Horizontal well casing damage prediction method and device and prevention and treatment method

Abstract

The invention relates to a horizontal well casing damage prediction method and device and a prevention and treatment method. The method comprises the steps that risk index parameters of a work area target well are obtained; dividing the numerical range of the risk index parameters into n sub-boundaries, and correspondingly dividing the scores from 0 to 100 into n score segments; determining a score corresponding to each risk index parameter value of the target well according to the score segments corresponding to the sub-boundaries of the risk index parameters; determining a risk prediction value of the target well by using a risk assessment formula according to the score; and determining the risk level of the target well according to the risk prediction value, and completing the casing damage prediction of the target well. The problems that during existing casing deformation risk prediction, the casing damage risk in the hydraulic fracturing process cannot be effectively predicted, casing damage caused by asymmetric extrusion on a casing when shearing activity occurs due to interruption-fracture in the hydraulic pressure process is not considered, and consequently the risk level of a casing damage point cannot be accurately predicted before construction, and the construction cost is reduced are solved. Therefore, the construction cost and the construction difficulty are increased, the fracturing effect is influenced, and the life cycle of a shaft is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil exploitation, and in particular to a method and device for predicting casing damage of a horizontal well, and a prevention and control method thereof. Background Art

[0002] my country has huge shale oil resources. The safe, economical and efficient development of shale oil is of great significance to ensuring national energy security. As a low-permeability resource, shale oil must be developed using large-scale horizontal well hydraulic fracturing technology, and the overall development test stage at home and abroad. Shale oil has great development potential, but it faces serious casing damage problems. According to statistics, casing damage accounts for 41.7% of the horizontal wells tested. Casing damage will not only cause the bridge plug to fail to set in place, reduce the number of subsequent fracturing stages, and affect the fracturing effect, but also increase construction costs and difficulty, shorten the life cycle of the wellbore, and thus reduce the overall economic benefits of shale oil development.

[0003] In recent years, the problem of casing damage in horizontal wells during the development of low-permeability resources such as shale gas and shale oil has attracted much attention. At present, domestic and foreign scholars mainly analyze the casing damage mechanism from the perspectives of geology and engineering, which generally includes five categories: asymmetric fracturing, poor cementing quality, temperature effect, lithology interface slip, fault or natural fracture shear slip leading to casing deformation and damage. In general, there is no clear understanding at present, so it is impossible to effectively predict the casing damage risk during hydraulic fracturing, which in turn affects the prevention and control of casing damage.

[0004] Tong Hengmao and others have made it clear through a systematic analysis of the geomechanical mechanism of casing deformation that casing deformation is caused by shearing of pre-existing faults or large cracks (hereinafter referred to as faults-cracks) in areas with significant tectonic action (large differential stress) during large-scale hydraulic fracturing, resulting in asymmetric compression of the casing by the two strata of the faults-cracks. However, this understanding only analyzes casing damage from the perspective of geomechanics. At present, there is no technical method that combines multiple parameters such as geomechanics, temperature effects, and wellbore performance to quickly predict casing damage in shale horizontal wells. Summary of the invention

[0005] The present invention proposes a method, device and prevention method for predicting casing damage of a horizontal well, so as to solve the problem that in the existing casing change risk prediction, the casing damage risk in the hydraulic fracturing process cannot be effectively predicted, and the casing damage caused by asymmetric squeezing of the casing when shearing activity occurs during the hydraulic pressure break-fracture process is not considered, resulting in the inability to accurately predict the risk level of the casing damage point before construction, thereby increasing the construction cost and construction difficulty, affecting the fracturing effect, and shortening the wellbore life cycle.

[0006] According to one aspect of the present invention, a method for predicting casing damage in a horizontal well is provided, comprising:

[0007] Obtaining risk index parameter values ​​of target wells in the work area, wherein the risk index parameters at least include: relative activity coefficient of fault-crack at casing damage risk point, shale reservoir brittleness index, extension length of fault-crack surface, angle between fault-crack surface and wellbore, shale reservoir fracture pressure, wellbore temperature difference before and after fracturing, and perforation density;

[0008] Divide the numerical range of the risk indicator parameter into n sub-limits, divide the score of 0 to 100 into n score segments, and correspond the sub-limits of the risk indicator parameter to the score segments;

[0009] Determine the score corresponding to each risk indicator parameter value of the target well according to the score segment corresponding to the sub-limit of the risk indicator parameter;

[0010] According to the score corresponding to each risk indicator parameter value of the target well, a risk prediction value of the target well is determined using a risk assessment formula;

[0011] According to the risk prediction value, the risk level of the target well is determined, and the casing damage prediction of the target well is completed.

[0012] Preferably, before dividing the numerical range of the risk indicator parameter into n sub-limits, the method further includes:

[0013] It is determined whether the risk indicator parameter exceeds the applicable limit. If yes, casing loss risk prediction is not performed for the target well.

[0014] Preferably, the applicable limit of the fault-crack relative activity coefficient is 0 to 5, the applicable limit of the shale reservoir brittleness index is 0 to 100, the applicable limit of the fault-crack surface extension length is 0 to 1000 m, the applicable limit of the angle between the fault-crack surface and the wellbore is 0 to 90°, the applicable limit of the shale reservoir fracture pressure is 20 to 120 MPa, the applicable limit of the wellbore temperature difference before and after fracturing is 0 to 100°C, and the applicable limit of the perforation density is 0 to 40 perforations / m.

[0015] Preferably, before obtaining the risk index parameters of the target well in the work area, the method further includes: determining the relative activity coefficient of the fracture at the casing damage risk point in the risk index parameters of the target well, wherein the method includes:

[0016] The relative activity coefficient calculation formula is used to determine the fracture-fracture relative activity coefficient at the casing damage risk point;

[0017] Wherein, the relative activity coefficient calculation formula includes formula (1) or (2);

[0018]

[0019] Where: f ais the relative activity coefficient of the fault-crack, σ1, σ2, σ3 are the three principal stresses of the layer where the fault-crack is located at the casing damage risk point, θ is the angle between the fault-crack surface and the σ1 axis, α is the angle between the intersection of the fault-crack surface and the σ2-σ3 plane and the σ3 axis, C P is the fracture-fracture surface cohesion, μ P is the friction coefficient of the fracture surface, and P is the fluid pressure of the fracture surface;

[0020]

[0021] Where: f a is the relative activity coefficient of the fault-crack, σ1, σ2, σ3 are the three principal stresses of the fault-crack layer at the casing damage risk point, β is the angle between the fault-crack surface inclination and the σ1 axis, is the fracture-crack surface inclination angle, C W is the fracture-crack surface cohesion, μ is the fracture-crack surface friction coefficient, and P is the fracture-crack surface fluid pressure.

