Deep water, high pressure

Chevron planned an extended well test in the deepwater Jack No. 2 well in the Gulf of Mexico. Reliable, uninterrupted real-time data had to be obtained in 7,000 ft of water and a total depth of 27,500 ft, plus very high pressure of 25,000 psi. Reservoir uncertainties and extremely high daily rig spread rates required maximum efficiency.

Robust gauge system

With the drillstem test string, Schlumberger ran a reliable WellWatcher permanent gauge system consisting of three quartz pressure and temperature gauges—rated for 25,000-psi and 425 degF—deployed using one dual and one single solid gauge mandrel and welded Intellitite electrical dry-mate connectors. The proven reliability of the welded connector technology used in this system was considered a key advantage over wireline-deployed gauge options to acquire this data.

The electrical signal was routed through the SenTREE high-pressure subsea well control system on the seafloor. At the surface, the pressure and temperature information was monitored by Chevron and Schlumberger personnel in real time during well test operations. This real-time surface readout was critical to the safety and efficiency of this well test.

Uninterrupted data stream

The Schlumberger gauge system transmitted critical downhole annulus and flow-stream bottomhole pressure and temperature information uninterrupted for 48.5 days. The well test averaged 6,000 bbl/d of oil.

The system facilitated onsite transient analysis of the downhole flowing and buildup data, allowed engineered execution of the well test, maximized well test flow rates while minimizing the risk of excessive drawdowns, minimized the rig time required to fulfill the objectives, and supplied invaluable assistance to drillstem test specialists.

The Schlumberger gauge system transmitted critical downhole annulus and flow-stream bottomhole pressure and temperature information uninterrupted for 48.5 days.