Fractures as Stress Raisers in Rock Mass in Oil and Gas Production
A. M. Svalov
Institute of Oil and Gas Problems, Russian Academy of Sciences, Moscow, 119333 Russia
Keywords: Rock discontinuities, disjunctive cleavage, productive strata, rock creep, reservoir infeed
Abstract
The spotlight is on the stress patterns in oil and gas reservoirs and in enclosing rock mass containing displaced fractures (disjunctive cleavages). The mathematical modeling finds out that with the decreasing reservoir pressure in rock mass subject to elastic deformation, the shearing stress raisers arise on the surfaces of displaced fractures and can make an initially impermeable fracture to become fluid-conductive. Creeping widens the fractures, which also contributes to hydrodynamic connection between a pay zone and the upper- and low-lying permeable strata. This process of formation of the permeable channels in rock mass can be an explanation for the mechanism of oil and gas reservoir infeed with fluid flows from the lower-lying fluid-bearing strata.
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