[0022] Preferably, before obtaining the risk index parameters of the target well in the work area, the method further includes: determining the shale reservoir brittleness index in the risk index parameters of the target well, wherein the method includes:

[0023] Determine the brittleness index of the shale reservoir using formula (3) or (4) or (5);

[0024] B YB =[(E s -E min ) / (E max -E min )+(ν max -ν s ) / (ν max -ν min )]*100 / 2(3);

[0025] In the formula, B YB Shale rock mechanics brittleness index, E s Static Young's modulus of the sample, E min The lower limit of static Young's modulus of shale, E max The upper limit of static Young's modulus of shale, ν s Sample static Poisson's ratio, ν min The lower limit of the static Poisson's ratio of shale, ν max The upper limit of static Poisson's ratio of shale;

[0026] B M1 =(αX quartz +βX dolomite +γX calcite +ηX feldspar +ζX pyrite +ωX clay+k)*100(4);

[0027] B M2 =(X quartz +X dolomite +X calcite +X feldspar +X pyrite )*100(5);

[0028] In the formula, B M1 is the shale mineral brittleness index of rock mechanics weight method, B M2 is the brittle mineral index of shale minerals by brittle mineral method, X quartz is the mass fraction of quartz in the sample, X dolomite is the mass fraction of dolomite in the sample, X calcite is the mass fraction of calcite in the sample, X feldspar is the mass fraction of feldspar in the sample, X pyrite is the mass fraction of pyrite in the sample, X clay is the mass fraction of clay minerals in the sample; α, β, γ, η, ζ, ω are the weight coefficients of quartz, dolomite, calcite, feldspar, pyrite and clay minerals respectively, and k is the correction constant term.

[0029] Preferably, the risk assessment formula includes formula (6);

[0030] F=C1*α1+C2*α2+C3*α3+C4*α4+C5*α5+C6*α6+C7*α7,

[0031] α1+α2+α3+α4+α5+α6+α7=1(6);

[0032] Where F is the risk prediction value, C1 is the score corresponding to the fault-crack relative activity coefficient, α1 is the C1 weight coefficient, C2 is the score corresponding to the shale reservoir brittleness index, α2 is the C2 weight coefficient, C3 is the score corresponding to the fault-crack extension length, α3 is the C3 weight coefficient, C4 is the score corresponding to the angle between the fault-crack surface and the wellbore, α4 is the C4 weight coefficient, C5 is the score corresponding to the shale reservoir fracture pressure, α5 is the C5 weight coefficient, C6 is the score corresponding to the wellbore temperature difference before and after fracturing, α6 is the C6 weight coefficient; C7 is the score corresponding to the perforation density, α7 is the C7 weight coefficient.

[0033] Preferably, the risk assessment formula includes formula (7);

[0034] F=(C1*C2*C3*C4*C5) 1 / 5 *α1+(C6*C7) 1 / 2 *α2, α1+α2=1(7);

[0035] Where F is the risk prediction value, C1 is the score corresponding to the fault-crack relative activity coefficient, C2 is the score corresponding to the shale reservoir brittleness index, C3 is the score corresponding to the fault-crack extension length, C4 is the score corresponding to the angle between the fault-crack surface and the wellbore, C5 is the score corresponding to the shale reservoir fracture pressure, C6 is the score corresponding to the wellbore temperature difference before and after fracturing, C7 is the score corresponding to the perforation density, α1 is the weight coefficient of C1*C2*C3*C4*C5, and α2 is the weight coefficient of C6*C7.

[0036] Preferably, the method for determining the risk level of the target well according to the risk prediction value comprises:

[0037] When the risk prediction value is between 0 and 25, the target well is determined to be at low risk of horizontal well casing damage; when the risk prediction value is between 25 and 50, the target well is determined to be at medium risk of horizontal well casing damage; when the risk prediction value is between 50 and 75, the target well is determined to be at high risk of horizontal well casing damage; and when the risk prediction value is between 75 and 100, the target well is determined to be at ultra-high risk of horizontal well casing damage.

[0038] According to one aspect of the present invention, a horizontal well casing damage prediction device is provided, comprising:

[0039] An acquisition unit is used to acquire risk index parameters of a target well in a work area, wherein the risk index parameters at least include: a relative activity coefficient of a fault-crack at a casing damage risk point, a brittleness index of a shale reservoir, an extension length of a fault-crack surface, an angle between a fault-crack surface and a wellbore, a shale reservoir fracture pressure, a temperature difference of the wellbore before and after fracturing, and a perforation density;

[0040] A sub-limit division unit is used to divide the numerical range of the risk indicator parameter into n sub-limits, divide the score of 0 to 100 into m score segments, and correspond the sub-limits of the risk indicator parameter to the score segments;

[0041] A risk indicator parameter score determination unit, used to determine the score corresponding to each risk indicator parameter value of the target well according to the score segment corresponding to the sub-limit of the risk indicator parameter;

[0042] A risk prediction value determination unit, used to determine the risk prediction value of the target well according to the score corresponding to each risk indicator parameter value of the target well and using a risk assessment formula;

[0043] The risk level determination unit is used to determine the risk level of the target well according to the risk prediction value and complete the casing damage prediction of the target well.

[0044] According to one aspect of the present invention, a method for preventing and controlling casing damage in a horizontal well is provided, comprising: if the risk level of a target well is high risk or ultra-high risk, all risk index parameters are divided into four categories, wherein the first category includes the relative activity coefficient of the fault-crack at the casing damage risk point and / or the brittleness index of the shale reservoir and / or the angle between the fault-crack surface and the wellbore and / or the rupture pressure of the shale reservoir, the second category includes the extension length of the fault-crack surface, the third category includes the temperature difference of the wellbore before and after fracturing, and the fourth category includes the perforation density; if one or more parameter values ​​in one or more risk index parameters are greater than or equal to 50, the corresponding prevention and control method of the category is selected to prevent and control the target well, wherein the prevention and control method corresponding to the first category is The fracturing pressure is reduced to 90-98% of the original value and the injection volume of the fracturing fluid is reduced to 80-95% of the original value. The corresponding prevention and control method of the second category is the injection of temporary plugging agents. The corresponding prevention and control method of the third category is to increase the injection temperature of the fracturing fluid to 120-200% of the original value and reduce the injection and return speed of the fracturing fluid to 80-95% of the original value. The corresponding prevention and control method of the fourth category is to use engineering methods to strengthen the wellbore; among which, the engineering methods to strengthen the wellbore include: one or more of cement squeezing, lowering packers, casing patching, casing back-connection, chemical plugging or casing replacement methods; the temporary plugging agent is one or more of cross-linked polymer temporary plugging agents, fiber temporary plugging agents, inorganic salt temporary plugging agents or composite material temporary plugging agents.

[0045] The present invention has at least the following beneficial effects:

[0046] The present invention proposes a method, device and prevention method for predicting casing damage of a horizontal well, which comprehensively includes seven risk index parameters, including the relative activity coefficient of the fault-fracture that can reflect the shear slip generated by the fault-fracture through the well during hydraulic fracturing, the brittleness index of the shale reservoir, the extension length of the fault-fracture surface, the angle between the fault-fracture surface and the wellbore, the rupture pressure of the shale reservoir, the temperature difference between the wellbore before and after fracturing, and the perforation density, and divides each risk index parameter into sub-boundaries and assigns corresponding scores to determine the risk prediction value of the target well, and divides the risk level according to the risk prediction value, so as to provide a basis for the early formulation of casing damage risk prevention and control measures, ensure the normal progress of hydraulic fracturing, solve the technical problems of long risk assessment cycle and high cost at the casing damage risk point of the horizontal well, and at the same time can reduce the casing damage rate and improve the economic benefits of shale oil development. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification. These drawings illustrate embodiments consistent with the present invention and, together with the specification, are used to explain the technical solutions of the present invention.

