CN106194145B - Multistage temporary plugging deep network acid fracturing method - Google Patents
Multistage temporary plugging deep network acid fracturing method Download PDFInfo
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- 230000035699 permeability Effects 0.000 claims abstract description 22
- 239000011229 interlayer Substances 0.000 claims abstract description 5
- 238000005530 etching Methods 0.000 claims abstract description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 58
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- 238000002347 injection Methods 0.000 claims description 24
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- 238000010276 construction Methods 0.000 claims description 20
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
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- E21B43/26—Methods for stimulating production by forming crevices or fractures
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Abstract
The invention discloses a multistage temporary plugging deep network acid fracturing method, and belongs to the technical field of yield increase modification of oil and gas wells. The method comprises the following steps: forming a bridge plug in the artificial crack by using the temporary plugging material liquid in the crack, forcing the artificial crack to form a plurality of branch cracks, and etching the crack by using a main body acid; and (3) forming a bridge plug at the seam of the artificial crack by using the seam temporary plugging material liquid, so that the crack is forced to crack at a new position of the well wall, and the interlayer steering is realized. The multistage temporary plugging deep network acid fracturing method provided by the invention has the advantages of simple process, convenience in operation and the like, can enable different permeability zones of a multilayer, thick layer or horizontal well long well section in the carbonate rock to form a complex fracture network by combining the principle of hydraulic self-search and artificial regulation, increases the probability of communicating an oil-gas area, reduces the oil-gas seepage resistance, improves the yield of a single well, and enables the carbonate rock reservoir to be developed efficiently and economically.
Description
Technical Field
The invention relates to the technical field of yield increasing transformation of oil and gas wells, in particular to a multistage temporary plugging depth network acid fracturing method for improving the yield of a carbonate oil and gas well, which is used for repeated transformation of an old well and yield increasing transformation of a new well.
Background
Fracture acidizing is one of the important yield increasing technologies for carbonate oil and gas reservoirs. In the oil and gas well with multiple layers, thick layers or long well sections of a horizontal well, because the permeability difference of each layer section is large, the conventional multi-oil (gas) layer whole-well acidizing fracturing can only reform a certain weak layer, and therefore the layer-by-layer reformation is needed to ensure the reformation of the layer section with low permeability. Currently, the processes used include blocking ball zonal acid fracturing, packer acid fracturing, temporary plugging agent zonal acid fracturing, and the like. Firstly, plugging ball layering is only suitable for perforation completion; secondly, mechanical packing equipment is complex to operate, high in corrosion resistance requirements and high in cost, and temporary plugging agent delamination can overcome the problems.
In addition, each layer is required to be efficiently reformed while the fact that each layer is reformed is ensured. The yield-increasing effect of acid fracturing is closely related to the length and the number of artificial fractures. Because the permeability of the carbonate rock matrix is low, a complex fracture network is formed by utilizing high-density artificial fractures as much as possible in the acid fracturing process, so that the oil-gas seepage resistance and the seepage distance to the fracture are greatly reduced. In order to obtain complex fractures of high density, a suitable intra-fracture chemical bridging agent is used to cause the fracturing fluid to partially bridge within the fracture to form a differential pressure value above the fracture pressure, and the fracturing fluid enters a high stress zone or a new fracture layer to promote the generation of new fractures. Currently common chemical diversion methods include: foam diversion, cross-linked polymer diversion, and viscoelastic surfactant diversion. The above chemical diversion methods all have certain limitations: the foam steering can not be used for an oil layer, is greatly influenced by temperature, has a high leakage phenomenon in a reservoir with extremely high permeability, has very low effectiveness and needs ground nitrogen-containing equipment; the crosslinked polymer steering technology has great damage to the stratum, and the thorough gel breaking is difficult; viscoelastic surfactants are expensive to turn.
Disclosure of Invention
In order to solve the problems of high corrosion resistance requirement, complex mechanical packing operation, limited steering of chemical temporary plugging agents and the like in the existing layered acidizing and fracturing of oil and gas wells, the invention provides a multistage temporary plugging deep network acid fracturing method, which comprises the following steps: forming a bridge plug in the artificial crack by using the temporary plugging material liquid in the crack, forcing the artificial crack to form a plurality of branch cracks, and etching the crack by using a main body acid; and (3) forming a bridge plug at the seam of the artificial crack by using the seam temporary plugging material liquid, so that the crack is forced to crack at a new position of the well wall, and the interlayer steering is realized.
