Horizontal Well Water Plugging Technology Decision-making Method

Abstract

The present invention provides a decision-making method for water plugging technology in horizontal wells. The decision-making method for water plugging technology in horizontal wells includes: Step 1, on the basis of clarifying the potential of the oil well, according to the equivalent seepage resistance method, optimize the plugging strength of the plugging agent; Step 2, select the water plugging depth, i.e., the dosage of the plugging agent, according to the liquid production and flowing fluid level of the reservoir where the horizontal well is located; Step 3, predict the water plugging effect according to the initial production, water cut and plugging depth of the reservoir where the horizontal well is located. The decision-making method for water plugging technology in horizontal wells is used in the high water cut or extra-high water cut development stage of horizontal wells to improve the development effect of horizontal wells. Mainly based on the equivalent seepage resistance method, it clarifies the strength, dosage and effect prediction of the plugging agent, providing a theoretical basis and pertinence.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and particularly to a decision-making method for water plugging technology in horizontal wells. Background Art

[0002] As an advanced technology in oil and gas field development, horizontal wells have been widely used in various types of oil and gas reservoirs. However, high water cut has become one of the difficult problems in current horizontal well production. For example, in Shengli Oilfield, the number of horizontal wells with extremely high water cut accounts for 50% of the opened wells. Currently, there are two methods for water plugging in horizontal wells: water finding and plugging, and water plugging without water finding. The cost of water finding and plugging is high, and the fixed-point plugging technology after finding water has not been widely applied. Compared with the water plugging technology without water finding, because the selective plugging agent and selective injection method are simple and easy to operate, the water plugging technology without water finding is more mature in field application.

[0003] The water plugging technology in horizontal wells mainly consists of plugging agent optimization, plugging agent dosage design, water plugging parameters, and effect prediction, etc. When selecting wells, those with high initial production and fast rising water cut are mostly selected, mainly based on the production dynamics of oil wells. When designing water plugging parameters, for bottom water, the method of installing a baffle is adopted, and for edge water, controlling the tongue advance is the main method. Among them, the key parameters of the plugging dosage, such as the baffle thickness and treatment radius, mostly use empirical formulas and rely on on-site construction experience, lacking certain methods and theoretical basis.

[0004] Based on theoretical analysis and on-site practice summary, it is considered that the reason for the unsatisfactory water plugging effect in horizontal wells is related to the decision-making method of water plugging technology, which is mainly manifested in the following points:

[0005] First, the selection of plugging agent strength, based on on-site experience and experimental results under ideal indoor conditions, leads to inaccurate strength optimization; second, the design of plugging agent dosage, based on the volume method and on-site experience to design the dosage, leads to inaccurate dosage optimization; third, the prediction of water plugging effect, based on intuitive factors such as previous production to judge the water plugging effect, leads to inaccurate effect prediction.

[0006] In the Chinese patent application with the application number: CN200410020825.6, it relates to a water plugging technology method for heavy oil wells to plug water layers and improve production effects. This method is based on the principle of "deep profile control and shallow plugging". First, a large-radius selective plugging of the oil layer is carried out using a degradable organic plugging agent, and then a high-temperature-resistant inorganic plugging agent is used for sealing. At the same time, selective water plugging is achieved through pressure control and the degradation of organic substances. This water plugging method is reasonably designed and based on reliable principles. Compared with other heavy oil water plugging methods, it has the characteristics of low construction risk, high success rate, and long validity period, providing a new and effective method for solving the water plugging problem of heavy oil wells, especially medium-depth heavy oil wells.

[0007] In the Chinese patent application with the application number CN201510576592.6, a water shutoff technology string for horizontal wells is involved, including a tubing string, an elastic centralizer, a safety joint, a setting tool, an inner pipe, an inner pipe type packer, and a rotatable bridge plug. The elastic centralizer and the safety joint are respectively sleeved at the end of the horizontal section of the tubing string, and the elastic centralizer is located at the left end of the safety joint. The horizontal section of the tubing string is connected to the inner pipe type packer through the setting tool or the inner pipe. The rotatable bridge plug is located at the right end of the inner pipe type packer and has a clearance therewith. The structure is simple, which can realize the pressure holding and waiting for setting of high-strength plugging agent, and can realize leaving a plugging surface in the casing of high-strength plugging agent for horizontal wells.

[0008] In the Chinese patent application with the application number CN201810860853.0, a water shutoff method for screen horizontal wells is involved. The water shutoff method includes the following steps: injecting nitrogen into the horizontal well to form slug one; injecting powder temporary plugging agent and water-based profile control agent to form slug two; injecting nitrogen to form slug three; injecting water-based profile control agent to form slug four; injecting composite temperature-resistant plugging agent to form slug five; displacing polyacrylamide solution to form slug six; waiting for setting, and injecting steam for 3500m 3 -5000m 3 , soaking the well for 24h; injecting liquid carbon dioxide to form slug seven, and completing the water shutoff of the screen horizontal well.

[0009] The above existing technologies are quite different from the present invention. The existing water shutoff string and empirical methods lack theoretical basis and pertinence, affect the water shutoff efficiency of horizontal wells, and fail to solve the technical problems we want to solve. Therefore, we have invented a new water shutoff technology decision-making method for horizontal wells. Summary of the Invention

[0010] The purpose of the present invention is to provide a water shutoff technology decision-making method for horizontal wells in the high water cut or extra-high water cut development stage, which can improve the development effect of horizontal wells.

[0011] The purpose of the present invention can be achieved by the following technical measures: a water shutoff technology decision-making method for horizontal wells, which includes:

[0012] Step 1, on the basis of clarifying the potential of the oil well, according to the equivalent seepage resistance method, optimize the plugging strength of the plugging agent;

[0013] Step 2, select the water shutoff depth, that is, the dosage of the plugging agent, according to the liquid production and flowing liquid level of the reservoir where the horizontal well is located;

[0014] Step 3, predict the water shutoff effect according to the initial production, water cut and plugging depth of the reservoir where the horizontal well is located.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] In Step 1, according to r e the liquid supply radius, r e1 the plugging range of the plugging agent, r w the wellbore radius, R w the seepage resistance of the water-producing section and the seepage resistance of the oil-producing section after water plugging, calculate the seepage resistance R0 of the oil-producing section; and calculate the seepage resistance R of the water-producing section after gel water plugging w ; the seepage resistance R of the water-producing section after gel water plugging w is directly related to the viscosity μ of the gel gel and the residual resistance coefficient R after plugging ff The viscosity μ of the gel gel and the residual resistance coefficient R after plugging ff The greater they are, the greater the seepage resistance R of the water-producing section after gel water plugging w will be.

