oa Role of Sedimentology and Petrography in the Development of Khuff Reservoirs,<br>Bahrain Field - a Case Study

This paper highlights the petrography and sedimentology study carried out for Khuff gas reservoir of<br>Bahrain field. The topics include a review of the core analysis Electrical, Sonic, Full bore Formation<br>Micro Imager (FMI) logs, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) studies. The<br>study helped in explaining the mineralogy, dolomitization, diagenesis and evolution of the pore system of the reservoir.<br>The study indicated four different facies (a) Peloidal-lime-grainstone to Packstone, Skeletal lime<br>grainstone facies which is interpreted as being very coarse grained, deposited relatively with a high<br>energy, shoal environment, (b) Bioturbated-Lime- Mudstone & Lime-wackestones facies, which are<br>interpreted to be that of lagnoonal environment. (c) Dolomudstone facies, with dolomitized mud<br>supported sediments are interpreted as shallow, restricted lagoon in a supratidal setting. (d)<br>Dolopackstone facies, interpreted as being deposited within a shoal environment.<br>According to the study, depositional environment is identified as lagoonal during transgressive phase<br>and shoal during regressive phase. The diagenesis is dominated by compaction indicated by tight<br>textures in mud rich samples and deformation of framework grains. Porosity enhancement is seen due<br>to the grain dissolution and rare fracturing while porosity destruction is carried by compaction of<br>sparse calcite cement and dolomite. Calcite is the dominant mineral in some samples. The clay content<br>is found to be very minor.<br>SEM analysis showed the presence of good porosity including inter-particle and inter-crystalline<br>porosity. The average porosity is about 17% and the permeability is about 60 md and very few<br>fractures are observed in this formation.<br>This integrated study helped in understanding the reservoir heterogeneity and its potential based on<br>which current wells were completed appropriately and this would also aid in completing the future wells productively.