_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 224044, “The Evolution of Riserless Wireline Subsea Intervention in Deepwater Gulf of Mexico: Doing More With Less, ” by Strethen E. Townsend, Jose Duenas, SPE, and Lawrence W. Ramnath, BP. The paper has not been peer reviewed. _ Riserless light well interventions (RLWIs) were conducted within the deepwater subsea environment of the Gulf of Mexico. The main drivers for RLWI were cost reduction and acceleration of intervention scopes in order to improve well productivity and prevent production deferrals. During the period 2020–24, target wells for interventions were challenged by low margins. However, per the original objectives of RLWI, financial metrics for the candidate wells were still found to be attractive, yielding double-digit net present value and internal rate of return values. A heuristic payback period of 1 to 2 years also was consistently achieved. While the complete paper is divided into two major sections, the first concentrating on capabilities and lessons learned during 2020–21, this synopsis emphasizes the period during 2022–24. Capabilities: 2022–24 The latter part of the deepwater RLWI campaign saw an increase in conveyance through wireline (electric line) leading to more mechanical capabilities such as high-accuracy plug setting for water shutoffs, reperforating, manipulation of downhole flow-control completion equipment, and installation of subsurface safety valves. In addition to added capabilities, the use of wireline also provided alternative means to disconnect from bottomhole assemblies (BHAs). In situations where tools needed to be released downhole, slickline typically only provided single mechanical-release mechanisms without the use of memory timers. For deepwater RLWI, reliance on a single mechanical downhole release or a timed-release device is a significant risk. Wireline allowed electronic release devices to be included in the toolstring. Some emergency release devices also incorporated a secondary release logic that would disconnect after a set time if communication to the tools were lost. This capability was particularly beneficial in the deeper, high-pressure wells. In addition to an enhanced downhole toolbox and improved options for stuck-tool recovery, deepwater RLWI was expanded to harsher well environments during the latter campaigns. These included an additional 13 wells undergoing mechanical intervention. Challenges, Solutions, and Lessons Learned: 2022–24 Loss of Grease Seal. This phenomenon was experienced primarily on the cased and perforated wells in Asset 1. On-the-job troubleshooting and post-job investigations identified inadequate grease delivery as the root cause of the loss-of-grease-seal events. Several improvements to the grease-management and pressure-control system led to a solution that resulted in jobs after Well 11 no longer experiencing loss of grease seal. Some improvements in the grease-management system and pressure control included the following: - A conservative approach was taken to specify grease-injection pressure at the pressure-control head based on absolute shut-in tubing pressure without accounting for the approximately 2, 500-psi hydrostatic pressure caused by the water column. To help monitor the grease-injection pressure, subsea pressure gauges were added at the grease-injection points for accurate measurements. - In addition to the subsea pressure gauges, grease-supply flowmeters were added to the surface grease-injection system. - Specific flow-tube configurations and grease-injection points were defined for positive and subambient wells. - Flow-tube sizing was aligned and clarified to resolve conflicts in operators’ and suppliers’ requirements. - Hoses used to deliver grease to the pressure-control head were replaced with larger-diameter hoses. - Manual-control grease regulators and controls were replaced with automatic models. A less-viscous grease was implemented during Well 11 and for all subsequent wells.
Chris Carpenter (Wed,) studied this question.