Matrix to Fracture Flow Inferences from Core Measurements and Structural Fabric (Whitby UK)

Abstract

The Early Jurassic (Toarcian) Shales in Northern Europe are investigated as possible unconventional sources for gas, where gas in shales is trapped in poorly connected micro pores and is sorbed within particles of organic material and clay minerals in the matrix of the host rock. Having a dual permeable medium consisting of a high permeable fracture network together with a tight shale matrix will improve gas flow rates from matrix to well. The Whitby Mudstone is currently outcropping on the Yorkshire coast hence getting sufficient sample material for permeability experiments is easily available, in combination with mapping of the natural occurring fractures in the cliffs and pavements along the coast this area is an ideal natural analogue to investigate matrix characteristics in combination with the natural fracture network. The studies show that fracture spacing on average is in the order of 10 centimeters and that in combination with a matrix permeability of 1∙10-18 m2 results in gas residue times in the matrix in the order of hours to tens of days depending on the input parameters used.