Method for stabilizing the wellbore in ultra-deep reservoir drilling

Abstract

The application provides a method for stabilizing the well wall of ultra-deep reservoir drilling, and relates to the technical field of oil and gas drilling engineering. The method for stabilizing the well wall of ultra-deep reservoir drilling comprises the following steps: establishing a three-dimensional geomechanical model of an ultra-deep reservoir, and loading a preliminary well trajectory into the three-dimensional geomechanical model of the ultra-deep reservoir; obtaining the fault occurrence of the intersection position of the preliminary well trajectory and a fault in the three-dimensional geomechanical model of the ultra-deep reservoir and the drilling parameters near the fault; obtaining an optimized well trajectory according to the fault occurrence and the drilling parameters; determining a safe drilling mud window according to the optimized well trajectory and the drilling parameters; and drilling according to the optimized well trajectory and the safe drilling mud window. Thus, the method for stabilizing the well wall of ultra-deep reservoir drilling can improve the stability of the well wall, reduce the occurrence of drilling accidents, and improve the drilling efficiency.

Description

Technical Field

[0001] This application relates to the field of oil and gas drilling engineering technology, and in particular to a method for stabilizing the wellbore in ultra-deep reservoir drilling. Background Technology

[0002] Currently, during the development of ultra-deep storage, problems such as deep burial depth, development of fractures and cracks, high ground temperature, strong ground stress, and high formation pressure can easily lead to catastrophic drilling accidents during the drilling process.

[0003] Therefore, how to reduce the occurrence of drilling accidents has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a method for stabilizing the wellbore in ultra-deep reservoir drilling.

[0005] To address the aforementioned technical problems, this application provides the following technical solutions:

[0006] The first aspect of this application provides a method for wellbore stabilization in ultra-deep reservoir drilling, comprising:

[0007] A three-dimensional geomechanical model of the ultra-deep reservoir was established, and the preliminary well trajectory was loaded into the three-dimensional geomechanical model of the ultra-deep reservoir.

[0008] Obtain the fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault;

[0009] The optimized well trajectory is obtained based on the fault occurrence and the drilling parameters;

[0010] The safe drilling mud window is determined based on the optimized well trajectory and the drilling parameters.

[0011] Drilling is performed based on the optimized well trajectory and the safe drilling mud window.

[0012] In some modified embodiments of the first aspect of this application, obtaining the fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault, includes:

[0013] Determine the intersection point between the preliminary well trajectory and the fault zone in the three-dimensional geomechanical model of the ultra-deep reservoir;

[0014] Obtain the fault attitude, including fault dip and fault dip angle, at the intersection location;

[0015] In some modified embodiments of the first aspect of this application, obtaining the optimized well trajectory based on the fault occurrence and the drilling parameters includes:

[0016] The optimized well trajectory azimuth and well inclination angle are obtained based on the fault occurrence and the drilling parameters.

[0017] In some modified embodiments of the first aspect of this application, the extraction of drilling parameters, including in-situ stress, rock physical parameters, and wellbore parameters, near the fault includes:

[0018] The geostress, including the horizontal maximum principal stress, the horizontal minimum principal stress, and the vertical stress, is extracted near the fault.

[0019] The rock physical parameters, including rock compressive strength and rock shear strength, are extracted from the fault perimeter.

[0020] The wellbore parameters extracted from the fault perimeter include wellbore radius, distance from wellbore to wellbore perimeter, wellbore angle, drilling fluid bottomhole fluid column pressure, formation pore pressure, rock porosity, Poisson's ratio, formation pore pressure gradient, internal friction coefficient, and Biot coefficient.

[0021] In some modified embodiments of the first aspect of this application, determining the safe drilling mud window based on the optimized well trajectory and the drilling parameters includes:

[0022] The six-dimensional stress around the well is obtained based on the in-situ stress, the optimized well trajectory, and the wellbore parameters;

[0023] The safe drilling mud window is obtained based on the rock physical parameters and the hexaaxial stress around the well.

[0024] In some modified embodiments of the first aspect of this application, obtaining the safe drilling mud window based on the rock physical parameters and the hexaaxial stress around the well includes:

[0025] The minimum safe drilling mud window pressure value is obtained based on the rock compressive strength, rock shear strength, and the circumferential stress of the well.

