Structural Analysis of the Kirthar Fold Belt and Lower Indus Basin, Southern Pakistan.
Dias, Jose V.
Honours Degree, 2006
University of Adelaide
The Kirthar Fold Belt (KFB) has been a recent focus of attention for hydrocarbon and mineral exploration, and in recent years, there have been several large gas discoveries in the mountain front and foreland of the fold belt. Exploration success in the foreland led to activity in the hinterland of the fold belt, where many large structures remain undrilled. Understanding the type of structure and the involvement, or noninvolvement, of the reservoir within structural closure is critical to hydrocarbon exploration in the area.
This study documents and explains the structural style and evolution of the Zamzama and Hallel structures, located in the KFB. The shortening estimates along the Zamzama structure describe deformation which is similar to that of fault propagation folds. Hence the Zamzama structure is interpreted as a fault propagation fold. This also implies that there exists a decollement below the structure and hence that Zamzama is a thin skinned structure with no basement involvement in the deformation.
The Hallel structure is located and interpreted using seismic lines and well data. The well picks suggested a substantial thickening of the Laki Formation, which is believed to be due to a structural repetition of the Formation or a stratigraphic growth sequence. Hence three possible structural models (simple thrust, back thrust and passive roof duplex system) and one stratigraphic model (carbonate buildup) are presented and discussed.
Fault seal analysis is performed to test the sealing capacity of the Zamzama and Hallel faults, using juxtaposition and shale gouge ratio diagrams. This analysis suggests evidence for a potential cross-fault leakage where the Pab is juxtaposed against itself along the Zamzama fault, creating a sand-sand juxtaposition window. The Hallel fault F1 partially seals the reservoir, while the Hallel fault F2 is interpreted to be similar to the Zamzama fault since they have a similar stratigraphy and fault throw.