Fracture Network Growth for Prediction of Fracture Characteristics and Connectivity in Tight Reservoir Rocks

Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by growth and coalescence of fractures to form a connected fracture network. Fluid-driven fracture growth is represented by preferential fracture growth occurring initially at the high fluid pressure part of the rock. With prolonged durations of high fluid pressure at the tip of the newly formed fractures, the network propagates rapidly through the sample and away from the high fl uid pressure reservoir. This difference in fracture network growth and the differences in fracture statistics between both scenarios have important control on the flow of hydrocarbons in fractured reservoirs and thus on hydrocarbon productivity. Differences in fracture statistics can eventually be used as improved input into reservoir and production models. 3D X-ray tomography analyes of a fractured specimen show very early 3D fracture connectivity, much earlier than depicted from conventional 2D analyses. The early 3D connectivity of fractures and enhanced permeability may also be critical to the understanding of hydrocarbon storage and migration or seal integrity.