Online Journal for E&P Geoscientists

Sunjay, Sunjay ^*1
(1) Geophysics, Banaras Hindu University, Varanasi, India.

With a view to energy security of the world ,unconventional energy resources - Basin Centered Gas ,coalbed methane (CBM) , Methane GasHydrate,shale gas, tight gas,oil shale and heavy oil- exploration and exploitation is pertinent task before geoscientist.Basin-centered gas systems (BCGS) represent an important component of the tight gas sand resource base. A BCGS is generally defined as a regionally pervasive unconventional resources of natural gas encompassing very large area and may occur as single, isolated reservoirs or as multiple, stacked reservoirs, low-permeability sand accumulation that is gas saturated, is abnormally pressured, and lacks a down dip water contact.BCGS are categorised on the basis of source rock quality; a direct BCGS has a gas prone source rock and an indirect BCGS has an oil prone source rock and a hybrid system.The exploration strategy for BCGS can be assigned as follows:Reconnaissance phase, where identification of basins suitable for BCGS exploration is carried out. Identification of source rock and its type, existence of reservoir and its quality, exploration history of the basin, if available, form the critical parameters in this phase. Confirmation phase entails determination of reservoir pressure, since most BCGS are abnormally pressured. In the delineation phase, the vertical and areal distribution of the accumulation is mapped on the basis of pressure data or thermal maturity values. BCGS reservoir properties (sweet spots) can be identified ,which may be structural or stratigraphic in nature and always occur within the abnormal pressure envelope.Permeability Jail (no-flow región) and Implications for Basin Centered Gas production:two petrophysical properties stand out- the strong stress dependence of permeability , relative permeability that is not widely known or documented but its effects are widely observed. Nano Science and Technology (surfactant-nanofluids) can be made fashionable to quit permeability jail.Wavelet Analysis is employed for high resolution BCGS imaging.