The method specifically comprises the following steps:
injecting a front acid, a fracturing fluid and a main acid into the stratum to form an artificial fracture; the discharge capacity of the preposed acid is reversely calculated by a steady-state flow formula of a constant-pressure boundary oil layer:
wherein: qiPre acid displacement, m3/min；Ki-reservoir permeability, mD; h isi-reservoir effective thickness, m; pf-minimum rupture pressure, MPa, of each level;-well area mean reservoir pressure, MPa; μ -pre-acid viscosity, mPa · s; r ise-oil and gas well drainage radius, m; r isw-wellbore radius, m; s-epidermal coefficient;
the fracturing fluid is hyperbranched fracturing fluid crosslinked under a weak acid condition;
injecting a temporary plugging material liquid into the stratum, forming a bridge plug in the artificial fracture, and forcing the artificial fracture to form a plurality of branch fractures;
repeating the steps of injecting the fracturing fluid, injecting the main acid and injecting the temporary plugging material liquid into the seam for multiple times according to the reservoir conditions and actual needs, thereby forming a complex seam network;
injecting closed acid into the stratum, wherein the dosage of the closed acid is 20% -40% of that of the main acid, and the dosage of the closed acid is 1.0-3.0 m3The discharge volume of the injection is 20-150 m to the stratum3The blocking acid of (a);
injecting a seam temporary plugging material liquid into the stratum to form a bridge plug at the seam of the artificial crack, so that the crack is forced to crack at a new layer of the well wall, and the interlayer steering is realized. The step of injecting the seam temporary plugging material liquid into the stratum specifically comprises the following steps: forming a bridge plug at the seam by using low-concentration seam temporary plugging material liquid, wherein the method comprises the steps of bridging by using 1-3 mm temporary plugging materials, reducing the permeability of a bridging part by using 0.125-1 mm temporary plugging materials, and gradually opening a crack and increasing the width along with the increase of pressure in the seam formed by the bridge plug; the concentration of the temporary plugging agent material liquid at the seam is increased to complete the plugging of the seam, so that enough pressure is obtained to open the low-permeability layer;
the pre-acid and the closed acid are formed by mixing hydrochloric acid with the concentration of 10-20%, a corrosion inhibitor, a resistance reducing agent and a gelling agent; the seam temporary plugging material liquid is formed by mixing a seam temporary plugging agent and weak acid; wherein the concentration of the temporary plugging agent for the seam is 3-15%; the performance indexes of the temporary plugging agent for the seam are as follows: the grain size is 0.125-3 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 4-8 h.
The main acid comprises one or more of gelled acid, ground cross-linking acid, temperature-control variable viscosity acid, foam acid and emulsified acid which take hydrochloric acid as a main component.
The temporary plugging material liquid in the gap is formed by mixing a temporary plugging agent in the gap and weak acid; wherein the concentration of the temporary plugging agent in the seam is 3-15%; the performance indexes of the temporary plugging agent in the seam are as follows: the grain size is 0.125-1 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 3-5 h.
The discharge capacity of the temporary plugging material liquid in the seam is as follows:
wherein: q2Discharge of temporary plugging material liquid in the slot, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q1-the flow rate of temporary plugging material liquid in the slot for laboratory experiment, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2；
The dosage of the temporary plugging agent in the seam is as follows:
M1＝Q2t1N1(1+η1)
wherein: m1-amount of temporary plugging agent in the seam, kg; q2Discharge of temporary plugging material liquid in the slot, m3/min；t1-laboratory experiment injection time, min; n is a radical of1Concentration of temporary plugging agent in the suture, g/L η1-rate of loss of temporary plugging agent in the joint,%.
The discharge capacity of the seam temporary plugging material liquid is as follows:
wherein: q4Discharge of material liquid for temporary closure of the seam, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q3-laboratory experimental injection flow of seam temporary plugging material liquid, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2；
The dosage of the temporary plugging agent at the seam opening is as follows:
M2＝Q4t2N2(1+η2)
wherein: m2-amount of temporary plugging agent for the seam, kg; q4Discharge of material liquid for temporary closure of the seam, m3/min；N2-seam temporary blocking agent concentration, g/L; t is t2Laboratory experiment injection time, min η2-rate of loss of temporary plugging agent at the seam opening,%.
