Effects of strain rate and confining pressure on the deformation and failure of shale

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · SPE (Society of Petroleum Engineers) Drilling Engineering; (United States)

DOI:https://doi.org/10.2118/19944-PA· OSTI ID:5678874

Cook, J M ^[1]; Sheppard, M C ^[2]; Houwen, O H ^[3]

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1. Schlumberger Cambridge Research (GB)
2. Anadrill/Schlumberger (US)
3. Sedco Forex (FR)

Previous work on shale mechanical properties has focused on the slow deformation rates appropriate to wellbore deformation. Deformation of shale under a drill bit occurs at a very high rate, and the failure properties of the rock under these conditions are crucial in determining bit performance and in extracting lithology and pore-pressure information from drilling parameters. Triaxial tests were performed on two nonswelling shales under a wide range of strain rates and confining and pore pressures. At low strain rates, when fluid is relatively free to move within the shale, shale deformation and failure are governed by effective stress or pressure (i.e., total confining pressure minus pore pressure), as is the case for ordinary rock. If the pore pressure in the shale is high, increasing the strain rate beyond about 0.1%/sec causes large increases in the strength and ductility of the shale. Total pressure begins to influence the strength. At high stain rates, the influence of effective pressure decreases, except when it is very low (i.e., when pore pressure is very high); ductility then rises rapidly. This behavior is opposite that expected in ordinary rocks. This paper briefly discusses the reasons for these phenomena and their impact on wellbore and drilling problems.

• OSTI ID: 5678874
• Journal Information: SPE (Society of Petroleum Engineers) Drilling Engineering; (United States), Journal Name: SPE (Society of Petroleum Engineers) Drilling Engineering; (United States) Vol. 6:2; ISSN 0885-9744; ISSN SDENE
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020300* -- Petroleum-- Drilling & Production
03 NATURAL GAS
030300 -- Natural Gas-- Drilling
Production
& Processing
BOREHOLES
CAVITIES
DEFORMATION
DRILL BITS
DRILLING
DRILLING EQUIPMENT
EQUIPMENT
MECHANICAL PROPERTIES
PRESSURE EFFECTS
RESERVOIR PRESSURE
ROCKS
SEDIMENTARY ROCKS
SHALES
STRAINS
STRESSES
WELL DRILLING