Enhanced Gas Recovery (EGR) Methods and Production Enhancement Techniques for Shale & Tight Gas Reservoirs

Natural gas is one of the primary sources of energy. With conventional resources depleting and rising energy demands, the world is swiftly moving towards exploiting the indigenous unconventional resources. Unconventional resources refer to ultralow permeability reservoirs that include shale and tight gas systems. Tight gas systems may include sandstone and carbonate rocks which possess low permeability but shale systems possess permebailities in the order of nano-darcies. Challenges presented by these unconventional resources led to various production enhancement techniques and enhanced gas recovery (EGR) methods that have enabled an efficient and economic recovery from such resources.

This paper discusses the production enhancement techniques for shale and tight gas reservoirs such as hydraulic fracturing, CO₂, sequestration, magnetic nano-particle technology for optimum fracture propagation, fracturing with dynamic loading or pneumatic fracturing, thermal (cryogenic) fracturing, mechanical cutting of the shale formation, enhanced bacterial methanogenesis and heating of the rock mass.

Further, CO₂ Sequestration as an EGR method is discussed in detail as it is mutually beneficial for the enhancement of hydrocarbon production as well as environment to sequester CO₂ reducing its harmful impact and contribution to global warming. A comparison of re-fracturing strategy with CO₂ Sequestration has also been presented and thus a suitable strategy for the application of CO₂ Sequestration is presented. An experimental analysis is also presented in the end to show the affinity of shales to methane, CO₂ etc. Further, the validity of Langmuir's isotherm to model gas desorption phenomenon is also discussed with experimental investigation of CH₄, CO₂ and 10%CO₂-90%CH₄ mixture at 100°C and pressure up to 44 bar. The results showed that CO₂ adsorption is 3.7 times CH₄ adsorption.