[0048] Figure 1 A flow chart of a method for predicting casing damage in a horizontal well according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0049] Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0050] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0051] The term "and / or" herein is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the term "at least one" herein represents any combination of at least two of any one or more of a plurality of. For example, including at least one of A, B, and C can represent including any one or more elements selected from the set consisting of A, B, and C.

[0052] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0053] Figure 1 A flow chart of a method for predicting casing damage in a horizontal well according to an embodiment of the present invention is shown. Figure 1 As shown, a method for predicting casing damage of a horizontal well includes: step S01: obtaining the value of the risk index parameter of the target well in the work area, wherein the risk index parameter at least includes: the relative activity coefficient of the fault-crack at the casing damage risk point, the brittleness index of the shale reservoir, the extension length of the fault-crack surface, the angle between the fault-crack surface and the wellbore, the shale reservoir fracture pressure, the wellbore temperature difference before and after fracturing, and the perforation density; step S02: dividing the value range of the risk index parameter into n sub-limits, dividing the score of 0 to 100 into n fractional segments, and making the sub-limits of the risk index parameter correspond to the fractional segments; step S03: determining the score corresponding to each risk index parameter value of the target well according to the fractional segments corresponding to the sub-limits of the risk index parameter; step S04: determining the risk prediction value of the target well according to the score corresponding to each risk index parameter value of the target well by using the risk assessment formula; step S05: determining the risk level of the target well according to the risk prediction value, and completing the casing damage prediction of the target well.

[0054] The horizontal well casing damage prediction method provided by the embodiment of the present invention specifically includes the following steps:

[0055] Step S01: Obtain risk index parameters of the target well in the work area, wherein the risk index parameters at least include: the relative activity coefficient of the fault-crack at the casing risk point, the brittleness index of the shale reservoir, the extension length of the fault-crack surface, the angle between the fault-crack surface and the wellbore, the shale reservoir fracture pressure, the wellbore temperature difference before and after fracturing, and the perforation density.

[0056] In an embodiment of the present invention, the intersection of formation faults and fractures and the trajectory of the target well can be determined through the seismic attribute data of the target layer in the work area and the drilling data of the target well, which is the casing damage risk point; wherein the seismic attribute data may include attribute data such as amplitude, frequency, continuity characteristics, and ant body of the original seismic profile. From the seismic attribute data, the positions of faults and fractures in the formation of the work area can be determined, and combined with the actual drilling data information, the intersection of the faults and fractures with the well trajectory is determined, that is, the casing damage risk point of the target well, thereby determining the relative activity coefficient of the faults and fractures at the casing change risk.

[0057] In the present invention, before dividing the numerical range of the risk indicator parameter into n sub-limits, the method further includes:

[0058] It is determined whether the risk indicator parameter exceeds the applicable limit. If yes, casing loss risk prediction is not performed for the target well.

[0059] In the present invention, the applicable limit of the relative activity coefficient of the fault-crack is 0-5, the applicable limit of the brittleness index of the shale reservoir is 0-100, the applicable limit of the extension length of the fault-crack surface is 0-1000m, the applicable limit of the angle between the fault-crack surface and the wellbore is 0-90°, the applicable limit of the shale reservoir fracture pressure is 20-120MPa, the applicable limit of the wellbore temperature difference before and after fracturing is 0-100°C, and the applicable limit of the perforation density is 0-40 / m.

[0060] In the embodiment of the present invention, it is determined whether each risk indicator parameter value exceeds the corresponding applicable limit. If one or more of the risk indicator parameters exceed the applicable limit, the horizontal well is not suitable for the horizontal well casing damage risk prediction of the present invention; if all the horizontal well risk indicator parameters are within the applicable limit, the horizontal well is suitable for the horizontal well casing damage risk prediction, and the following steps are continued.

[0061] In the present invention, before obtaining the risk index parameters of the target well in the work area, it also includes: determining the relative activity coefficient of the fracture at the casing damage risk point in the risk index parameters of the target well, and the method includes:

[0062] The relative activity coefficient calculation formula is used to determine the fracture-fracture relative activity coefficient at the casing damage risk point;

[0063] Wherein, the relative activity coefficient calculation formula includes formula (1) or (2);

[0064]

[0065] In formula (1): f a is the relative activity coefficient of the fracture, σ1, σ2, σ3 are the three principal stresses of the fracture layer at the casing damage risk point, θ is the angle between the fracture plane (or weak plane) (or weak plane) and the σ1 axis, α is the angle between the intersection of the fracture plane (or weak plane) and the σ2-σ3 plane and the σ3 axis, C P is the cohesion of the fracture-fracture surface (or weak surface), μ P is the friction coefficient of the fracture surface (or weak surface), and P is the fluid pressure of the fracture surface (or weak surface);

[0066]

[0067] In formula (2): f a is the relative activity coefficient of the fracture, σ1, σ2, σ3 are the three principal stresses of the fracture layer at the casing damage risk point, β is the angle between the fracture plane (or weak plane) and the σ1 axis, is the inclination angle of the fracture plane (or weak plane), C W is the cohesive force of the fracture surface (or weak surface), μ is the friction coefficient of the fracture surface (or weak surface), and P is the fluid pressure of the fracture surface (or weak surface).

[0068] In equations (1) and (2), the fluid pressure P at the fault surface (or weak surface) is the sum of the formation fluid pressure and the fluid pressure increment caused by hydraulic fracturing, and is calculated as follows:

[0069] P = P0 + ΔP (8);

[0070] Where: ΔP is the fluid pressure increment caused by hydraulic fracturing, and P0 is the formation fluid pressure.

[0071] In formula (8), the calculation formula for the formation fluid pressure P0 is:

[0072] P0=kρ w gh(9);

[0073] Where: k is the fluid pressure coefficient, ρ w is the density of water, g is the acceleration of gravity, h is the vertical depth of the casing damage risk point, and k=1.85.

[0074] According to the formation fluid pressure P0 at the casing change risk point and the modeling data of the geostress field, the sum of the formation fluid pressure and the fluid pressure increment caused by hydraulic fracturing is calculated by the "Generalized Fracture Theory Application System V1.0" software to obtain the fault-fracture surface fluid pressure P.

[0075] In equations (1) and (2), the cohesion and friction coefficient are determined based on experimental data. If there is no experimental data, the cohesion can be taken as 1.0 MPa and the friction coefficient can be taken as 0.6.

[0076] According to formula (1) or (2), the relative activity coefficient f of fracture at each casing damage risk point is calculated. a , f a The larger it is, the stronger the activity of the fault surface (or weak surface) is, and the higher the risk of casing damage is.