[0026] The minimum safe drilling mud window value is determined based on the minimum safe drilling mud window pressure value.

[0027] In some modified embodiments of the first aspect of this application, the step of obtaining the minimum safe drilling mud window pressure value based on the rock compressive strength, rock shear strength, and the wellbore six-dimensional stress further includes:

[0028] Based on the rock compressive strength and the three normal stresses in the circumferential stress of the well, the drilling fluid bottomhole fluid column pressure corresponding to the three normal stresses at different depths of the well section is obtained;

[0029] The minimum safe drilling mud window pressure value is further determined based on the rock shear strength, the three shear stresses in the three axial stresses of the well, and the drilling fluid bottom column pressure of the three normal stresses.

[0030] In some modified embodiments of the first aspect of this application, determining the minimum safe drilling mud window value based on the minimum safe drilling mud window pressure value includes:

[0031] The minimum safe drilling mud window value is the density corresponding to the minimum safe drilling mud window pressure value.

[0032] In some modified embodiments of the first aspect of this application, the step of obtaining the safe drilling mud window based on the rock physical parameters and the hexaaxial stress around the wellbore further includes:

[0033] Obtain the critical initiation pressure of the crack;

[0034] The maximum safe drilling mud window value is determined based on the critical opening pressure.

[0035] In some modified embodiments of the first aspect of this application, obtaining the critical initiation pressure of the crack includes:

[0036] The critical initiation pressure of the fracture was obtained based on the three-dimensional geomechanical model and the optimized well trajectory.

[0037] Compared to existing technologies, the method for stabilizing the wellbore in ultra-deep reservoirs provided in the first aspect of this application first establishes a three-dimensional geomechanical model of the ultra-deep reservoir, which includes faults. A preliminary well trajectory is then loaded into this model to obtain the fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model, as well as drilling parameters near the fault. An optimized well trajectory is then obtained based on the fault occurrence and drilling parameters near the fault. Finally, a safe drilling mud window is determined based on the optimized well trajectory and drilling parameters. Drilling can then be performed according to the optimized well trajectory and safe drilling mud window obtained in this application. The method for stabilizing the wellbore in ultra-deep reservoir drilling provided in this application establishes a three-dimensional geomechanical model of the ultra-deep reservoir, thereby simulating the geomechanical conditions of the ultra-deep reservoir. Based on the optimized well trajectory and drilling parameters obtained from the three-dimensional geological model of the ultra-deep reservoir, a safe drilling mud window is determined. Drilling is then carried out using the optimized well trajectory and drilling parameters obtained in this application to determine the safe drilling mud window, which can ensure the stability of the wellbore during ultra-deep reservoir drilling. Wellbore stability refers to the regular size and shape of the wellbore formed during the drilling and completion process, which ensures drilling safety. Therefore, the method for stabilizing the wellbore in ultra-deep reservoir drilling in this application can improve the stability of the wellbore, thereby reducing the occurrence of drilling accidents and improving drilling efficiency. Attached Figure Description

[0038] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein:

[0039] Figure 1 A flowchart illustrating a method for stabilizing the wellbore in ultra-deep reservoir drilling, provided as an embodiment of this application;

[0040] Figure 2 A flowchart illustrating another method for stabilizing the wellbore in ultra-deep reservoir drilling, provided as an embodiment of this application;

[0041] Figure 3 A flowchart illustrating another method for stabilizing the wellbore in ultra-deep reservoir drilling, provided as an embodiment of this application;

[0042] Figure 4 A schematic diagram of directional six-dimensional stress around a well, provided for an embodiment of this application;

[0043] Figure 5 A schematic diagram showing the input parameters in the GMI-SFIB module of petroleum industry commercial software, provided as an embodiment of this application;

[0044] Figure 6 Another schematic diagram showing the input parameters in the GMI-SFIB module of petroleum industry commercial software provided in this application embodiment;

[0045] Figure 7 A schematic diagram of an optimal well trajectory orientation and well inclination angle provided for an embodiment of this application;