[0017] In Step 1, determine the plugging degree based on the original permeability differential between the water-producing section and the oil-producing section and the differential under the current water cut. In principle, the seepage resistance R of the water-producing section after water plugging w should be greater than the seepage resistance R of the oil-producing section o so that the water-producing section can be plugged and the oil-producing section can be effectively started; on-site water plugging practice and laboratory research have shown that the seepage resistance R of the water-producing section after water plugging w should be more than 10 times greater than the seepage resistance R of the oil-producing section o for a greater likelihood of good water plugging effect.

[0018] In Step 1, the calculation formulas for R w and R o are as follows:

[0019]

[0020] Where: R0—the seepage resistance of the oil-producing section, atm / (cm 3 / s);

[0021] μ0—the viscosity of underground crude oil, mPa.s;

[0022] μ gel —the viscosity of the gel, mPa.s;

[0023] μ w —the viscosity of the oil-water mixture in the water channeling path, mPa.s;

[0024] K—the average formation permeability, μm 2 ;

[0025] h0—the length of the oil-producing section, cm;

[0026] R w — Seepage resistance of the water-producing section after water plugging, atm / (cm 3 / s);

[0027] h w — Length of the water-producing section, cm;

[0028] r e — Liquid supply radius, cm;

[0029] r w — Wellbore radius, cm;

[0030] R ff — Gel residue resistance coefficient;

[0031] r e1 — Plugging range of the plugging agent, cm.

[0032] In step 2, starting from the principle of fluid seepage, taking the seepage resistance of the oil phase, water phase and oil-water phase as the research object, the plugging depth is calculated according to the equivalent seepage resistance method and the maximum production pressure difference; the dosage of the plugging agent is calculated according to the requirement of the plugging range.

[0033] In step 2, according to the liquid volume Q and the flowing fluid level m of the water-injection well to be plugged, under the condition of predicting the maximum production pressure difference ⊿P, based on the economic production rate, the plugging depth r is calculated e1 That is, the limit water plugging radius:

[0034]

[0035]

[0036] In the formula: Q—Production rate, m 3 ;

[0037] ⊿P—Production pressure difference, atm;

[0038] R—Section resistance, atm / (cm 3 / s);

[0039] R o — Resistance of the oil-producing section, atm / (cm 3 / s);

[0040] R w — Resistance of the water-producing section, atm / (cm 3 / s).

[0041] In step 2, the production pressure difference is the difference between the formation pressure and the bottom-hole flowing pressure, and the bottom-hole flowing pressure of the oil well is calculated as follows:

[0042] p wf= p1 + p2 + p2..................(5)

[0043] Where: p1—casing pressure of the oil well, MPa;

[0044] p2—liquid column pressure from the flowing fluid level to the pump depth of the oil well, MPa;

[0045] p3—liquid column pressure of the mixture from the pump depth to the mid-depth of the oil reservoir, MPa;

[0046] p2 = ρ0gH2.................(6)

[0047] ρ0—density of formation crude oil, Kg / m 3 ;

[0048] H2—distance from the flowing fluid level to the pump depth (deep part of the drawdown), m; Where:

[0049] H2 = L2 - L1.................(7)

[0050] L2—pump setting depth, m;

[0051] L1—flowing fluid level depth, m;

[0052] p3 = ρ h gH3................(8)

[0053] ρ h —density of the oil-water mixture, kg / m 3 ;

[0054] H3—distance from the pump depth to the mid-depth of the oil reservoir, m;

[0055] H3 = L - L2...............(9)

[0056] L—mid-depth of the oil reservoir, m;

[0057] ρ k = f w ρ w +(1 - f w )ρ0...............(10)

[0058] f w —water cut, %;

[0059] ρ0—density of formation crude oil, kg / m 3 ;

[0060] ρ w —density of formation water, kg / m 3 。

[0061] In step 2, the dosage of the plugging agent is related to parameters such as the length of the plugging section, the effective porosity, and the plugging depth. Statistical data of the water finding test results at the site of high water cut horizontal wells shows that the length of the water producing section of high water cut horizontal wells accounts for 10% - 20% of the production well section length. The water production situation of horizontal wells is relatively complex. For the water shutoff dosage of horizontal wells, it is necessary to combine the water production position and the water production shape to conduct research on dosage optimization design.

[0062] In step 2, the calculation formula for the dosage of the plugging agent is:

[0063] Q = πr e1 2 Lφc...........(11)

[0064] Where: Q—the dosage of the plugging agent, m 3 ;

[0065] r e1 —the plugging range of the plugging agent, cm;

[0066] L—the length of the plugging section, m;

[0067] φ—the effective porosity, %;

[0068] c—the correction coefficient.

[0069] In step 3, according to the production pressure difference obtained after setting the water shutoff, the liquid volumes of the oil well section and the water producing well section are calculated. That is, the liquid volume of the oil producing section is the ratio of the production pressure difference to the resistance of the oil producing section (⊿P / R o ), and the liquid volume of the water producing section is the ratio of the production pressure difference to the resistance of the water producing section (⊿P / R w ); the water cut values of the oil well section and the water producing well section are the water cut values during their respective production processes. That is, the water cut value of the oil well section is the water cut value at the initial stage of well opening, and the water cut value of the water producing well section is the water cut value before water shutoff; then the oil production after water shutoff of the water producing section and the oil producing section is calculated, and the sum of the two is the predicted daily oil production after water shutoff.

[0070] In step 3, the calculation formula for the daily oil production R o after water shutoff is:

[0071] R o = Q1×W1 + Q2×W2.........................(12)

[0072] Where: R o —the daily oil production after water shutoff, t;

[0073] Q1—the daily liquid production of the oil well section, m 3 ;

[0074] Q2 - Liquid production per day in the water - producing well section, m 3 ;

[0075] W1 - Water cut in the oil - producing well section, %;

[0076] W2 - Water cut in the water - producing well section, %.

[0077] The horizontal well water shut - off process decision - making method in the present invention has the following technical effects compared with the prior art:

[0078] (1) Established a horizontal well water shut - off process decision - making method: Based on the theory of equivalent seepage resistance method, calculation methods for the strength selection, dosage design of plugging agents, and prediction of water shut - off effects were established.

[0079] (2) Applied numerical calculation methods to clarify the performance parameters of plugging agents under different reservoir conditions; On the basis of clarifying the potential of oil wells, according to the equivalent seepage resistance method, the numerical value of the plugging strength of the plugging agent was accurately calculated.

