oa Exploration Campaign Drilling for Low-Relief Channel-Sand Prospects, South Central Oman

During 2009/10, PDO Exploration is executing a ‘peephole’ exploration/appraisal campaign for 2<br>prospects in the vicinity of a field which was developed using several grid drilling campaigns since<br>1990. The Field, discovered in 1986, is a low relief anticline (approximately 45m relief and 100 km2<br>closure) located in central Oman. The oil is produced from the Permian Upper Gharif channel sands,<br>deposited within a predominantly muddy floodplain and hence with a relatively low net/gross of some<br>30%. The oil is 24o API with a viscosity of 45cP. Experience, gained during the appraisal and early<br>development stages of the field, is being brought to bear on the exploration and appraisal of its<br>satellites. The initial field development was based on the drilling of high-angle, deviated wells aimed at<br>maximising the chance of finding the fluvial channels. This achieved a low rate of success at a high<br>drilling cost. A new strategy of drilling multiple, low-cost, vertical wells (peepholes) was implemented.<br>The economics of this campaign drilling could tolerate the expected low success rate, eventually<br>improving understanding of the reservoir distribution patterns and reducing uncertainty in targeting<br>productive sands. The first peephole campaign in the field started in 2001. Twenty wells were drilled<br>with a success rate of 60%. The ensuing second campaign drilled another 12 wells with a success rate<br>of 66 %. Both campaigns resulted in a substantial production increase and met both the economic and<br>geological success criteria. Using this field development as an analogue, 12 wells have been<br>incorporated on the Exploration drilling sequence to appraise the first satellite prospect. A further 10<br>wells are planned on a second prospect in 2010. This paper will share the results and learnings of the<br>first drilling campaign. The first campaign well proved an oil bearing zone with a much higher net/gross<br>than the historical exploration well.