Wellbore stability
A variety of factors can cause wellbore instabilities. Shale hydration can develop swelling pressures that may cause hole failures. Balanced activity oil muds and polymer muds provide means for controlling this type of hole instability. The wellbore fluid pressure must not exceed the fracturing pressure and must be greater than the blowout pressure. In geopressured formations the difference between the upper and lower bounds on wellbore pressure can be small. Low wellbore pressure also can lead to hole collapse and to solid particle influx. Predictive methods have been developed during the past 4 decades for dealing with these various causes of hole instability. Elastic-plastic analysis methods are available for computing stresses around inclined holes with static and moving formation pore fluids. Yield conditions can account for strain softening during plastic flow of the rock around the wellbore. However, improved constitutive relations are needed to provide a more realistic description of the mechanical behavior of rock such as including the effects of rock anisotropy. Better in-situ earth stress determinations and physical rock-properties measurements can aid greatly in providing improved wellbore stability control. With continued progress in the areas described in this article, wellbore stability engineering should become less of an art and more of an engineering science.
- Research Organization:
- Dept. of Mech Eng., Rice Univ., Houston, TX
- OSTI ID:
- 6371861
- Journal Information:
- J. Pet. Technol.; (United States), Vol. 36:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
WELL DRILLING
CONTROL
HYDRAULICS
ROCK MECHANICS
DRILLING FLUIDS
FORMATION DAMAGE
NATURAL GAS WELLS
OIL WELLS
RESERVOIR ROCK
STABILITY
WELL PRESSURE
DRILLING
FLUID MECHANICS
FLUIDS
MECHANICS
RESERVOIR PRESSURE
WELLS
020300* - Petroleum- Drilling & Production
030300 - Natural Gas- Drilling
Production
& Processing