Reservoir Friendly Rigid Setting Fluid Arrests Lost Circulation While Minimizing Reservoir Damage

Abstract

Currently, many producing formations are carbonates and/or depleted sands that are characterized by highly permeable flow paths or vugs. Severe-to-total loss of drilling fluid in these formations is a major concern from both the drilling and reservoir damage perspectives. Conventional particulate lost circulation materials (LCMs), such as acid-soluble ground marble, might not effectively cure severe losses. Furthermore, because the application is in a producing formation, avoiding reservoir damage is a major criterion that any potential solution should satisfy. The "band-width" of available solutions that are both efficient and reservoir friendly is narrow, leading to both high cost and potentially risky drilling practices.A possible solution is using an acid-soluble right-angle-setting composition (RAS-Co) that was developed to provide the industry with a more efficient solution for plugging and isolating producing zones that have high drilling fluid loss rates. RAS-Co is formulated from inorganic, nonhazardous powders and fluids mixed in fresh water or seawater. RAS-Co is engineered to be a low-viscosity (18 to 30 cp) fluid containing small particulates, which allows it to be mixed at the rigsite and pumped through any drillstring configuration. It is designed to react at a specific bottomhole circulating temperature (BHCT) in a consistent and controllable manner with a "right-angle" set. Once it is spotted/placed in the suspected loss zone, it helps eliminate further fluid losses and formation damage. The small particle size distribution acts as a pore-bridging material while in the fluid state, and the right-angle-set characteristic makes the material non-invasive to the formation and allows it to be easily drilled or removed with acid. It can be used in zones with up to 300°F circulating temperature and tolerates up to 50% contamination with water or drilling fluids. This paper describes attributes of RAS-Co along with successful field applications that illustrate it is an effective solution for controlling reservoir damage by helping to stop severe lost circulation events.

Alternative Lost Circulation Material for Depleted Reservoirs

“…(Lécolier et al 2005;Savari et al 2014) • Temperature is the parameter that most affects the gelation kinetics of crosslinked polymers.…”