A Review on Factors Influencing the Rock Mechanics of the Gas Bearing Formations

Efforts towards producing low-carbon fossil fuels and renewable energy resources have increased significantly within the last two decades and are expected to grow even more in the upcoming years. The aim of these efforts is firstly, to decrease the carbon footprint from the earth and address some global warming concerns, and secondly, to supply the increasing global energy demand in the upcoming decades. Natural gas, as the cleanest burning fossil fuel, has attracted much attention because it has the smallest footprint among other fossil fuel resources. Understanding the rock mechanics of gas-bearing formations is a critical element to efficiently exploit this low-carbon fuel and reach the two goals that were mentioned. In this paper, we present a review of the geomechanical properties of the gas-bearing formations. While we include both conventional and unconventional reservoirs in this review, our focus is on unconventional reservoirs for two primary reasons. First, production from conventional reservoirs is well understood and is similar to the oil reservoir. Second, the unconventional reservoirs have more complicated geomechanics and require more challenging techniques such as horizontal drilling and hydraulic fracturing to enable gas production. The unconventional reservoirs in this review include tight gas, shale gas, coal bed methane (CBM), and methane hydrates. We also briefly review some geomechanics related topics such as hydraulic fracturing, refracturing, and wellbore stability.