Material selection of oil and gas wells must be reliable, cost-effective, and meet corrosion resistance criteria during a well-operating lifecycle. During a well lifecycle, significant changes can occur in the fluids produced or the way wells are operated. Some anticipated and unanticipated changes can occur during design life, and material selection shall be adequate for primary and secondary exposures from design to final abandonment. Various well components such as Christmas tree, wellhead, production tubing, tubing hanger, downhole jewelry, elastomers, and surface casing are exposed to excursions during production/interventions. Any level of corrosion of these critical components is not acceptable, and the compromise of the integrity of these components could result in functional failure and incur production deferment and HSE consequences. Materials of these components are continuously exposed to corrosion risks due to reservoir souring, sand production, water breakthrough, acid stimulation, poor cementing, lack of cathodic protection etc., and directly impact the performance of well integrity barriers. This paper aims to share field experience of unexpected corrosion failures of various materials exposed to excursions during production, well interventions, acid stimulations, annulus fluid changes etc. A review of contributing factors in corrosion of materials in Oil and Gas wells were discussed.
The unstable oil market demand in the petroleum industry, the oil financial crisis and the Covid-19 pandemic have pushed the Oil and Gas operators to look for optimized, cost effective and more reliable strategies of design and operation. Large part of CAPEX is invested in the well materials. Hence, materials of Oil and Gas wells should be selected to withstand both internal and external threats to ensure integrity and availability while maintaining on focus on affordability over the lifecycle.1
The impact which results from wells material failure can be significant to an organization from safety, environmental, and business perspective. The calculated costs of deferment, well intervention and workovers, and reactive maintenance can reach to millions of dollars. Top quartile Oil and Gas operators should aim at taking learnings from premature and unscheduled failure to prevent it from reoccurring, by using continuous Improvement tools such as practical problem-solving (PPS), causal Learning, root Cause Investigation and, for the simplest investigations, five Why's.1