Integrated Geophysical Analysis For The Unconventional Potential Of The Sembar Formation, Badin Area, Lower Indus Basin, Pakistan

Abstract

An ever-increasing energy demand and a huge load over natural reserves has led to a deficiency in the amount of oil and gas resources available across the globe. The compensation for such demands can only be achieved using alternative routes. Unconventional shale gas reserves therefore play a pivotal role in shaping the economic future of any country. Pakistan being an industrially burgeoning country is no different in that perspective. With that in mind, studying shale gas reserves within the basins of Pakistan is crucial for a geophysicist. A study shows that approximately 51 TCF of shale gas reserves in Pakistan are recoverable. Major source rocks in context of unconventional resource potential in Pakistan include Sembar, Talhar, Ranikot, and Patala shales. This study focuses on demarcation and integrated characterization of Sembar formation using Tarai Deep – 02 well located in Tarai area in Central Indus Basin, Pakistan. Horizon demarcation, structural interpretation, Total Organic Content (TOC) estimation using multiple techniques, petrophysical and petroelastic properties evaluation, and TOC seismic section generation were used as the main tools for characterization of the formation. Sembar formation was marked using seismic to well tie. Presence of normal faults pertaining to the extensional forces led to creation of extensional regime within the vicinity. Petrophysical analysis of the wells showed high shale volume (VSH) values and low effective porosity. TOC curves generated Passey's ΔLogR, Schmoker's approach, and Schwarzkopf formulation gave reasonable TOC results for the Sembar formation, averaging 3-4%. Rock physics modelling is done on well Tarai Deep – 02 and calculating the elastic properties of the subsurface. These elastic properties calculated now has the information of subsurface rock properties and is more accurate picture describer of the subsurface. Monte Carlo simulation is used to construct uncertainty models for shale probability in the Sembar formation of Tarai deep-02. These elastic properties are then used for stochastic inversion. Calculated TOC’s are spatially distributed by the inverted volume and TOC is distributed all along the seismic