Evaluation method for brittleness of shale

Abstract

An evaluation method for brittleness of shale includes the following steps: (1) obtaining shale cuttings returned from a target shale gas well bottom, and separately performing microscopic nanoindentation, X-ray diffraction and density tests; (2) based on obtained data of the microscopic nanoindentation, X-ray diffraction and density tests, separately calculating an elastic modulus, a component content and rock debris sample density constituted by various types of mineral substances of each of the shale cuttings; and (3) substituting the elastic modulus, mineral component content and a shale cuttings density value constituted by the various types of mineral substances of each of the shale cuttings into a brittleness evaluation model formula, wherein Wi represents a content of an i mineralcomponent in the shale; Ei represents the elastic modulus of i mineral composition in the shale, GPa; [rho] represents shale density, g / cm3, and a B value obtained by the model reflects a brittlenesscharacteristic of a shale reservoir where the shale is located. The method can perform real-time evaluation on the brittleness of the shale simply, quickly and at low cost.

Description

technical field [0001] The invention relates to the technical field of oil drilling, in particular to a shale brittleness evaluation method while drilling. Background technique [0002] During the shale gas drilling process, the real-time and correct evaluation of shale brittleness is helpful for the timely prevention and control of wellbore stability, the optimization of fracturing intervals and the optimization of fracturing effects, and it also has certain implications for the selection of drilling equipment and cement slurry density influences. Existing shale brittleness evaluation methods can be mainly divided into six categories based on mineral composition, elastic mechanical parameters, rock strength, penetration test, rock fragmentation degree, and indoor stress-strain. These evaluation methods mainly rely on post-drilling logging interpretation. And the mechanical experiment of rock sample preparation, logging interpretation cannot be used for real-time shale brit...

AI Technical Summary

Problems solved by technology

Existing shale brittleness evaluation methods can be mainly divided into six categories based on mineral composition, elastic mechanical parameters, rock strength, penetration test, rock fragmentation degree, and indoor stress-strain. These evaluation methods mainly rely on post-drilling logging interpretation. And the mechanical experiment of rock sample preparation, logging interpretation cannot carry out real-time shale brittleness evaluation while drilling, the process of preparing rock samples for mechanical experiments is complicated, the cost is high, and it is also impossible to carry out real-time shale brittleness evaluation while drilling

Images