Analysis of wastewater disposal in depleted tight gas reservoirs: A sustainable resources approach

Wastewater injection into oil and gas fields is implemented for various purposes via injection wells. Disposing of wastewater, which is mostly waste saltwater produced with hydrocarbons in oil and gas fields, into underground petroleum reservoirs are usually tied with environmental purposes. Injection of wastewater into geologic strata may encompass different applications: hazardous or non-hazardous wastewater disposal, enhanced recovery from petroleum reservoirs or merely wastewater storage. Aside from the purpose of wastewater injection, modeling of wastewater flow in porous media of underground rock strata can be challenging in different petroleum reservoirs and wells. In this study, a tight gas reservoir (TGR)—as a large-scale sustainable material to store wastewater—is considered to be studied for water disposal via a multistage fractured horizontal well (MSFHW) by numerical simulation. Host rock layer is considered to be initially saturated with low-pressure methane gas and water injection has to be performed through the hydraulic fractures of the MSFHW into the rock pore volume. Injection is performed under constant bottomhole flowing pressure and several sensitivity analyses are investigated to outline important rock characteristics in TGRs affecting performance of wastewater injection into them.