[0077] Among them, fault-crack surface refers to fault plane and fracture surface; weak surface refers to fault plane, fracture surface and formation interface; fault-crack surface extension length refers to the length of the fault plane or fracture surface in the longest extension direction; the angle between the fault-crack surface and the wellbore refers to the minimum acute angle formed by the fault plane or fracture plane and the horizontal section of the horizontal wellbore, including the right angle formed by the fault plane or fracture plane and the horizontal section of the horizontal wellbore; the wellbore temperature difference before and after fracturing refers to the temperature difference of the horizontal section of the horizontal wellbore before and after fracturing.

[0078] In the present invention, before obtaining the risk index parameters of the target well in the work area, it also includes: determining the shale reservoir brittleness index in the risk index parameters of the target well, and the method includes:

[0079] Determine the brittleness index of the shale reservoir using formula (3) or (4) or (5);

[0080] B YB =[(E s -E min ) / (E max -E min )+(ν max -ν s ) / (ν max -ν min )]*100 / 2(3);

[0081] In formula (3), B YB is the rock mechanical brittleness index of shale, E s is the static Young's modulus of the sample, E min is the lower limit of the static Young's modulus of shale, E max is the upper limit of the static Young's modulus of shale, ν s is the static Poisson's ratio of the sample, ν min is the lower limit of the static Poisson's ratio of shale, ν max is the upper limit of the static Poisson's ratio of shale;

[0082] B M1 =(αX quartz +βX dolomite +γX calcite +ηX feldspar +ζXpyrite +ωX clay +k)*100(4);

[0083] B M2 =(X quartz +X dolomite +X calcite +X feldspar +X pyrite )*100(5);

[0084] In formula (4) and (5), B M1 is the shale mineral brittleness index of rock mechanics weight method, B M2 is the brittle mineral method shale mineral brittleness index, X quartz is the mass fraction of quartz in the sample, X dolomite is the mass fraction of dolomite in the sample, X calcite is the mass fraction of calcite in the sample, X feldspar is the mass fraction of feldspar in the sample, X pyrite is the mass fraction of pyrite in the sample, X clay is the mass fraction of clay minerals in the sample; α, β, γ, η, ζ, ω are the weight coefficients of quartz, dolomite, calcite, feldspar, pyrite and clay minerals respectively, and k is the correction constant term.

[0085] In an embodiment of the present invention, the fault-fracture plane extension length, the angle between the fault-fracture plane and the wellbore, the shale reservoir fracture pressure, the wellbore temperature difference before and after fracturing, and the perforation density parameters are acquired through the shale reservoir parameter data, horizontal well parameter data, and fracturing parameter data of the target horizontal well.

[0086] Step S02: Divide the numerical range of the risk indicator parameter into n sub-limits, divide the score of 0 to 100 into n score segments, and correspond the sub-limits of the risk indicator parameter to the score segments.

[0087] In the embodiment of the present invention, n is an integer greater than or equal to 1, wherein the mth sublimit corresponds to the mth risk score segment, m is an integer greater than or equal to 1 and less than or equal to n (m=1, 2, 3.......n), and the value of the risk indicator within the mth sublimit is linearly related to the risk score in the mth risk score segment, that is, the risk score is in a linear piecewise function relationship with respect to the value of the risk indicator. With the value of the risk indicator as the independent variable, and within the applicable limit, the value of the risk indicator is divided into n intervals (sublimits), and any interval has a different linear function relationship with the corresponding score segment.

[0088] Among them, when the sub-limits correspond to the score segments, the sub-limits of the values ​​that are relatively most likely to cause casing loss correspond to the score segment with the largest score range, that is, the values ​​that are more likely to cause casing loss correspond to higher scores, and so on, the sub-limits of the values ​​that are least likely to cause casing loss correspond to the score segment with the smallest score range; that is, the sub-limits are sorted from high to low according to the ability to cause casing loss, and the score segments are sorted from large to small according to the score range, and the two are matched one by one after the sorting is completed. The larger the value of n, the more detailed the impact of the risk indicator on the casing loss risk can be.

[0089] Since the impact of risk indicator parameters on horizontal well casing damage may not change at a uniform rate, changes in parameter values ​​within a certain range have a greater impact on casing damage, while the impact is relatively smaller beyond the sensitive section; for example, the fault-fracture surface extension length is mostly concentrated in 200-400, which has a more obvious impact on casing damage, and the impact is greater than 400, but the extension length is less than 400, and occasionally there will be a value close to 1000. When dividing the sub-boundaries, 400-1000 can be divided into one section, 200-399 can be divided into one section, and so on, to complete the sub-boundary division of each risk indicator parameter.

[0090] The numerical ranges of various risk indicator parameters are as follows: fault-fracture relative activity coefficient is 0-5, shale reservoir brittleness index is 0-100, fault-fracture surface extension length is 0-1000m, the angle between the fault-fracture surface and the wellbore is 0-90°, the shale reservoir fracture pressure is 20-120MPa, the wellbore temperature difference before and after fracturing is 0-100°C and the perforation density is 0-40 / m.

[0091] If n=4, the numerical range of the risk index parameter is divided into four sub-limits, and the score of 0-100 is evenly divided into 4 score segments, namely 0-25 points, 25-50 points, 50-75 points, and 75-100 points; each sub-limit corresponds to a different risk index score segment, among which the first sub-limit is very unfavorable for the formation of horizontal well casing damage, and the corresponding score segment is 0-25 points; the second sub-limit is unfavorable for the formation of horizontal well casing damage, and the corresponding score segment is 25-50 points; the third sub-limit is favorable for the formation of horizontal well casing damage, and the corresponding score segment is 50-75 points; the fourth sub-limit is most favorable for the formation of horizontal well casing damage, and the corresponding score segment is 75-100 points.

[0092] The first sub-limit of the relative activity coefficient of fracture-rupture is 0-0.5, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 0.5-1, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 1-1.5, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 1.5-5, corresponding to the casing damage risk score range of 75-100.

[0093] The first sub-limit of the shale reservoir brittleness index is 0-30, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 30-55, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 55-65, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 65-100, corresponding to the casing damage risk score range of 75-100.

[0094] The first sub-limit of the fault-crack extension length is 0-100, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 100-200, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 200-400, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 400-1000, corresponding to the casing damage risk score range of 75-100.

[0095] The first sub-limit of the angle between the fault-fracture surface and the wellbore is 0-10, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 10-20, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 20-50, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 50-90, corresponding to the casing damage risk score range of 75-100.

[0096] The first sub-limit of shale reservoir fracture pressure is 20-40, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 40-60, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 60-80, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 80-120, corresponding to the casing damage risk score range of 75-100.

[0097] The first sub-limit of the wellbore temperature difference before and after fracturing is 0-25, corresponding to the casing damage risk score range of 0-25; the second sub-limit is 25-60, corresponding to the casing damage risk score range of 25-50; the third sub-limit is 60-80, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit is 80-100, corresponding to the casing damage risk score range of 75-100.

[0098] The first sub-limit of the perforation density is 0-1, corresponding to the casing damage risk score range of 0-25; the second sub-limit of the perforation density is 1-10, corresponding to the casing damage risk score range of 25-50; the third sub-limit of the perforation density is 10-20, corresponding to the casing damage risk score range of 50-75; the fourth sub-limit of the perforation density is 20-40, corresponding to the casing damage risk score range of 75-100.

