North Oman Tight Gas Development

摘要

Production from conventional non-associated gas fields operated by PDO in North Oman has largely met demand from Oman’s domestic and LNG export requirements to-date. However, with domestic demand growing at around 5% per year and with continuing significant LNG sales contracts to be met, exploration has been stepped up in recent years to meet this demand, especially as new opportunities from conventional gas accumulations become rarer. Exploration successes over the last five years are increasingly restricted to deep, tight Amin sandstone reservoirs with porosities ranging from 2 to 10% and (ambient) permeabilities from 0.001 to 1 mD. Following an extensive exploration campaign including a hunt for Basin Centre Gas during 2009-2011 focus has now shifted to the appraisal and early development of the Khulud cluster of fields, located in the Yibal-Fahud area. Significant challenges exist over and above the tightness of the rock: target reservoirs are deep (4700-5200 m below Ground Level) and have high reservoir temperatures (160 to 190°C). Rock geomechanics are a critical issue: high fracture gradients mean that not all hydraulic fracturing jobs are successful. On top of all this, longer term well production will be impacted by relatively high Condensate Gas Ratios and associated water production. With significant Gas-In-Place, the presence of infrastructure, notably the nearby Yibal gas processing plant, and the proven presence of sweet spots make the Khulud Cluster a prime candidate to provide the 2nd wave of production following conventional reservoirs and a possible working model for future tight and unconventional gas developments. A 1 mln m~3/d capacity Early Production System (EPS) is currently being constructed to de-risk and ‘right-size’ a cluster development by assessing Expected UltimateRecovery (EUR) per well.