[0046] Figure 8 A schematic diagram illustrating the relationship between void pressure and directional well depth, provided for an embodiment of this application;

[0047] Figure 9 A schematic diagram illustrating the influence of crack direction as provided in an embodiment of this application;

[0048] Figure 10 A schematic diagram illustrating the relationship between effective normal stress and shear stress provided in an embodiment of this application; Detailed Implementation

[0049] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0050] like Figure 1 As shown, this application provides a method for wellbore stabilization in ultra-deep reservoir drilling, comprising:

[0051] S101, Establish a three-dimensional geomechanical model of the ultra-deep reservoir and load the preliminary well trajectory into the three-dimensional geomechanical model of the ultra-deep reservoir;

[0052] The three-dimensional geomechanical model of this ultra-deep reservoir includes at least formation lithology, faults, natural fractures, and in-situ stress. The preliminary well trajectory is a well trajectory used in practical drilling with existing technology, but this trajectory is not applicable to drilling in ultra-deep reservoirs. The preliminary well trajectory can be a well trajectory used for drilling existing shallow (within 4500m) or directional wells with relatively simple formations within the well, or it can be a well trajectory under other conditions.

[0053] S102, obtain the fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault;

[0054] When the preliminary well trajectory is loaded into the three-dimensional geomechanical model of the ultra-deep reservoir, the faults in the three-dimensional geomechanical model of the ultra-deep reservoir will intersect with the preliminary well trajectory. The fault occurrence at the intersection and the drilling parameters near the fault are obtained.

[0055] S103, Obtain the optimized well trajectory based on the fault orientation and the drilling parameters;

[0056] S104, Determine the safe drilling mud window based on the optimized well trajectory and the drilling parameters;

[0057] S105, Drilling is performed based on the optimized well trajectory and the safe drilling mud window.

[0058] This application provides a method for wellbore stabilization in ultra-deep reservoir drilling. First, a three-dimensional geomechanical model of the ultra-deep reservoir is established, including faults. A preliminary well trajectory is loaded into this model. The fault occurrence at the intersection of the preliminary well trajectory and the fault in the ultra-deep reservoir's three-dimensional geomechanical model, as well as drilling parameters near the fault, are obtained. Then, an optimized well trajectory is obtained based on the fault occurrence and drilling parameters near the fault. Finally, a safe drilling mud window is determined based on the optimized well trajectory and drilling parameters. Drilling can then be performed according to the optimized well trajectory and safe drilling mud window obtained in this application. The method for stabilizing the wellbore in ultra-deep reservoir drilling provided in this application establishes a three-dimensional geomechanical model of the ultra-deep reservoir, thereby simulating the geomechanical conditions of the ultra-deep reservoir. Based on the optimized well trajectory and drilling parameters obtained from the three-dimensional geological model of the ultra-deep reservoir, a safe drilling mud window is determined. Drilling is then carried out using the optimized well trajectory and drilling parameters obtained in this application to determine the safe drilling mud window, which can ensure the stability of the wellbore during ultra-deep reservoir drilling. Wellbore stability refers to the regular size and shape of the wellbore formed during the drilling and completion process, which ensures drilling safety. Therefore, the method for stabilizing the wellbore in ultra-deep reservoir drilling in this application can improve the stability of the wellbore, thereby reducing the occurrence of drilling accidents and improving drilling efficiency.

[0059] like Figure 2 As shown, this application provides another method for wellbore stabilization in ultra-deep reservoir drilling, including:

[0060] S201, Establish a three-dimensional geomechanical model of the ultra-deep reservoir and load the preliminary well trajectory into the three-dimensional geomechanical model of the ultra-deep reservoir;

[0061] S202, determine the intersection of the preliminary well trajectory and the fault zone in the three-dimensional geomechanical model of the ultra-deep reservoir;

[0062] S203, Obtain the fault orientation, including fault dip and fault dip angle, at the intersection location;

[0063] S204, extract drilling parameters, including geostress, rock physical parameters, and wellbore parameters, near the fault.

