Surface Management of Gas Breakthrough in Thin Oil Rim Waxy Reservoir: A Case Study

Abstract

With technological advancements, new and improved techniques have progressively been deployed to maximize recovery from a thin oil rim development. While some of them have a lasting influence on the well behavior such as placement of the well bore in the oil column, others such as zonal control using Sliding Side Doors (SSDs), Interval Control Valves (ICVs) or Interval Control Devices (ICDs) provide flexibility for altering well performance during operating life of the well. However, any intervention be it the subsurface zone manipulation or surface choke manipulation or ICV control needs to be justified in view of the anticipated gains against the risk incurred and resources required for the intervention on the basis of well performance (test data) and subsurface interpretation. The field for this case study is a thin oil rim with a large gas cap and a high wax content facing twin challenges – gassing out of wells and waxing of tubulars and flowlines – both of which require an optimization of preventive interventions to minimize deferment and corrective interventions. The required interventions such as choke and gas lift changes, zone changes, scraping, hot-oiling, steaming and pigging consume significant man-hours for surveillance, planning, execution and monitoring of the impact of the job on well performance. The desire to follow each intervention by a well test for system optimization overwhelms an already stretched routine well testing schedule. The resultant deferment due to sub-optimal production was estimated to be 10-15%. The solution was in breaking down the problem into mini-challenges and addressing them by deploying robust technologies and adopting smarter ways of working. In this paper a simple surface technology that helps managing gas breakthrough is presented. This technology when combined with smart surveillance techniques enables efficient Well, Reservoir and Facility Management (WRFM) for thin oil rims with added wax challenge. Following impacts have been seen: An average increase in production by 10% was realized. The project payback was less than 2 months.Up to 80 man-hours per week were freed allowing team to focus on additional barrel generating opportunities.Reduced Health, Safety, Security and Environment (HSSE) risk corresponding to reduced well intervention besides stabilized production.Reduced deferment by optimal timing of preventive intervention and reduced risk of incurring cost and deferment from a corrective or reactive intervention.Improved team productivity and fresh energy from use of smart ways of working. The novelty of this surface technology for managing gas breakthrough is in its ability to optimize, accelerate and thereby squeeze production from a thin oil rim development in the license period. The resulting production stability then provides a basis for deploying smart surveillance techniques for sustainable increased efficiency.