PTC Gas Lift System: Surface Safety System Enhances Gas Lift Safety and Optimizes Surface Line Architecture on Island Wells
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.
The authors describe a Lift Gas Safety System (LGSS) to be implemented that will prevent venting lift gas during both a dropped object and other unplanned incidents leading to loss of integrity (e.g. ESD). The system also provides benefits through improved annular pressure monitoring (APM) and confining barriers within the wellhead. Outlined is the implementation process by which the system was selected and which subsequently led to optimization of surface facilities from the well cellars through the production manifold.
Gas Lift Reliability: Taking the gas lift valves to a new level of reliability
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. This paper discusses the development of a new validation standard, where the intention is to prove the equipment's safety capacity, as well as new equipment developed to meet these challenges.
GoLift Straddle: Retrofit Gas-Lift Straddles in the North Sea
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 optimise well performance or to reinstate well integrity.
Retrievable straddle packers are commonly used to isolate water and/or gas production in the sandface completion or reinstate well integrity in the upper completion. This paper will review different methods used to reinstate gas-lift, and describe the gas lift design process and straddle configuration using case studies from the North Sea.
In particular, Premier Oil undertook a subsea well intervention campaign to restore production, which had ceased following the suspected failure of the gas-lift system. Analysis of the well performance data suggested that one or more gas-lift valves were inoperable and that the original valve depths were not ideal for the encountered reservoir conditions.
The operation was performed from a light well intervention (LWI) vessel, deploying a retrievable Interwell straddle and PTC GoLift™ Straddle system, installed in the tubing across and between the existing side pocket mandrels, creating a retrofit, triple packer, gas-lift straddle.
Premier performed a safe and successful LWI operation, returning the well back to its full production potential, having met all well intervention objectives. Running the retrievable straddle packer solution with PTC's GoLift™gas-lift system helped to optimise production and saved the need for a costlier rig-based upper completion workover.
This paper will further look at the design and development of these technologies, examine in depth one case study for the Brenda D3 design and installation.