[0099] Step S03: Determine the score corresponding to each risk indicator parameter value of the target well according to the score segment corresponding to the sub-limit of the risk indicator parameter.

[0100] In the embodiment of the present invention, if the value of the relative activity coefficient of the break-crack in the risk indicator parameter is 0.55, it is located in the sub-limit of 0.5 to 1, and the score segment of the risk indicator parameter corresponding to the sub-limit is 25 to 50. According to the linear relationship between the sub-limit and the score segment, it is concluded that for every increase of 0.1 in the value of the relative activity coefficient of the break-crack, the score of the risk indicator parameter increases by 5, so the score of the risk indicator parameter corresponding to the value of the relative activity coefficient of the break-crack of 0.55 is 27.5. If the relative activity coefficient of the break-crack is 1.73, it is located in the sub-limit of 1.5 to 5, and the score of the risk indicator parameter corresponding to the sub-limit is 75 to 100. It is concluded that for every increase of 0.1 in the value of the relative activity coefficient of the break-crack, the score of the risk indicator parameter increases by 0.71, so the score of the risk indicator parameter corresponding to the relative activity coefficient of the break-crack of 1.73 is 76.6.

[0101] The risk indicator parameter scores corresponding to other risk indicator parameter values ​​are obtained by the above method, that is, first determine the sub-limit where the risk indicator parameter value is located, and the risk indicator parameter score segment corresponding to the sub-limit, then determine the rate of change of the risk indicator parameter score with the increase of the risk indicator value, and then combine the end value of the sub-limit and the score of the risk indicator score segment corresponding to the end value to obtain the score corresponding to the risk indicator parameter value.

[0102] Step S04: According to the score corresponding to each risk indicator parameter value of the target well, a risk prediction value of the target well is determined using a risk assessment formula.

[0103] In the present invention, the risk assessment formula includes formula (6) or (7);

[0104] F=C1*α1+C2*α2+C3*α3+C4*α4+C5*α5+C6*α6+C7*α7,

[0105] α1+α2+α3+α4+α5+α6+α7=1(6);

[0106] In formula (6), F is the risk prediction value, C1 is the score corresponding to the relative activity coefficient of fault-crack, α1 is the weight coefficient of C1, C2 is the score corresponding to the brittleness index of shale reservoir, α2 is the weight coefficient of C2, C3 is the score corresponding to the extension length of fault-crack surface, α3 is the weight coefficient of C3, C4 is the score corresponding to the angle between fault-crack surface and wellbore, α4 is the weight coefficient of C4, C5 is the score corresponding to the fracture pressure of shale reservoir, α5 is the weight coefficient of C5, C6 is the score corresponding to the temperature difference of wellbore before and after fracturing, α6 is the weight coefficient of C6; C7 is the score corresponding to the perforation density, α7 is the weight coefficient of C7.

[0107] F=(C1*C2*C3*C4*C5) 1 / 5 *α1+(C6*C7)1 / 2 *α2, α1+α2=1(7);

[0108] In formula (7), F is the risk prediction value, C1 is the score corresponding to the relative activity coefficient of fault-crack, C2 is the score corresponding to the brittleness index of shale reservoir, C3 is the score corresponding to the extension length of fault-crack surface, C4 is the score corresponding to the angle between fault-crack surface and wellbore, C5 is the score corresponding to the fracture pressure of shale reservoir, C6 is the score corresponding to the temperature difference of wellbore before and after fracturing, C7 is the score corresponding to the perforation density, α1 is the weight coefficient of C1*C2*C3*C4*C5, and α2 is the weight coefficient of C6*C7.

[0109] In an embodiment of the present invention, in formula (6), the values ​​of the weight coefficients are: α1=0.2, α2=0.15, α3=0.16, α4=0.1, α5=0.14, α6=0.17, α7=0.08, or the values ​​of the weight coefficients are α1=0.3, α2=0.16, α3=0.14, α4=0.1, α5=0.1, α6=0.15, α7=0.05.

[0110] In formula (7), the values ​​of the weight coefficients are: α1 = 0.6, α2 = 0.4, or the values ​​of the weight coefficients are: α1 = 0.7, α2 = 0.3.

[0111] Step S05: Determine the risk level of the target well according to the risk prediction value, and complete the casing damage prediction of the target well.

[0112] In the present invention, the method for determining the risk level of the target well according to the risk prediction value includes: when the risk prediction value is 0-25, that is, when the risk prediction value is greater than or equal to 0 and less than 25, the target well is determined to be at low risk of horizontal well casing damage; when the risk prediction value is 25-50, that is, when the risk prediction value is greater than or equal to 25 and less than 50, the target well is determined to be at medium risk of horizontal well casing damage; when the risk prediction value is 50-75, that is, when the risk prediction value is greater than or equal to 50 and less than 75, the target well is determined to be at high risk of horizontal well casing damage; when the risk prediction value is 75-100, that is, when the risk prediction value is greater than or equal to 75 and less than or equal to 100, the target well is determined to be at ultra-high risk of horizontal well casing damage.

[0113] The present invention also provides a method for preventing and controlling casing damage in a horizontal well, comprising: if the risk level of the target well is high risk or ultra-high risk, all risk index parameters are divided into four categories, wherein the first category includes the relative activity coefficient of the fault-crack at the casing damage risk point and / or the brittleness index of the shale reservoir and / or the angle between the fault-crack surface and the wellbore and / or the rupture pressure of the shale reservoir, the second category includes the extension length of the fault-crack surface, the third category includes the temperature difference of the wellbore before and after fracturing, and the fourth category includes the perforation density; if one or more parameter values ​​in one or more categories of risk index parameters are greater than or equal to 50, the corresponding prevention and control method of the category is selected to prevent and control the target well, and if there are multiple categories with risk index parameter values ​​greater than or equal to 50, multiple prevention and control methods are selected to be implemented simultaneously. The first type of prevention and control method is to reduce the fracturing pressure to 90-98% of the original pressure and reduce the injection volume of the fracturing fluid to 80-95% of the original pressure; the second type of prevention and control method is to inject temporary plugging agent; the third type of prevention and control method is to increase the injection temperature of the fracturing fluid to 120-200% of the original pressure and reduce the injection and flowback speed of the fracturing fluid to 80-95% of the original pressure; the fourth type of prevention and control method is to use engineering methods to strengthen the wellbore; wherein, the engineering method to strengthen the wellbore includes: one or more of cement squeezing, packer installation, casing patching, casing tie-back, chemical plugging or casing replacement; the temporary plugging agent is one or more of cross-linked polymer temporary plugging agent, fiber temporary plugging agent, inorganic salt temporary plugging agent or composite material temporary plugging agent.

[0114] In an embodiment of the present invention, after the risk level of the target well is determined, a corresponding prevention and control method can be selected for prevention and control. For low-risk and medium-risk wells, since the risk of casing damage is low, casing damage prevention and control may not be performed temporarily, but various downhole parameters are regularly collected to re-determine the risk level, thereby saving construction costs; when the re-determined risk level becomes high risk or ultra-high risk, casing damage prevention and control is performed on the target well.

