Design method for improving recovery efficiency through oil washing, energy storage, capacity expansion and huff-puff of tight oil horizontal well

Abstract

The invention belongs to the field of tight gas reservoir evaluation and research, and particularly relates to a design method for improving the recovery efficiency through tight oil horizontal well washing oil energy storage capacity expansion huff and puff, and the design method comprises the following steps: S1, preferably selecting a nanometer surfactant system suitable for target tight oil horizontal well matrix pores and pore throat sizes, S2, designing parameters of a washing oil slug part, and S3, designing the parameters of the washing oil slug part. According to the method, by means of the oil washing, energy storage and capacity expansion combined mode, secondary transformation and production increasing of the depletion type exploitation tight oil horizontal well are achieved, and the recovery efficiency of the tight oil horizontal well is improved. According to the method, eight wells are tested on site in Hongshan and Qianan tight oil blocks of Jilin oil fields, a good application effect is achieved, obvious liquid increasing and oil increasing effects are shown, and high practicability is achieved.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field development, and in particular relates to a design method for improving the recovery rate of a tight oil horizontal well by washing oil and storing energy and expanding the capacity. Background Art

[0002] The development of tight oil horizontal wells in Jilin Oilfield is based on volume fracturing. In the later stage, the main method is depletion. The initial production is high, but the stable production capacity is poor and the production decreases rapidly. After 14-31 months of self-flowing, the pumping is carried out. The liquid production decreases by 25%-30% in the first year after the stable production period, and the oil production decreases by 15%-16%. The dynamic liquid level drops (wells below 1000m account for 43%), the daily oil production decreases (wells below 3t account for 25%), and the formation is empty (flowback rate is 244%). The energy replenishment opportunity of the existing technology is mainly concentrated after the horizontal well fracturing is completed and exhausted for a period of time, that is, in the middle and late stages of the horizontal well life cycle, energy is replenished by injecting water or gas. The effective permeability of the reservoir is low, the average pore throat radius is below 500nm, the movable fluid saturation is low, and the liquid systems such as guar gum, slick water, and conventional surfactants used for fracturing are all micron-sized, which makes it difficult to effectively enter the matrix pores. The injection start-up pressure of small pores is high, and the reservoir migration capacity is poor. Therefore, how to combine the physical properties of tight oil reservoirs, how to wash out the crude oil in the micropores and carry it out of the well, and how to maximize the overall effect of tight oil layers have become the key and difficulty of improving the recovery rate of horizontal wells in tight oil reservoirs.

[0003] At present, the commonly used methods for improving the recovery rate of tight oil horizontal wells are mainly based on water injection, CO2 injection, and fracturing injection. The main principle is to increase the energy of the formation, and to achieve the purpose of increasing oil by realizing the dialysis replacement of the reservoir matrix through long-term well shut-in, which has achieved certain results overall. Water injection and CO2 injection storage are mainly based on the original fracture space, and the treatment target has not been further expanded; the natural dialysis replacement with water and CO2 as the medium has poor replacement effect and efficiency, and the oil-increasing capacity is insufficient; water injection and CO2 storage based on single well or multi-well asynchronous are mainly based on the original fracture channel and space, which is easy to form invalid circulation channels, and the ultimate recovery rate is limited. Simply fracturing "A fracturing method for replenishing formation energy in tight oil reservoirs" can further expand the swept volume, but for tight oil horizontal wells with severe depletion, a large amount of liquid is needed to replenish the energy of the original reservoir. Early injection by fracturing has been shown in field applications to be mainly focused on the expansion and filling of original fractures, and it is difficult to open new fractures and further expand the swept volume. Under the premise of achieving the basic goal of achieving an original formation pressure of more than 1.0 for energy storage, the liquid consumption is high and the cost is high, and the effect of improving recovery rate and economic benefits are poor.

[0004] Based on this, it is urgent to study a method based on a three-dimensional well network to improve the dialysis capacity of horizontal wells, increase reservoir energy, and further increase the transformation volume to control decline, extend the stable production period, and improve the recovery rate. Summary of the invention

