Abstract:
Manzalai is one of the latest gas fields in the Kohat sub-Basin which is mostly tectonically disturbed due to the presence of salt in the sub-surface. The basic objective of the research is to understand the sub-surface geometry, crustal shortening nature, and
styles of deformation of the Manzalai area. The study also aimed to evaluate reservoir potential and reserve estimation of Eocene and Paleocene reservoirs. To achieve the target, structural interpretation along with the well analysis of the Manzalai field was carried out, followed by a cross-section balancing technique to properly comprehend the scale of deformation at the sub-tectonic level. To accomplish the structural geometry, horizons were demarcated on the seismic profiles and mapped to describe the structural variations and complexity in the subsurface. In the last step, 2D structural restoration model is generated by using MOVE software. Seismic structural interpretation revealed an overall anticlinal geometry with an axial plane trending in NW-SE direction at the Cretaceous-Paleocene level with major disrupt of oppositely dipping fault F2 and F3 bounding an up-thrown block. By Following the application of various petrophysical parameters, it is determined that the Lumshiwal Formation holds superior reservoir characteristics compared to the Hangu Formation. 2D structural restoration model revealed maximum shortening along the North dipping fore thrust and sequential development of a back thrust resulting into a pop-up geometry followed by compressional geometries at the younger stratigraphic level.
