Gas Field Subsurface Integrity: Performance Analysis of Glass Reinforced Epoxy Tubing Completion at High H2S Wells at Offshore Caspian Sea

摘要

As the BHQ-field matures, sustaining well productivity throughout its lifespan requires an essential need to focus on the field's well subsurface integrity. Wells in BHQ that were completed with Glass Reinforced Epoxy (GRE) tubing have been undergoing a unique and targeted monitoring program for the past few years, parallel to the objective to understand the performance of well integrity of the BHQ-field wells as a whole, and GRE tubing at high H2S wells in particular. The main challenge is related to H2S production as the field is producing around 100 - 500 ppm of H2S. During the well design stage where reference was made to the reservoir data obtained from a series of appraisal wells, the field development plan has concluded that the wells’ tubing is to be coated with GRE. The trim and sealing elements of the wellhead and Christmas tree were also made compatible to H2S. However, irregularities can still be observed at the surface apparatus during the production phase. In order to avoid more serious integrity issues, diagnostic surveys and logging were performed. The result from the field monitoring activities together with existing reservoir data were then combined and analyzed. The result from the analysis has significantly contributed towards an understanding of GRE tubing performance and behavior at high H2S wells. Logging data of a calliper log ran at few wells with a one-year gap indicated that the corrosion did not appear to be present. However, it could be observed that the wellhead and Christmas tree sealing element made from a certain type of component is not compatible. The result from the analysis also has become important data for investment comparison for well development and production teams, between GRE and other types of completion tubing, such as 13-chrome and Super 13- chrome, for future project's reference. On top of this, the effectiveness of the well integrity program at BHQ- field, such as 6- monthly wellhead preventive maintenance, actuators and choke maintenance and annulus pressure diagnostic in relation to production sustainability and overall assurance of health and safety aspects of the field operation, can be concluded as meeting the standard with minor improvement. This paper will provide the analysis on GRE tubing performance at gas wells with high H2S production. The analysis will present the data on GRE tubing compatibility with a harsh environment. It also allows the investment comparison to be made with other types of completion tubing. This paper also will provide the process flow in determining the effectiveness of the well integrity program and process safety program at gas wells with H2S production in the Caspian region.