved, reduces the natural decline, increases the oil production rate, and finally improves the recovery factor.

[0024] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes a detailed description as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the specific embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is the superimposed map of the remaining reserves of Reservoir A in the embodiment of the present invention;

[0027] Figure 2 It is the fracture network diagram of Reservoir A after energy storage fracturing in the embodiment of the present invention;

[0028] Figure 3 It is the cumulative oil production change curve of Reservoir A after energy storage fracturing in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to make the objects, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0030] As a specific embodiment of the present invention, a method for increasing the single-well production of fault-block reservoirs includes:

[0031] Step 1: Screen eligible reservoirs. Specifically, the screening of reservoirs needs to meet the following conditions: 1.0 mD < reservoir permeability < 10.0 mD, reservoir effective thickness ≥ 13.0 m, injection-production correspondence rate < 50%, oil production rate < 0.5%, and recovery factor < 5.0%.

[0032] Step 2: Determine the remaining oil reserves and remaining oil locations in the eligible reservoirs;

[0033] The specific method for determining the remaining oil reserves in the eligible reservoirs is as follows: Taking different fault blocks as units, the volume method is used to calculate the reserves of each fault block and then determine the remaining oil reserves in the reservoir. The calculation formula of the volume method is:

[0034] N = 100 × A × φ × H × S oi × ρ o / B oi

[0035] Where: A is the oil-bearing area of the reservoir, ρ o is the crude oil density, φ is the porosity, B oi is the original formation volume factor, S oi is the average oil saturation of the original formation oil, H is the average effective thickness of the formation, and N is the geological reserves;

[0036] The remaining oil locations in the eligible reservoirs are determined by establishing a three-dimensional three-phase numerical simulation model. The method for establishing the three-dimensional three-phase numerical simulation model is as follows: First, establish a three-dimensional geological model, establish a numerical simulation model based on the three-dimensional geological model, then establish an oil reservoir numerical simulation fitting model based on the numerical simulation model, and finally obtain the three-dimensional three-phase numerical simulation model to clarify the distribution location of the remaining potential of the reservoir.

[0037] Step 3: Increase the dialysis replacement area of the remaining oil locations in the reservoir by overall increasing the pore pressure and matrix permeability. The specific implementation parameters are: reservoir energy storage fracturing sand addition amount ≥ 70 m 3 、displacement ≥ 5.0 m 3 / min, preflush fluid volume ≥ 1100 m 3 and shut-in time after fracturing < 15 days. That is to say, by adopting large-displacement construction, increasing the net pressure in the fracture, breaking the tight reservoir, forcing the fracture to branch, forming a complex fracture network, and increasing the seepage channel of tight oil; by injecting a large amount of fluid, storing energy through shut-in after fracturing, dialysis of oil and water, and replacement, overall increasing the pore pressure and matrix permeability to achieve the purpose of energy-enhanced oil displacement.

[0038] Step 4: Improve the validity period of the single-well increment. The specific method is as follows: Based on the dynamic evaluation of flowing pressure, pressure maintenance level, oil production rate, and monthly decline in the development technical policy, clarify the injection conversion location and well numbers, perfect the injection-production well pattern, and clarify the oil stabilization period.

[0039] Step 5: Field test and effect evaluation. The specific method is as follows: Judge whether the daily oil increment, oil production rate, natural decline, and pressure maintenance level of a single well reach the expectations.

[0040] The present invention will be further described in detail below in conjunction with specific embodiments:

[0041] Embodiment:

[0042] Overview of test block A in an oil production plant in Changqing Oilfield: It was put into development in 2013. A total of 8 faults trending northwest-southeast are developed, among which 4 are northeast-dipping faults and 4 are southwest-dipping faults. The reservoir permeability is 2.48 mD, the effective thickness of the reservoir is 15.6 m, the injection-production correspondence rate is 48.5%, the oil production rate is 0.38%, and the recovery degree is 3.27%. Using the method of the present invention to increase the single-well output of the fault-block reservoir, the specific steps are as follows:

[0043] Step 1: Screen eligible reservoirs:

[0044] The screening of the reservoir needs to meet the following conditions: 1.0 mD < reservoir permeability < 10.0 mD, effective thickness of the reservoir ≥ 13.0 m, injection-production correspondence rate < 50%, oil production rate < 0.5%, and recovery degree < 5.0%.

[0045] This reservoir has well-developed faults, with a reservoir permeability of 2.48 mD, an effective thickness of the reservoir of 15.6 m, an injection-production correspondence rate of 48.5%, an oil production rate of 0.38%, and a recovery degree of 3.27%, meeting the reservoir screening criteria of the present invention, and the present invention can be implemented.

[0046] Step 2: Determine the remaining oil reserves and remaining oil positions in the eligible reservoir;

[0047] Taking different fault blocks as units, calculate the reserves of each fault block by the volume method;

[0048] The geological reserves are determined by the following formula: N = 100 × A × φ × H × S oi × ρ o / B oi

[0049] In the formula: A—the oil-bearing area of the reservoir (km 2 );

[0050] ρ o —crude oil density (g / cm 3 );

[0051] φ—porosity;

[0052] B oi —Original formation volume factor;

[0053] S oi —Average oil saturation of original formation oil;

[0054] H—Average effective thickness of formation (m);

[0055] N—Geological reserves (10 4 t).

