Borehole wall sloughing analysis method

An analysis method, a technology of wellbore collapse, applied in the field of wellbore stability analysis in strain softening plastic formations and drilling wellbore instability analysis

Inactive Publication Date: 2011-09-14
CNPC DRILLING RES INST +1
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There is no report on the application of strain softening model and ...

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Embodiment 1

[0091] Embodiment 1: Taking the well wall collapse analysis of a well as an example, the present invention is further described in detail.

[0092] Taking Dabei 101 well in Tarim Oilfield as an example, the 1323-1340m well section of the well is analyzed by using the well wall collapse analysis method of the present invention:

[0093]The wellbore collapse analysis method includes: collecting and inputting parameters 1, initial stress treatment 2, first stress release 3, second stress release step 4A, second stress release step 4B, eigenvalue evaluation 5, generalized force and Generalized displacement 6, equilibrium path curve 7, collapse pressure processing 8, output collapse pressure and plastic zone distribution map. refer to figure 1 .

[0094] (A) Firstly, the wellbore rock material parameters, including elastic modulus, Poisson’s ratio, internal friction angle, cohesion, softening coefficient, yield function type, and internal variables, are acquired through the loggi...

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Abstract

The invention relates to a borehole wall sloughing analysis method which comprises the steps of parameter collection and input (1), initial stress processing (2), first time of stress release (3), first step of second time of stress release (4A), second step of second time of stress release (4B), characteristic value evaluation (5), generalized force and generalized displacement (6), path curve balancing (7), and collapse pressure processing (8). Evaluation is conducted according to a minimum obtained characteristic value (Mu1) m, and when the minimum obtained characteristic value (Mu1) m is more than 0, if m is less than M, m plus 1 arrows m, thus entering the second step of the second time of the stress release (4B); otherwise, a total field is obtained; when the minimum characteristic value (Mu1) m is less than 0, a disturbance field is calculated according to an interpolation method; and the collapse pressure qcr and a plastic area distribution area corresponding to the qcr are calculated, so as to determine the density of collapse prevention drilling fluid. The borehole wall sloughing analysis method has the effect of being capable of analyzing the borehole wall stability of a strain softening plastic stratum under the condition of non-uniform ground stress; and the density of the collapse prevention drilling fluid is designed, thus playing the role of protecting a reservoir stratum during on-site drilling.

Description

technical field [0001] The invention relates to the technical field of petroleum drilling engineering, in particular to the instability analysis of the drilling borehole wall, and is a method for analyzing the stability of the borehole wall of the strain-softened plastic formation under the condition of non-uniform ground stress. Background technique [0002] At present, elastic mechanics combined with strength criterion method is widely used in petroleum engineering to explain wellbore collapse mechanism and predict collapse pressure. For example, the wellbore stability analysis GMI system, which is considered to be the best in the world, uses the wellbore collapse model based on the elastic mechanics combined with the strength criterion method. The latest theoretical research on the mechanism of wellbore collapse shows that the wellbore collapse is essentially an extreme point-type instability phenomenon. The collapse pressure in the sense of mechanical stability can be d...

Claims

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Application Information

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IPC IPC(8): E21B49/00
Inventor 陈朝伟王倩王瑛周英操赵庆刘玉石
Owner CNPC DRILLING RES INST
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