The multistage temporary plugging deep network acid fracturing method provided by the invention has the advantages of simple process, convenience in operation and the like, and can form a complex fracture network in different permeability zones of a multilayer, thick layer or horizontal well long well section in the carbonate rock by combining the principle of hydraulic self-search and artificial regulation, increase the probability of communicating oil-gas regions, reduce the oil-gas seepage resistance, improve the yield of a single well, and efficiently and economically develop the carbonate rock reservoir. The multistage temporary plugging depth network acid fracturing method provided by the invention can be used for the yield increasing transformation construction of a vertical well, and can also be used for the yield increasing transformation construction of a horizontal well, an inclined well and the like.
Drawings
FIG. 1 is a schematic structural diagram of a vertical well fracturing string of the multistage temporary plugging depth network acid fracturing method of the embodiment;
FIG. 2 is a schematic diagram of a manual network sewing of the multistage temporary plugging deep network acid fracturing method according to the embodiment;
fig. 3 is a flowchart of the multistage temporary plugging deep network acid fracturing method according to the present embodiment.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Referring to fig. 3, the multistage temporary plugging deep network acid fracturing method provided by the embodiment of the present invention includes the following steps:
step S1: and setting the dosage and the displacement of the pre-acid according to the characteristic attributes of the reservoir, and injecting the pre-acid into the stratum so as to improve the liquid absorption capacity of the reservoir.
The reservoir characteristic attributes mainly comprise reservoir thickness, pore permeability characteristics and the like. The dosage and the discharge capacity of the preposed acid are set according to the thickness of a reservoir layer, pore permeability characteristics and the like. The purpose of injecting the preposed acid is to dredge a reservoir stratum in a near wellbore area, remove pollution and promote stratum imbibition, which is equivalent to a simple matrix acidification, so that the blockage removal radius R is 1.2m according to the conventional matrix acidification, and the thickness of each reservoir stratum is hi(i ═ 1, 2, 3, 4, 5) meters, and the average porosity of the reservoir is φi(i ═ 1, 2, 3, 4, 5) corresponding to permeability K1>K2>K3>K4>K5Therefore, the amount of pre-acid used in each reservoir is VFront side＝πR2hiφiAnd the acid injection amount of each stage is calculated according to the corresponding thickness from high to low of the reservoir permeability. According to the principle of minimum resistance, acid liquor enters each interval from high to low in sequence according to the permeability. The displacement of the pre-acid (i.e. the displacement of the pre-acid delivery pump) is increased as much as possible under the premise that the construction pressure is lower than the formation fracture pressure. The displacement of the preposed acid is reversely calculated by a steady-state flow formula of a constant-pressure boundary oil layer:
wherein: qiPre acid displacement, m3/min；Ki-reservoir permeability, mD; h isi-reservoir effective thickness, m; pf-minimum rupture pressure, MPa, of each level;
-well area mean reservoir pressure, MPa; μ -pre-acid viscosity, mPa · s; r ise-oil and gas well drainage radius, m; r isw-wellbore radius, m; s-skin coefficient (related to completion mode, well wall contamination, etc., obtained from pressure recovery curve interpretation).
And after the dosage and the discharge capacity of the front acid are determined, injecting the front acid into the stratum through a front acid delivery pump. The front acid is formed by mixing hydrochloric acid with the concentration of 10-20%, a corrosion inhibitor, a resistance reducing agent and a gelling agent.
Step S2: and injecting fracturing fluid into the stratum to suppress the reservoir stratum to form an artificial crack.
The method comprises the steps of firstly calculating wellhead pressures under different discharge capacities, determining that the wellhead pressures are lower than wellhead pressure limiting to obtain a discharge capacity range, then calculating the half-seam length, seam height, upper seam height, lower seam height and average seam width under the conditions of different discharge capacities and fracturing fluid consumption by using fracturing software, then determining whether seam control is needed according to well water layers, natural fractures and fault development conditions, optimizing the discharge capacity of the fracturing fluid according to the requirements of seam control, ① increasing the discharge capacity of the fracturing fluid as much as possible within a wellhead pressure bearing range if seam control is not needed, if the discharge capacity of the fracturing fluid is larger, the longer the seam made by the same volume of the fracturing fluid is, the minimum using amount of the fracturing fluid required by the same length of the seam is obtained, ② if the well zone development or the adjacent layer is thin, simulating the fracture height extension conditions under different well zones on the premise of determining top and bottom discharge capacity, ensuring that the fracture cannot communicate with a lower water body or a through layer, obtaining a discharge capacity range of the fracturing fluid, optimizing the discharge capacity of the fracturing fluid, determining the corresponding to the optimal fracturing fluid, and reducing the construction cost of the half-fracture height of the fracturing fluid, the optimal fracturing fluid, the fracturing fluid.