[0064] The geostress includes the horizontal maximum principal stress, horizontal minimum principal stress, and vertical stress, thereby extracting the horizontal maximum principal stress, horizontal minimum principal stress, and vertical stress near the fault in the three-dimensional geomechanical model of ultra-deep reservoirs. The horizontal maximum principal stress, horizontal minimum principal stress, and vertical stress all include both magnitude and direction. Rock physical parameters include rock compressive strength and rock shear strength, which have already accounted for the effects of fractures and natural fissures. Wellbore parameters include wellbore radius, wellbore-to-wellbore distance, wellbore angle, drilling fluid bottomhole column pressure, formation pore pressure, rock porosity, Poisson's ratio, formation pore pressure gradient, internal friction coefficient, and Biot coefficient.

[0065] S205, Based on the fault occurrence and the drilling parameters, the optimized well trajectory azimuth and well inclination angle are obtained.

[0066] Fault occurrence includes fault dip, fault dip angle, fault cohesion, and fault internal friction coefficient. Drilling parameters include wellbore radius, wellbore-to-wellbore distance, wellbore angle, drilling fluid bottomhole column pressure, formation pore pressure, rock porosity, Poisson's ratio, formation pore pressure gradient, internal friction coefficient, and Biot coefficient. By inputting these parameters into the SFIB module of the commonly used industry software GMI according to the rules, an optimized well trajectory can be obtained. The well trajectory includes well trajectory azimuth (AZIM) and well inclination angle (DIP), where the well trajectory azimuth ranges from 0° to 360°, and the well inclination angle ranges from 0° to 90°.

[0067] S206, Determine the safe drilling mud window based on the optimized well trajectory and the drilling parameters;

[0068] S207, Drilling is performed based on the optimized well trajectory and the safe drilling mud window.

[0069] Therefore, this application provides another method for stabilizing the wellbore in ultra-deep reservoirs. First, a three-dimensional geomechanical model of the ultra-deep reservoir is established, and a preliminary well trajectory is loaded into the three-dimensional geological model of the ultra-deep reservoir. The fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault, are obtained. Then, based on the fault occurrence and the drilling parameters near the fault, an optimized well trajectory is obtained using GMI software. Finally, a safe drilling mud window is determined based on the optimized well trajectory and drilling parameters. Drilling can then be carried out according to the optimized well trajectory and safe drilling mud window obtained in this application. The method for stabilizing the wellbore in ultra-deep reservoir drilling provided in this application, from the perspective of wellbore stability, establishes a three-dimensional geomechanical model of the ultra-deep reservoir. Based on the optimized well trajectory and drilling parameters obtained from the three-dimensional geological model, a safe drilling mud window is determined. Drilling is then carried out using the optimized well trajectory and drilling parameters obtained in this application to determine the safe drilling mud window, which can ensure the stability of the wellbore during ultra-deep reservoir drilling, ensure the success rate of drilling and the achievement of geological objectives, avoid premature abandonment due to drilling engineering problems, thereby reducing the occurrence of drilling accidents and improving drilling efficiency.

[0070] like Figure 3 As shown, this application provides another method for wellbore stabilization in ultra-deep reservoir drilling, comprising:

[0071] S301, Establish a three-dimensional geomechanical model of the ultra-deep reservoir and load the preliminary well trajectory into the three-dimensional geomechanical model of the ultra-deep reservoir;

[0072] S302, determine the intersection of the preliminary well trajectory and the fault zone in the three-dimensional geomechanical model of the ultra-deep reservoir;

[0073] S303, Obtain the fault attitude, including fault dip and fault dip angle, at the intersection location;

[0074] S304, extract drilling parameters, including in-situ stress, rock physical parameters, and wellbore parameters, near the fault.

[0075] S305, Based on the fault occurrence and the drilling parameters, the optimized well trajectory azimuth and well inclination angle are obtained.

[0076] S306, the six-dimensional stress around the well is obtained based on the ground stress, the optimized well trajectory, and the wellbore parameters;

[0077] like Figure 4 The diagram shown is a schematic of the six-axis stress around the well.

