Enhance the Gas Productivity for Shale Gas Reservoirs Using Thermochemical Treatment

In shale reservoirs, the gas productivity is severely reduced due to the formation tightness. The extreme low permeability of shale formations can result in reducing the gas flow into the borehole, and consequently the gas production can be significantly reduced. This paper presents an effective technique for enhancing the gas productivity for shale gas reservoirs using thermochemical fluids. The used chemicals can generate heat and pressure in-situ and improve the flow condition by creating micro- factures in the shale rocks. Experimental measurements and analytical calculations were carried out to investigate the enhancement in gas productivity for shale samples due to the injection of thermochemical fluids. Coreflooding experiments and rate transient analysis (RTA) were conducted as well as nuclear magnetic resonance (NMR) measurements. Tight core samples from eagle ford formation were used in the flooding experiments. The improvement in gas productivity due to thermochemical injection was evaluated using rate transient analysis. The profiles of pressure-drop and gas flow-rate were used to estimate the gas productivity before and after the chemical treatment. NMR measurements were used to study the changes in the pore network due to thermochemical stimulation. The T2 signal distribution was obtained before and after the chemical injection. Furthermore, analytical calculations were performed to estimate the enhancement in gas productivity due to the thermochemical treatment. The increase in absolute open flow (AOF) and the productivity index (PI) due to the chemical treatment were determined. Results showed that treating shale rocks with thermochemical fluids can enhance the gas productivity by 62% and reduce the capillary pressure by more than 45%. Also, the absolute open flow can be increased four times due to the thermochemical injection into shale reservoirs. The generated heat and pressure due to thermochemical treatment can induce permanent alterations in the shale matrix and then improve the hydrocarbon flow for long term. NMR measurements, before and after the treatment, confirm the creation of tiny fractures during the chemical injection. The novelty of this work is that an effective treatment is presented to enhance the gas productivity for shale formations. Ultimately, this study will be very useful for treating the shale reservoirs with thermochemical fluids to improve the gas productivity, and consequently enhance the total gas production from shale reservoirs.