Step S3: and injecting main acid into the stratum to remove rocks or pollutants in the artificial cracks or communicated natural cracks, and etching the wall surfaces of the cracks to improve the stability and the flow conductivity of the cracks.
The dosage of the main acid is obtained by simulation calculation and optimization of Meyer software. Firstly, acid liquor consumption and discharge capacity are used as independent variables, acid corrosion seam length and flow conductivity are used as objective functions, and acid corrosion seam length under different acid liquor consumption and discharge capacities is calculated through software, so that the acid liquor consumption and discharge capacity corresponding to the optimal acid corrosion seam length and flow conductivity which can be obtained under the condition of site construction are selected. In specific application, the main acid comprises one or more of gelled acid, ground cross-linking acid, temperature-controlled variable viscosity acid, foam acid and emulsified acid which take hydrochloric acid as a main component.
Step S4: injecting a temporary plugging material liquid into the stratum, wherein the temporary plugging agent in the seam forms a bridge plug at a narrow part in the artificial fracture, and the artificial fracture is forced to form a plurality of branch fractures on the plane.
The using amount and the discharge capacity of the temporary plugging material liquid in the gap are determined by simulating the change relation of the plugging pressure gradient of different temporary plugging agent concentrations under different discharge capacities along with the injection time through an indoor experiment by utilizing a manual slit rock core, wherein: the diameter of the core drill is 25mm, and the length of the core drill is 30-80 mm.
The experimental conditions are as follows: closing pressure PClosing deviceThe experimental temperature T is the actual formation parameter of the target block, and the fracture width W1The mean slit width obtained by simulation in step S2. By preparing temporary plugging material liquid with different concentrations, the temporary plugging material liquid is continuously injected into a manual seam rock core under different discharge capacities, and the change relation between the inlet pressure gradient and the plugging rate (representing the permeability change before and after plugging of the rock core) along with the injection time is tested. According to the placeThe required plugging pressure gradient and plugging rate are selected according to the concentration N of the temporary plugging material liquid under the corresponding experimental conditions1(in g/L), appropriate injection displacement Q1(in mL/min), injection time t1(unit is min), according to the principle of motion similarity criterion, the discharge capacity of the temporary plugging material liquid in the seam under the actual construction condition on site is as follows:
in formula (1): q2Discharge of temporary plugging material liquid in the slot, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q1-the flow rate of temporary plugging material liquid in the slot for laboratory experiment, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2。
The dosage of the temporary plugging agent in the gap is as follows:
M1＝Q2t1N1(1+η1) (2)
in formula (2): m1-amount of temporary plugging agent in the seam, kg; q2Discharge of temporary plugging material liquid in the slot, m3/min；t1-laboratory experiment injection time, min; n is a radical of1Concentration of temporary plugging agent in the suture, g/L η1The loss rate of the temporary plugging agent in the seams is percent (the temporary plugging agent in the seams can enter other natural fractures or a well bore to be retained in an actual stratum due to small size to cause loss, and the loss rate is generally 70-90 percent).
In a specific application, the intra-seam temporary plugging material liquid delivery pump injects the intra-seam temporary plugging material liquid into a stratum at the obtained discharge capacity, and the intra-seam temporary plugging agent forms bridge plugging at a narrow part in an artificial fracture to force the artificial fracture to form a plurality of branch fractures on a plane or excite a potential natural fracture, as shown in fig. 2. The temporary plugging material liquid in the gap is formed by mixing a temporary plugging agent in the gap and weak acid (such as organic acid such as formic acid); wherein, the concentration of the temporary plugging agent in the seam is 3 to 15 percent; the performance indexes of the temporary plugging agent in the gap are as follows: the grain size is 0.125-1 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 3-5 h. In a specific application, the steps S2 to S4 may be repeatedly performed for a plurality of times according to reservoir conditions and actual needs, so as to form a complex seam network.