[0078]

[0079] in,

[0080] σ H σ is the maximum horizontal principal stress; h Horizontal minimum principal stress; σ v It is vertical stress;

[0081] Ω is the angle between the maximum horizontal principal stress and the well trajectory azimuth;

[0082] Ψ is the well inclination angle;

[0083] The following is Formula 2:

[0084]

[0085] Where, σ θθ σ rr σ zz τ rθ τ θz τ rz The six directions of circumferential force on the well wall;

[0086] R is the wellbore radius, in meters;

[0087] r is the distance from the center of the well to the circumference of the well, r≥R, and the unit is m;

[0088] γ is Poisson's ratio, ranging from 0.2 to 0.5, and is dimensionless;

[0089] θ is the wellbore circumference angle that rotates clockwise around the wellbore along the well trajectory, where 0° < θ < 360°;

[0090] δ is the cake coefficient, 0 < δ < 1, dimensionless;

[0091] p i p is the bottom hole pressure of the drilling fluid. i =ρg h, unit is MPa; ρ is the drilling fluid density, unit is kg / m3; g is the acceleration due to gravity, g = 9.8066 m / s². 2 h represents the vertical depth of the directional well, in meters (m).

[0092] P P This represents the formation pore pressure, expressed in MPa.

[0093] α is the biot coefficient, which takes values ​​from 0 to 1 and is dimensionless;

[0094] Rock porosity, expressed as a percentage (%).

[0095] The six-dimensional stress around the well is obtained using Formula 1 and Formula 2.

[0096] S307, obtaining the drilling fluid bottom-hole hydrostatic pressure corresponding to three normal stresses at different depths of the well section according to the rock unconfined compressive strength and the three normal stresses in the six-way stresses around the wellbore;

[0097] In the calculation process of Formula 2:

[0098] Let: r=1.2R, σ θθ , σ rr , σ zz are the three normal stresses in the six-way stresses around the wellbore, σ θθ ≤UCS 基质 , σ rr ≤UCS 基质 , σ zz ≤UCS 基质 , wherein UCS 基质 is the rock unconfined compressive strength, wherein the maximum value of the normal stress is equal to the bottom-hole drilling fluid pressure, and the bottom-hole drilling fluid pressure cannot be greater than the rock unconfined compressive strength, so as to obtain the bottom-hole drilling fluid pressures P i(σθθ) , P i(σrr) , P i(σzz) corresponding to different depths of the directional well section;

[0099] S308, determining the minimum safe drilling mud window pressure value according to the rock shear strength, the three shear stresses in the six-way stresses around the wellbore and the drilling fluid bottom-hole hydrostatic pressures corresponding to the three normal stresses.

[0100] τ rθ , τ θz , τ rz are the three shear stresses in the six-way stresses around the wellbore, 丨τ rθ 丨≤UCS-E 基质 , 丨τ θz 丨≤UCS-E 基质 , 丨τ rz 丨≤UCS-E 基质 , wherein UCS-E 基质 is the rock shear strength;

[0101] While satisfying P min ≥{max(P i(σθθ) , P i(σrr) , P i(σzz) )}, it is also required to satisfy that P min cannot be less than UCS-E 基质 , {max(丨τ rθ 丨, 丨τ θz 丨, 丨τ rz 丨)}≤UCS-E 基质The absolute values ​​of the three shear stresses cannot exceed the compressive strength of the rock. The higher the bottom hole drilling fluid pressure, the greater the shear stress. Therefore, the bottom hole drilling fluid pressure cannot exceed the compressive strength of the rock. Thus, the compressive strength of the rock can be used as a limiting condition for the collapse pressure, which further limits the minimum safe drilling mud window pressure value, resulting in the minimum safe drilling mud window pressure value.

[0102] S309, determine the minimum safe drilling mud window value based on the minimum safe drilling mud window pressure value.

[0103] The equivalent mud density is calculated based on the minimum safe drilling mud window pressure value, which serves as the wellbore collapse pressure.

[0104] ρ min =P min / (g*h), unit is g / cm³ 3 ;

[0105] ρ min This is the minimum safe drilling mud window value.

[0106] S310, the critical initiation pressure of the fracture is obtained based on the three-dimensional geomechanical model and the optimized well trajectory.