[0080] (3) Applied numerical calculation methods to clarify the dosage parameters of plugging agents under different reservoir conditions; According to parameters such as the liquid production volume and flowing liquid level of the reservoir where the horizontal well is located, the water shut - off depth (dosage of plugging agent) was accurately calculated to ensure that the oil well is not blocked after water shut - off, providing technical guarantee for increasing oil production by reducing water cut.

[0081] (4) Applied numerical calculation methods to clarify the effects after water shut - off under different plugging agent strength and dosage conditions; According to the initial production, water cut, and plugging degree of the reservoir where the horizontal well is located, the daily oil production and water cut after water shut - off were relatively accurately predicted.

[0082] (5) The horizontal well water shut - off process decision - making method of this invention patent not only provides a decision - making method and theoretical basis for horizontal well water shut - off, but also provides a basis for economically effective decision - making of horizontal well water shut - off during the low - oil - price period. Brief Description of the Drawings

[0083] Figure 1 It is a flowchart of a specific embodiment of the horizontal well water shut - off process decision - making method of the present invention;

[0084] Figure 2 It is a schematic diagram of the oil - water distribution and plugging in a horizontal well in a bottom - water reservoir in a specific embodiment of the present invention;

[0085] Figure 3 It is a graph of injection pressure before and after plugging with a weak gel system in a specific embodiment of the present invention;

[0086] Figure 4 It is a graph of injection pressure before and after plugging with a medium - strong gel system in a specific embodiment of the present invention;

[0087] Figure 5Injection pressure curve before and after plugging with a strong gel system in a specific embodiment of the present invention;

[0088] Figure 6 Production curve before and after water plugging of D**P16 in a specific embodiment of the present invention. Detailed implementation manners

[0089] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0090] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0091] As Figure 1 shown, Figure 1 is a flow chart of the horizontal well water plugging process decision-making method of the present invention. The horizontal well water plugging process decision-making method includes the following steps:

[0092] (1) On the basis of clarifying the potential of the oil well, according to the equivalent seepage resistance method, optimize the plugging strength of the plugging agent; (2) Select the water plugging depth (amount of plugging agent) according to the liquid production and flowing liquid level of the reservoir where the horizontal well is located; (3) Predict the water plugging effect according to the initial production, water cut and plugging depth of the reservoir where the horizontal well is located.

[0093] Step 101: Optimization of plugging strength of plugging agent

[0094] On the basis of clarifying the potential of the oil well, according to the equivalent seepage resistance method, optimize the strength of the plugging agent. The goal of plugging is to increase the seepage resistance of the water-producing well section after water plugging and greatly reduce the liquid volume of the high-water-cut well section; by enlarging the production pressure difference, mobilize the remaining oil in the high-oil-bearing well section. Therefore, first calculate the seepage resistance R0 of the high-oil-bearing well section, and then calculate the seepage resistance R that needs to be achieved after water plugging in the high-water-cut well section according to the seepage resistance of the high-oil-bearing well section, so as to calculate the plugging strength that the plugging agent needs to achieve; the optimization of the plugging strength of the plugging agent is based on the viscosity μ after gel formation w and the residual resistance coefficient R after plugging gel . According to the original range difference of the permeability of the high-water-cut water-channeling channel and the oil-bearing layer section and the current range difference under the water cut, determine the plugging degree. In principle, the resistance R after water plugging in the high-water-cut water-channeling channel ff should be greater than the resistance R of the crude oil flow in the oil-bearing layer section w should be greater than the resistance R of the crude oil flow in the oil-bearing layer sectiono , the water channel can be blocked and the oil layer can be effectively started. Field water shutoff practices and laboratory studies have shown that after water shutoff, the resistance R of the high water cut water channel after water shutoff w should be more than 10 times the resistance R of the crude oil flowing in the oil-bearing section o . There is a greater possibility of good water shutoff effect.

[0095]

[0096]

[0097] Where: R0—seepage resistance of the oil production section, atm / (cm 3 / s);

[0098] μ0—underground crude oil viscosity, mPa.s;

[0099] μ gel —gel viscosity, mPa.s;

[0100] μ w —viscosity of the oil-water mixture in the water channel, mPa.s;

[0101] K—average formation permeability, μm 2 ;

[0102] h0—length of the oil production section, cm;

[0103] R w —seepage resistance of the water production section after water shutoff, atm / (cm 3 / s);

[0104] h w —length of the water production section, cm;

[0105] r e —liquid supply radius, cm;

[0106] r w —wellbore radius, cm;

[0107] R ff —gel residual resistance coefficient;

[0108] r e1 —blocking agent plugging range, cm.

[0109] Step 102: Calculation of water shutoff depth (blocking agent dosage)

[0110] Select the water shutoff depth (blocking agent dosage) according to the formation capacity of the reservoir where the horizontal well is located, the liquid production volume of the oil well, and the flowing fluid level, to avoid the phenomena of low liquid level, blocked well, or no decrease in water cut after water shutoff. An appropriate water shutoff depth should be selected to ensure a certain water shutoff effect after water shutoff of the oil well.

[0111] The goal of water plugging is to achieve the maximum oil production rate and the lowest water cut. However, after water plugging, it is necessary to ensure the liquid supply capacity of the oil well. Therefore, it is necessary to study the reasonable plugging depth to ensure the normal production of the oil well after water plugging. Starting from the principle of fluid seepage, taking the seepage resistance of the oil phase, water phase and oil-water phase as the research object, the plugging depth is calculated according to the equivalent seepage resistance method (Formula 1, Formula 2) and the maximum production pressure difference; the dosage of the plugging agent is calculated according to the required plugging range.

[0112] According to the liquid volume (Q) and flowing fluid level (m) of the oil well to be water plugged, predict the maximum production pressure difference (⊿P) and calculate the plugging depth (r e1 , the limit water plugging radius) on the basis of the economic production rate.

