Chemical Sealant Loss Circulation Materials for Fractured Formations: Right-Angle Viscosity Development with High Plugging Efficiency

Abstract

Numerous lost circulation materials (LCMs) are sold in the global market to cure losses in highly fractured formations, but the success rate remains minimal. Lost circulation (LC) is a common challenge of global operators and service companies during either drilling or the oilwell construction phase of development and exploration. A new chemical-sealant-based LCM (CS-LCM) was developed to cure severe-to-total losses in highly fractured formations. The new CS-LCM is dispersed in a nonaqueous carrier fluid (NAF) and quickly forms a highly malleable viscous mass upon exposure to an aqueous reactant fluid and then sets harder under a wide range of temperatures. Comprehensive and systematic tests were conducted on the new CS-LCM to determine the speed of the reaction at an optimized interval of time upon interaction with the reactant. Testing performed on the new CS-LCM included evaluating its flowability before and after the reaction and estimating the compressive strength. Additionally, the developed strength robustness of the CS-LCM was evaluated by its ability to withstand large differential pressures across extra-large holes (31 mm) in test media (simulating vugs in a formation). The reaction rate of the CS-LCM showed measurable right-angle viscosity (RAV) development once the CS-LCM was preconditioned at a bottomhole circulation temperature (BHCT) and allowed to mix with preconditioned (at BHCT) reactant. A significant amount of compressive strength (>500 psi) buildup was observed in less than 1 hour of reaction time, which sustained more than 1,000 psi differential pressure on large vugs. The fast increase in viscosity (i.e., RAV) and quick strength development are the result of fast-reacting chemical additives present in the mixture. Additionally, the resultant set CS-LCM was determined to be soluble in 15% hydrochloric (HCl) acid at ambient temperature; hence, it is a viable solution for a reservoir section. The new CS-LCM was developed to mitigate severe-to-total losses in highly fractured formations by means of RAV development followed by rapid strength buildup in a short interval of time, thus helping prevent overdisplacement away from the wellbore, hence minimizing nonproductive time (NPT) and drilling mud losses.

Nanosilica-Based Loss Circulation Composition to Cure Moderate to Severe Losses

“…A new chemical-sealantbased loss circulation material was developed to cure severe-to-total losses in highly fractured formations. The new sealant, which is dispersed in a non-aqueous carrier fluid, quickly forms a highly malleable viscous mass upon exposure to an aqueous reactant fluid and then subsequently sets harder under a wide range of temperatures [15]. The use of appropriately sized lost circulation materials has been shown to change the particle size distribution of a drilling fluid.…”