Analysis of influencing factors of wellbore stability in shale formations
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In the process of drilling, wellbore instability in shale formations is frequent and makes it hard to drill. In order to find causes of wellbore instability in shale formations, this paper proposed a wellbore instability analysis model to reveal the combined effects of anisotropic strength of shale, occurrence of stratification, strength reduction, and seepage stresses caused by drilling fluid on wellbore instability. The results show that when the occurrence of bedding planes is certain, it can maintain wellbore stability in the condition of lower mud weight to choose a reasonable azimuthal angle. With changes of shale strength and porous flow, the wellbore would increase the level of instability with drilling time, which means mud weight needs to be increased to keep the wellbore from collapsing.
KeywordsWellbore stability Shale Mud density Bedding planes Anisotropic strength
This research was supported by the Key National Science and Technology Projects (2016ZX05044-004-001 and 2016ZX05051-004-008).
- Aadnoy B, Chenevert ME (1987) Stability of highly inclined boreholes. SPE Drill Eng 64–74Google Scholar
- Cai MF, He MC, Liu DY (2009) Rock mechanics and engineering. Science Press, BeijingGoogle Scholar
- Chen TY, Feng XT, Zhang XW (2014) Experimental study on mechanical and anisotropic properties of black shale. Chin J Rock Mech Eng 33(9):34–46Google Scholar
- Jin Y, Chen M, Chen ZX (2010) Mechanics model of sidewall stability of straight wells drilled through weakly consolidated formations. Drill Prod Technol 22(3):13–14Google Scholar
- Li QH, Chen M, Jin Y (2012) Experimental research on failure modes and mechanical behaviors of gas-bearing shale. Chin J Rock Mech Eng 31(2):67–79Google Scholar
- Liu XJ, Chen YJ, Xiao Y (2001) Effect of weak plane dip angle and dip azimuth angle on wellbore stability. Journal of Southwest Petroleum Institute 23(6):12–13Google Scholar
- Mastin LG, Heinemann B, Krammer A, Fuchs K, Zoback MD (1991) Stress orientation in the KTB pilot hole determined from wellbore breakouts. Sci Drill 2:1–12Google Scholar
- Mu JF (2016) Anisotropic investigation of the mechanical property of shale. Unconventional Oil and Gas 3:114–120Google Scholar
- Okland D, Cook JM (1998) Bedding-related borehole instability in high-angle wells. SPE/ISRM: Rock Mech Petro Eng 1:413–422Google Scholar
- Willson SM, Last NC, Zoback MD, Moos D (1999) Drilling in South America: a wellbore stability approach for complex geologic conditions. The SPE Latin American & Caribbean Petroleum Engineering Conference SPE 53940Google Scholar
- Yang HL, Shen RC, Fu L (2013) Composition and mechanical properties of gas shale. Pet Dril Tech 41(5):31–35Google Scholar