Stimulation Treatment Design Compatible with Glass Reinforced Epoxy Lining

Glass reinforced epoxy (GRE) lining is a polymer composite material, the main components of which are a thermosetting resin and a fiberglass reinforcement. The combined properties of its components result in a material with excellent chemical, thermal and mechanical performance. GRE lining is typically used as a coating on production tubulars in oil wells to protect metallurgy of tubulars from corrosive environments, thereby extending the life of tubulars and realizing cost savings. GRE lining is chemically compatible with many acids used in well stimulation to restore productivity. Typical acids such as hydrochloric, formic, acetic etc. involve carbonate removal followed using hydrofluoric (HF) based acids for removal of small formation particles. However, the use of HF is typically not recommended in GRE lined tubulars due to potential interactions with HF. Yet, in most sandstone reservoirs, HF fluids contribute greatly to restoring well productivity due to formation damage removal related to fines and clays. While GRE lining is a well-known technology, its chemical compatibility with acids is challenging to predict due to its heterogenous nature and requires specific testing to understand potential for mechanical degradation. Prior studies at BP focused on evaluation of GRE performance with 9% HCl: 1% HF under ambient boundary conditions of 77°F for 24 hours. These tests caused unacceptable levels of mechanical degradation to GRE and plans to execute stimulation treatments in GRE lined wells were abandoned. However, an increasing number of GRE lined underperforming water injector well stock necessitated a less aggressive acid design involving 0.5% HF. Therefore, 0.5% HF was assessed for GRE lining compatibility, mechanical and physical property changes under specific well boundary conditions at elevated temperatures of 120°F and 140°F and extended times of up to 72 hours. Core flow tests were also carried out to evaluate the effect of GRE exposed acid to any potential for formation damage. This study demonstrated that exposure of GRE lining to 0.5% HF resulted in acceptable retention of mechanical properties and did not show any formation damage impacts. These results were also reflected in field performance where a significant injectivity index improvement of >4 was achieved, thereby opening the door to a significant increase in number of GRE lined wells to be treated across multiple regions.