High-Density High-Strength Phase Transforming Lost Circulation Material to Cure Severe to Total Losses in Reservoir and Non Reservoir Sections

Abstract

AbstractLost circulation is one of the biggest expenses in terms of rig time and safety in oil and gas well drilling. Uncontrolled lost circulation can results a dangerous pressure control situation and loss of the well. Drilling through large natural fractures is a big challenge. This paper focus on developing high-density, high-strength, Fluid-Gel-Solid based lost circulation material (LCM) using novel surfactant with acid soluble sealant powder to cure the severe losses scenario.Particulate material, polymer based system, cement, resin etc. has been used as lost circulation mitigation solutions but they have their own limitations of particle size, rheology, tolerance to contaminations, strength to cure sever to complete loss events. A novel fluid system is developed to mitigate these issues. Laboratory customization of the fluid has been evaluated with different temperature and pressure conditions. High pressure high temperature (HPHT) consistometer for setting time, rheometer for rheology and ultrasonic analyzer is used for measuring compressive strength. Tolerance to drilling fluids, spacer and cement contamination also evaluated. This acid soluble system has ease of cleaning if premature gelation occurs.The fluid has thixotropic properties, viscous under static condition and shear thinning upon pumping, achieved through mixing of novel amphoteric surfactant along with water and sealant powder. This is a phase transforming fluid where amphoteric surfactant forms elongated worm-like micelle structure in presence of monovalent and/or divalent salts. Rheological study conducted to show the fluids elastic behavior and pumping property. This will help to assess the displacement of the LCM fluid. The sealant powder, working as weighting agent, sets hard with respect to temperature and time; and a setting control additive controls the hardening or setting process. Finally a high compressive strength solid plug is formed which can withstand the losses of fluids into the formation. Another added advantage of the system is – it can be optimized with seawater; fresh water is not a limitation.The fluid technology is based on thixotropic-gelled using novel surfactant that resists the flow and loss of LCM fluid into the fractures once pumping is stopped. Tailor-made system with high-strength acid soluble sealant can be customized for low to high-density fluid formulations as per applications without any additional incremental treatment for seawater.