[0113]

[0114]

[0115] Where: Q—production rate, m 3 ;

[0116] ⊿P—production pressure difference, atm;

[0117] R—section resistance, atm / (cm 3 / s);

[0118] R o —oil production section resistance, atm / (cm 3 / s);

[0119] R w —water production section resistance, atm / (cm 3 / s);

[0120] Predict the maximum production pressure difference:

[0121] The production pressure difference is the difference between the formation pressure and the bottom-hole flowing pressure. The bottom-hole flowing pressure of the oil well is calculated as follows:

[0122] p wf = p1 + p2 + p3..................(5)

[0123] Where: p1—casing pressure of the oil well, MPa;

[0124] p2—liquid column pressure from the flowing fluid level to the pump depth of the oil well, MPa;

[0125] p3—mixed liquid column pressure from the pump depth to the mid-depth of the oil reservoir of the oil well, MPa;

[0126] p2 = ρ0gH2.................(6)

[0127] ρ0—the density of formation crude oil, Kg / m 3 ;

[0128] H2—the distance from the flowing fluid level to the pump depth (submergence depth in the deep part); where:

[0129] H2 = L2 - L1.................(7)

[0130] L2—the pump setting depth, m;

[0131] L1—the flowing fluid level depth, m;

[0132] p3 = ρ h gH3................(8)

[0133] ρ h —the density of the oil - water mixture, kg / m 3 ;

[0134] H3—the distance from the pump depth to the mid - depth of the oil reservoir, m;

[0135] H3 = L - L2...............(9)

[0136] L—the mid - depth of the oil reservoir, m;

[0137] ρ k = f w ρ w +(1 - f w )ρ0...............(10)

[0138] f w —the water cut, %;

[0139] ρ0—the density of formation crude oil, kg / m 3 ;

[0140] ρ w —the density of formation water, kg / m 3 ;

[0141] Calculation of the dosage of plugging agent:

[0142] Generally, the dosage of plugging agent is related to parameters such as the length of the plugging section, effective porosity, plugging depth, etc. Statistical data of the water - finding test results of high - water - cut horizontal wells on site show that, generally, the length of the water - producing section of high - water - cut horizontal wells accounts for 10% - 20% of the production section length (the length of the water - producing section h w : the length of the oil - bearing section h O= 1:9 to 1:4). The water production situation of horizontal wells is relatively complex. For the water shutoff dosage of horizontal wells, it is necessary to combine the water production position and the water production shape to carry out research on dosage optimization design.

[0143] Q = πr e1 2 Lφc...........(11)

[0144] In the formula: Q—the dosage of the plugging agent, m 3 ;

[0145] L—the length of the plugging section, m;

[0146] φ—the effective porosity, %;

[0147] c—the correction coefficient.

[0148] Step 103: Prediction of water shutoff effect

[0149] Predict the water shutoff effect based on the initial production and water cut of the horizontal well to be water shutoff, the plugging strength and the plugging depth.

[0150] Based on the production pressure difference obtained after setting the water shutoff, calculate the liquid volume of the oil well section and the water production well section. That is, the liquid volume of the oil production section is the ratio of the production pressure difference to the resistance of the oil production section (⊿P / R o ), and the liquid volume of the water production section is the ratio of the production pressure difference to the resistance of the water production section (⊿P / R w ); for the water cut values of the oil well section and the water production well section, take the water cut values during their respective production processes. That is, for the oil well section, take the water cut value at the initial stage of opening the well (such as 30%), and for the water production well section, take the water cut value before water shutoff (such as 98%); then calculate the oil production after water shutoff for the water production section and the oil production section, and the sum of the two is the predicted daily oil production after water shutoff.

[0151] R o = Q1×W1 + Q2×W2.........................(12)

[0152] In the formula: R o —the daily oil production after water shutoff, t;

[0153] Q1—the daily liquid production of the oil well section, m 3 ;

[0154] Q2—the daily liquid production of the water production well section, m 3 ;

[0155] W1—the water cut of the oil well section, %;

[0156] W2—the water cut of the water production well section, %.

[0157] The following are several specific embodiments of applying the present invention.

[0158] Example 1:

[0159] Water Plugging Optimization Decision for Horizontal Well *P16

[0160] Taking *P16 as an example: This well was put into production in July 2018, producing NG(1+2)4 layers, with a perforated interval of 1586.0 - 1632.0 meters, a perforated thickness of 46 meters, and the permeability of the high-permeability layer section being 2025×10 -3 μm 2 , the formation pressure is 11.23 MPa, and the ground crude oil viscosity is 1859 mPa·s. It was put into production on July 3, 2018. The initial daily liquid production was 22.6 t, the daily oil production was 13.8 t, and the water cut was 39.1%. At the peak (July 18, 2018), the daily liquid production was 20.8 t, the daily oil production was 15.8 t, and the water cut was 23.9%. There is no corresponding water well for this well, and affected by the edge water, the water cut started to rise rapidly in October 2018. Before water plugging, the daily liquid production was 40.6 t, the daily oil production was 0.4 t, and the water cut was 99.1%.

[0161] Step 1: Optimization of Plugging Strength of Plugging Agent

[0162] 1. Evaluation of Gel Strength of Plugging Agent

[0163] Dynamic evaluation of gels with different strengths was carried out, mainly evaluating the plugging rate and the residual resistance coefficient.

[0164] Table 1 Gelation Performance of Gel Systems with Different Concentrations

[0165]

[0166] 2. Evaluation of Residual Resistance Coefficient of Plugging Agent

[0167] Plugging agents with different strengths were injected into single-tube cores with similar permeabilities for plugging effect evaluation.

[0168] (1) Experimental Raw Materials and Experimental Conditions

[0169] Core filling sand: River sand from Chengde, Hebei (screened), with main particle sizes of 20 - 40 mesh, 40 - 60 mesh, 60 - 80 mesh, 80 - 100 mesh, 100 - 120 mesh, and 120 - 160 mesh.

[0170] Experimental water: Sewage from Ng5 in the middle first area.

[0171] Polymer, crosslinking agent: China University of Petroleum (East China).

[0172] Experimental temperature: 65℃.

[0173] Reagents: Petroleum ether, acetone, ethanol, etc.

[0174] (2) Experimental Model

[0175] Columnar core tube, size: φ25mm×50cm;

[0176] Pressure measuring points: P injection, P1, P2, and P3, where the last three points divide the core tube into four equal sections.

[0177] Design core permeability: 2.0μm 2 .

[0178] (3) Main instruments and equipment and procedures of the experiment

[0179] Multifunctional core displacement device: The main components include horizontal flow pump, vacuum pump, core model tube, back pressure control system, pressure metering system, constant temperature system, vacuum saturation system, automatic pressure data acquisition system, etc.

[0180] Temperature control: accuracy +1℃

[0181] Analytical balance: sensitivity +0.0lg

[0182] Centrifuge: 0-5000r / min

[0183] Glass instruments: test tubes, measuring cylinders, beakers, etc.

[0184] (4) Main steps of the experiment

[0185] ①Made according to the permeability requirements:

[0186] Design permeability 2.0μm 2 , sand is mixed according to the ratio of 80-100 mesh: 100-120 mesh: 160-200 mesh = 1:2:2;

[0187] After the sand particles are mixed evenly, the core tube model is filled according to a certain degree of compaction.

