Successful Inorganic Scaling Prediction in Early Conceptual Design Phase: Gas Field Development Experience

Abstract

AbstractThe early stage in conceptual engineering design of a gas field development comprises an assessment study to evaluate the potential occurrence of inorganic scale within the upstream and downstream production system. Strategies for water treatment and water disposal are developed to avoid injectivity loss by scale generation. The contribution of drilling fluids or brine contaminants difficult the recovery of representative condensed water and formation water samples from HP/HT gas production wells and water disposal wells. The present study integrates bottom hole water sampling, well testing and geochemistry to predict future potential inorganic scaling during gas field development. A bottom hole water sample shows TDS concentration of 63,199 mg/l, a Cl-Na-Ca water type with slightly enriched trace elemental concentrations (Sr=40 mg/L, Ba=7 mg/L, Fe=2.8 mg/L) and neutral pH conditions (6.8). In contrast, K (1,340 mg/L) and Mg (1,126 mg/L) are relatively abundant in comparison to standard formation water concentrations across the formation, suggesting a mixing contribution with contaminant fluid. Representative formation water is characterized by a hypersaline brine composition with extremely high TDS abundance (231,000-297,000 mg/L). Various predicting scenarios for the scaling of self inorganic and water mixing scale were modeled and laboratory static testing were conducted. As a conclusion, all waters were compatible at pH range of 6.5-9.5 with different mixing ratios. No self-scaling was observed up to 140°F. A benchmarking to a nearby gas field and wells, being under production for about 2 years, also concur similar result. The study has successfully confirmed an optimum approach for scaling management during the initial phase of field design.