On December 8,1989 the Sidki production platform was struck and severely damaged by a cargo ship that had ventured outside the shipping lanes in the southern Gulf of Suez. The collision rendered the platform a total loss, and all wells had to be plugged and abandoned. The Sidki field production rate at the time of the accident was 6750 BOPD and 2836 SCF/STBO gas-oil ratio (GOR) from six active wells with three wells shut in.
Redevelopment commenced in 1993 with the setting of a new platform and initial plans to drill nine replacement wells to recover an estimated remaining 19.2 MMSTBO (to January 2006). But rather than simply redrill the existing wells, engineers examined ways to improve the redevelopment plan and optimize the remaining oil recovery from the Nubia reservoir. This paper discusses how one company applied advanced engineering methods to optimize this redevelopment.
Engineers systematically evaluated the static reservoir conditions found during drilling of the first three redevelopment wells, and then improved oil production rates and recovery by placing four additional 2000 foot horizontal wells at strategic locations. Through re-engineering the new field development, the very accident that so spectacularly destroyed the platform ultimately yielded a "second chance" for Sidki. Production during June, 1996 now averages 20,092 BOPD from only seven wells. Ultimate primary redevelopment reserves are expected to total 24.5 MMSTBO, with potential waterflooding increasing reserves to 38.6 MMSTBO.
The Sidki field, as shown in Fig. 1, is located in the southern Gulf of Suez, Egypt. The field is also located primarily within the GS 382 concession block, and was discovered with the drilling of the exploratory well GS 382-1A in January 1976. A 12 drilling slot platform, the Sidki "A", was subsequently set in 271 feet of water and production commenced in December 1977.
Production from the Sidki platform was abruptly halted on December 8, 1989 when the platform was struck by the errant cargo ship. The collision rotated and tilted the platform deck, ruptured well risers, and the collapsing deck severely damaged several wellheads (Fig. 2). Of the six wells naturally flowing on the platform at the time of the accident, control of only one well, Sidki 5A, was lost due to the failure of the subsurface safety valve to close. Sidki 5A was brought under control within one week, but the platform was considered a total loss and all wells were eventually plugged and abandoned. Two other remote fields which had their production routed through the Sidki platform were shut in as well. Additional details about the accident and emergency response are available in Reference 1.
Sidki production is from the Nubia sandstone at an average depth of 10,600 feet subsea. The 1000 foot thick Nubia is tilted at 30 degrees, providing ample opportunity for gravity segregation of reservoir fluids. Reservoir pressure reduction from production and limited aquifer support caused a large secondary gas cap to subsequently develop from the reservoir crest at -9400 feet subsea to -10480 feet subsea. Constant problems with gas coning plagued the Sidki wells from the start of production in 1977 due to this expanding gas cap. Redevelopment planning would have to deal with this problem.
Redevelopment work commenced in 1993 to replace the lost "A" platform and wells. With insurance proceeds funding the redevelopment, reservoir engineering plans to enhance ultimate oil recovery and rate had to work within the constraints of the insurance program. P. 231
