SPE Papers

The construction of drilling and production facilities for gas lift production and injection wells on artificial Islands provides a significant exposure to risk due to SIMOPS. Specifically, simultaneous drilling operations results in rig skidding operations over/near to live well cellars and production line trenches. This increases the risk of venting significant lift gas volumes to atmosphere in a manned area through dropped objects or other failures.

Gas lift valves are an integral part of the tubing in gas lifted wells. Many operators use tubing with premium threads for these wells. Additional safety equipment, including the packer and the downhole safety valve, has been subjected to a program intended to prove its capabilities as a safety device. This is not the case with standard gas lift valves, developed and delivered according to the governing standard, ISO 17078-2. On the contrary, this standard states that the valves are only intended to be a flow check and not a pressure safety device.

Deciding on the optimum design for any new well is a complex task, made often more difficult by a wide range of technical uncertainties. Getting the completion design right is particularly important for subsea wells, where the cost of intervention can be prohibitive. After several years of production, it is common to encounter significantly different reservoir and well conditions than were initially predicted at the time of the original well completion and artificial-lift designs. Gas-lift is not always required until later in the well life. While some gas-lift valves have an impressive reliability record, some can fail or be deemed sub-optimal for the well conditions and necessitate retrieval to optimize well performance or to reinstate well integrity.

Unplanned Sustained Annulus Pressure (SAP) in the A Annulus (sometimes referred to as the tubing/casing annulus or TCA), is the most common of all well integrity management challenges. Typically, this is as a result of a failure in a well integrity barrier envelope element / component. Monitoring for this situation is of critical importance because it generally means the ‘double barrier' well integrity policy that most OPCO's follow is breached.

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 South Oman, PDO is producing from high Sour Fields (H2S 1-10%) with high reservoir pressures ranging from 50,000 to 100,000kpa for more than 20 yrs. Operating these high sour wells comes with huge challenges and risks, which can easily get escalated to very high levels in case of any integrity issues with the wells. These situations not only provide significant exposure to expensive and risky well interventions but also pose threats to production due to Simultaneous Operations (SIMOPS) issues. The authors describe case studies where team was exposed to these challenging situations due to integrity failures in two such wells. New technologies were implemented which resulted in restoring the well integrity in a very cost effective manner (cost savings worth millions) and also reduced the HSE risks on the nearby operations.

The Extended Reach Drilling (ERD) field re-development of a giant offshore field in United Arab Emirates (UAE) from four artificial islands predominantly requires the use of artificial lift (gas lift) to assist in unloading the wells post-completion operations and enhance reservoir production recovery rates. The vision was to achieve a well completion that allows for intervention-less unloading via gas lift using shearable Gas Lift Valves (GLV) and Remote Actuated Barrier Devices (RABD). The key principals in developing a solution to achieve this vision were to reduce rig time by avoiding critical path unloading, minimize post-rig activity to install live gas lift valves, and eliminate HSE exposures.