State-owned Oil and Natural Gas Corporation (ONGC) has kicked off over Rs 8,800-crore redevelopment of the southern part of its Mumbai High fields, using a cost effective technology to maintain output from the prime western offshore fields.
"The Mumbai High South redevelopment Phase-II project will cost Rs 8,813.41 crore," a company official said.
The giant Mumbai High oil and gas field remains a challenge since its discovery in 1974. In its chequered production profile, the field hit a peak of 400,000 barrels per day before falling to current levels of 210,000 bpd, causing concerns in reservoir management.
"ONGC has decisively initiated schemes to maintain production from this field," he said, adding the complex reservoir has thin oil bearing zones, as slim as 3 metres, with a highly heterogeneous flow capacity of rock, varying in thickness.
The present scheme envisages incremental gain of 18.31 million tonnes of oil and 2.70 billion cubic meters of gas through drilling of 75 new wells and intervention in existing wells. The work includes enhancement of oil and gas processing capacity through installation of one process platform bridge connected to the existing ICP platform and installation of four new well head platforms.
"The latest platform, RS12 is a special innovation, first for ONGC and India, in the sense that this is a 16-slot platform rather than a conventional 9-slot or 12-slot platform," the official said. This means as many as 16 wells can be drilled from this platform. "Eleven wells are planned for drilling in the current phase of development," he said.
As opposed to conventional facilities for docking of drilling rigs for drilling wells, the platform is designed to accommodate the drilling rig on board.
The soil testing data of the platform location indicated that this part of Mumbai High field was likely to be 'punch through' and not hard enough to bear the load of a conventional jack-up rig. "The rig mounted 16-slot platform option chosen by ONGC has provided a cost-effective solution to development drilling and a technically feasible solution to the 'punch through' problem," he said.
The platform mounted rig technology has provided the opportunity of drilling wells, using modular rigs that are cheaper than conventional jack-up drilling rigs, at a cost of $169 million. NPCC of Abu Dhabi is installing the platform and scheduling completion by April 2011.
"Intervention in the wells in future can also be done by modular work-over rigs. This is expected to be particularly cost effective as the wells are planned to be ultimately put on production using electric submersible pumps (ESPs) for pumping out the oil from the bottom of the wells rather than using gas-lift for lifting and since the ESPs may need more frequent rig intervention for servicing, the cheaper platform mounted modular rig option will be available," he said.
The expected peak production of 12,000 barrels from RS12 will begin in 2012. "The challenge of proper placement of long horizontal drainholes in oil bearing zones of 3 to 5 meter thickness at depth of over 1,400 meter is being met through use of such tools and technologies," the official said.
Advanced well monitoring systems are being used during drilling with real time monitoring of drilling progress by ONGC geo-scientists at base through satellite data transmission and communication, he added.
