Rick Hagar
Gulf Coast News Editor
Placid Oil Co. and partners have shut down their pioneering Green Canyon Block 29 floating/subsea drilling and production system in the Gulf of Mexico.
Operations to plug and abandon the ultradeepwater site have begun in the wake of the Apr. 16 shutdown. The project's export pipeline bundle, Ship Shoal Block 207 processing platform, and Green Canyon 29 subsea drilling/production template will be mothballed in place.
Phil Clarke, Placid's vice-president of operations, said sustainable flow rates from the few wells drilled at the site were not high enough to justify continuation of the project.
Conoco Inc. has had similar problems with certain completions at its Jolliet tension leg well platform (TLWP) project in 1,750 ft of water on Green Canyon Block 184. Other completions, however, are performing as or better than expected.
Placid's $400 million Green Canyon 29 project went on stream in late 1988, signaling a new era of ultradeepwater development in the gulf (OGJ, Oct. 24, 1988, p. 28). At a time when other operators are stepping up exploration/development campaigns in the gulf's ultradeepwater, the failure at Green Canyon 29 serves as a reminder of the high risks involved (OGJ, Nov. 13, 1989, p. 21).
Clarke said Placid will regroup and continue an exploration/development program elsewhere. The company plans to participate in 20 wells this year.
Placid's partners in the Green Canyon 29 project are Enserch Exploration Partners Ltd., Louisiana-Hunt Petroleum Corp., Opubco Resources Inc., Hi Production Co., Penrod Drilling Co., Petro Hunt Corp., and Prosper Energy Corp.
WHAT HAPPENED
Placid and partners decided to cease operations after the Green Canyon 29 system's 31-4 satellite well on Green Canyon Block 31 was lost due to downhole equipment failure.
The well, in 2,243 ft of water, established the current world water depth record for production (OGJ, Nov. 21, 1988, p 31).
The 31-4 well went on stream Nov. 14, 1988, flowing 2.5 MMcfd of gas. The flow rate was gradually increased to 8.15 MMcfd and 1,066 b/d of condensate.
But the flow rate soon started an unexpected, steady decline, said Clarke. Late last year production ceased due to a downhole mechanical problem.
Two other subsea satellite wells and one template well had been drilled as part of the project, which was to involve as many as eight satellite and 12 template wells.
The 999-1 satellite well on Ewing Bank Block 999 was the first completed and the first to develop problems. The well sanded up early last year due to a gravel pack failure.
Clarke said the well had been gravel packed in two zones. The lower zone was being produced first. When the gravel pack failed, the deep zone was plugged and the upper zone perforated.
The 999-1 was still producing from the upper zone when it was shut in Apr. 16, but the flow rate had declined to moderate rates.
The 31-6 satellite well, in the same water depth as the 31-4 well on Green Canyon 31, had gravel pack problems from the day it went on stream, Clarke said. The single template well brought on stream also never performed as anticipated, he said.
SITE TO BE ABANDONED
Placid and partners are plugging and abandoning the four Green Canyon 29 wells.
Once that operation is complete, they will begin pulling the production riser and recovering things such as control systems on the subsea template and the floating platform's mooring system.
Clarke expects the operation to take 3 months. Then the Penrod 72 floating drilling/production platform will be removed and mothballed.
Placid plans to sell the recovered equipment to other ultradeepwater operators. The mothballed 16 in. and 14 in. export pipeline bundle, Ship Shoal 207 platform, and 24 well subsea template also will be offered for sale.
CONOCO'S EXPERIENCE
Cor Langewis, Conoco's general manager of the Jolliet project, said the company and its partners, OXY U.S.A. Inc. and Texaco Inc., attempted high risk completions in some low resistivity sands in the field. They haven't been successful.
Drillstem tests of the sands indicate good recovery, and initial flow rates from completions are high. But flow rates soon began to die.
The sands, which are shaly and silty, do not jeopardize the Jolliet project, Langewis said. Jolliet involves about 100 pay sands in a highly faulted area. The development plan is to tap 50-60 of the sands during a 20 year period starting with the deep pays and working up the hole with 20 wells, which were drilled prior to installation of the TLWP last year.
Langewis said the types of pay sands in the reservoir are varied between high risk, low resistivity sands that have never been successfully produced and what he terms good pay sands.
Completions in good sands, he said, have performed as or better than anticipated.
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