Abstract

The Azeri-Chirag-Gunashli (ACG) field is a giant oil development located in the Azerbaijan Sector of the Caspian Sea, consists of several stacked reservoir layers being produced through 6 platforms (Chirag, West Chirag, East Azeri, Central Azeri, West Azeri, and Deep Water Gunashli) and being operated under a Production Sharing Agreement (PSA). The ACG field is becoming more mature in its development and the need for artificial lift is becoming essential to maintain production and enable the startup of weak wells.

Gas Lift is the artificial lift mechanism currently selected for ACG and surface facilities are designed to support that method. The availability of high pressure gas for injection, and the high productivity potential of ACG wells were key factors in the selection process.

Not all of the older ACG well stock is equipped with downhole gas lift mandrels (GLMs) today. In order to retrofit conventional completions, the existing tubing is pulled from the well and a new tubing string with GLMs and a surface controlled annular subsurface safety valve (ASV) is installed, requiring around 30 days of rig time. This consequently delays drilling of new wells as only one rig operation on each platform is available. Overall, conventional recompletion is an expensive operation, and some wells don't have sufficient incremental production to justify execution of this high cost wellwork.

Alternatively, coil tubing nitrogen lift can be used to start up wells without gas lift, but it adds additional risk to platform operations, takes additional operations' time and deck space, is expensive, and it is not practical for continuous use.

In addition, completion running procedures did not allow for unloading valves installation during completion phase and use of more efficient venturi type orifice valve as opposed to square edged shear orifice. This creates a necessity for nitrogen lifting of new wells and unloading valve(s) installation at a later time adding to the rig time.

In this paper, an alternative method of introducing Gas Lift to existing wells and modifications done to completion running procedures will be discussed.

The proposed method utilizes a gas-lift insert system (GLIS) which includes a dual-packer with integral gas-lift valve that can be installed in the existing tubing using e-line. To mitigate the risk of annular gas release in the event that the tree is compromised, a Modular Surface Annular Safety Valve (MSAS) is installed, as installation of a conventional downhole ASV is not possible without replacing the tubing. The MSAS is a hydraulically actuated check valve that is installed in the valve replacement (VR) profile of the wellhead. Under normal operations it is held open by application of hydraulic pressure (using the existing platform safety system).

This paper will discuss recent successful field results where GLIS was installed using only 7–11 days of rig time and results of new completions running procedure application. Results of a successful well restart producing 3 mbd of oil with 3 MMscfd of continuous gas lift rate being injected via GLIS and new well start-up utilizing benefits of updated completion design will also be discussed.

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