This latest discovery can be attributed to three factors — revisiting the geophysical interpretation of seismic data in the area, making a bold decision that went against conventional thinking and drilling with new technology. The Shuaiba Formation has been yielding oil for Oman for quite some time. It contains, for example, the reservoirs of the Yibal field, which is now into its fourth decade of production. The Malaan location was first targeted in the year 2000 as a likely place to find more oil reserves in the formation. Yet the first well drilled there — Malaan-1 — proved a disappointment when it failed to produce oil at economic flow rates. However, perseverance and further studies of the seismic and well data uncovered an ancient shoreline stretching along the edge of the Malaan structure. "The analysis of the seismic and well data led to a revised interpretation of the geological setting, indicating a stratigraphic trap," said Stephen Hiebert, senior interpreter at PDO. A stratigraphic trap is a geological formation containing hydrocarbons within permeable rocks that have been sealed by impermeable sedimentary rocks deposited around it. Unlike the more common structural traps, stratigraphic traps are not characterised by folding or faulting, which can be readily detected on seismic images. In the case of the Malaan structure the stratigraphic trap was created by sedimentation around shoal rocks formed by ancient marine organisms, such as coral. "The new setting suggested that we could expect better-quality reservoirs and a higher oil content down the flank of the Malaan structure. But this theory is counter to the conventional thinking of petroleum prospectors, which holds that the most likely place for good oil production is at the crest of a geological structure," Hiebert added. Nevertheless, PDO took the risk. And in February of this year the Malaan-2 well, drilled horizontally around the flank of the structure, began to deliver 1,800 barrels of oil per day to the nearby Lekhwair production facilities. In June an appraisal well, Malaan-3, was successfully completed and tested, producing 2,600 barrels of oil per day. This success might not have been possible without the deployment of a new drilling technology that, for the first time ever, was used in an exploration well. Schlumberger's new Logging While Drilling (LWD) tool enabled the drillers to keep the well within the best-quality rock formation by detecting the boundary of the formation. "PDO and Schlumberger created value for Oman by combining this new technology and teamwork," said Mohsin Al Hadhrami of Schlumberger LWD Support. "Experience has shown that the most productive zones of the Shuaiba are often in the top few metres of the reservoir, just below overlying shale," said Mohammed Al Harthy, team leader of Shallow-oil, Near-field Exploration. "Without the use of the LWD tool, the successful production of Malaan-2 would not have been realised. The tool enabled us to steer the drill bit so that it was on average 1.8 metres below the top of the reservoir for a distance of 700 metres. This represents for us a step-change in 'geosteering' horizontal wells through relatively thin reservoirs. PDO now has good reason to review other dormant prospects in northern Oman that have a similar seismic image as Malaan. We haven't finished with the Shuaiba yet." Petroleum Development Oman is the major exploration and production company in the Sultanate and it accounts for about 90 per cent of the country's crude-oil production and nearly all of its natural-gas supply. PIN//Times Of Oman