Thermally Activated Lost Circulation Mitigation of Severe Losses in Fractured and Vugular Formations

Severe lost circulation occurs frequently in fractured and vugular media. When drilling fluid enters vugs or fractures, it experiences a temperature increase due to the reduced influence cooling from the wellbore and the growing influence of the higher in-situ formation temperature with invasion depth. This temperature increase can be exploited to help plug the vugs or fractures. If the lost fluid contains Thermally Activated Lost Circulation Materials (TALCMs), it experiences a strong temperature-induced increase in viscosity, making it effectively unpumpable and non-displaceable, thereby stopping further fluid losses. TALCMs can be employed as additives in drilling fluids, in dedicated treatment pills, or mixed with cement for dedicated squeezes. TALCMs are a new type of temperature-tunable material that can be engineered to mitigate severe losses in a variety of geological formations with varying temperature gradients and depths. By exploiting the formation’s own temperature gradient, effective fracture or vugular sealing can be obtained, which opens up an entirely new way to mitigate severe losses in oil, gas, and geothermal wells, where lost circulation is a prime source of non-productive time.