Coiled tubing (CT) is a well-established well intervention technique in deep water (1,001–4,999 ft [305–1,523 m] water depth) offshore environments in the Gulf of Mexico (GOM). Wells as deep as 25,000 ft [7,620 m] measured depth (MD) are routinely accessed, serviced, and abandoned with CT at the present time. However, as demand for oil and gas continues to increase, the industry is now expanding its activities into ultradeep waters (water depths greater than 5,000 ft [1,524 m]), ultradeep reservoirs (well depths greater than 30,000 ft [9,144 m]) and high pressures (maximum shut-in pressures close to 15,000 psi [100 MPa] at the seafloor and greater than 10,000 psi [69 MPa] at surface). Ultradeep water projects are becoming central to the overall deep water investments being made by the major oil & gas operators, with several projects slated for 2015.
Coiled tubing is considered one of the critical contingency operations that may be required during the completion of these ultradeep high pressure wells. CT interventions are also expected to be part of future well workover/maintenance operations. The extreme downhole and surface conditions that exist in these ultradeep high pressure wells pose many significant challenges to the CT industry, as it strives to provide safe and reliable access to these wells. In order to address some of these challenges, the CT industry has to re-evaluate various aspects of its coiled tubing design and operations, including the minimum yield stress of the pipe material, surface equipment, downhole tools, fluids, and wellbore access modeling software in order to identify any technology gaps that may affect its ability to effectively service these ultradeep, high-pressure wells. Once these gaps have been identified, they must be converted into specific action items to be addressed by all parties, ranging from service companies and equipment manufacturers to operators.
This technical feasibility study on coiled tubing deployment for an ultradeep high pressure project in the GOM describes the evaluation criteria used, identifies technology gaps and outlines the specific solutions proposed.