[0107] From the three-dimensional geomechanical model, the orientation of faults and natural fractures encountered during drilling is extracted along the optimized well trajectory. The Mofracs module in GMI software is used to simulate fracture activity. GMI software represents current technology, and the critical fracture opening pressure P is obtained. 开启 .

[0108] S311, determine the maximum value of the safe drilling mud window based on the critical opening pressure.

[0109] The method for calculating the maximum mud density at the mud window is as follows:

[0110] ρ max =P 开启 / (g*h), unit is g / cm³ 3 ;

[0111] S312, Drilling is performed based on the optimized well trajectory and the safe drilling mud window.

[0112] This application provides another method for wellbore stabilization in ultra-deep reservoir drilling. First, a three-dimensional geomechanical model of the ultra-deep reservoir is established, and a preliminary well trajectory is loaded into this model. The fault attitude at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model, as well as drilling parameters near the fault, are obtained. Then, based on the fault attitude and drilling parameters near the fault, an optimized well trajectory is obtained using GMI software. Finally, a safe drilling mud window is determined based on the optimized well trajectory and drilling parameters. When obtaining the mud window, the wellbore perimeter is first determined using in-situ stress, the optimized well trajectory, and wellbore parameters. The method for stabilizing the wellbore in ultra-deep reservoirs is derived by first determining the six-dimensional stress of the rock, then obtaining the minimum safe drilling mud window pressure value based on the rock compressive strength, rock shear strength, and the six-dimensional stress of the wellbore. The minimum safe drilling mud window value is then calculated based on this pressure. Finally, the critical fracture opening pressure is obtained using a three-dimensional geomechanical model and the optimized well trajectory. The maximum safe drilling mud window value is then determined based on the critical opening pressure. The minimum and maximum safe drilling mud window values ​​constitute the safe drilling mud window. Drilling can then be performed based on the optimized well trajectory and the safe drilling mud window obtained in this application. The method for stabilizing the wellbore in ultra-deep reservoirs provided in this application, from the perspective of wellbore stability, truly considers the stress conditions of the surrounding rocks in directional wells. It considers not only the collapse caused by rock shear failure but also the collapse caused by tensile stress around the wellbore. This avoids the shortcomings of traditional collapse pressure calculation models that only consider the stress on the surface rocks of the wellbore and only consider shear failure, thus improving the accuracy of collapse pressure calculation. Furthermore, the calculation of the upper limit of the mud window provided in this application fully considers the shear failure and leakage of the well wall. While ensuring the stability of the well wall, it avoids the occurrence of well leakage, thereby further improving the stability of the well wall. This provides a strong guarantee for the design of directional wells in ultra-deep reservoirs, avoids premature abandonment due to drilling engineering problems, reduces the occurrence of drilling accidents, and improves drilling efficiency.

[0113] This application provides an embodiment of a method for wellbore stabilization through ultra-deep reservoir drilling, comprising:

[0114] A three-dimensional geomechanical model of the ultra-deep reservoir is established. This model should include all information on formation lithology, faults, natural fractures, geostress, etc., and the preliminary well trajectory is loaded into the three-dimensional geomechanical model of the ultra-deep reservoir.

[0115] Obtain the fault attitude, including fault dip and fault dip angle, at the intersection location. The parameters of the fault attitude are shown in Table 1.

[0116] F1 70° 280° 5 (MPa) 0.6 (dimensionless)

[0117] Table 1

[0118] Drilling parameters including in-situ stress, petrophysical parameters and borehole parameters are extracted near the fault, and the parameters are shown in Table II, wherein the biot coefficient generally takes an empirical value of 0.85 in ultra-deep reservoirs;

[0119]

[0120]

[0121] as shown in Figure 5 and Figure 6 , input the obtained parameters above into the GMI-SFIB module, a commercial software in the petroleum industry, and obtain the optimal well trajectory azimuth and well inclination angle conducive to borehole wall stability through calculation;

[0122] according to Figure 7 as shown in Figure 7 for the range result shown in, and in combination with the actual on-site drilling conditions, the well trajectory azimuth is finally selected as 140° and the well inclination angle is 45°;

[0123] S405, taking the position of 6200m on the borehole wall of a directional well as an example, firstly, apply Formula 1, Formula 2 and the parameters in Table 3 to calculate the stress on the directional well section:

