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中南大学学报(英文版)

Journal of Central South University

Vol. 25    No. 7    July 2018

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Stress distribution and its influencing factors of bottom-hole rock in underbalanced drilling
ZHANG Ran(张然)1, 2, LI Gen-sheng(李根生)2, TIAN Shou-ceng(田守嶒)2

1. Key Laboratory of Fluid and Power Machinery of Ministry of Education, Xihua University,Chengdu 611743, China;
2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum,Beijing 102249, China

Abstract:The underbalanced drilling has been widely used due to its advantages of high drilling efficiency and low cost etc., especially for hard formation drilling. These advantages, however, are closely related to the stress state of the bottom-hole rock; therefore, it is significant to research the stress distribution of bottom-hole rock for the correct understanding of the mechanism of rock fragmentation and high penetration rate. The stress condition of bottom-hole rock is very complicated while under the co-action of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature etc. In this paper, the fully coupled simulation model is established and the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on stress distribution of bottom-hole rock are studied. The research shows that: in air drilling, as the well depth increases, the more easily the bottom-hole rock is broken; the mud pressure has a great effect on the bottom hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock; the max principle stress of the bottom-hole increased with the increasing of mud pressure, well depth and temperature difference. The bottom-hole rock can be divided into 3 regions respectively according to the stress state, 3 direction stretch zone, 2 direction compression area and 3 direction compression zone; the corresponding fragmentation degree of difficulty is easily, normally and hardly.

 

Key words: thermo-poroelastoplasticity; bottom-hole rock stress; fully coupled; numerical solution; fragmentation mechanism

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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