TIGHT GAS: FROM PORE-SCALE TO WELL DECLINE CURVE ANALYSIS

Tight gas sands and gas shales are characterized by extremely low permeability of the rock. The efficiency of recovery operations depends on better understanding of the underlying pore-scale mechanisms of single and multi-phase gas flow. Micron-scale computed tomography and focused ion beam imaging techniques reveal the complexity of the 3D pore space geometry. A volume of tens of microns across can include a very rich diversity of minerals and grain sizes. The images also show how different the rock samples from different formations can be. Application of the pore-scale analysis to modeling gas flow into a fractured well leads to an analytically-described decline type curve. The curve consists of two regimes: a square-root-of-time decline in early production is followed by an exponential decline later on. Even though the underlying assumptions include great simplifications, production data from a number of gas shale wells verify the modeling results.