[0115] If the risk level of the target well is high risk or ultra-high risk, all risk indicator parameters are divided into four categories, the first category includes the fault-crack relative activity coefficient at the casing damage risk point and / or the shale reservoir brittleness index and / or the angle between the fault-crack surface and the wellbore and / or the shale reservoir fracture pressure, the second category includes the extension length of the fault-crack surface, the third category includes the wellbore temperature difference before and after fracturing, and the fourth category includes the perforation density. If one or more risk index parameters have one or more parameter values ​​greater than or equal to 50, then the corresponding prevention and control method of the category is selected to prevent and control the target well (if there are multiple categories with risk index parameter values ​​greater than or equal to 50, then multiple prevention and control methods are selected and implemented simultaneously), among which, the first category corresponding prevention and control method is to reduce the fracturing pressure to 90-98% of the original and reduce the injection volume of the fracturing fluid to 80-95% of the original, the second category corresponding prevention and control method is to inject temporary plugging agent, the third category corresponding prevention and control method is to increase the injection temperature of the fracturing fluid to 120-200% of the original and reduce the injection and return speed of the fracturing fluid to 80-95% of the original, and the fourth category corresponding prevention and control method is to use engineering methods to strengthen the wellbore. Among them, the engineering method to strengthen the wellbore includes: one or more of cement squeezing, packer installation, casing compensation, casing tie-back, chemical plugging and / or casing replacement methods; the temporary plugging agent is one or more of cross-linked polymer temporary plugging agent, fiber temporary plugging agent, inorganic salt temporary plugging agent or composite material temporary plugging agent.

[0116] In the embodiment of the present invention, taking the target horizontal wells S1 to S5 as an example, a numerical table of each risk indicator parameter corresponding to each horizontal well is shown in Table 1 below.

[0117] Table 1: Target horizontal well casing damage risk indicator parameter value table

[0118] Horizontal well number-risk point S1-H1 S2-H3 S3-H5 S4-H7 S5-H8 Fracture-fracture relative activity coefficient 1.28 0.55 1.16 1.73 1.57 Shale reservoir brittleness index 30.6 55.0 38.0 46.5 59.8 Fracture-crack extension length (m) 470 350 85 180 880 Angle between fault-fracture surface and wellbore (°) 10.0 56.0 39.0 42.0 77.0 Shale reservoir fracture pressure (MPa) 40 46.8 52.8 60.3 69.6 Wellbore temperature difference before and after fracturing (℃) 20.5 40.0 30.0 63.2 55.3 Perforation density (perforation / m) 16 12 24 8 16

[0119] According to the four sub-limits divided by the above risk indicator parameters, the sub-limit of each risk indicator parameter value in Table 1 is determined. According to the score segment corresponding to the sub-limit and the linear relationship between the two, the score corresponding to each risk indicator parameter value in Table 1 is determined, as shown in Table 2 below.

[0120] Table 2: Target horizontal well casing damage risk indicator parameter score table

[0121] Horizontal well number-risk point S1-H1 S2-H3 S3-H5 S4-H7 S5-H8 Fracture-fracture relative activity coefficient 64 27.5 58.0 76.6 75.5 Shale reservoir brittleness index 25.6 50.0 33.0 41.5 62.0 Fracture-crack extension length 77.9 68.8 21.3 45.0 95.0 Angle between fault-fracture surface and wellbore 25.0 78.8 55.8 68.3 91.9 Shale reservoir fracture pressure 25.0 33.5 41.0 50.4 62.0 Wellbore temperature difference before and after fracturing 17.1 33.3 25.0 64.0 46.1 Perforation density 65.0 55.0 80.0 44.4 65.0

[0122] According to the score corresponding to each risk indicator parameter, the risk prediction value corresponding to each target horizontal well is determined using formula (6) or (7). The specific calculation results are shown in Table 3 below.

[0123] Table 3: Calculation table of casing damage risk prediction value of target horizontal well

[0124]

[0125]

[0126] According to the risk prediction value obtained, each horizontal well is divided into risk levels, and the final results are shown in Table 4 below.

[0127] Table 4: Target horizontal well casing damage risk level table

[0128]

[0129] Different prediction values ​​show that the casing damage prediction of the horizontal well S4 risk point H7 is high risk, the casing damage prediction of the horizontal well S5 risk point H8 is high risk, and the rest are medium risk. The data collected through actual on-site construction show that the horizontal well casing damage risk level in Table 4 is consistent with the actual situation.

[0130] After determining the risk level of the target well, an appropriate method can be selected to carry out prevention and control construction operations according to the risk level, thereby preventing the target well casing damage caused by selecting a prevention and control construction method with too low a level, or increasing construction costs due to selecting a prevention construction method with a high level.

[0131] It can be understood that the above-mentioned various method embodiments mentioned in the present invention can be combined with each other to form a combined embodiment without violating the principle logic. Due to space limitations, the present invention will not go into details.

[0132] The execution subject of the horizontal well casing damage prediction method may be a horizontal well casing damage prediction device, for example, the horizontal well casing damage prediction method may be executed by a terminal device or a server or other processing device, wherein the terminal device may be a user equipment (UE), a mobile device, a user terminal, a terminal, a cellular phone, a cordless phone, a personal digital assistant (PDA), a handheld device, a computing device, a vehicle-mounted device, a wearable device, etc. In some possible implementations, the horizontal well casing damage prediction method may be implemented by a processor calling a computer-readable instruction stored in a memory.

[0133] Those skilled in the art will appreciate that, in the above method of specific implementation, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of the steps should be determined by their functions and possible internal logic.

[0134] The present invention also provides a horizontal well casing damage prediction device, comprising: an acquisition unit, used to acquire risk index parameters of a target well in a work area, wherein the risk index parameters at least include: a relative activity coefficient of a fault-crack at a casing damage risk point, a shale reservoir brittleness index, a fault-crack surface extension length, a fault-crack surface and a wellbore angle, a shale reservoir rupture pressure, a wellbore temperature difference before and after fracturing, and a perforation density; a sub-boundary division unit, used to divide the numerical range of the risk index parameter into n sub-boundaries, divide the score of 0 to 100 into m fractional segments, and correspond the sub-boundaries of the risk index parameter to the fractional segments; a risk index parameter score determination unit, used to determine the score corresponding to each risk index parameter value of the target well according to the fractional segments corresponding to the sub-boundaries of the risk index parameter; a risk prediction value determination unit, used to determine the risk prediction value of the target well according to the score corresponding to each risk index parameter value of the target well by using a risk assessment formula; a risk level determination unit, used to determine the risk level of the target well according to the risk prediction value, and complete the casing damage prediction of the target well.

[0135] In some embodiments, the functions or modules and units included in the device provided by the embodiment of the present invention can be used to execute the method described in the above method embodiment. Its specific implementation can refer to the description of the above method embodiment. For the sake of brevity, it will not be repeated here.

