Patent ID: 8978764
Filing Date: 2015-03-17
Classification: E21B

Abstract:
1. A method of generating an extended fracture network in a rock formation, said formation characterized by a network of native fractures and incipient fractures and a minimum hydraulic fracturing pressure and rate whereby fluid injected at a higher rate and pressure causes the formation to fracture, said method comprising the sequential steps of i) injecting a non-slurry aqueous solution into the formation at a pressure and rate which is slightly above the minimum hydraulic fracturing pressure and rate whereby a zone of essentially self-propping fractures is generated by increased pore pressure, shearing, and dilation of the native fractures and incipient fractures, and wherein said step (i) is performed until the maximum possible stimulated volume of the formation has been substantially attained for a given injection site as determined by formation response measurement data; ii) injecting a plurality of slurries comprising a carrying fluid and sequentially larger-grained granular proppants into said formation whereby said steps i and ii generate an inner zone of fractures that are propped with said granular proppant and at least some of the fractures therein are widened, and an outer zone surrounding the inner zone essentially comprising self-propped fractures; and iii) further extending and propagating the outer zone by additional injection of non-slurry aqueous solution into the formation at a pressure and rate slightly above the minimum hydraulic fracturing pressure and rate.