Step S5: and injecting closed acid into the stratum to further etch the wall surface of the crack, deepen the non-uniform grooves on the wall surface, stabilize the flow conductivity of the crack and improve the permeability of the existing artificial crack.
The dosage of the closed acid needs to be determined by combining the on-site stratum condition and the construction effect of an adjacent well, and the dosage of the closed acid is about 20 to 40 percent of the dosage of the main acid generally. Controlling the injection discharge of the closed acid to be 1.0-3.0 m under the condition that the injection pressure is lower than the fracture closing pressure3And/min. In specific application, the closed acid delivery pump is 1.0-3.0 m3The discharge volume of the injection is 20-150 m to the stratum3The closed acid of (1). The closed acid is formed by mixing 10-20% hydrochloric acid, corrosion inhibitor, resistance reducing agent, gelling agent and the like.
Step S6: injecting a seam temporary plugging material liquid into the stratum, forming bridge plugging at the seam of the artificial crack by using the seam temporary plugging agent, building pressure in the shaft, increasing the pressure at the bottom of the shaft, forcing the crack to crack at a new layer of the well wall, and transforming the layer with relatively poor physical properties.
The longer the distance of the temporary plugging material liquid at the seam is, the larger the pressure can be held, so that the temporary plugging material liquid at the seam can be injected in a variable concentration manner in the construction process, and the method specifically comprises the following steps: firstly, forming a bridge plug at a seam by using low-concentration seam temporary plugging material liquid, namely bridging by using 1-3 mm temporary plugging materials, reducing the permeability of a bridging part by using 0.125-1 mm temporary plugging materials, and gradually opening a crack and increasing the width along with the increase of pressure in the seam formed by the bridge plug; then the concentration of the temporary plugging agent material liquid at the seam is increased to complete the plugging of the seam, thereby obtaining enough pressure to open the low permeability layer. The using amount and the discharge capacity of the joint temporary plugging material liquid are determined by simulating the change relation of the plugging pressure gradient of different joint temporary plugging agent concentrations under different discharge capacities along with the injection time through an indoor experiment by utilizing a manual seam cutting core, wherein: the diameter of the core drill is 25mm, and the length of the core drill is 30-80 mm.
The experimental conditions are as follows: closing pressure PClosing deviceThe experimental temperature T is the actual formation parameter of the target block, and the fracture width W2The mean slit width obtained by simulation in step S2. The temporary plugging material liquid for the seam mouths with different concentrations is prepared and continuously injected into the rock core of the artificial seam under different discharge capacities, and the change relation of the inlet pressure gradient along with the injection time is tested. Selecting the concentration N of the temporary plugging material liquid of the seam under the corresponding experimental conditions according to the pressure gradient required by the site construction2(in g/L), appropriate injection displacement Q3(in mL/min), injection time t2(unit is min), according to the principle of motion similarity criterion, the discharge capacity of the temporary plugging material liquid at the seam opening under the actual construction condition on site is as follows:
in formula (3): q4Discharge of material liquid for temporary closure of the seam, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q3-laboratory experimental injection flow of seam temporary plugging material liquid, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2。
The dosage of the temporary plugging agent at the seam is as follows:
M2＝Q4t2N2(1+η2) (4)
in formula (4): m2-amount of temporary plugging agent for the seam, kg; q4Discharge of material liquid for temporary closure of the seam, m3/min；N2-seam temporary blocking agent concentration, g/L; t is t2Laboratory experiment injection time, min η2The loss rate of the temporary plugging agent at the seam opening is percent (the temporary plugging agent at the seam opening has larger size compared with the temporary plugging agent in the seam, has smaller probability of entering a natural seam, has smaller loss rate, and is generally 50 to 70 percent).
In the specific application, the temporary plugging material liquid delivery pump injects the temporary plugging material liquid into the stratum according to the obtained discharge capacity, the temporary plugging agent for the seam forms bridge plugging at the seam of the artificial crack, the pressure is suppressed in the shaft, the pressure at the bottom of the well is increased, and the crack is forced to crack at a new layer of the well wall. The seam temporary plugging material liquid is formed by mixing a seam temporary plugging agent and weak acid (such as organic acid such as formic acid); wherein, the concentration of the temporary plugging agent at the seam is 3 to 15 percent; the performance indexes of the temporary plugging agent for the seam are as follows: the grain size is 0.125-3 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 4-8 h. In a specific application, the steps S1 to S5 are repeatedly carried out for a plurality of times, and acid fracturing construction of different reservoirs is realized.