[0136] The existing casing damage prediction methods mainly include: 1. Establishing a casing damage risk warning model under the influence of various geological factors and development factors based on mathematical statistical methods. This method needs to consider many factors and requires a large amount of statistical analysis data in the early stage (this condition is lacking in new blocks such as shale oil). The workload is large and has significant uncertainty; 2. It is believed that the micro-fold points of the formation passed by the horizontal well are casing damage risk points. The casing change risk is predicted by identifying micro-folds through seismic data processing technology. However, existing research and practice have shown that micro-folds are not the main controlling factors causing casing change. This technical method is difficult to achieve effective prediction of casing damage risk; 3. It is believed that natural fracture slip is the main factor causing casing change, and the shear stress on the wellbore at the natural fracture surface through the well is calculated. Stress can be compared with the shear strength of the wellbore casing to determine whether there is a risk of casing deformation in the horizontal well. However, this method has two problems: on the one hand, this method ignores the stress concentration effect. The risk of casing deformation depends on whether the natural fracture slips. That is, once the natural fracture slips, the casing blocks the slip of the natural fracture, resulting in stress concentration near the intersection of the casing and the natural fracture, and quickly reaches the yield strength of the casing. As a result, no matter how strong the casing is, it cannot resist the slip and deforms; on the other hand, the effect of the scale of the natural fracture on the degree of casing deformation is not considered. Generally speaking, the slip amount of small and medium-sized natural fractures (according to the empirical value, the plane extension length is <100m) is generally very small, and due to the buffering effect of the cement ring outside the casing, it generally does not cause casing deformation. 4. It is believed that fault activation during hydraulic fracturing is the main factor causing casing deformation. By analyzing the changes in the b-value of microseismic events generated by hydraulic fracturing, early warning of fault slip and casing change risks can be provided. However, this method can only be implemented during the fracturing process, and the monitoring accuracy of microseismic events is insufficient to determine the specific location of the casing change risk. Therefore, it is not possible to make a coordinated plan for the overall fracturing construction of a platform for casing change prevention and control, which has obvious limitations. 5. It is believed that when the casing is deformed by external forces, magnetic anomalies will occur. By monitoring the magnetic anomaly characteristics of the casing during each perforation operation, the degree of casing change and its development trend can be monitored in real time. However, like 4, this method can only be implemented during the fracturing process and cannot guide the early formulation of casing change prevention and control measures.

[0137] The present invention is based on the scientific understanding of the geomechanical mechanism of casing damage in shale oil areas (caused by shear slippage induced by fault-fracture in the process of large-scale hydraulic fracturing, which leads to asymmetric squeezing of the casing by the two strata of the fault-fracture), combined with the geological and engineering conditions of the region, and applies the generalized shear activity criterion theory created by Tong Hengmao et al. to create a method for predicting casing damage of horizontal wells in shale oil development.

[0138] The present invention overcomes the shortcomings of existing casing damage prediction technologies, provides an effective casing damage risk quantitative prediction method for shale oil horizontal well development, provides a basis for the early formulation of casing damage risk prevention and control measures, and achieves the purpose of reducing the casing damage risk in shale oil development.

[0139] The method of the present invention integrates seven risk index parameters, namely, the relative activity coefficient of fault-crack, the brittleness index of shale reservoir, the extension length of fault-crack surface, the angle between fault-crack surface and wellbore, the fracture pressure of shale reservoir, the temperature difference between wellbore before and after fracturing, and the perforation density, and divides the value range of each risk index parameter into n sub-limits, and corresponds the sub-limits that are prone to casing damage from high to low to the score range from large to small, so that the risk index parameter value that is more likely to cause casing damage corresponds to a higher score; according to the scores of all risk index parameters, the risk prediction value corresponding to the target well is calculated using the risk assessment formula, and the risk level of the target well is divided according to the risk prediction value. The seven risk index parameters cover three major categories of parameters that mainly affect casing damage, namely, reservoir geological parameters, fracturing parameters, and wellbore parameters, among which the relative activity coefficient of fault-crack, the brittleness index of shale reservoir, the extension length of fault-crack surface, the angle between fault-crack surface and wellbore are geological parameters, the fracture pressure of shale reservoir and the temperature difference between wellbore before and after fracturing are fracturing parameters, and the perforation density is a wellbore parameter. It fully reflects the casing damage risk at the risk points of horizontal well casing damage, improves the accuracy of casing damage prediction at the risk points of horizontal well casing damage, and thus can achieve accurate and rapid quantitative prediction of the risk level of horizontal well casing damage, solving the technical problems of long risk assessment cycle and high cost at the risk points of horizontal well casing damage. Since the casing damage prediction is completed before fracturing, it can provide a basis for the early formulation of casing damage risk prevention and control measures to ensure the normal progress of hydraulic fracturing, reduce the casing damage rate, and improve the economic benefits of shale oil development.

[0140] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for predicting casing damage in a horizontal well, characterized in that: include: Obtaining risk index parameter values ​​of target wells in the work area, wherein the risk index parameters at least include: relative activity coefficient of fault-crack at casing damage risk point, shale reservoir brittleness index, extension length of fault-crack surface, angle between fault-crack surface and wellbore, shale reservoir fracture pressure, wellbore temperature difference before and after fracturing, and perforation density; Divide the numerical range of the risk indicator parameter into n sub-limits, divide the score of 0 to 100 into n score segments, and correspond the sub-limits of the risk indicator parameter to the score segments; Determine the score corresponding to each risk indicator parameter value of the target well according to the score segment corresponding to the sub-limit of the risk indicator parameter; According to the score corresponding to each risk indicator parameter value of the target well, a risk prediction value of the target well is determined using a risk assessment formula; According to the risk prediction value, the risk level of the target well is determined, and the casing damage prediction of the target well is completed.

2. The method for predicting casing damage of a horizontal well according to claim 1, characterized in that: Before dividing the value range of the risk indicator parameter into n sub-limits, the method further includes: It is determined whether the risk indicator parameter exceeds the applicable limit. If yes, casing loss risk prediction is not performed for the target well.

3. The method for predicting casing damage in a horizontal well according to claim 2, characterized in that: The applicable limit of the fault-crack relative activity coefficient is 0 to 5, the applicable limit of the shale reservoir brittleness index is 0 to 100, the applicable limit of the fault-crack surface extension length is 0 to 1000m, the applicable limit of the angle between the fault-crack surface and the wellbore is 0 to 90°, the applicable limit of the shale reservoir fracture pressure is 20 to 120MPa, the applicable limit of the wellbore temperature difference before and after fracturing is 0 to 100°C, and the applicable limit of the perforation density is 0 to 40 perforations / m.

4. The method for predicting casing damage of a horizontal well according to claim 1, characterized in that: Before obtaining the risk index parameters of the target well in the work area, the method further includes: determining the relative activity coefficient of the fracture at the casing damage risk point in the risk index parameters of the target well, wherein the method includes: The relative activity coefficient calculation formula is used to determine the fracture-fracture relative activity coefficient at the casing damage risk point; Wherein, the relative activity coefficient calculation formula includes formula (1) or (2); Where: f a is the relative activity coefficient of the fault-crack, σ1, σ2, σ3 are the three principal stresses of the layer where the fault-crack is located at the casing damage risk point, θ is the angle between the fault-crack surface and the σ1 axis, α is the angle between the intersection of the fault-crack surface and the σ2-σ3 plane and the σ3 axis, C P is the fracture-fracture surface cohesion, μ P is the friction coefficient of the fracture surface, and P is the fluid pressure of the fracture surface; Where: f a is the relative activity coefficient of the fault-crack, σ1, σ2, σ3 are the three principal stresses of the fault-crack layer at the casing damage risk point, β is the angle between the fault-crack surface inclination and the σ1 axis, is the fracture-crack surface inclination angle, C W is the fracture-crack surface cohesion, μ is the fracture-crack surface friction coefficient, and P is the fracture-crack surface fluid pressure.

