Abstract
The brittleness of rock is an important parameter that influences and controls the evolution mechanism of the fracture and formation of a fracture net. The existing methods of brittle characterization are describing the brittleness of rock mass as a whole. They lack reliability descriptions to guide the fracture strike and improve the volume of the reservoir. It is considered that the macroscopic brittle fracture of a rock is the process of continuous initiation and propagation of local fractures in the rock mass under the action of external loads. The macroscopic fracture is the appearance caused by a local rupture to a certain extent, and the local rupture is the root cause of macroscopic fracture. The study of the local brittleness of a rock can reveal the intrinsic nature of its fracture behavior and can reflect the evolution mechanism of fracture more directly and accurately. In this paper, coring sampling in field outcrop is first carried out, and the break evolution law of core is described by a CT scanner. The mineral compositions in the core are determined by a mineral analysis diffractometer. The regulation of the rock local brittleness with different mineral contents is analyzed. And a new method for local brittle region division and characterization of rock has been developed. This method gives the connotation relation of the rock brittle fracture as a whole induced by a local brittle fracture. And it provides a new approach to study the law of a rock fracture.
Highlights
With the shortening of the proven oil and gas reserves, unconventional oil and gas exploitation is the inevitable development trend in the future to ensure the sustained and stable oil and gas production
As a new type of clean energy, unconventional oil and gas has the advantages of wide resource distribution, abundant reserves, and long exploitation life
Because the macrofracture of a rock is caused by the local brittle fracture and expansion, how to characterize the rock local brittleness has become an important research content in this paper
Summary
With the shortening of the proven oil and gas reserves, unconventional oil and gas exploitation is the inevitable development trend in the future to ensure the sustained and stable oil and gas production. Most of these methods are put forward to specific problems, applicable to different disciplines, each with its own advantages and limitations During this period, Zhaoping and Suping [24] applied the methods of X-ray diffraction, fluorescence spectrum analysis, and mechanical test to study the mineral composition and chemical composition characteristics of coal-bearing mudstone. They established a qualitative and quantitative relationship. WenLong’s [27] analysis shows that the rock with high contents of quartz, feldspar, and carbonate is brittle This kind of rock is easy to form natural fractures and induced fractures under the action of external forces, and its development degree is generally positively correlated with the content of brittle minerals. × 100, ð1Þ where BRIT is the rock brittleness index and V is the mineral volume
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