[0124] Wellbore / Enlargement R / r 1.2 Dimensionless Formation pressure <![CDATA[P p ]]> 76 MPa 1.26*0.00981*6200 Mud cake coefficient δ 0 Dimensionless BIOT coefficient α 0.85 Dimensionless Poisson's ratio γ 0.25 Dimensionless Porosity Φ 7 ％ Rock matrix compressive strength <![CDATA[UCS 基质 ]]> 193 MPa tensile strength of rock matrix <![CDATA[UCS-E 基质 ]]> 16 MPa Well inclination angle ψ 45 ° The angle between principal stress and well trajectory azimuth Ω 10 °

[0125] Table 3

[0126] obtained through calculation:

[0127] P min ={max(P i(σθθ) , P i(σrr) , P i(σzz) )}=90MPa;

[0128] ρ min =P min / (g*h)=90 / (0.00981*6200)=1.48g / cm 3 ;

[0129] and max(丨τ rθ 丨,丨τ θz 丨,丨τ rz 丨)=max(12.03,2,0.3)=

[0130] 12.0MPa≤ UCS-E基质 , the condition is satisfied, so the minimum value of the minimum safe drilling mud window is 1.48g / cm 3 .

[0131] Secondly, in the three-dimensional geomechanical model, natural fracture occurrences are extracted along the well trajectory at 6200-6300m, as shown in Table IV;

[0132]

[0133]

[0134]

[0135] Table 4

[0136] Natural fracture data and rock physical parameters extracted from the 3D geomechanical model were imported into the GMI-Mofrac module, and the simulation yielded a critical fracture initiation pressure gradient of 1.90SG. Figures 8 to 10 As shown, when the density corresponding to the pore pressure of the bottom hole fluid column reaches 1.90 g / cm³, 3 At that time, faults and natural fractures are on the verge of opening.

[0137] Therefore, it was finally determined that the wellbore azimuth of this directional well section was 140°, the well inclination angle was 45°, and the safety mud window was 1.48-1.90 (g / cm³). 3 ).

[0138] The method for stabilizing the wellbore in ultra-deep reservoirs provided in the first aspect of this application involves first establishing a three-dimensional geomechanical model of the ultra-deep reservoir, which includes faults. A preliminary well trajectory is then loaded into this model. The fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model, as well as drilling parameters near the fault, are obtained. An optimized well trajectory is then obtained based on the fault occurrence and drilling parameters near the fault. Finally, a safe drilling mud window is determined based on the optimized well trajectory and drilling parameters. Drilling can then be performed according to the optimized well trajectory and safe drilling mud window obtained in this application. The method for stabilizing the wellbore in ultra-deep reservoir drilling provided in this application establishes a three-dimensional geomechanical model of the ultra-deep reservoir, thereby simulating the geomechanical conditions of the ultra-deep reservoir. Based on the optimized well trajectory and drilling parameters obtained from the three-dimensional geological model of the ultra-deep reservoir, a safe drilling mud window is determined. Drilling is then carried out using the optimized well trajectory and drilling parameters obtained in this application to determine the safe drilling mud window, which can ensure the stability of the wellbore during ultra-deep reservoir drilling. Furthermore, the method for determining the azimuth and inclination angle of the directional well trajectory, from the perspective of wellbore stability, ensures the success rate of drilling and the achievement of geological objectives, avoiding the problem of premature abandonment due to drilling engineering issues. In confirming the safe drilling mud window, from the perspective of wellbore stability, the stress situation of the surrounding rock of the directional well is truly considered. It not only considers the collapse caused by rock shear failure, but also the collapse caused by tensile failure around the well, avoiding the shortcomings of traditional collapse pressure calculation models that only consider the stress on the surface rock of the wellbore and only consider shear failure, thus improving the accuracy of collapse pressure calculation. Furthermore, the calculation of the upper limit of the mud window provided in this application fully considers the shear failure and leakage of the well wall. While ensuring the stability of the well wall, it avoids the occurrence of well leakage, thereby further improving the stability of the well wall. This provides a strong guarantee for the design of directional wells in ultra-deep reservoirs, avoids premature abandonment due to drilling engineering problems, reduces the occurrence of drilling accidents, and improves drilling efficiency.

