OTC ’15: Chevron’s Jack-St Malo – Lower Tertiary success, on time and under budget
PRAMOD KULKARNI, Editor
HOUSTON – The Lower Tertiary Wilcox trend is at the leading edge of the deepwater frontier in the Gulf of Mexico. Following the successes of Shell’s Perdido (120 Mbopd) and Petrobras’ Cascade (40 Mbopd) is Chevron’s Jack-St Malo (JSM) field, which produced first oil on December 1, 2014. JSM is now producing 70 Mbopd.
Steve Thurston, Chevron’s Vice President of Exploration & Projects, set the stage for an overview of the JSM project at a luncheon session on Wednesday at the OTC, by describing the prolific nature of the Gulf of Mexico basins. “As an industry, we’ve produced, thus far, 40 Bboe from the Gulf of Mexico shelf and 9 Bboe from deepwater fields. About 24 Bboe have been discovered from deepwater fields, and we expect additional deepwater discoveries of 40 Bboe. As such, the deepwater will be producing as much oil as production from the shelf.”
Speaking about the Lower Tertiary activity, Thurston reported that a total of 55 wells have been drilled in the trend, of which Chevron has drilled 20. “Our success ratio for the wildcat wells is 58%, resulting in 23 fields with commercial potential.”
Thurston said that Lower Tertiary field can be prolific, but there are significant technical and logistical challenges. “The wells have to be drilled in water depths down to 8,000 ft and each well extends to 26,000 ft to 36,000 ft. However, the reservoir intervals are typically over 1,000-ft thick.”
Jack and St Malo are two fields, 25 mi apart. Next on the agenda is tie-back from Exxon Mobil’s Julia field. Lower Tertiary fields to follow JSM are Moccasin and Buckskin.
“We developed the Jack and St Malo as a joint development to reduce cost and capture scale, accomplished the field development two stages for learning and risk reduction,” Thurston explained. “The design is intended to incorporate future need and applied news technologies on a selective basis.”
Stage 1 of the JSM had as its goal production level of 170,000 bopd from 10 subsea producers, the use of seafloor single-phase pumps and provisions for tie-backs. Stage 2 will involve acquisition of new seismic data, drilling of two additional wells and associated subsea infrastructure.
“Among the new technologies applied at JSM included detailed seismic imaging through ocean-bottom cable (OBC) seismic,” Thurston explained. “For effective stimulations, we worked with Halliburton to develop single-trip, multi-zone ESTMZ frack pack completions with 1,400-ft laterals at 28,000-ft depth. For seafloor boosting, we worked with Cameron and OneSubsea to develop single-phase pumps with 30,000 psi shut-in pressure rating and capacity of 60,000 bopd.”
The result? JSM was accomplished over a timeline starting with discovery in 2003, first production on Dec. 1, 2014, and development drilling to take place 2014-2017. “First oil occurred on schedule,” Thurston reported. “We had only three days away from work, despite over 20 million man-hr of work. We now have five wells producing 70,000 bopd at natural flow, with on-budget stage 1 investment of $7 billion.”
“The outlook for Chevron includes development at NW Keathley Canyon, Buckskin, Moccasin and Anchor fields, Thurston concluded. “We have plenty of work to do.”
