Identification of sealing potential through fault seal analysis: a case study of Badin area, Lower Indus Basin, Pakistan

Abstract

The sealing potential of a fault can be originated from reservoir/nonreservoir rock juxtaposition. The present study focuses on the assessment of the sealing potential of the Lower Goru Formation of Badin area, Lower Indus Basin, Pakistan. The uni-directional force is one of the causes of leakage through the upper reservoirs of Lower Goru Formation, i.e. sand A, B and C and thus made a good seal as sand D. The fault properties associated with sealing capacity and leakage are estimated using algorithms. These algorithms are based on the juxtaposition of the reservoir rock against sealing lithology, deformation and present stage of stress regime within the fault plane relative to leakage. Time and depth contour maps of top of the Lower Goru Formation represent a half-graben structure showing uni-directional force in the area. An Allan-type diagram depicted a sand-sand juxtaposition for sand A and juxtaposition of sand A with sand B, thus eliminating any chances of sealing conditions. A similar diagram confirmed shale-sand juxtaposition for sands C and D. The juxtaposition diagram referred to an increase in shale gouge ratio (SGR) values from sand A to sand D with maximum values at sand D, thus classifying good fault sealing potential at sand D. Therefore, it is confirmed that sealing capacity of the fault (F2) increases from sand A (poor seal) where SGR = 0.44% – 0.9% and shale smear factor (SSF) = 0.23 – 1 to sand D (moderate seal) where SGR = 10% – 44% and SSF = 0.05 – 0.22 which means that sand D is more sealed than any other sand in the study area.