In-Situ Stress Distribution and Its Effects on Borehole Stability in the Longmenshan Earthquake Fault Zone

详细信息   

• 责任者：Zhang Peifeng (Institute of Exploration Engineering ; Beijing 100083 ; China)
• 刊名：Geology and Prospecting
• 出版年：2012
• 卷期：48(2)
• 关键词：地应力 ; geostress ; 井壁稳定 ; wellbore stability
• 页码：p.379-386
• 图表：3 illus., 21 refs.
• 分类号：2000
• issnNo：ISSN0495-5331
• isbnNo：CN11-2043/P

摘要

The Longmenshan earthquake fault zone is one of the most active fault zones in China. It is characterized by fractured formation and anomalous in-situ stress which cause Frequent down hole drilling accidents due to formation expanding. The borebale stability is a serious problem. This paper presents the down hole drilling accidents that occurred during the scientific drilling （ WFSD at the Wenchuan earthquake fault zone. The statistics and regression analysis of the in-situ stress produced the curves that describe the maximum and minimum horizontal stresses changing with depth. The maximum horizontal stress gradient is about 4.52MPa/100m, and the minimum horizontal stress gradient is about 2.51 MPa/100m. Taking the borehole WFSD-2 as an example, the effects of stress, especially gouge stress on borehole stability is analyzed. A simple method is introduced that the formation caving pressure and fracture pressure are measured by density fine adjustment of drilling fluid applied to formation expanding and diameter shrinkage.