Advanced characterization and numerical simulation of indentation induced damage in hard sandstone

HJ Jun and NV Bangaru and GI Block and V Gupta, ROCK MECHANICS: MEETING SOCIETY'S CHALLENGES AND DEMANDS, VOLS 1 AND 2: VOL: FUNDAMENTALS, NEW TECHNOLOGIES & NEW IDEAS; VOL 2: CASE HISTORIES, 647-+ (2007).

DOI: 10.1201/NOE0415444019-c79

The trend in drilling for oil and gas is hard rock and deeper formations. Rate Of Penetration (ROP) is the single most important factor impacting drilling costs and performance, as well as the economic development of certain difficult to reach hydrocarbon resources. A fundamental understanding of the micro-mechanisms of rock fracture and rock microstructure-fracture relationships is essential in optimizing drilling parameters for high ROP and drill bit performance. Although indentation damage is fundamental to rock cutting in roller cone and even in drag bit drilling, rock fracture and damage even under simple indention are poorly understood, especially as they relate to rock microstructure. Advanced analytical electron microscopic characterization techniques have been utilized to study rock microstructure, damage, and fracture under simple indention in a hard marine sandstone from the Piceance Basin. Advanced Electron Backscattered Diffraction in a scanning electron microscope have revealed that many of the sandstone grits are characterized by polycrystalline structures and that the propagation of indention induced micro-cracks is along various interfaces but not via trans-granular cleavage. Numerical simulations using a discrete element code are being developed to model rock damage processes under the complex stress paths developed under the indenter.

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