Stability of boreholes drilled through salt formations displaying plastic behavior

Conference · Wed Jan 01 04:00:00 EST 1986

OSTI ID:7075745

Infante, E F; Chenevert, M E

This paper presents a mathematical and laboratory analysis which provides solutions to the problem of plastic flow of salt formations into wellbores. Depending on well conditions, this paper predicts how the salt will flow and what type of mud might be used to control such flow. In the mathematical analysis it is assumed that the incipience of plasticity in the formation is regulated by the level of octahedral shear stress and that the formation is neither permeable nor porous, but homogeneous and isotropic. The stress distribution in the neighborhood of the borehole is studied, and conditions under which this distribution is elastic, elastoplastic, or plastic are determined. Equations are derived that, in terms of two constants of the formation material, yield the limit of elasticity, the radius of the plastic front, and the percent of the borehole diameter shrinkage as a function of mud weight used. This study was prompted by past failures in drilling through the Louann Salt formation at depths of 12,500 to 14,000 feet, a formation which exhibits rapid plastic flow at low mud weights and at the temperatures and pressures encountered. The techniques presented in this paper were applied to subsequent drilling of this salt section and the zone was penetrated without experiencing the problem of plastic flow.

• Research Organization: Univ. of Minnesota
• OSTI ID: 7075745
• Report Number(s): CONF-861080-
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020300* -- Petroleum-- Drilling & Production
03 NATURAL GAS
030300 -- Natural Gas-- Drilling
Production
& Processing
36 MATERIALS SCIENCE
360603 -- Materials-- Properties
ANALYTICAL SOLUTION
BOREHOLES
CAVITIES
CREEP
DEFORMATION
DRILLING
DRILLING FLUIDS
ELASTICITY
FAILURE MODE ANALYSIS
FLUIDS
GEOLOGIC DEPOSITS
HIGH PRESSURE
HIGH TEMPERATURE
MECHANICAL PROPERTIES
MECHANICS
NATURAL GAS WELLS
OIL WELLS
PERMEABILITY
PLASTICITY
POROSITY
ROCK DRILLING
ROCK MECHANICS
SALT DEPOSITS
SHRINKAGE
STABILITY
STRESS ANALYSIS
SYSTEM FAILURE ANALYSIS
SYSTEMS ANALYSIS
TENSILE PROPERTIES
WELL DRILLING
WELLS