[0005] In order to make up for the shortcomings of the prior art, the present invention is based on the integrated technology of oil washing, energy storage and capacity expansion, with the goal of further improving the matrix dialysis replacement capacity and further increasing the transformation volume of the target well. For tight oil horizontal wells that lack effective energy supplementation, the well throughput method is adopted to effectively improve the recovery rate. A design method. The main body adopts a 0.3-0.5% high-concentration nano-permeability non-ionic surfactant system to effectively enter the basic pores and roar channels of the tight oil reservoir, increase the number of capillaries by reducing the oil-water interfacial tension, and improve the matrix dialysis replacement capacity; a 0.05-0.1% low-concentration nano-permeability non-ionic surfactant system is used for energy supplementation, and the reservoir energy supplement is completed with a low-cost system, which effectively improves the oil washing capacity in the original volume fracturing cracks while achieving energy supplementation; a 0.1-0.3% medium-concentration nano-permeability non-ionic surfactant system is used to temporarily plug the diverted fracturing, and the transformation volume of the reservoir is further increased on the basis of the original volume fracturing transformation, and the high-efficiency surfactant system is used to further expand the swept volume, so as to achieve the effect of improving the recovery rate of tight oil horizontal well throughput. At the same time, this method can be applied to a single well, and can also be carried out simultaneously in multiple wells such as parent and child wells. On the basis of the above effects, effective interference of multiple wells can be achieved, and on the basis of the above effects, the displacement effect of multiple wells can be achieved.

[0006] The purpose of the present invention is to provide a design method for improving oil recovery by washing oil, storing energy and expanding capacity of tight oil horizontal wells. In order to achieve the above-mentioned purpose, the present invention provides a tight oil horizontal well throughput development method based on a single well and a three-dimensional well pattern, wherein the method comprises:

[0007] S1 Optimize the nano-surfactant system suitable for the matrix pores and pore size of the target tight oil horizontal well, with the principle of "enter, wash, go far, and flow out", based on the dialysis, oil washing, and surface tension evaluation experiments of the target well core and oil products, determine the use range of different concentrations of the nano-surfactant system; Based on the characteristics of the tight oil horizontal wells in Jilin Oilfield, from the distribution relationship between the core pore radius and the throat radius of different permeabilities, the diameter of the liquid system should be as small as possible. 54nm; The liquid system has a good oil washing efficiency and a good effect on improving wettability; The liquid system has a good ability to resist formation core adsorption, and the effective ingredients can play a role at the oil-water interface as much as possible; The mixture of the liquid system and crude oil should be able to smoothly pass through the throat and flow out;

[0008] The parameters of the S2 oil wash plug are designed to inject a certain volume of high-concentration nanosurfactant system. This step increases the number of capillaries by reducing the oil-water interfacial tension, improves the dialysis replacement capacity of the energy storage front matrix, and realizes partial energy storage function at the same time;

[0009] (1) Dosage design method:

[0010]

[0011] Q1: amount used in the oil washing stage; Q0: cumulative oil production, t; Ρ0: crude oil density, g / cm 3 ; B0: crude oil volume coefficient; Q 累产 : Cumulative liquid production of a single well, t; Q 压裂液 : Fracturing fluid injection volume, m 3 ; B w : Volume coefficient of water, 1.001 (constant); δ: Oil washing front coefficient, 0.33-0.5;

[0012] (2) Injection speed design:

[0013] CMG software was used to simulate and analyze the changes in injection volume and pressure during oil washing, energy storage and expansion based on historical matching. In the oil washing stage, as the injection rate increased, the injection time decreased, but the total injection volume increased slightly. A simulation study of well shut-in after energy storage at different injection rates was carried out. The formation pressure did not change much before and after well shut-in. The maximum injection rate was used without opening the reservoir.

[0014] The S3 energy storage segment plug parameter design injects a large amount of low-concentration nano-surfactant system for energy replenishment, which effectively improves the oil washing capacity in the original volume of fracturing fractures while achieving energy replenishment. The dosage design principle is based on the reservoir liquid deficit, and at the same time ensures that the reservoir pressure is ≥ the original formation pressure after the injection is completed;

[0015] (1) Dosage design method:

[0016]

[0017] Q2: amount used in the energy storage stage; Q1: amount used in the oil washing stage; Q0: cumulative oil production, t; Ρ0: crude oil density, g / cm 3 ; B0: crude oil volume coefficient Q 累产 : Cumulative liquid production of a single well, t; Q 压裂液 : Fracturing fluid injection volume, m 3 ; B w : Volume coefficient of water, 1.001 (constant); δ: Oil washing front coefficient, 0.33-0.5;

[0018] (2) Injection speed design:

[0019] CMG software was used to simulate and analyze the injection volume and pressure changes of oil washing, energy storage and expansion based on historical matching. A simulation study of well shut-in after energy storage at different injection rates was conducted. With the increase of injection rate, the bottom hole pressure change before and after well shut-in increased. The simulation study of expansion after low-displacement energy storage showed that the higher the injection rate, the less total time required to reach the target pressure; the pressure diffusion range was not much different at different injection rates, but the lower the injection rate, the more uniform the formation pressure distribution; considering the construction period comprehensively, the energy storage displacement was preferably a moderate displacement;