[0188] ② Connect the pipeline according to the experimental process, conduct permeability measurement, and calculate the permeability according to Darcy's law.

[0189] ③ Weigh the dry weight of the core m1, pump out the saturated formation water, weigh the wet weight m2, measure the pore volume (v = (m2-m1) / ρwater), and calculate the porosity.

[0190] ④ According to the experimental process, the core model is connected to the process and water drive is carried out.

[0191] ⑤ According to the experimental process, the 0.5PV design system (0.3% polymer + 0.15% cross-linking agent + 0.453% stabilizer, 0.4% polymer + 0.3% cross-linking agent + 0.453% stabilizer, 0.5% polymer + 0.4% cross-linking agent + 0.453% stabilizer) was reversely injected into the core model. After the injection, the subsequent water drive was carried out in the forward direction after the constant temperature of 65°C for 24 hours, and the experiment was terminated.

[0192] ⑥ Evaluate the plugging rate and residual resistance coefficient of plugging agents with different strengths.

[0193] (5) Experimental results and analysis

[0194] From the physical simulation displacement experiment results (Table 2, Figure 3 、 Figure 4 、 Figure 5 ), it shows that after injecting the plugging agents with three strengths into the core, good plugging performance and erosion resistance performance are generated during the subsequent water flooding. The injection pressure remains stable and shows an upward trend. After plugging with weak gel, the plugging rate of the core during water flooding of 3PV is 98.11%, and the residual resistance coefficient is 53.07; after plugging with medium-strong gel, the plugging rate of the core during water flooding of 3PV is 98.54%, and the residual resistance coefficient is 69.0; after plugging with strong gel, the plugging rate of the core during water flooding of 3PV is 98.80%, and the residual resistance coefficient is 83.2. Generally speaking, the higher the strength of the plugging agent, the higher the core plugging rate and the greater the residual resistance coefficient. The plugging agents with three strengths all have good plugging performance and erosion resistance performance.

[0195] Table 2 Data table of oil recovery rate before and after water plugging at different water cut stages

[0196]

[0197]

[0198] 3. Calculation and optimization of plugging strength of plugging agent

[0199] According to the equivalent seepage resistance method, calculate the seepage resistance R0 of the high oil-bearing well section, and the resistance R after plugging the water channel with high water cut after water plugging w should be more than 10 times the resistance R o of the crude oil flow in the oil-bearing layer section. Based on the calculated seepage resistance R w required to be achieved after water plugging in the high water cut well section, calculate the plugging strength that the plugging agent needs to reach. According to formula (1), formula (2) and the oil layer data table 3 of the water plugging well, calculate the gel-forming strength and residual resistance coefficient of the plugging agent required.

[0200] After calculation, according to the resistance of the oil-producing section of 0.554 atm / (cm 3 / s), to ensure the water plugging effect, according to on-site experience, the resistance of the water-producing section should be at least 10 times greater than the oil-producing resistance. Referring to the previous indoor experiments, take the viscosity μ gel of the plugging agent after gelation to reach more than 370 mPa·s and the residual resistance coefficient R ff after plugging to reach more than 50.

[0201] Table 3 Value table of each parameter of Well P16

[0202] Parameter Value Parameter Value Underground crude oil viscosity / mPa·s 1859 Residual resistance coefficient 50 Length of water production section / cm 1000 Viscosity of water channeling mixture / mPa·s 120 Liquid supply radius / cm 5000 Gel viscosity / mPa·s 370 Wellbore radius / cm 5 <![CDATA[Average formation permeability / μm 2 > 1.025 Porosity, % 33 Length of oil production section / cm 3600

[0203] Step 2: Calculation of water plugging depth (plugging agent dosage)

[0204] The goal of water plugging is to obtain the maximum oil production rate and the lowest water cut. However, the liquid supply capacity of the oil well needs to be ensured after water plugging. Therefore, it is necessary to study a reasonable plugging range to ensure the normal production of the oil well after water plugging.

[0205] The mid-depth of the oil reservoir of this well is 1450 m, the formation pressure is taken as 14 MPa, the pump depth is 1000 m. If the immersion depth for normal production is ensured to be 200 m, then the dynamic liquid level is taken as 800 m; after calculation, the maximum production pressure difference is 8.676 MPa. See the following table:

[0206] Table 4 Maximum production pressure difference table

[0207]

[0208] P1 Casing pressure of the oil well, P2 Hydrostatic pressure of the liquid column from the dynamic liquid level to the pump depth of the oil well, P3 Hydrostatic pressure of the mixed liquid column from the pump depth to the mid-depth of the oil reservoir of the oil well.

[0209] According to the liquid volume (Q) of the oil well to be water plugged, under the condition of predicting the maximum production pressure difference (⊿P), based on the economic production rate, according to the equivalent seepage resistance method, based on the oil reservoir data table 4 of the water plugging well, formula (1), formula (2), formula (3), formula (4), formula (5), formula (11), calculate the plugging range, and calculate the plugging depth (r e1 ).

[0210] After calculation, the plugging depth r of the plugging agent is required e1 to be 12 m and the dosage of the plugging agent is 1400 m 3 .

[0211] Step 3: Prediction of water plugging effect and implementation situation

[0212] Predict the water plugging effect according to the initial production rate and water cut of the horizontal well to be water plugged, the plugging strength and the plugging depth. Calculate the liquid production rate under the maximum production pressure difference; through the liquid production rates of the oil-producing section and the water-producing section, calculate the daily oil production and the comprehensive water cut after water plugging according to the water cut of each section.

[0213] According to the set maximum production pressure difference, after obtaining the production pressure difference, the liquid volume of the oil-producing section is the ratio of the production pressure difference to the resistance of the oil-producing section, and the liquid volume of the water-producing section is the ratio of the production pressure difference to the resistance of the water-producing section. Take the water cut during their respective production processes, such as taking the water cut at the initial stage of opening the well for the oil-producing section, taking 50%; taking the water cut before water plugging for the water-producing section, which is 98%, then calculate the oil production after water plugging for the water-producing section and the oil-producing section, and the sum of the two is the predicted daily oil production after water plugging.

[0214] Taking the above values, predict the production situation after water plugging. The liquid production per day is 17.1 m 3 , with a water cut of 54%, and the oil production per day is 7.86 tons; 800 cubic meters of weak gel and 600 cubic meters of medium-strong gel are injected on site in this well. The actual production situation after water plugging ( Figure 6 ) is that the liquid production per day is 22 m 3 , with a water cut of 66.5%, and the oil production per day is 7.60 tons. The cumulative oil increase is 1005 tons, and the effective period has reached more than 280 days, which is basically consistent with the predicted results, indicating that this method is reliable.

