Characterization of Hydrocarbon-bearing Fluid Inclusion in Sandstones of Jaisalmer Basin, Rajasthan: A Preliminary Approach

Abstract

The quartz grains from the sandstone of Jaisalmer, Pariwar and Goru Formations of the Jaisalmer basin, Rajasthan, India, exhibits a variety of primary and secondary fluid inclusions. Most of them are hydrocarbon bearing fluid inclusions. Laser Raman studies indicate that the primary fluid inclusions were mostly having aliphatic hydrocarbons with lower degree of maturity, while the secondary fluid inclusions were generally with aliphatic as well as aromatic hydrocarbons with higher degree of maturity. This inference was consistent with their fluorescence characteristics. The homogenization temperatures of primary monophase CH4 rich fluid inclusions varied from -80 degrees C to -100 degrees C, whereas the primary biphase fluid inclusions (CH4-CO2) homogenized between +80 degrees C and +150 degrees C. The secondary petroleum rich monophase fluid inclusions were having homogenization temperature between -80 degrees C to -90 degrees C, whereas the secondary biphase fluid inclusions homogenized between +130 degrees C and +180 degrees C. Most of the secondary biphase fluid inclusions were having the mixtures of H2O-CO2-NaCl, and were identified on the basis clathrate formation and they got homogenized between +140 degrees C and +250 degrees C. The three past events of migration of petroleum inferred in the host rock which were marked by the presence of characteristic secondary fluid inclusions. They were identified on the basis of cross-cutting relationships of different trails of fluid inclusions in the quartz. The cement generation in the basin might have been occurred in two stages as per the fluid inclusion petrography.