Abstract: Use of the Acoustic Scanning Tool in the Identification of Fractures: A Case Study from Pakistan

E. G. Bowles, J. Buchanan, C. Izatt, P. Elkington

Sandstones belonging to the Pab/Ranikot Formations of Palaeocene/Upper Cretaceous age are important gas/condensate bearing reservoirs in the Sulaiman Fold Belt (Central Pakistan). These indurated sandstones have poor to moderate porosites, but have enhanced permeabilities due to the presence of an extensive open fracture system. Evaluation of these fractures in the subsurface has proven difficult until the advent of the Acoustic Scanning Tool (AST). This borehole device contains a rotating transducer which makes a continuous scan of the borehole wall using repeated short bursts of sound energy. As the tool traverses the borehole, the surface computer constructs images from the travel time and amplitude data from which structural information pertaining to the fractures can be made.

The AST was run successfully on the British Gas Savi Ragha -1 discovery well and post well evaluation has allowed for a complete qualitative and quantitive analysis to be made of the fracture system. The well also offered a unique opportunity to record the influence of the fractures in reservoir production since the AST was run before and after completion of a successful openhole barefoot test.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France