CN-121993150-A - Method and system for determining reasonable weight on bit of pre-bent BHA

CN121993150ACN 121993150 ACN121993150 ACN 121993150ACN-121993150-A

Abstract

The invention discloses a method and a system for determining reasonable drilling pressure of a pre-bending BHA, which comprise the steps of measuring basic parameters, wherein the basic parameters comprise borehole track parameters, drill string structure parameters and stratum inclination angle parameters, calculating the maximum drilling pressure bit inclination prevention force of a drilling tool in a drilled stratum by utilizing a pre-bending BHA three-dimensional mechanical model according to the basic parameters, taking the maximum drilling pressure bit inclination prevention force as the deflecting force of the drilled stratum, inverting stratum anisotropy indexes based on the maximum drilling pressure bit inclination prevention force, calculating the inclination prevention force of stratum to be drilled under different drilling pressures according to stratum anisotropy indexes, and calculating the drilling pressure bit inclination prevention force of the stratum to be drilled under different drilling pressures according to the pre-bending BHA three-dimensional mechanical model, and optimizing reasonable drilling pressure based on the drilling pressure. The invention reasonably deduces reasonable weight on bit by taking the effective anti-skew force of the pre-bent BHA into consideration for weight on bit selection.

Inventors

YU YANG
WANG LONG
ZHAO CHANGJU
CHEN XIUPING
BAI MA
YE CHENG

Assignees

中国石油化工股份有限公司
中国石油化工股份有限公司西北油田分公司

Dates

Publication Date: 20260508
Application Date: 20241104

Claims (11)

