Gap Analysis Assessment of Performance of Conventional Drilling Fluids in High Temperature and High Pressure Environments

Abstract

The critical functions performed by drilling fluids during drilling operations include providing hydrostatic pressure to prevent formation fluids from entering into the wellbore, keeping the drill bit cool and clean during drilling, carrying out drill cuttings, and suspending the drill cuttings while drilling is paused. Others include control of formation pressures, prevent well-control issues, maintaining wellbore stability, minimize formation damage, cuttings transport from the wellbore to surface and minimize risk to personnel, the environment and drilling equipment. In adverse drilling environments such as High Pressure High and Temperature (HPHT) wells, the elevated temperatures and pressures encountered by the drilling fluids downhole may limit their technical performance and result in drilling problems if these factors are not well considered during the drilling fluid design. Hence, the objective of this study is to carry out a gap analysis on the performance of conventional drilling fluids in high pressure and high temperature environments using appropriate engineering methods. The outcome of the study identified some of the limitations of drilling fluids in HPHT drilling environment such as loss of rheology property control, fluid gelation at high temperature, high fluid loss at HPHT conditions, thermal degradation of the drilling fluid constituents, sagging of weighting materials etc. Benchmarks such as thermal stability of drilling fluid products and system, resilience to high temperature gelation, resistance to high temperature fluid loss, stable rheological properties control, resistance to solids sagging in HPHT environment etc were identified as top criteria for optimal performance of drilling fluids systems in HPHT wells. Potential steps or actions that that may be taken to bridge the existing gaps or shortcomings of conventional drilling fluids in HPHT drilling environment were then recommended.