Mechanical and flow properties of unconventional reservoir rocks and the influences of water on them.

Water-based hydraulic fracturing is usually used for the stimulation of low-permeability unconventional oil and gas reservoirs. However, large amounts of water is trapped in tight reservoirs after treatment which induces the water-rock interactions. The mechanical and flow properties of unconventional reservoir rocks and influences of water on them are investigated through a series of strength, water imbibition, permeability and fracturing laboratory tests for different reservoir conditions. The gas flow through unconventional reservoir rocks are modelled by using COMSOL. Water retention in micro pores after hydraulic fracturing is found to have significant effects on initial gas production from tight rocks.