[0215] Example 2:

[0216] Water plugging optimization decision for horizontal well *P6

[0217] Taking *P6 as an example: This well was put into production in January 2008. In the initial stage, the liquid production per day was 31 tons, the oil production per day was 15.1 tons, and the water cut was 51.1%. In the final stage, the liquid production per day was 83 tons, the oil production per day was 1.4 tons, and the water cut was 98.2%. The cumulative oil production was 16,540 tons, and the cumulative water production was 228,600 cubic meters. *P6 is located in the edge-bottom water reservoir. The vertical thickness of the oil layer in the production interval is 7.7 m. The production layer is developed horizontally, the single-well controlled area is large, and there is no corresponding water injection well. This well uses screen completion. The reservoir physical properties are the best in the interval of 1620 m - 1640 m, followed by 1404 m - 1430 m, and the reservoir physical properties in the intervals of 1660 m - 1685 m and 1514 m - 1540 m are relatively poor. The reservoir physical properties of *P6 well include permeability (0.823 μm2), porosity (35.27%), temperature (56 °C), crude oil viscosity (2808 mPa.S), and formation water salinity (27010 mg / L). The *P24 well that completed the water plugging construction in the early stage is located in the north of this well, 200 m away. The horizontal sections are nearly parallel, and the production horizons are the same. Through the analysis of the static data and water finding data of *P24 well, it is concluded that water production occurs near the B target of this well, and the oil increase effect is obvious after water plugging, proving that the judgment of the water production point is accurate. The plane distance between the B target of *P6 well and the B target of *P24 well is 200 m. The well section with the best reservoir physical properties in the production interval of *P6 well is concentrated near the B target, and is in the north-south strip with better physical properties together with the B target of *P24 well. Therefore, it is judged that the water production point of *P6 well is in the production interval near the B target. The water source of *P24 well comes from the bottom water, while the production interval of this well is near the small layer pinch-out line. Only the reservoir in the north is developed, and the small layers are pinched out in other directions; in addition, the vertical depth of the B target of *P6 well is 1094.34 m, and the vertical depth of the B target of *P24 well is 1096.86 m, with a height difference of 2.52 m. In summary, it is judged that the water source of *P6 well comes from the bottom water.

[0218] Step 1: Optimization of the plugging strength of the plugging agent

[0219] According to the equivalent seepage resistance method, calculate the seepage resistance R0 of the high oil-bearing well section and the resistance R after plugging the water channeling channel with high water cut after water plugging wshould be greater than 10 times the resistance R of the crude oil flowing in the oil-bearing formation section. Based on the calculated seepage resistance R that needs to be achieved after water shutoff in the high water cut well section o , the plugging strength that the plugging agent needs to achieve is calculated. Based on Formula (1), Formula (2) and the oil reservoir data table 3 of the water shutoff well, the gelation strength and residual resistance coefficient of the plugging agent required are calculated. w

[0220] After calculation, according to the resistance of the oil production section of 0.837 atm / (cm 3 / s), to ensure the water shutoff effect, based on field experience, the resistance of the water production section should be at least 10 times greater than the oil production resistance. Referring to the previous laboratory experiments, the viscosity μ of the plugging agent after gelation is taken gel to reach above 263 mPa·s and the residual resistance coefficient R ff after plugging to reach above 60.

[0221] Table 3 Parameter value table of Well P6

[0222]

[0223]

[0224] Step 2: Calculation of water shutoff depth (amount of plugging agent)

[0225] The goal of water shutoff is to obtain the maximum oil production and the lowest water cut. However, the liquid supply capacity of the oil well needs to be ensured after water shutoff. Therefore, it is necessary to study a reasonable plugging range to ensure the normal production of the oil well after water shutoff.

[0226] The mid-depth of the oil reservoir of this well is 1200 m, the formation pressure is taken as 11.5 MPa, the pump depth is 900 m. If the normal production immersion depth is 200 m, then the dynamic liquid level is taken as 700 m; after calculation (Table 4), the maximum production pressure difference is 6.84 MPa.

[0227] Table 4 Maximum production pressure difference table

[0228]

[0229] Casing pressure of Well P1, liquid column pressure from the dynamic liquid level of the oil well to the pump depth, and mixed liquid column pressure from the pump depth of the oil well to the mid-depth of the oil reservoir.

[0230] According to the liquid volume (Q) of the oil well to be water shutoff, under the condition of predicting the maximum production pressure difference (⊿P), based on the economic production, according to the equivalent seepage resistance method, based on the oil reservoir data table 4, Formula (1), Formula (2), Formula (3), Formula (4), Formula (5), Formula (11) of the water shutoff well, the plugging range is calculated, and the plugging depth (r e1 ) is calculated.

[0231] After calculation, the plugging depth r of the plugging agent is requirede1 is 8 m and the dosage of the plugging agent is 1000 m 3 .

[0232] Step 3: Prediction of water plugging effect and implementation situation

[0233] Predict the water plugging effect based on the initial production and water cut of the horizontal well to be water plugged, the plugging strength and the plugging depth. Calculate the liquid production volume under the maximum production pressure difference; through the liquid production volumes of the oil-producing section and the water-producing section, calculate the daily oil production and the comprehensive water cut after water plugging according to the water cut of each section.

[0234] According to the set maximum production pressure difference, after obtaining the production pressure difference, the liquid volume of the oil-producing section is the ratio of the production pressure difference to the resistance of the oil-producing section, and the liquid volume of the water-producing section is the ratio of the production pressure difference to the resistance of the water-producing section. Take the water cut during their respective production processes. For example, take the initial water cut when the well is opened for the oil-producing section, which is 51.1%; take the water cut before water plugging, which is 98.2% for the water-producing section. Then calculate the oil production after water plugging in the water-producing section and the oil-producing section. The sum of the two is the predicted daily oil production after water plugging.

[0235] Take the above values to predict the production situation after plugging. The daily liquid production is 55 m 3 , the water cut is 85%, and the daily oil production is 8.25 tons; 500 cubic meters of weak gel and 500 cubic meters of medium-strong gel are injected on site in this well. After water plugging, the actual production situation is that the daily liquid production is 62 m 3 , the water cut is 88.5%, the daily oil production is 7.13 tons, the cumulative oil increase is 630 tons, and the effective period has reached more than 210 days, which is basically consistent with the prediction result, indicating that this method is reliable.

