HPHT Well Basis of Design Case Study: Offshore Thailand Advanced Tubular Analyses Experience

In 2011, a major exploration and production oil company drilled and tested an HPHT well, the Tong Rang 3. This well is located in Bongkot field, Gulf of Thailand, about 722 km from Bangkok. This paper highlights the outcome of a post-drilling review using the Tong Rang 3 as a case study with respect to the well-design models and steps that the company will be taking towards optimizing its higher degree of HPHT development wells, which include future challenging prospects in the Gulf of Thailand. Aside from stress and pressure profiles, a good understanding of the temperature regime and heat transfer in HPHT wellbores is an important aspect of the planning process. The logs and actual well-testing operations in the Tong Rang 3 confirmed that the hydrocarbon produced contains gas condensate with 31.5% CO2. The maximum circulating temperature was diagnosed to be around 207°C while drilling to TD with a mud-cooling system in place and bottomhole temperature in excess of 227°C during well testing and a tubing-head temperature of 60°C. To improve the quality of the well design and planning process, the company has realized the importance of a case study to establish a guideline in their well-integrity process, thereby allowing the drilling team to plan similar wells using proper engineering assumptions, including basis of design refinement, based on the company’s well engineering policies. The study will not only enable aiding the wellbore and completion optimization, but can be used to improve decision making throughout the field-development campaign, thus avoiding possible underdesign and achieving long-term well integrity and cost optimization. This paper will detail aspects of the well design incorporated in the Tong Rang 3 and provide a discussion and comparison between the plans vs. the actual design throughout the execution of this HPHT well, focusing on advanced tubular design from a temperature simulations aspect. It will also highlight the effect of tubular heat-up through comprehensive sensitivity analyses, while understanding how the currently available technology can be used to support an integrated basis of design model to successfully establish a representative HPHT wellbore configuration, subsequently signifying relevant well-construction parameters to ensure an effective and safe design for future HPHT wells.