China's first offshore ultra-deep extended-reach drilling project, the Enping 21-4 Oilfield, has commenced full operation in the Pearl River Mouth Basin of the South China Sea, announced the field's operator China National Offshore Oil Corporation (CNOOC) on Thursday.
The Enping 21-4 oilfield, located about 200 kilometers southwest of Shenzhen, features an average water depth of 86 meters. It was developed through two ultra-deep, extended-reach wells, which are based on an offshore platform situated eight kilometers away.
One of these wells, named A1H, began operation in April of this year. With a depth of 9,508 meters and a horizontal displacement of 8,689 meters, it set two records: the deepest well with the longest horizontal reach in China's offshore drilling.
Extended-reach wells utilize a specialized drilling technique where the drilling does not proceed straight downward. Instead, after reaching a certain depth, the drill takes a turn to access the predetermined oil zone. This method allows precise development of oil and gas fields located several kilometers away from the drilling platform.
"The Enping 21-4 oilfield is of rather small reserve, and its economic benefit would be low if conventional technology is applied to its development. We use extended-reach drilling technology for long-distance development, this also offers a useful reference for the development of similar offshore oil and gas fields in China," said Wan Nianhui, the oilfield's president.
Such a drilling method could be used for efficient development of marginal oil resources around several hundred offshore oil fields in the basin, saving investment costs by some 40 percent and rediscovering the economic viability of fields that were once considered unprofitable or of limited value. It has the potential to expand the exploitable marginal oil reserves in the basin to over 50 million tons.
"This time in the Enping 21-4 oilfield, the two extended-reach wells have set four new national records and yielded 13 technical achievements across five categories. Utilizing this approach, oil and gas resources within a 10,000-meter radius of offshore platforms can be harnessed in the future, significantly improving the development efficiency of oil and gas fields," said Zhang Weiguo, general manager of the Deepwater Engineering Technology Center under CNOOC's Shenzhen Branch.
China's 1st ultra-deep extended-reach drilling project in operation