[0236] Example 3:

[0237] Optimization decision-making for water plugging of horizontal well *P6 well

[0238] Taking *3P1 well as an example: It was produced on October 7, 2016. The initial daily liquid production was 26.9 tons, the daily oil production was 10.1 tons, and the water cut was 62.4%. Currently, the daily liquid production is 74.7 tons, the daily oil production is 1.3 tons, and the water cut is 98.3%. The cumulative oil production is 0.3358 million tons, and the cumulative water production is 57,008 cubic meters. The geological reserve of this well is 75,000 tons, the cumulative oil production in the well area is 16,000 tons, the remaining recoverable reserve is 17,000 tons, and the recovery degree of the well area is 25.8%. Since this well was affected by bottom water since its production, the water cut reached more than 95% in less than two years, the water cut increased rapidly, and the recovery degree was low. The physical properties of the oil layer of this well are permeability (0.815 μm 2 ), porosity (33%), temperature (74 °C), crude oil viscosity (765 mPa·S), and formation water salinity (16,086 mg / L).

[0239] The 21st layer of the lower Guantao Submember III produced by this well is a nose-shaped structure blocked by a fault, belonging to a natural bottom water oil reservoir, and the high water cut comes from the bottom water. The vertical thickness of the oil layer is 7m, the horizontal section is 6m away from the bottom water and 1m away from the top boundary of the oil layer. The production interval is 1977m - 2012m (35m). Judging from the logging interpretation results data, the permeability difference in the production interval is not significant. Judging from the wellbore trajectory diagram, the vertical swing of the horizontal section is not large (Point A: vertical depth 1736.92m, inclined depth 1953.42m; Point B: vertical depth 1736.82m, inclined depth 2065.40m), and it is judged that the possibility of water production at the target point of section B is relatively high.

[0240] Step 1: Optimization of the plugging strength of the plugging agent

[0241] According to the equivalent seepage resistance method, calculate the seepage resistance R0 of the high oil-bearing interval and the resistance R after plugging the water channel with high water cut after water plugging. w should be more than 10 times the resistance R of the crude oil flow in the oil-bearing interval. Based on the calculated seepage resistance R that needs to be achieved after plugging the high water cut interval. o , and then calculate the plugging strength that the plugging agent needs to achieve. According to Formula (1), Formula (2) and the oil reservoir data table 3 of the water injection well, calculate the gelation strength and residual resistance coefficient of the plugging agent required. w , and then calculate the gelation strength and residual resistance coefficient of the plugging agent required.

[0242] After calculation, according to the resistance of the oil production section of 0.292 atm / (cm 3 / s), to ensure the water plugging effect, according to on-site experience, the resistance of the water production section should be at least 10 times greater than the oil production resistance. Referring to the previous laboratory experiments, take the viscosity μ of the plugging agent after gelation gel to reach more than 220 mPa·s and the residual resistance coefficient R after plugging ff to reach more than 35.

[0243] Table 3 Parameter value table of Well P6

[0244] Parameter Value Parameter Value Underground crude oil viscosity / mPa·s 765 Residual resistance coefficient 35 Length of water production section / cm 1500 Viscosity of water channeling mixture / mPa·s 160 Liquid supply radius / cm 5000 Gel viscosity / mPa·s 220 Wellbore radius / cm 5 <![CDATA[Average formation permeability / μm 2 > 0.815 Porosity, % 33 Length of oil production section / cm 2000

[0245] Step 2: Calculation of the water plugging depth (amount of plugging agent)

[0246] The goal of water plugging is to obtain the maximum oil production and the lowest water cut, but the liquid supply capacity of the oil well needs to be ensured after water plugging. Therefore, it is necessary to study a reasonable plugging range to ensure the normal production of the oil well after water plugging.

[0247] The mid-depth of the oil layer of this well is 1746m. Taking the formation pressure of 16.5 MPa and the pump depth of 1000m, if the normal production drawdown is 200m, then the flowing fluid level is taken as 800m; after calculation (Table 4), the maximum production pressure difference is 7.2 MPa.

[0248] Table 4 Maximum production pressure difference table

[0249]

[0250] In the table, P1 is the casing pressure of the oil well, P2 is the liquid column pressure from the flowing fluid level to the pump depth of the oil well, and P3 is the mixed liquid column pressure from the pump depth to the mid-depth of the oil reservoir of the oil well.

[0251] According to the liquid volume (Q) of the water shutoff oil well to be treated, under the condition of predicting the maximum production pressure difference (⊿P), based on the economic production rate, according to the equivalent seepage resistance method, based on the oil reservoir data table 4, formula (1), formula (2), formula (3), formula (4), formula (5), formula (11) of the water shutoff well, the plugging range is calculated, and the plugging depth (r e1 ) is calculated.

[0252] After calculation, the plugging depth r of the plugging agent is e1 10 m and the dosage of the plugging agent is 800 m 3 .

[0253] Step 3: Prediction of water shutoff effect and implementation situation

[0254] Predict the water shutoff effect according to the initial production rate and water cut of the horizontal well to be water shutoff, the plugging strength and the plugging depth. Under the maximum production pressure difference, calculate the liquid production rate; through the liquid production rates of the oil-producing section and the water-producing section, calculate the daily oil production and the comprehensive water cut after water shutoff according to the water cut of each section.

[0255] According to the set maximum production pressure difference, after obtaining the production pressure difference, the liquid volume of the oil-producing section is the ratio of the production pressure difference to the resistance of the oil-producing section, and the liquid volume of the water-producing section is the ratio of the production pressure difference to the resistance of the water-producing section. Take the water cut in their respective production processes, such as taking the water cut at the initial stage of well opening for the oil-producing section, which is 62.4%; the water cut of the water-producing section is taken as 98.3% before water shutoff, then calculate the oil production after water shutoff of the water-producing section and the oil-producing section, and the sum of the two is the predicted daily oil production after water shutoff.

[0256] Taking the above values, predict the production situation after plugging. The daily liquid production is 55 m 3 , the water cut is 90%, and the daily oil production is 5.5 tons; 800 cubic meters of medium-strength gel is injected on site in this well. After water shutoff, the actual production situation is that the daily liquid production is 58 m 3 , the water cut is 89%, the daily oil production is 6.38 tons, the cumulative oil increment is 520 tons, and the valid period has reached more than 180 days, which is basically consistent with the prediction result, indicating that this method is reliable.

[0257] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0258] Except for the technical features described in the specification, the rest are known technologies to those skilled in the art.

