Plasticity effects in hydraulic fracturing

Conference · Wed Sep 01 04:00:00 EDT 1982 · Soc. Pet. Eng. AIME, Pap.; (United States)

OSTI ID:5326724

Medlin, W L; Masse, L

The importance of reservoir rock plasticity in fracturing operations has been investigated by means of laboratory experiments and field results. A Lagrangian formulation for crack propagation provided the basis for the laboratory experiments. A simple crack propagation experiment showed that plasticity effects can be observed. It was further shown that the importance of plasticity depends on the relative magnitudes of surface energy and energy dissipated in plastic deformation of the reservoir rock. The latter can be evaluated by laboratory measurements of a plasticity coefficient ..cap alpha.. which comes out of the Lagrangian analysis. To measure ..cap alpha.. the authors developed a triaxial system for applying tensile stress to rock cores under confining pressure at strain rates characteristic of fracturing operations. These methods were used to evaluate ..cap alpha.. in a variety of cores from reservoirs where fracturing treatments had been conducted. The Lagrangian theory predicts that plasticity will show up in fracturing records as abnormal treating pressures and will result in fractures which are shorter and wider than normal. All of these effects have been observed in massive frac treatments in the Piceance Basin, and modest treating pressure increases have been observed in Muddy-J frac treatments in the Denver Basin. However, the authors found only slight plasticity in well cores from these formations. Severe plasticity was found in some deep Carboniferous cores from the Oldenberg Field in north Germany. However, the expected fracturing problems were only found in one of many wells. The authors attribute this to sampling problems connected with inhomogeneous formation properties. They conclude that plasticity can explain fracturing problems in some but not many reservoirs, and that core analysis is not a very practical means of anticipating it.

• Research Organization: Mobil Research and Development Corp.
• OSTI ID: 5326724
• Report Number(s): CONF-820927-
• Conference Information: Journal Name: Soc. Pet. Eng. AIME, Pap.; (United States) Journal Volume: SPE11068
• Country of Publication: United States
• Language: English

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BENCH-SCALE EXPERIMENTS
COMMINUTION
CRACK PROPAGATION
DATA
DIFFERENTIAL EQUATIONS
DRILL CORES
EQUATIONS
EXPERIMENTAL DATA
FRACTURE PROPERTIES
FRACTURING
HETEROGENEOUS EFFECTS
HYDRAULIC FRACTURING
INFORMATION
LAGRANGE EQUATIONS
MEASURING INSTRUMENTS
MECHANICAL PROPERTIES
NUMERICAL DATA
PARTIAL DIFFERENTIAL EQUATIONS
PLASTICITY
RESERVOIR ROCK
STRAIN GAGES
STRAIN RATE
STRESS ANALYSIS