Oilex Ltd, an oil and gas exploration and production company focused on onshore unconventional opportunities around the Indian Ocean Rim, has provided an update in relation to flowback operations at Cambay-77H well in Cambay Basin, Gujarat. As announced last month, the chemical treatment and well intervention was completed and a significant improvement in recovery rates was observed.
During flowback operations Oilex planned to replace the frac tree with a standard production tree. As part of removing the frac tree, two retrievable bridge plugs (RBP) are set in the well as safety barriers against the well flowing. In this instance, the first plug did not set and seal properly and moved downhole where it became stuck. Recovery operations were successfully completed in about 13 days.
Subsequent to the operations and further chemical treatment, flowback and clean-up recommenced including recovery of frac water, oil and gas, and the well exhibited significantly improved performance. While the flowing tubing head pressure remains quite high compared to previous flow periods, nitrogen lift and reduced choke settings are being utilised to minimise the reintroduction of potential blockages.
From 1,130 hours October 4 to October 6, 2014, after a second acid treatment subsequent to the recovery of the RBP: Average liquid (oil and water) recovery rate – 229 barrels per day; average gas rate – 0.41 mmscfd, (excluding nitrogen); estimated 76 per cent of frac water recovered; choke size varied between 20-22 (64ths inch); and average flowing tubing head pressure – 857 psig.
Efforts are underway to optimise all the operational parameters for the well to improve the water recovery, including ceasing to use nitrogen lift, to hasten commencement of the production test. As this is a proof-of-concept well and the first well of this type to achieve flow back in the Cambay Basin, valuable data and information is being compiled for use in future activities.
Ron Miller, Managing Director, Oilex, said, “Oil and gas continue to be produced along with recovery of frac water. Oil is sold to a local refinery and the application process to sell Cambay-77H gas has commenced. It is unfortunate that the RBP malfunctioned, especially after the contractor had twice successfully completed the same operation on Cambay-77H. Setting aside the operational delays to recover the RBP and clean the well bore, Oilex is pleased with the well’s performance at a relatively small choke. Flowback is all about removing the water put into the reservoir during frac and coil tubing operations, as this impairs the hydrocarbon production rates. We look forward to the improved water recovery leading to better oil and gas production.”