1. A method for determining a reasonable weight on bit for a pre-bent BHA, comprising: Measuring basic parameters including borehole trajectory parameters, drill string structural parameters and formation dip parameters; according to basic parameters, calculating the drill bit inclination preventing force of the drilling tool under the maximum drilling pressure in the drilled stratum by utilizing a pre-bending BHA three-dimensional mechanical model; Taking the drill bit anti-tilting force under the maximum drilling pressure as the deflecting force of the drilled stratum, and inverting the stratum anisotropy index based on the deflecting force; According to the stratum anisotropy index, calculating the inclination force of the stratum to be drilled under different drilling pressures, according to the pre-bending BHA three-dimensional mechanical model, calculating the inclination preventing force of the stratum to be drilled under different drilling pressures, and based on the inclination preventing force, preferably reasonable weight on bit.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises, The well track parameters comprise well depths, well angles, azimuth angles and dog legs under corresponding well depths; the drill string structural parameters comprise the bent angle and the position of a screw rod or a pre-bent short joint, the outer diameter, the inner diameter, the length and the density of a drilling tool, and the drilling tool comprises a drill bit, a drill collar, a stabilizer and an adapter; The formation dip angle parameters include the dip angle of the formation being drilled and the dip angle of the formation to be drilled.
3. The method of claim 2, wherein calculating the bit anti-tip force at the given bit pressure using the pre-curved BHA three-dimensional mechanical model based on the base parameters comprises: determining the current well inclination angle and the mechanical parameters of the drill string under the appointed drilling pressure according to the basic parameters, wherein the mechanical parameters of the drill string comprise the axial pressure at the bottom end of the drill string and the contact pressure between the stabilizer and the well wall; According to the current well inclination angle, the mechanical parameters and the basic parameters of a drill string under the appointed drilling pressure, calculating the lateral force of the drill bit under any tool face angle by utilizing a pre-bending BHA three-dimensional mechanical model; calculating combined oblique force and combined azimuth force according to the lateral force of the drill bit under any tool face angle; And calculating the drill bit anti-tilting force and the direction thereof according to the combined tilting force and the combined azimuth force.
4. The method of claim 3, wherein the step of, Calculating the drill bit anti-tilting force of the drilled stratum according to the corresponding maximum bit pressure when the drilling tool does not tilt in the drilled stratum; and calculating the drill bit anti-inclination force of the stratum to be drilled under the appointed alternative weight-on-bit condition according to the well inclination angle of the section to be drilled and at least one alternative weight-on-bit data.
5. The method of claim 3 or 4, wherein the pre-curved BHA three-dimensional mechanical model is represented by the following expression: Wherein f a 、f t represents the axial and tangential friction coefficients respectively, x represents the coordinate along the axis of the drill string taking the bottom end of the ith section of drill string as a starting point, E i represents the elastic modulus of the ith section of drill string, I i represents the section moment of inertia of the ith section of drill string, u i represents the deflection of the ith section of drill string in the y direction, v i represents the deflection of the ith section of drill string in the z direction, M ti represents the torque exerted on the ith section of drill string, q i represents the weight per unit length of the ith section of drill string in drilling fluid, alpha i represents the well inclination angle of the well section where the ith section of drill string is located, B i represents the axial pressure of the bottom end of the ith section of drill string, L i represents the length of the ith section of drill string, N i represents the contact pressure between the lower end of the ith section of drill string and the well wall, and D w represents the diameter of the well bore; Bit side force was calculated using the following expression: wherein ω represents a tool face angle, F α(ω) , Respectively representing bit side forces in different directions at the toolface angle ω.
6. The method of any one of claims 3-5, wherein the combined oblique force, combined azimuth force, drill bit anti-oblique force, and anti-oblique force direction are calculated using the following expressions: Wherein F sα represents a combined oblique force, The resultant force is represented by F s , the drill bit tilting prevention force is represented by α s , and the total calculated number of times obtained by equally dividing one rotation of the drill bit is represented by n.
7. The method according to any one of claims 1 to 6, wherein the step of taking the bit anti-dip force at the maximum drilling pressure as a whipstock force of the drilled formation and inverting the formation anisotropy index based thereon comprises: Establishing a whipstock calculation formula for representing the relation among the formation whipstock, the weight on bit, the formation anisotropy index and the formation dip angle; Obtaining a current stratum anisotropy index according to the drill bit anti-tilting force under the maximum drilling pressure, the formation inclination angle and the formation maximum drilling pressure by using the deflecting force calculation formula; in the step of calculating the producing bias force of the formation to be drilled at different drilling pressures based on the formation anisotropy index, comprising: And calculating the formation deflection force under different specified drilling pressure conditions by using the deflection force calculation formula according to the current formation anisotropy index, the formation inclination angle to be drilled and the specified drilling pressure.
8. The method of claim 7, wherein the whipstock calculation is represented by the following expression: Wherein F m represents the formation making bias, W represents the weight on bit, h represents the formation anisotropy index, c=pi/180, β represents the formation dip angle, and α represents the well dip angle.
9. The method according to any one of claims 1-8, characterized in that it comprises, depending on the formation-making and bit-tilting forces of the formation to be drilled at different drilling pressures, preferably a reasonable weight on bit: calculating effective anti-tilting force of the stratum to be drilled under different drilling pressures according to the stratum tilting force and the drill bit anti-tilting force of the stratum to be drilled under different drilling pressures; performing curve fitting on the effective anti-skew force of the stratum to be drilled under different bit pressures to obtain a relation curve of the bit pressure and the effective anti-skew force; And identifying reasonable weight-on-bit according to the weight-on-bit and effective anti-skew force relation curve, wherein the weight-on-bit corresponding to the effective anti-skew force is extracted from the weight-on-bit and effective anti-skew force relation curve, so that the reasonable weight-on-bit of the stratum to be drilled is obtained.
10. The method of claim 9, wherein the effective anti-tilt force at the corresponding drill point is obtained by calculating the difference between the drill bit anti-tilt force at the same drill point and the formation induced tilt force.
11. A system for determining a reasonable weight on bit for a pre-bent BHA, wherein the system is configured to implement the method of any one of claims 1-10, wherein the system comprises: A measurement device configured to measure basic parameters including wellbore trajectory parameters, drill string structure parameters, and formation dip parameters; The drill bit anti-tilting force calculation module of the drilled stratum is configured to calculate the drill bit anti-tilting force of the drilling tool under the maximum drilling pressure in the drilled stratum by utilizing a pre-bending BHA three-dimensional mechanical model according to basic parameters; A formation anisotropy index generation module configured to take the bit anti-skew force at the maximum drilling pressure as a whipstock force of the drilled formation, and based thereon, invert a formation anisotropy index; the drilling pressure optimization module is configured to calculate the inclination force of the stratum to be drilled under different drilling pressures according to the stratum anisotropy index, calculate the inclination preventing force of the stratum to be drilled under different drilling pressures according to the pre-bending BHA three-dimensional mechanical model, and based on the inclination preventing force, preferably reasonable drilling pressure.