5. The method for predicting casing damage of a horizontal well according to claim 1, characterized in that: Before obtaining the risk index parameters of the target well in the work area, the method further includes: determining the shale reservoir brittleness index in the risk index parameters of the target well, and the method includes: Determine the brittleness index of the shale reservoir using formula (3) or (4) or (5); B YB =[(E s -E min ) / (E max -E min )+(n max -n s ) / (n max -n min )]*100 / 2(3); In the formula, B YB Shale rock mechanics brittleness index, E s Static Young's modulus of the sample, E min The lower limit of static Young's modulus of shale, E max The upper limit of static Young's modulus of shale, ν s Sample static Poisson's ratio, ν min The lower limit of the static Poisson's ratio of shale, ν max The upper limit of static Poisson's ratio of shale; B M1 =(αX quartz +βX dolomite +γX calcite +ηX feldspar +ζX pyrite +ωX clay +k)*100(4); B M2 =(X quartz +X dolomite +X calcite +X feldspar +X pyrite )*100(5); In the formula, B M1 is the shale mineral brittleness index of rock mechanics weight method, B M2 is the brittle mineral index of shale minerals by brittle mineral method, X quartz is the mass fraction of quartz in the sample, X dolomite is the mass fraction of dolomite in the sample, X calcite is the mass fraction of calcite in the sample, X feldspar is the mass fraction of feldspar in the sample, X pyrite is the mass fraction of pyrite in the sample, X clay is the mass fraction of clay minerals in the sample; α, β, γ, η, ζ, ω are the weight coefficients of quartz, dolomite, calcite, feldspar, pyrite and clay minerals respectively, and k is the correction constant term.

6. The method for predicting casing damage of a horizontal well according to claim 1, characterized in that: The risk assessment formula includes formula (6); F=C1*α1+C2*α2+C3*α3+C4*α4+C5*α5+C6*α6+C7*α7, α1+α2+α3+α4+α5+α6+α7＝1(6)； Where F is the risk prediction value, C1 is the score corresponding to the fault-crack relative activity coefficient, α1 is the C1 weight coefficient, C2 is the score corresponding to the shale reservoir brittleness index, α2 is the C2 weight coefficient, C3 is the score corresponding to the fault-crack extension length, α3 is the C3 weight coefficient, C4 is the score corresponding to the angle between the fault-crack surface and the wellbore, α4 is the C4 weight coefficient, C5 is the score corresponding to the shale reservoir fracture pressure, α5 is the C5 weight coefficient, C6 is the score corresponding to the wellbore temperature difference before and after fracturing, α6 is the C6 weight coefficient; C7 is the score corresponding to the perforation density, α7 is the C7 weight coefficient.

7. The method for predicting casing damage of a horizontal well according to claim 1, characterized in that: The risk assessment formula includes formula (7); F=(C1*C2*C3*C4*C5) 1 / 5 *α1+(C6*C7) 1 / 2 *α2,α1+α2=1(7); Where F is the risk prediction value, C1 is the score corresponding to the fault-crack relative activity coefficient, C2 is the score corresponding to the shale reservoir brittleness index, C3 is the score corresponding to the fault-crack extension length, C4 is the score corresponding to the angle between the fault-crack surface and the wellbore, C5 is the score corresponding to the shale reservoir fracture pressure, C6 is the score corresponding to the wellbore temperature difference before and after fracturing, C7 is the score corresponding to the perforation density, α1 is the weight coefficient of C1*C2*C3*C4*C5, and α2 is the weight coefficient of C6*C7.

8. The method for predicting casing damage of a horizontal well according to any one of claims 1 to 7, characterized in that: The method for determining the risk level of the target well according to the risk prediction value includes: When the risk prediction value is between 0 and 25, the target well is determined to be at low risk of horizontal well casing damage; when the risk prediction value is between 25 and 50, the target well is determined to be at medium risk of horizontal well casing damage; when the risk prediction value is between 50 and 75, the target well is determined to be at high risk of horizontal well casing damage; and when the risk prediction value is between 75 and 100, the target well is determined to be at ultra-high risk of horizontal well casing damage.

9. A horizontal well casing damage prediction device, characterized in that: include: An acquisition unit is used to acquire risk index parameters of a target well in a work area, wherein the risk index parameters at least include: a relative activity coefficient of a fault-crack at a casing damage risk point, a brittleness index of a shale reservoir, an extension length of a fault-crack surface, an angle between a fault-crack surface and a wellbore, a shale reservoir fracture pressure, a temperature difference of the wellbore before and after fracturing, and a perforation density; A sub-limit division unit is used to divide the numerical range of the risk indicator parameter into n sub-limits, divide the score of 0 to 100 into m score segments, and correspond the sub-limits of the risk indicator parameter to the score segments; A risk indicator parameter score determination unit, used to determine the score corresponding to each risk indicator parameter value of the target well according to the score segment corresponding to the sub-limit of the risk indicator parameter; A risk prediction value determination unit, used to determine the risk prediction value of the target well according to the score corresponding to each risk indicator parameter value of the target well and using a risk assessment formula; The risk level determination unit is used to determine the risk level of the target well according to the risk prediction value and complete the casing damage prediction of the target well.

10. A method for preventing and controlling casing damage in a horizontal well, characterized in that: include: If the risk level of the target well is high risk or ultra-high risk, all risk indicator parameters are divided into four categories, of which the first category includes the relative activity coefficient of the fault-crack at the casing risk point and / or the brittleness index of the shale reservoir and / or the angle between the fault-crack surface and the wellbore and / or the shale reservoir fracture pressure, the second category includes the extension length of the fault-crack surface, the third category includes the wellbore temperature difference before and after fracturing, and the fourth category includes the perforation density; if one or more of the risk indicator parameters have one or more parameter values ​​greater than or equal to 50, the corresponding prevention and control method of this category is selected to prevent and control the target well, of which the first category The corresponding prevention and control method is to reduce the fracturing pressure to 90-98% of the original and reduce the injection volume of the fracturing fluid to 80-95% of the original. The second type of corresponding prevention and control method is to inject temporary plugging agents. The third type of corresponding prevention and control method is to increase the injection temperature of the fracturing fluid to 120-200% of the original and reduce the injection and return speed of the fracturing fluid to 80-95% of the original. The fourth type of corresponding prevention and control method is to use engineering methods to strengthen the wellbore; among which, the engineering method to strengthen the wellbore includes: one or more of the methods of squeezing cement, lowering packers, casing compensation, casing tie-back, chemical plugging or replacing casing; The temporary plugging agent is one or more of a cross-linked polymer temporary plugging agent, a fiber temporary plugging agent, an inorganic salt temporary plugging agent or a composite material temporary plugging agent.

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