Pore connectivity and pore size distribution estimates for Wolfcamp and Eagle Ford shale samples from oil, gas and condensate windows using adsorption-desorption measurements

Pore size distribution and pore connectivity are vital parameters governing the hydrocarbon production of subsurface reservoirs. We estimate pore size distribution and pore connectivity of shale samples by processing the low-pressure nitrogen adsorption-desorption measurements. Our hypothesis is that the connectivity of shale pore structure can be quantified in terms percolation and fractal parameters. The proposed analysis is performed on 35 samples from various maturity windows of Eagle Ford and Wolfcamp formations. The samples were collected from 100 feet interval in the Eagle Ford gas window, 30 feet interval in the Eagle Ford oil window, and 60 feet interval in the Wolfcamp condensate window. Eagle Ford samples were low-temperature plasma ashed to study the impact of removal of organic matter on the pore size distribution and pore connectivity. The estimated pore size distribution of Wolfcamp samples differ significantly from that of Eagle Ford samples that supports the mineralogical differences between the two formations. Wolfcamp samples exhibit higher fractal dimension indicating higher pore complexity. Eagle Ford samples exhibit better long-range pore connectivity and lower pore complexity compared to Wolfcamp samples despite lower porosity.