Step S7: after acid liquor is injected into all reservoirs, displacing liquid is injected into a stratum shaft, the acid liquor is pushed into the deep part of the stratum, the existing cracks are dredged, and the pump is stopped to react and then the reservoir is open-blown to obtain the production.
The usage amount of the displacement fluid is equal to or slightly less than the volume of the well bore, and the displacement is equal to the displacement of the acid injection. In specific application, the displacement liquid (formed by mixing clear water and an anti-swelling agent) pushes the acid liquid into the deep part of the stratum, so that not only can existing cracks be dredged, but also the corrosion of a shaft by accumulated acid of the shaft can be avoided.
The temporary plugging agent in the seam and the temporary plugging agent at the seam opening of the embodiment of the invention can be naturally and completely degraded under the stratum condition, and any gel breaker does not need to be added, so that the permeability in the artificial seam net can be ensured. According to the reservoir conditions and the field requirements, the steps can be repeated during construction, temporary plugging material liquid is added for multiple times to form multiple plugging, the pressure in the cracks is increased to obtain a greater number of branch cracks, and therefore the high-permeability artificial seam network is formed.
According to the multistage temporary plugging deep network acid fracturing method provided by the embodiment of the invention, bridge plugging is realized in the artificial crack through the temporary plugging material liquid in the crack, the net pressure in the crack is improved, so that the artificial crack is forced to form a plurality of branch cracks or communicated natural cracks on a plane, the artificial crack keeps the flow conductivity by combining the main acid and the closed acid, the crack network is repeatedly formed for multiple times, then plugging is realized at the crack opening through the temporary plugging material liquid at the crack opening, the well bottom pressure is increased, the crack is promoted to crack at a new layer, and the uniform deep reconstruction of different permeable layers is realized.
The multistage temporary plugging deep network acid fracturing method provided by the embodiment of the invention has the advantages of simple process, convenience in operation and the like, and can form a complex fracture network in different permeability zones of a multi-layer, thick-layer or horizontal well long well section in the carbonate rock by combining the principle of hydraulic self-search and artificial regulation, increase the probability of communicating an oil-gas area, reduce the oil-gas seepage resistance, improve the yield of a single well, and efficiently and economically develop a carbonate rock reservoir. The multistage temporary plugging deep network acid fracturing method provided by the embodiment of the invention can be used for the yield increasing transformation construction of a vertical well, and can also be used for the yield increasing transformation construction of a horizontal well, an inclined well and the like.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A multistage temporary plugging deep network acid fracturing method is characterized by comprising the following steps: forming a bridge plug in the artificial crack by using the temporary plugging material liquid in the crack, forcing the artificial crack to form a plurality of branch cracks, and etching the crack by using a main body acid; forming a bridge plug at the seam of the artificial crack by using the seam temporary plugging material liquid, forcing the crack to crack at a new position of a well wall, and realizing interlayer steering; the method specifically comprises the following steps:
injecting a front acid, a fracturing fluid and a main acid into the stratum to form an artificial fracture; the discharge capacity of the preposed acid is reversely calculated by a steady-state flow formula of a constant-pressure boundary oil layer:
wherein: qiPre acid displacement, m3/min；Ki-reservoir permeability, mD; h isi-reservoir effective thickness, m; pf-minimum rupture pressure, MPa, of each level;
-well area mean reservoir pressure, MPa; μ -pre-acid viscosity, mPa · s; r ise-oil and gas well drainage radius, m; r isw-wellbore radius, m; s-epidermal coefficient;
the fracturing fluid is hyperbranched fracturing fluid crosslinked under a weak acid condition;
injecting a temporary plugging material liquid into the stratum, forming a bridge plug in the artificial fracture, and forcing the artificial fracture to form a plurality of branch fractures;
repeating the steps of injecting the fracturing fluid, injecting the main acid and injecting the temporary plugging material liquid into the seam for multiple times according to the reservoir conditions and actual needs, thereby forming a complex seam network;
