A New Method for Simultaneously Testing Fracture Brittleness and Conductivity

Abstract

Multistage hydraulic fracturing of horizontal wells is the prevailing technology for developing unconventional hydrocarbon reserves like the Wolfcamp tight formation in the Permian Basin, USA. Hydraulic fracturing treatment assumes the stimulation will create brittle and conductive fractures in all clusters of each stage. The stimulation outcome with respect to fracture brittleness and the scope of fracture conductivity should be determined experimentally and simultaneously. To our knowledge, existing technologies test fracture brittleness and fracture conductivity separately. This paper introduces a new method that measures fracture brittleness and fracture conductivity simultaneously. Testing results on Testing results on Indianan limestone show that: (1) Confining pressure is a dominant factor in controlling whether the rock fractures in brittle mode or fails in ductile mode. (2) If the rock fractures in a brittle mode, the rock matrix permeability, and subsequently the fracture conductivity increases rapidly during and post fracturing/failing process. (3) If the rock fails in a ductile mode, matrix permeability decreases monotonically before, during and post the fracturing process. (4) Transitional behaviors have been observed when the rock fails between semi-brittle and semiductile modes under an intermediate range of confining pressures. The latter corresponds to reservoir conditions in most of the real world cases.(5) The new testing has shown it can provide means to increase the possibility of creating brittle and conductive fractures.