[0056] Table 1 Reserve calculation table

[0057]

[0058]

[0059] Analysis of the reserves of each fault block shows that the reserves are mainly concentrated in Fault Blocks ③, ②, ⑤, and ①. The reserves of each fault block are about 1 million tons, and the reserves are 545.67×10 4 t, accounting for 62.4% of the total geological reserves;

[0060] Combined with the fluid and dynamics of the reservoir, a three-dimensional three-phase numerical simulation model is established to clarify the distribution location of the remaining potential of the reservoir. Attached Figure 1 It can be seen that generally, the remaining reserves are mainly concentrated in Fault Blocks ① and ②, mainly concentrated in the edges of the fault blocks, areas with poor reservoir physical properties and areas not controlled by the well pattern.

[0061] Step 3: Increase the dialysis replacement area at the location of the remaining oil in the reservoir;

[0062] Implementation parameters of energy storage fracturing: average sand addition volume of 70m 3 、average displacement of 5.0m 3 / min, average preflush volume of 1200m 3 、average shut-in time after fracturing of 12 days, forming a complex fracture network, injecting a large volume of fluid, storing energy by shut-in after fracturing, oil-water dialysis, replacement, and through numerical simulation Figure 2 It can be seen that a complex fracture network is formed in Reservoir A after energy storage fracturing, and the well conductivity increases by 3 times.

[0063] Step 4: Increase the effective period of the single-well increment;

[0064] Based on the evaluation of the development technical policy after overall energy storage fracturing: the reasonable flowing pressure should be 12.0 MPa, the current flowing pressure is 9.0 MPa, which is less than the reasonable value; the reasonable pressure maintenance level is 70%, and the actual pressure maintenance level is 65%, which is less than the reasonable value; the reasonable oil production rate is 0.65, and the actual oil production rate is 0.41, which is less than the reasonable value; 9 oil wells in segmented blocks are converted to injection wells, realizing the reconstruction of the injection-production system, the flowing pressure is restored to 12.0 MPa, the pressure maintenance level is restored to 70.0%, the oil production rate is increased to 0.66, and the validity period of effectively increasing the single-well production is achieved.

[0065] Step 5: Field test and effect evaluation;

[0066] After adopting this technology for treatment in this oil reservoir, the average single-well production has increased by 2.5 times, and the oil production rate has increased from 0.38 to 0.65%. At the same time, by converting oil wells to injection wells, the problem of the oil increment period after the increase in single-well production is effectively solved, the natural decline is reduced by 1.5 percentage points, and the monthly recovery rate of the pressure maintenance level is 9.5%. As Figure 3 , it is predicted that the cumulative oil production will increase by 260,000 tons by 2028, and the recovery rate will increase by 3.0 percentage points, effectively increasing the single-well production of the fault-block oil reservoir.

[0067] Finally, it should be noted that: the above-described embodiments are only specific implementation manners of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for increasing the single-well production of fault-block reservoirs, characterized in that Including: Step 1: Screen eligible reservoirs: The screening of reservoirs needs to meet the following conditions: 1.0 mD < reservoir permeability < 10.0 mD, reservoir effective thickness ≥ 13.0 m, injection-production correspondence rate < 50%, oil production rate < 0.5%, recovery factor < 5.0%; Step 2: Determine the remaining oil reserves and remaining oil locations in the eligible reservoirs; Taking different fault blocks as units, calculate the reserves of each fault block using the volumetric method; the geological reserves are determined by the following formula: Where: A—the oil-bearing area of the reservoir, km 2 ; ρ o — Crude oil density, g / cm 3 ; — Porosity; B oi — Original formation volume factor; S oi — Average oil saturation of the original formation oil; H—the average effective thickness of the formation, m; N - Geological reserves, 10 4 t; Combined with the fluid and dynamics of the reservoir, establish a three-dimensional three-phase numerical simulation model to clarify the distribution location of the remaining potential of the reservoir; Step 3: Increase the dialysis replacement area of the remaining oil location in the reservoir; Implementation parameters of energy storage fracturing: average sand addition volume 70 m 3 、average displacement 5.0 m 3 / min, average preflush fluid volume 1200 m 3 、average shut-in time after fracturing 12 days, forming a complex fracture network, injecting a large volume of fluid, storing energy during shut-in after fracturing, oil-water dialysis, replacement Step 4: Increase the incremental validity period of a single well; Based on the evaluation of the development technical policy after overall energy storage fracturing: judge whether the daily incremental oil production, oil production rate, natural decline, and pressure maintenance level of a single well reach the expectations; When the reasonable flowing pressure should be 12.0 MPa, the actual flowing pressure is 9.0 MPa, less than the reasonable value; the reasonable pressure maintenance level is 70%, the actual pressure maintenance level is 65%, less than the reasonable value; the reasonable oil production rate is 0.65, the actual oil production rate is 0.41, less than the reasonable value; implement the conversion of oil wells to injection wells in different fault blocks to realize the reconstruction of the injection-production system, the flowing pressure is restored to 12.0 MPa, the pressure maintenance level is restored to 70.0%, and the oil production rate is increased to 0.6; Step 5: Field test and effect evaluation.

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