Evaluation of source rocks using one dimensional maturity modeling in Lower Indus Basin, Pakistan

Out of the numerous potential petroleum source rocks, present in the Lower Indus Basin, Sembar Formation is the most promising rock unit. One-dimensional maturity modeling of source rocks in Lower Indus Basin is conducted to find out the lateral and vertical extents of maturity levels of Sembar Formation. This study is also aimed to infer the extent of petroleum generation in the region. The study is based on one-dimensional basin modeling (maturity modeling) of 22 main exploration wells, drilled in the region. Stratigraphic input to model includes thickness, formation tops, ages of deposition and lithology, age and amounts of erosion, and ages of non-depositional events. Isopach map of Sembar Formation demonstrates the lateral and vertical extents of the formation, whereas temperature and vitrinite reflectance (Ro) contour maps indicate its maturity levels in different parts of the study area. It is inferred that the thickness of the overlying rock units (overburden) control the maturity level of the Sembar Formation. It may be noticed that the findings of this study are fully in conformity with the ground realities of the Lower Indus Basin. Discovery patterns and the lateral distribution of various types of hydrocarbons (such as oil, condensate, and dry gas) in the region coincide with the modeling results of the study, as can be seen from the burial history diagrams of the 12 wells. The study shows that Sembar Formation is mature enough to be considered as conventional petroleum source rock or can be exploit as unconventional shale gas/oil source.