Well-surrounding near-well-wall stratum damage evaluation method based on logging information

Abstract

The invention discloses a well-surrounding near-well-wall stratum damage evaluation method based on logging information. The method comprises the steps: calculating a rock anisotropic rigidity coefficient according to full-wave-train dipole acoustic logging information; calculating the elastic modulus, Poisson's ratio and Thomsen coefficient of the rock and the flexibility coefficient of the rock; according to the full-wave-train dipole acoustic logging information, obtaining the radial section of the acoustic velocity of the stratum around the well wall; calculating the flexibility tensor variable quantity of any position close to the well wall; and according to the flexibility tensor variable quantity of any position near the well wall, calculating dispersion damage parameters of stratum rocks at any position near the well wall. According to the method, acoustic logging is adopted to evaluate the damage characteristics of the stratum close to the well wall, the stratum is regarded as a transverse isotropic medium, and acoustic logging information is utilized to calculate and analyze rock mechanical parameters, Thomsen anisotropy coefficients and mechanical damage parameters of different lithology and different radial positions; and the method plays a very important role in ground stress evaluation, borehole wall stability analysis, hydraulic fracturing and the like.

Description

technical field [0001] The invention relates to a method for evaluating formation damage around a well near the wellbore wall based on well logging data. Background technique [0002] During the drilling process, wellbore collapse, block loss, diameter expansion and other wellbore instability problems are often encountered. In the process of hydraulic fracturing, the formation with natural micro-fractures often cracks before the rock body, so that the hydraulic fractures are extended. During the process, the micro-fractures are preferentially extended along the surface, which reduces the success rate of fracturing. There are many micro-fractures in the deep formation itself. The problem of wellbore instability in drilling engineering and the fracture propagation problem of hydraulic fracturing can be regarded as the expansion, convergence and penetration of micro-fractures under the action of external factors (mechanical and chemical factors). Macroscopic cracks, the proces...

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Problems solved by technology

[0005] However, the current research on rock anisotropic damage is mainly based on indoor core testing. Although the change of confining pressure is considered during the experiment, it cannot fully reflect the real situation of the formation around the wellbore, and it cannot reflect the rock mechanical parameters in the formation near the wellbore. , anisotropy, radial distribution and evolution characteristics of damage characteristics, in addition, there are disadvantages such as difficult coring, expensive testing, and limited data obtained in indoor testing

Acoustic logging data contains a wealth of formation information, and has the advantages of relatively low acquisition cost and continuous sampling points. At present, there are no reports on the use of acoustic logging data to evaluate formation damage near the borehole wall.

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