[0020] The parameters of the S4 expansion segment plug are designed to inject a certain volume of medium-concentration nano-surfactant system in the form of temporary plugging and sand fracturing, further increasing the reservoir reconstruction volume on the basis of the original volume fracturing reconstruction, and further expanding the swept volume with a high-efficiency surfactant system;

[0021] Combined with the reservoir geological characteristics and adjacent well characteristics of the target well, the fracture length and height range of the target well during the expansion phase are determined. Combined with the on-site well conditions, the fracturing technology and materials are determined, and the injection volume, injection speed and sand addition amount during the expansion phase are determined using PT software;

[0022] The S5 well soaking time design injects a certain volume of medium-concentration nano-surfactant system by temporarily plugging and switching to sand fracturing. On the basis of the original volume fracturing stimulation, the reservoir stimulation volume is further increased, and the swept volume is further expanded with the efficient surfactant system.

[0023]

[0024] ΔL——half the distance from the fracture network to the matrix center, m; фm——porosity, %; μ——liquid viscosity, mPa.s; Km——matrix permeability, mD; ΔP——driving pressure, MPa; G——starting pressure gradient, MPa / m.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The advantage of the present invention is that through the combination of oil washing, energy storage and capacity expansion, the secondary transformation and production increase of the exhausted tight oil horizontal wells can be achieved, thereby improving the recovery rate of the tight oil horizontal wells. The surfactant system required by the invention can enter the nano-matrix pores of the tight oil to achieve efficient oil washing; the effective recovery of reservoir energy and the dialysis replacement under the surfactant system can be achieved in the energy storage segment plug; in the capacity expansion stage, the transformation volume of the tight oil horizontal wells is further expanded by using the method of efficient temporary plugging and diverting fracturing (sand fracturing); in the later stage, the recovery rate of the tight oil horizontal wells can be improved through a reasonable well soaking and oil production system. The invention has been tested on 8 wells in the Honggang and Qian'an tight oil blocks of Jilin Oilfield, and has achieved good application results, showing obvious effects of increasing fluid and oil, and has high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The invention provides the knowledge of reservoir matrix pore distribution;

[0028] Figure 2 The particle size distribution of the nano surfactant system provided by the present invention;

[0029] Figure 3 The present invention provides a mechanism for the storage and washing of oil in a tight oil horizontal well to expand the capacity and discharge the oil;

[0030] Figure 4 The CMG software simulation injection speed optimization in the energy storage stage provided by the present invention;

[0031] Figure 5 The expansion stage provided by the present invention combines the crack length and height parameter optimization design;

[0032] Figure 6 This is a well soaking time calculation model provided by the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical means and objectives adopted by the present invention easy to understand, the present invention is further described below in conjunction with specific implementation methods.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0035] Embodiment 1:

[0036] Well Example 1: Nano-infiltration nonionic surfactant (ZY-2#) with high concentration of 0.3%, medium concentration of 0.2%, and low concentration of 0.1% is selected as the main surfactant system for oil washing; the total deficit of this well according to geological reserve calculation is 10000m 3 ; By calculating the amount of wash oil plug 3300m 3 (0.3%ZY-2#); energy storage segment plug 6300m 3 (0.1% ZY-2#); high-strength temporary plugging agent + multi-size temporary plugging balls for temporary plugging and sand fracturing, slick water variable displacement design 10-12-14m 3 / min, single-stage sand volume 100m 3 , 4 clusters are opened in a single stage, the half-slit length of each cluster is 105m, the support seam height is 20m, and the total liquid volume in the optimized expansion stage is 7000m 3 , total sand volume is 680m3.

[0037] Embodiment 2:

[0038] Well Example 2: ZY-2# nano surfactant high concentration 0.3%, medium concentration 0.2%, low concentration 0.1% is preferred as the main surfactant system for oil washing; the total deficit of this well is 6000m based on geological reserve calculation.3 ; By calculating the amount of wash oil plug 3000m 3 (0.3%ZY-2#); energy storage segment plug 3000m 3 (0.1% ZY-2#); high-strength temporary plugging agent + multi-size temporary plugging ball temporary plugging fracturing (without adding sand) is adopted for capacity expansion, and the variable displacement design of slick water is 10m 3 / min, the length of each cluster half seam is 100m, the support seam height is 15m, and the total liquid volume in the optimization expansion stage is 4500m 3 .

[0039] Although some embodiments of the present invention have been given herein, those skilled in the art should understand that the embodiments of the present invention may be modified without departing from the spirit of the present invention. The above embodiments are merely exemplary and should not be used as a limitation on the scope of the present invention.

