Experimental Investigationof Water Absorption And Its Significance To Pore Network Connectivity In Mudstone From Silurian Longmaxi Formation, Sichuan Basin

With the application and development of horizontal well fracturing, shale oil and gas have been an available unconventional resource, which is an important alternative energy resource in the future. But the mining coefficient is only 5% to 10%. The organic rich shale develops micro-nano pores, which provide space and migration pathway for oil and gas. Therefore, the pore network connectivity in shale is the key factor in improving mining coefficient of shale oil and gas. The water absorption, water uptake and main controlling factors on the organic-rich mudstone of Longmaxi Formation are investigated by water absorption experiment, N2 absorption and TOC and clay mineral contents. The primary results show that:(1) TOC and clay mineral contents are key factors that affect water absorption on mudstone.(2) Water uptake in mudstone has a positive correlation with BET surface area, and the water uptaking in mudstone absorption is spontaneous and reversible physical adsorption. Based on the linear correlation between saturated water uptake of the same sample with different sample size and the samples’volume, the calculated effective porosity is 6.23%, which is more accurate than nitrogen adsorption method.(3) The different result between columns of parallel and vertical to bed plane shows that the permeability in parallel direction is better than vertical direction. The difference can be quantified by wax-sealed experiment.(4) The water uptaking can be fit by first-order kinetic equation, which can be used to predict the water uptaking characteristic of underground shale. Water absorption experiment provides a new method to measure the connected and effective porosity.