Petroleum play in North Pakistan comprises of naturally fractured reservoirs (NFR) both in clastics and carbonates. These fractures play key role in the determination of reservoir quality and production behavior of the formations and is a subject of interest for E & P companies particularly working in Kohat Plateau.
In TAL Block, naturally fractured Lockhart formation has very low matrix porosity and fractures provide the main source for storage and fluid flow in it. It has also been observed that all the fracture sets in carbonate reservoirs do not contribute to flow. Flow variations have been observed with different fracture trends identified from open-hole logs based on their connectivity, fracture apertures and secondary porosity. This leads to the development of an integrated approach using existing information from open hole logs, image logs, formation tester and production logs to optimize the reservoir modeling, history matching and selection of future perforation intervals.
In this paper, data from six wells located in different structures in TAL Block has been utilized to study the behavior of naturally fractured carbonate reservoir. During the study, it was observed that in some wells, the top part of Lockhart formation was contributing more to production while in others, the bottom part was more productive. These flow variations could be associated with different fracture trends, their connectivity, fracture apertures and secondary porosity. This problem was addressed by sub-dividing Lockhart in to different layers/facies based on fracture evaluation (types, density, secondary porosity, nodularity and rock texture), open hole logs, formation tester results and production logs interpretation.