Description

Method and system for determining reasonable weight on bit of pre-bent BHA Technical Field The invention relates to the technical field of oilfield drilling, in particular to a method and a system for determining reasonable weight on bit of a pre-bent BHA. Background For ultra-deep and ultra-deep wells, the fast anti-whipping is one of the important concerns, not only directly related to the well quality, but also closely related to the dynamic safety of the drill string. Although the vertical drilling system plays a good role in drilling ultra-deep wells and ultra-deep wells, the use cost is high. The pre-bending dynamics anti-diagonal drilling quick technology utilizes the BHA with the pre-bending structure to perform anti-diagonal operation, has large anti-diagonal force and obvious accelerating effect, has obvious comprehensive economic benefit and has extremely strong competitiveness in some areas although the anti-diagonal drilling quick effect is slightly worse than that of a vertical drilling system. How to determine the maximum weight-on-bit, i.e., the appropriate weight-on-bit for a given pre-bent BHA, based on formation characteristics and pre-bent BHA structural parameters has not been addressed. In the literature technology of test study of pre-bending dynamics anti-tilting fast drilling technology, according to the on-site pre-bending dynamics anti-tilting fast drilling technology experiment, compared with a pendulum drilling tool combination, the drilling pressure increase of the pendulum drilling tool combination is found out to be more than 50%. In addition, in the literature technology of the conventional drilling tool combination anti-inclined drilling quick drilling pressure optimization and application, based on the longitudinal and transverse bending beam and tubular column bending theory, the influence of stratum inclined force on well inclination is considered, the minimum comprehensive acting force of a drill bit is taken as a criterion, and the buckling critical force is taken as a constraint condition, so that a conventional drilling tool combination vertical well anti-inclined drilling quick drilling pressure optimization model is established. However, the reasonable weight-on-bit determination method provided by the prior document is mainly based on experimental groping, is theoretically not combined with drilling characteristics such as actual well inclination angle, formation anisotropy index and the like of drilling, and does not consider the pre-bending structure anti-inclination limit weight-on-bit. In view of the foregoing, there is a need in the art to provide a rational weight-on-bit determination scheme that considers both drilling characteristics and pre-bend configuration. Disclosure of Invention It is an object of the present invention to provide a rational weight-on-bit determination scheme that considers both drilling characteristics and pre-bend configuration. In order to solve the technical problems, the embodiment of the invention provides a method for determining reasonable drilling pressure of a pre-bending BHA, which comprises the steps of measuring basic parameters including borehole track parameters, drill string structure parameters and stratum inclination angle parameters, calculating bit anti-tilting force of a drilling tool under the maximum drilling pressure in a drilled stratum by utilizing a pre-bending BHA three-dimensional mechanical model according to the basic parameters, taking the bit anti-tilting force under the maximum drilling pressure as the deflecting force of the drilled stratum, inverting stratum anisotropy indexes based on the bit anti-tilting force, calculating the making tilting force of stratum to be drilled under different drilling pressures according to the stratum anisotropy indexes, and calculating bit anti-tilting force of stratum to be drilled under different drilling pressures according to the pre-bending BHA three-dimensional mechanical model, wherein reasonable drilling pressure is optimized based on the bit anti-tilting force. Preferably, the well track parameters comprise well depths and well angles, azimuth angles and dog legs at corresponding well depths, the drill string structural parameters comprise bent angles and positions of screw rods or pre-bent shorts, and outer diameters, inner diameters, lengths and densities of drilling tools, the drilling tools comprise drill bits, drill collars, stabilizers and conversion joints, and the stratum inclination parameters comprise inclination angles of stratum to be drilled and inclination angles of stratum to be drilled. Preferably, according to basic parameters, a pre-bending BHA three-dimensional mechanical model is utilized to calculate the drill bit anti-tilting force under the designated drilling pressure, wherein the method comprises the steps of determining the current well tilting angle and the drill string mechanical parameters under the designated drilling pressure a