Oil and Natural Gas Corporation (ONGC) operates the Vasai East Field in western offshore India. The reservoir is challenging to drill and complete because of the inherent risks of gas and water coning, permeability differences, and declining reservoir pressures. An innovative horizontal completion strategy for new wells to meet the many unusual challenges was required. The need for appropriate zonal isolation was identified after the wells in the Vasai West Field had been completed without segmentation in the open hole. The requirements included:

  • Oil production without breakthrough of gas or water

  • Effective hydraulic seal in washed-out hole conditions

  • Contingency options for intervention, if needed

  • Equipment to withstand high bottomhole static temperature.

This paper describes how the challenges were met using swellable-packer, high-temperature isolation systems placed between perforated tubing/sliding-sleeve circulating devices and blank pipe spaced out across the oil-bearing zones. The swellable packer systems were located at the ends of each facies change to isolate the local high-permeability zones. Swellable packers use expanding rubber around the packer mandrel that expands to seal the annulus and create a permanent seal when it contacts liquid hydrocarbon or water in both cased or openhole environments.

Five wells have been completed in Vasai East field to date with swellable packers in conjunction with pre-perforated liners or sliding sleeves. PLT logs have been run in one of the wells post completion, and isolation has been verified. Low water cuts and low gas/oil ratios (GOR) also verify that the packers isolate the various sections of the wells as planned. On the success of these completions, this technology is currently being planned for ONGC's completions in other fields.

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