[0139] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for stabilizing the wellbore in ultra-deep reservoir drilling, characterized in that, include: A three-dimensional geomechanical model of the ultra-deep reservoir was established, and the preliminary well trajectory was loaded into the three-dimensional geomechanical model of the ultra-deep reservoir. The fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault, are obtained. The drilling parameters include in-situ stress, rock physical parameters, and wellbore parameters. The rock physical parameters include rock compressive strength and rock shear strength. The optimized well trajectory is obtained based on the fault occurrence and the drilling parameters; The safe drilling mud window is determined based on the optimized well trajectory and the drilling parameters. Drilling is performed based on the optimized well trajectory and the safe drilling mud window; The optimized well trajectory obtained based on the fault orientation and the drilling parameters includes: The optimized well trajectory azimuth and well inclination angle are obtained based on the fault occurrence and the drilling parameters. Determining the safe drilling mud window based on the optimized well trajectory and the drilling parameters includes: The six-dimensional stress around the well is obtained based on the in-situ stress, the optimized well trajectory, and the wellbore parameters; The safe drilling mud window is obtained based on the rock physical parameters and the hexaaxial stress around the well. The process of obtaining the safe drilling mud window based on the rock physical parameters and the hexaaxial stress around the well includes: The minimum safe drilling mud window pressure value is obtained based on the rock compressive strength, rock shear strength, and the circumferential stress of the well. The minimum safe drilling mud window value is determined based on the minimum safe drilling mud window pressure value.

2. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 1, characterized in that, The acquisition of the fault occurrence at the intersection of the preliminary well trajectory and the fault in the three-dimensional geomechanical model of the ultra-deep reservoir, as well as the drilling parameters near the fault, includes: Determine the intersection point between the preliminary well trajectory and the fault zone in the three-dimensional geomechanical model of the ultra-deep reservoir; Obtain the fault attitude, including fault dip and fault dip angle, at the intersection location; Drilling parameters, including geostress, rock physical parameters, and wellbore parameters, are extracted near the fault.

3. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 1, characterized in that, The drilling parameters extracted near the fault, including in-situ stress, rock physical parameters, and wellbore parameters, include: The geostress, including the horizontal maximum principal stress, the horizontal minimum principal stress, and the vertical stress, is extracted near the fault. The rock physical parameters, including rock compressive strength and rock shear strength, are extracted near the fault. The wellbore parameters, including wellbore radius, distance from wellbore to wellbore perimeter, wellbore angle, drilling fluid bottomhole fluid column pressure, formation pore pressure, rock porosity, Poisson's ratio, formation pore pressure gradient, internal friction coefficient, and Biot coefficient, are extracted near the fault.

4. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 3, characterized in that, The method of obtaining the minimum safe drilling mud window pressure value based on the rock compressive strength, rock shear strength, and the six-dimensional stress of the wellbore also includes: Based on the rock compressive strength and the three normal stresses in the circumferential stress of the well, the drilling fluid bottomhole fluid column pressure corresponding to the three normal stresses at different depths of the well section is obtained; The minimum safe drilling mud window pressure value is determined based on the rock shear strength, the three shear stresses in the three axial stresses of the well, and the drilling fluid bottom column pressure corresponding to the three normal stresses.

5. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 4, characterized in that, The determination of the minimum safe drilling mud window value based on the minimum safe drilling mud window pressure value includes: The minimum safe drilling mud window value is the density corresponding to the minimum safe drilling mud window pressure value.

6. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 4, characterized in that, The method of obtaining the safe drilling mud window based on the rock physical parameters and the hexaaxial stress around the well also includes: Obtain the critical initiation pressure of the crack; The maximum safe drilling mud window value is determined based on the critical opening pressure.

7. The method for stabilizing the wellbore in ultra-deep reservoir drilling according to claim 6, characterized in that, The critical opening pressure for obtaining the crack includes: The critical initiation pressure of the fracture was obtained based on the three-dimensional geomechanical model and the optimized well trajectory.

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