Insight Value of the Stress Field Dynamics in Hydrocarbon Exploration Within the Highly Deformed Thrust Belts; An Example From Lesser and Outer Himalayas Along Main Boundary Thrust Fault, Hazara-Margalla Hill Ranges, North Pakistan

Abstract

Abstract

One of the most striking aspects of the Himalayan orogeny is the lateral continuity of its major tectonic elements. The Main Boundary Thrust Fault (MBT) is oriented east-west with a pronounced convexity to the north-northeast, makes a sharp bend around the Hazara Kashmir Syntaxis in north Pakistan forming the topographic front of the southern Hill ranges of the Lesser Himalayas. The present subsurface seismic data along with the earth quake seismology and recent Geological modelling indicates that the Main Boundary Thrust (MBT) appears to be involved in thick-skinned mode of deformation.

This paper attempts to the structural and stratigraphic relationships of the hanging and footwall of the Main Boundary Thrust (MBT) as well as its hydrocarbon prospectivity while understanding the stress fields dynamics of the structures associated with the MBT; a boundary fault between lesser and outer Himalayas along Hazara-Margalla hill ranges. At least three distinct lines of folding events are present within the hanging wall strata of the MBT, detached at the level of Jurassic rocks which are structurally linked to a regional basal detachment at the base of Precambrian rocks, fabricate the Hazara-Margalla Hill ranges. At surface steep dips and a strong retro-folding events are prominent that supports the idea of transpression.

At present level of knowledge after the drilled section (Well X-1) in the hanging wall of Main Boundary Thrust (MBT) proves that surface to near surface structures do not mimic with the lower subsurface configuration on seismic data. Confrontation of dips measured in the well X-1 and seismic sections indicate that the strong reflection packages are actually representing major shear zones which were initially anticipated as an antiform and thus seems that its main subsurface high (antiform) may be somewhere towards southwest or northeast of its strike extension, which would be actual potential exploration lead.

In order to address such type of disharmonically deformed, peculiar structural belt and thrust nappes associated with regional fault boundary (MBT), structures stress fields along with the associated subsurface gravitational field anomalies must be analyzed and integrated with the structural model and seismic data cube in order to understand the proper sub-thrust structural trap geometry for hydrocarbon exploration in the vicinity of Hazara-Margalla Hills, north Pakistan as well as other highly deformed fold and thrust belts in the world.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016