Well Equipment Reliability Analyses, Failure Predictions and Well Lifetime Simulations to Establish Future Required Well Interventions in a Subsea Deep-Water Field Lifetime Extension Project
Authors: Jenssen Hans Peter , Garg Shashank 
Published: September 2023

TotalEnergies is performing a life extension project for one of its deepwater fields offshore Gulf of Guinea. As part of this work, a Well life extension study was performed in 2022. The main objective was to establish quantitative input to the assessment of expected future well intervention requirements for the subsea oil producers and water injectors, based on historical operational data captured for the wells on this deepwater field. The specific activities for the study were:

Collect data for the wells and run component reliability analyses. Wells were initially designed for 20 years of life. Run well lifetime simulations using WRMS for water injector and Oil producer wells. Establish the expected number of failures and intervention frequency for each well component type during the extended lifetime periods being considered Establish the expected number of the required well interventions per intervention-type (e.g., DHSV failure, UC failure, Sand screen failure and XMT failure) per well type for each case, and for the total number of wells to be in operation during the defined LIFEX period from 2027 through to 2045: Casing side-track well workover due to lower completion sand screen failures.Well intervention to install a WRSCSSV as a temporary barrier for the failed TRSCSSV.Upper completion change-out due to Tubing, Tubing hanger, Production packer and TRSCSSV Control line failuresX-mas tree change-out due to failures of the main barrier valves

Equipment and component failure data for each well was collected and reviewed. Component reliability analyses were performed for all components included in the well models for the simulations (subsea X-mas tree valves, SCM and Choke module, upper and lower Completion). The most critical components with respect to expected downtime due to failures and required interventions were identified. The reliability data of each component is required input to the well lifetime simulations.

Well simulation models were established for the subsea oil producers and water injectors. Rules for interventions with resources such as MODU/Rig, Light Well Intervention (LWI) vessel and Multipurpose Service (MPS) vessels were applied in the simulations. It was assumed that vessel-type well interventions can be performed at the water depths for these wells. The simulations were run with a Monte Carlo type RAM well simulator.

Main results were:

Number of required well interventions per Component-type per well-type per year and total number of interventions, for four different life extension periods being evaluated. Results included X-mas tree main valves, SCM, Choke module, upper and lower completions. The results provided the required input to the field Life Extension Project (LIFEX).

This paper presents the overall methodology developed and applied to the life extension Case study that was conducted. It further describes the various tasks involved during the study, the main results and how these were achieved, including some examples of the displayed results from the well lifetime simulations that were run. A short summary with the main conclusions is provided at the end of the paper.