tapping the unreachable at jack/st. malo

August 7, 2015 – Technology is not only one of Chevron's major business strategies, but a key driver in tapping oil and gas in reservoirs once thought unreachable. And in the darkness of the deep water in the U.S. Gulf of Mexico, the Jack/St. Malo project is a shining example of Chevron's technological performance, innovation and leadership.

floating production unit

Technologies make the impossible possible at Chevron's Jack/St. Malo project in the deepwater U.S. Gulf of Mexico. Shown here is a view of the platform from the floating production unit's "Floatel."

The Jack/St. Malo floating production unit (FPU) sits in 7,000 feet (2,134 meters) of water and will tap reservoirs beginning at 19,500 feet (5,944 m) beneath the seafloor—representing a total depth of 26,500 feet (8,077 m), or roughly the same height as the last base camp a climber reaches before summiting Mount Everest.

To locate and produce resources from these depths,Chevron has conquered extreme conditions with technological breakthroughs that are game-changers for the company and the industry.

Ocean Bottom Nodes

When costs begin at $300 million to drill and complete a well in the deep water, finding the right spot on the first try is critical. It is also challenging, given the environment of extreme depths, complex geologic faults, and tricky salt features. To improve Chervron's understanding of subsurface structures at the Jack and St. Malo fields, the company utilized a seismic technology known as Ocean Bottom Nodes (OBN) surveying.

In conventional seismic surveying, a boat tows long lines of seismic receivers across the ocean surface. With the OBN technology, remotely operated vehicles safely position 100-pound receivers, or nodes, in a grid directly on the seafloor enabling them to collect high-quality seismic data without the distortion of the water column. The nodes capture sound energy reflected from subsurface geologic structures, like trenches, ridges and salt features, which can distort seismic signals.

Collection of OBN seismic data can occur either before or after field construction. After production begins, the nodes can be returned to the same locations to conduct follow-up time-lapse surveys to show geologists how fluid movement within the rock and reservoir changes during production.

At each of the Jack and St. Malo fields, 1,100 nodes were placed on the seafloor at a water depth of 7,000 feet (2,134 m). The back-to-back surveys lasted 10 months, involving 100 people and two ships. The surveys also broke several records: number of nodes, the longest acquisition schedule, the deepest water and the largest source area.

Single-Trip, Multi-Zone Well Completion

At low-permeability reservoirs like Jack and St. Malo, engineers often pump an environmentally safe sand mixture called proppant into the reservoir to open tiny fractures and allow oil to flow more easily into the well. This process, called frac-packing, can be time- and cost-intensive because of the size of the producing rock formations. At Jack and St. Malo, some of these rocks are more than 1,000 feet thick (305 m), requiring large volumes of proppant to be pumped at high pressure. 

Typically, it can take five days to frac-pack each zone, but Chevron helped develop a new single-trip, multi-zone technology, which allows Chevron to stimulate multiple zones of the reservoir in a single run of the equipment downhole, cutting the time to 18 to 20 hours per zone. With a cost of about $1.2 million per day of rig time, improving completion time results in major cost savings.

Because the single-trip technology allows Chevron to capture oil from more layers of rock safely, it's cost effective, making this method of completing wells an attractive option. At one well in the Jack Field, Chevron stimulated a record-breaking six zones and pumped more than 2 million pounds of proppant in just a few days instead of the normal 30. Chevron also successfully tested the technology in an open-hole well—a well that hasn't been cased and sealed—for the first time in the industry.

Technological innovations that improve efficiency, safety and margins provide Chevron with a competitive advantage. "No one has ever done six stages in just a few days in deep water," said Bill Wood, a completions engineer working on the project.  

Subsea Boosting System

Although the Jack and St. Malo reservoirs are currently high pressure, the pressure will decrease over time due to production. A powerful pump installed on the ocean floor is needed to help boost the oil to the FPU.

Jack/St. Malo's three subsea pumps are built to withstand 13,000 pounds per square inch (psi) of pressure, are installed in 7,000 feet (2,134 m) of water, and consume 3 megawatts of power – a new industry record representing a significant improvement over previous models. Prior to this project, industry maximums were at 5,000 psi pressure, 5,500 feet (1,524 m) water depth, and required 2.7 megawatts of power for pumps of similar configuration.


Published: August 2015