Claims

1. A design method for improving oil recovery by washing oil, storing energy and expanding capacity for horizontal wells of tight oil, characterized by: The following steps are involved: S1 Based on the nano-surfactant system suitable for the matrix pores and pore size of the target tight oil horizontal well, with the principle of "entering, washing, moving far and flowing out", based on the dialysis, oil washing and surface interfacial tension evaluation experiments of the target well core and oil products, the use range of different concentrations of the nano-surfactant system is determined; S2 designs some parameters of the oil wash slug, including dosage and injection speed, and injects a certain volume of high-concentration nanosurfactant system; S3 designs some parameters of the energy storage segment plug, including dosage and injection speed. A large amount of low-concentration nanosurfactant system is injected for energy replenishment, which effectively improves the oil washing capacity in the original volume of fracturing fractures while achieving energy replenishment. The dosage design principle is based on the reservoir liquid deficit, and at the same time ensures that the reservoir pressure is ≥ the original formation pressure after the injection is completed; S4 designs the parameters of the expansion segment plug, injects a certain volume of medium-concentration nano-surfactant system in the way of temporary plugging and sand fracturing, further increases the reservoir transformation volume on the basis of the original volume fracturing transformation, and further expands the affected volume with a high-efficiency surfactant system; determines the fracture length and fracture height range of the target well in the expansion stage in combination with the reservoir geological characteristics and the characteristics of the adjacent wells, determines the fracturing technology and materials to be used in combination with the on-site well conditions, and uses PT software to determine the injection volume, injection speed and sand addition volume in the expansion stage; S5 designs the well shut-in time and injects a certain volume of medium-concentration nano-surfactant system in the way of temporary plugging and switching to sand fracturing. On the basis of the original volume fracturing transformation, the transformation volume of the reservoir is further increased, and the swept volume is further expanded with a high-efficiency surfactant system.

2. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1 is characterized in that: The diameter of the nano-surfactant system is less than 54 nm.

3. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1 is characterized in that: The nano surfactant system has good oil washing efficiency and good wettability improvement effect; it has good resistance to formation core adsorption, and the effective ingredients can play a role at the oil-water interface as much as possible.

4. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1, characterized in that: The mixture of the nano surfactant system and crude oil flows out smoothly through the throat.

5. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1, characterized in that: The design method of the dosage in step S2 is: Q1: amount used in the oil washing stage; Q0: cumulative oil production, t; Ρ0: crude oil density, g / cm 3 ; B0: crude oil volume coefficient; Q 累产 : Cumulative liquid production of a single well, t; Q 压裂液 : Fracturing fluid injection volume, m 3 ; B w : Volume coefficient of water, 1.001 (constant); δ: Oil washing front coefficient, 0.33-0.

5.

6. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1, characterized in that: The injection rate design method described in step S2 is: using CMG software to carry out simulation analysis of oil washing, energy storage and expansion injection volume and pressure changes based on historical matching. In the oil washing stage, as the injection rate increases, the injection time decreases, but the total injection volume increases slightly. A simulation study of well shut-in after energy storage at different injection rates is carried out. The formation pressure does not change much before and after well shut-in, and the maximum injection rate is used without pressurizing the reservoir.

7. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells according to claim 1, characterized in that: The design method of the dosage in step S3 is: Q2: amount used in the energy storage stage; Q1: amount used in the oil washing stage; Q0: cumulative oil production, t; Ρ0: crude oil density, g / cm 3 ; B0: crude oil volume coefficient Q 累产 : Cumulative liquid production of a single well, t; Q 压裂液 : Fracturing fluid injection volume, m 3 ; B w : Volume coefficient of water, 1.001 (constant); δ: Oil washing front coefficient, 0.33-0.

5.

8. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells as claimed in claim 1 is characterized in that: The injection rate design method described in step S3 is: using CMG software to carry out simulation analysis of oil washing, energy storage and expansion injection volume and pressure change based on historical fitting, and simulate well shut-in after energy storage at different injection rates. As the injection rate increases, the bottom hole pressure change before and after shut-in increases. The simulation study of capacity expansion after low-displacement energy storage believes that the higher the injection rate, the less total time required to reach the target pressure; the pressure diffusion range is not much different for different injection rates, but the lower the injection rate, the more uniform the formation pressure distribution; taking into account the construction period, the energy storage displacement is preferably a moderate displacement.

9. The design method for improving oil recovery by washing oil and storing energy for horizontal tight oil wells as claimed in claim 1, characterized in that: The soaking time in step S5 is calculated according to the following formula: ΔL——half the distance from the fracture network to the matrix center, m; фm——porosity, %; μ——liquid viscosity, mPa.s; Km——matrix permeability, mD; ΔP——driving pressure, MPa; G——starting pressure gradient, MPa / m.

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