Claims

1. A decision-making method for water shutoff technology in horizontal wells, characterized in that, The decision-making method for water plugging technology in horizontal wells includes: Step 1: On the basis of clarifying the potential of the oil well, determine the plugging strength of the plugging agent according to the equivalent seepage resistance method. Step 2: Select the water plugging depth, i.e., the dosage of the plugging agent, according to the liquid production and flowing fluid level of the reservoir where the horizontal well is located. Step 3: Predict the water plugging effect according to the initial production, water cut and plugging depth of the reservoir where the horizontal well is located. In Step 2, starting from the principle of fluid seepage, taking the seepage resistance of the oil phase, water phase and oil-water phase as the research object, calculate the plugging depth according to the equivalent seepage resistance method and the maximum production pressure difference; calculate the dosage of the plugging agent according to the need of the plugging range. In Step 2, the dosage of the plugging agent is related to parameters such as the length of the plugging section, effective porosity and plugging depth; statistical data of on-site water finding test results of high water cut horizontal wells show that the length of the water producing section of high water cut horizontal wells accounts for 10% - 20% of the production well section length. The water production situation of horizontal wells is relatively complex. The dosage of water plugging in horizontal wells needs to be optimized in combination with the water production position and water production shape. In Step 2, the calculation formula for the dosage of the plugging agent is: Q = πr e1 2 Lφc...........(11) Where: Q—the dosage of plugging agent, m 3 ; r e1 — Plugging range of plugging agent, cm; L—the length of the plugging section, m; φ—effective porosity, %; c—correction coefficient.

2. The decision-making method for water shutoff technology in horizontal wells according to claim 1, characterized in that, In step 1, according to r e the liquid supply radius, r e1 the plugging range of the plugging agent, r w the wellbore radius, R w the seepage resistance of the water-producing section after water plugging, and the seepage resistance of the oil-producing section R0, calculate the seepage resistance R0 of the oil-producing section; and calculate the seepage resistance R of the water-producing section after gel water plugging w ; the seepage resistance R of the water-producing section after gel water plugging w is directly related to the viscosity μ of the gel gel and the residual resistance coefficient R after plugging ff The viscosity μ of the gel gel and the residual resistance coefficient R after plugging ff The greater they are, the greater the seepage resistance R of the water-producing section after gel water plugging w will be.

3. The decision-making method for water shutoff technology in horizontal wells according to claim 2, characterized in that, In step 1, according to the original differential permeability between the water-producing section and the oil-producing section and the differential at the current water cut, determine the degree of plugging. After water plugging, the seepage resistance R of the water-producing section w should be greater than the seepage resistance R of the oil-producing section o so that the water-producing section can be plugged and the oil-producing section can be effectively started.

4. The decision-making method for water shutoff technology in horizontal wells according to claim 3, characterized in that, In step 1, R w , R o The calculation formula for is: where: R0—the seepage resistance in the oil outlet section, atm / (cm 3 / s); μ0—underground crude oil viscosity, mPa·s; μ gel — Gel viscosity, mPa.s; μ w — Viscosity of the oil-water mixture in the water channeling path, mPa·s; K—the average formation permeability, μm 2 ; h0—the length of the oil production section, cm; R w — Seepage resistance of the water outlet section after water plugging, atm / (cm 3 / s); h w — Length of the water outlet section, cm; r e — Liquid supply radius, cm; r w — Wellbore radius, cm; R ff — Gel residual resistance factor; r e1 — Plugging range of plugging agent, cm.

5. The decision-making method for water shutoff technology in horizontal wells according to claim 1, characterized in that, In step 2, according to the liquid volume Q and the flowing fluid level m of the water-injection and oil-production well to be plugged, under the condition of predicting the maximum production pressure difference ⊿P, based on the economic production rate, the plugging depth r is calculated. e1 That is, the limit water plugging radius: Where: Q—output, m 3 ; ⊿P—production pressure difference, atm; R - section resistance, atm / (cm 3 / s); R o — Resistance of the oil outlet section, atm / (cm 3 / s); R w — Resistance of the water outlet section, atm / (cm 3 / s).

6. The horizontal well water plugging process decision-making method according to claim 5, wherein, In Step 2, the production pressure difference is the difference between the formation pressure and the bottom hole flowing pressure. The calculation of the bottom hole flowing pressure of the oil well is as follows: p wf = p1 + p2 + p3..................(5) Where: p1—casing pressure of the oil well, MPa; p2—the liquid column pressure from the flowing fluid level to the pump depth of the oil well, MPa; p3—the mixed liquid column pressure from the pump depth to the mid-depth of the oil layer of the oil well, MPa; p2 = ρ o gH2.................(6) ρ o — Density of formation crude oil, Kg / m 3 ; H2—the distance from the flowing fluid level to the pump depth, m; where: H2 = L2 - L1.................(7) L2—pump setting depth, m; L1—flowing fluid level depth, m; p3 = ρ h gH3................(8) ρ k — Density of the oil-water mixture, kg / m 3 ; H3—the distance from the pump depth to the mid-depth of the oil layer, m; H3 = L - L2...............(9) L—the mid-depth of the oil layer, m; ρ k = f w ρ w + (1 - f w )ρ o ...............(10) f w — Moisture content, %; ρ o — Density of formation crude oil, kg / m 3 ; ρ w — Density of formation water, kg / m 3 .

7. The horizontal well water plugging process decision-making method according to claim 1, wherein, In step 3, according to the production pressure difference obtained after setting water plugging, the liquid volumes of the oil well section and the water producing well section are calculated. That is, the liquid volume of the oil producing section is the ratio of the production pressure difference to the resistance of the oil producing section (⊿P / R o ), and the liquid volume of the water producing section is the ratio of the production pressure difference to the resistance of the water producing section (⊿P / R w ); for the water cut values of the oil well section and the water producing well section, the water cut values during their respective production processes are taken. That is, the water cut value of the oil well section is taken as the water cut value at the initial stage of well opening, and the water cut value of the water producing well section is taken as the water cut value before water plugging; then the oil production amounts after water plugging for the water producing section and the oil producing section are calculated, and the sum of the two is the predicted daily oil production after water plugging.

8. The horizontal well water plugging process decision-making method according to claim 1, wherein, After water plugging in Step 3, the daily oil production R o is calculated by the following formula: R o = Q1 × W1 + Q2 × W2.......................(12) Where: R o — Oil production per day after water shutoff, t; Q1 - Liquid production per day in the oil production well section, m 3 ; Q2 - Liquid production per day in the water outlet well section, m 3 ; W1—water cut of the oil production well section, %; W2—water cut of the water production well section, %。

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