Study of the Effect of Borehole Size on Wellbore Stability

Abstract:

Based on the size effect of rock strength, the borehole stability analysis model is established, which the borehole size is taken into consideration. Through this model, the relation between borehole size and collapse pressure under borehole pressure, ground stress and drilling fluid flow function is analyzed. The analysis shows that with the increase of borehole diameter, collapse pressure increases significantly, and borehole stability becomes poor, but the variation of borehole size is not proportional to collapse pressure: the bigger the borehole, the smaller the variation. When borehole diameter increases from 152.4 mm to 444.5 mm, wellbore collapse pressure increases from 1.18g/cm³ to 1.315g/cm³ and the rate of the increase is 11.44%. When slimhole drilling technology is applied, the density of minimum fluid that maintains wellbore stability is lower than the one used in conventional wellbore drilling.

• Periodical: Applied Mechanics and Materials (Volume 574)
• Pages: 214-218
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.574.214
• Online since: July 2014
• Authors: Hao Yong Huang*, Yuan Fang Cheng, Wei Zhao, Chong Cheng, Wen Biao Deng
• Keywords: Borehole Collapse, Rock Strength, Size Effect, Slim Hole

References

[1] GAO Li-ping. Slim hole well test and production performance. Foreign petroleum machinery Magazine, China, 1996, 7(z): 56-65.

[2] Liu Shuo-qiong, Tan Ping, Zhang Hanling, Slim hole drilling technology, third ed., Petroleum Industry Press, Bei Jing, (2005).

[3] Haimson B C, Herrick C G. Borehole breakouts and in-situ stress: proceedings of the 12th annual energy-sources technology conference and exhibition, Houston, January 22-25, (1989).

[4] Zhang Zhe, Tang Chun-an, et al. Numerical investigation on stability of wellbore during coal bed gas mining process. China Mining Magazine, China, 2006, 15(9): 55-58.

[5] CHENG Chao-wei, ZHOU Yinh-cao, et al. Wellbore stability analysis considering rock size effects. Petroleum Drilling Techniques, 2009, 37(3): 38-40.

[6] CHENG Yuan-fang, ZHANG Feng, WANG Jing-yin, et al. Analysis of borehole collapse cycling time for shale . Journal of China University of Petroleum (Edition of Natural Science), 2007, 31(1): 63-67.

[7] CHENG Yuan fang, HUANG Rong zun, Steady mechanics analysis of mud shale borehole well in drilling engineering. Journal of the University of Petroleum, China(Edition of Natural Science), 1993, 17(4): 27-29.

[8] Liu Baochen, Zhang Jisheng, Du Qizhong. A study of size effect for compression strength of rock. Chinese Journal of Rock Mechanics and Engineering, China, 1998, 17(6): 611~614.

[9] YANG Sheng-qi, SU Cheng-dong, XU Wei-dong, et al. Experimental and theoretical study of size effect of rock material. Engineering mechanics, China, 2005, 22(4): 112-118.