75% Increase in Gas Injection Depth Optimizes Oil Production in Extended-Reach Wells, North Sea | Schlumberger
Tech Report
Location
Norway, Europe, Offshore
Details
North Sea
Offshore Platform
 
Well depth
17,800 ft [5,425 m]
 
7-in liner setting depth
9,100 ft [2,774 m]
 
Gas injection depth
15,900 ft [4,846 m]
Background
Extended-reach wells presented a challenge to the use of gas lift in the North Sea. The smaller liner sizes used at greater depths limit mandrel and gas lift valve diameters. Moreover, at high inclinations, the use of slickline for changing out valves becomes more problematic. CT and electric line tractors provide a solution but increase intervention costs. Setting the valve higher up the well where the inclination is smaller would facilitate slickline usage but result in suboptimal production. 
Products Used

75% Increase in Gas Injection Depth Optimizes Oil Production in Extended-Reach Wells, North Sea

1-in Barrier Series gas lift valves and slim side pocket mandrels maximize performance and enhance reliability

Graphic: Schlumberger installed two 1-in Barrier Series gas lift valves in slim 41/2-in side pocket mandrels that had a special 6-in drift OD suitable for the 32-lbm/ft, 7-in liner. As a result, the gas injection depth was extended from 9,095 ft (just above the liner top) to 15,900 ft, where the well deviation is 69°, optimizing drawdown and production.

Schlumberger installed two 1-in Barrier Series gas lift valves in slim 4 1/2-in side pocket mandrels that had a special 6-in drift OD suitable for the 32-lbm/ft, 7-in liner. As a result, the gas injection depth was extended from 9,095 ft (just above the liner top) to 15,900 ft, where the well deviation is 69°, optimizing drawdown and production.

Each barrier valve incorporates a high-specification, metal-to-metal back check sealing module that has been developed and tested to meet strict quality, leak-rate, and performance standards, providing a robust seal between the tubing and the casing annulus. The check design uses enhanced geometry to minimize erosion during high-rate operations.

The improved design specifications increase performance and reliability of the gas lift system, minimizing well interventions.

Tubing-to-annulus communication is tested every 6 months. Since the initial installation in early 2016, no leakage has been detected.

Products Used

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