injecting closed acid into the stratum, wherein the dosage of the closed acid is 20% -40% of that of the main acid, and the dosage of the closed acid is 1.0-3.0 m3The discharge volume of the injection is 20-150 m to the stratum3The blocking acid of (a);
injecting a seam temporary plugging material liquid into the stratum to form a bridge plug at the seam of the artificial crack, so that the crack is forced to crack at a new layer of the well wall, and the interlayer steering is realized; the step of injecting the seam temporary plugging material liquid into the stratum specifically comprises the following steps: forming a bridge plug at the seam by using low-concentration seam temporary plugging material liquid, wherein the method comprises the steps of bridging by using 1-3 mm temporary plugging materials, reducing the permeability of a bridging part by using 0.125-1 mm temporary plugging materials, and gradually opening a crack and increasing the width along with the increase of pressure in the seam formed by the bridge plug; the concentration of the temporary plugging agent material liquid at the seam is increased to complete the plugging of the seam, so that enough pressure is obtained to open the low-permeability layer;
the pre-acid and the closed acid are formed by mixing hydrochloric acid with the concentration of 10-20%, a corrosion inhibitor, a resistance reducing agent and a gelling agent; the seam temporary plugging material liquid is formed by mixing a seam temporary plugging agent and weak acid; wherein the concentration of the temporary plugging agent for the seam is 3-15%; the performance indexes of the temporary plugging agent for the seam are as follows: the grain size is 0.125-3 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 4-8 h.
2. The multi-stage temporary plugging deep network acid fracturing method according to claim 1, wherein the main acid comprises one or more of gelled acid, ground crosslinked acid, temperature-controlled variable viscosity acid, foamed acid and emulsified acid which take hydrochloric acid as a main component.
3. The multi-stage temporary plugging deep network acid fracturing method according to claim 1, wherein the intra-seam temporary plugging material liquid is composed of an intra-seam temporary plugging agent and a weak acid in a mixed manner; wherein the concentration of the temporary plugging agent in the seam is 3-15%; the performance indexes of the temporary plugging agent in the seam are as follows: the grain size is 0.125-1 mm, the temperature resistance range is 120-180 ℃, and the complete degradation time is 3-5 h.
4. The multi-stage temporary plugging deep network acid fracturing method according to claim 3, wherein the displacement of the temporary plugging material liquid in the seam is as follows:
wherein: q2Discharge of temporary plugging material liquid in the slot, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q1-the flow rate of temporary plugging material liquid in the slot for laboratory experiment, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2；
The dosage of the temporary plugging agent in the seam is as follows:
M1＝Q2t1N1(1+η1)
wherein: m1-amount of temporary plugging agent in the seam, kg; q2Discharge of temporary plugging material liquid in the slot, m3/min；t1-laboratory experiment injection time, min; n is a radical of1Concentration of temporary plugging agent in the suture, g/L η1-rate of loss of temporary plugging agent in the joint,%.
5. The multi-stage temporary plugging deep network acid fracturing method according to claim 1, wherein the discharge capacity of the seam temporary plugging material liquid is as follows:
wherein: q4Discharge of material liquid for temporary closure of the seam, m3/min；A2Construction string internal diameter cross-sectional area, m2；Q3-laboratory experimental injection flow of seam temporary plugging material liquid, mL/min; a. the1Cross-sectional area of the inner diameter of the laboratory test line, m2；
The dosage of the temporary plugging agent at the seam opening is as follows:
M2＝Q4t2N2(1+η2)
wherein: m2-amount of temporary plugging agent for the seam, kg; q4Discharge of material liquid for temporary closure of the seam, m3/min；N2-seam temporary blocking agent concentration, g/L; t is t2Laboratory experiment injection time, min η2-rate of loss of temporary plugging agent at the seam opening,%.
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| CN112431570B (en) * | 2020-11-06 | 2023-06-30 | 中国石油天然气股份有限公司 | Test method of temporary plugging agent for temporary plugging of acid fracturing |
| CN114718541A (en) * | 2021-01-05 | 2022-07-08 | 中国石油天然气股份有限公司 | Acidification process |
| CN115434658B (en) * | 2021-06-02 | 2024-04-30 | 中国石油天然气股份有限公司 | Method, device, equipment and storage medium for determining plugging material dosage |
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