Objectives/Scope: Having a reliable backup plan is vital to ensure successful riserless light well intervention (RLWI) operations. This paper will present learnings from a subsea operation where the contingency solution was engaged to resolve a critical issue. The need for thorough back-up planning will be discussed along with the planning process, execution and lessons learned.Methods, Procedures, Process: Crown plugs are conventionally retrieved using slickline jarring; however, high performance shifting tools on electric line are gaining foothold due to their ability to apply a focused, axial force downhole. Up to 33,000 lbs of force can be exerted through the use of a bi-directional, hydraulic ram. These electric line (e-line) stroking tools can be fitted with various shifting or pulling tools for lightweight mechanical services. For subsea interventions this is good news as space is particularly limited on vessels, which means that intervention solutions that simplify logistics by reducing equipment and crew is sought after. Results, Observations, Conclusions:The case to be presented is from a RLWI operation in the Gulf of Mexico where a crown plug had failed to release. Slickline (SL) was the first method to be put into action. On the first attempt 148 jars failed to retrieve the plug, then another 199 jars yielded the same result. It was believed that these repetitive attempts had broken the seal, resulting in saltwater inflow that had created hydrates. 25% Methanol Ethanol Glycol was pumped while jarring, but eventually the contingency plan was activated. This consisted of a hydraulic stroking tool, which successfully managed to remove the upper crown plug and thus allowed the operation to continue without further downtime.The operator would have had six months of deferred production (being unable to open the sleeve to the upper zone) if the crown plug was not retrieved as they would have needed to wait for a riser. This underlines the importance of having an adequate contingency solution to overcome the challenges in riserless interventions. The benefits will be increased operational efficiency and reduced overhead costs. Novel/Additive Information:This was the first operation where a crown plug was pulled during a RLWI operation with an e-line bi-directional stroking tool. The tool in this case was capable of 33,000 lbs of force; however, since the execution of this operation, further developments in engineering have led to a redesigned stroking tool with the ability to apply up to 60,000 lbs of force. What opportunities that opens up for RLWI operations will also be presented.
Capabilities in the industry have been expanded on a recent operation performed in the Gulf of Mexico, where a new electric line (e-line) water depth record was set in addition to demonstrating that asphaltenes can be removed on e-line with Riserless Light Well Intervention (RLWI).The operator had planned to set a removable hold open sleeve with a subsurface-controlled PB valve across a failed surface controlled subsurface safety valve (SCSSV) on one of their subsea wells. The well had not been re-entered since production start-up, which meant that the downhole conditions were unknown. During the slickline gauge run, the toolstring hung up after only 581 ft in the well and could not be jarred any deeper. After a failed attempt to chemically remediate the blockage, the client decided to try e-line milling, consisting of an e-line tractor for conveyance and a cleaning tool fitted with a reverse circulating bit to mill through the obstruction and capture any debris. This toolstring was initially set down in the production tubing at 4,083 ft ELM and was picked-up to 4,000 ft ELM. At this depth the cleaning tool was engaged and was able to mill at 10 fph past the previous hang up depth (HUD) of the slickline gauge. We continued downhole another 1,217 ft where an obstruction was encountered at 5,778 ft ELM and the toolstring became stuck. The toolstring was worked free and brought to the surface where it was established that the bit was packed with solid debris and the bailer sections were full of dense, hardpacked asphaltenes. The operator concluded that this very dense material would continue all the way down the well and decided that it was would not be feasible to continue milling as there were almost certain, terminal sticking risks.Based on the samples recovered, the operator was able to avoid unnecessary costs incurred from attempting to work further downhole under these conditions. They decided to suspend operations until they had fully analyzed the samples and could make an informed decision on how best to remove the asphaltenes. This paper will discuss job planning, operations, and lessons learned. Increased Demand Drives Increased E&P in Deep WaterOil has powered the world in the form of transportation fuels for more than a century, and demand is expected to grow over the long term. Global energy demand is projected to increase 53 percent between 2008 and 2035 (Chevron 2013). Thus, the industry is striving to find new resources to replace diminishing reserves and to meet increasing global demand; these factors are moving exploration and development into deeper water offshore, where currently more new fields are being developed subsea than from platforms (Strategic Offshore Research Ltd. 2012).Subsea wells. One of the major challenges with subsea wells is that recovery factors are much lower-typically 10 to 30% less-compared to recovery rates of dry-tree, platform-based wells (Osmundsen 2011).Deepwater Gulf of Mexico oil fields typically have ultimate recovery factors in the 10% -35% range, because reservoirs...
A requirement 1 within a conventional offshore well's completion design per operator standard design and/or governmental regulation 2 is the installation of a "subsurface safety device." Among the list of permitted safety devices, subsurface safety valves (SSVs), if maintained properly, can fulfill such a requirement in well control and isolation.Whether it is of the surface-controlled (SC), subsurface-controlled (SSC), wireline-retrievable (WR), tubing-retrievable (TR), ball check, or flapper valve variety, subsurface safety valves can easily be damaged during through-tubing (wireline, coiled tubing [CT], etc.) deployment through the valve if steps, such as equalization before opening, slowing toolstring running speed, etc., are not taken to properly safeguard valve integrity. A problem that could occur during these deployments, specifically in reference to the SSV flapper-type valve, is shearing of the hinge pin on which the valve flapper rotates, allowing the flapper to "float" in a cavity directly below its rotation point, creating an effective downhole obstruction.A traditional intervention operation to repair this includes using a slickline (SL) rotating wedge to manipulate the flapper to a position that will allow a subsequent, suitably 3 sized sleeve installation through the cavity, bypassing the flapper. This will allow for both toolstring deployment past the obstruction to assist in future uphole recompletion operations and continued production without slugging from unexpected valve flapper reseating.This paper discusses a case history in which the above-mentioned conventional SL manipulation toolstring was deemed not suitable, as it was currently designed for a small cavity-type Tubing Retrievable Surface Controlled Subsurface Safety Valve (TRSCSSV), and alternative intervention means were developed. Five full-scale 4 tests were performed with four different toolstrings (one SL and three electric line [EL]) engineered to provide a method of inserting a bypass sleeve with predetermined minimum inside diameter requirements for future tubing cutter deployment. Of the four toolstring options developed, two were deemed field ready and deployed with the offshore operation itself, while the other two required additional engineered modifications. Details of the successful intervention deployment are also given in which desired flapper orientation and isolation was not only achieved by toolstring manipulation but also by well-production characteristics.Three benefits can instantly be noted from the developments and lessons learned. First, the toolstring solutions could be used for obstruction isolation of many varieties. Second, this rigless operation is part of the ongoing efforts in the Gulf of Mexico and elsewhere in the world to intervene in wells in the most economically feasible, least hazardous, and most expedited manner. Lastly, the intervention means employed here incorporates toolstring components readily available on the market. Lead time and operational use are minimized, and rig campaign schedules ...
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