Application of a Self-Solidifying Lost Circulation Material in Well G21X3 in Jidong Oilfield

The Well G21X3 is a key exploratory well drilled at the upper part of the Gao-21 fault in Gaonan slope. The designed completion depth of this well is 4,392m. When drilled to 2,670 m, the bit drilled into caves and the mud lost return. In drilling the Dongying-1 member and Dongying-2 member, totally four times of mud losses occurred and eight times of mud loss control jobs were performed. Totally, 250 m³ of mud was lost into the formation. To deal with the mud losses in the future, a new technology was presented based on the analyses of the deficiencies of the mud loss control techniques previously used. The new technology involves the use of a self-solidifying lost circulation material (LCM). Laboratory evaluation of the self-solidifying LCM was performed on its morphological feature, solidifying state at different temperatures and the pressure bearing capacity of the formation plugged with the self-solidified LCM. The mechanism of the self-solidifying LCM is to coat LCMs such as mica, fiber, nutshell and silica with a layer of resin, and these LCMs are then pumped into the loss channel, depositing there. The resin on the surface of the LCMs then condenses at the temperature prevailing in the loss zone and solidifies into hard lumps, thereby increasing the strength and stability of the LCMs. This technology has been successfully used in controlling mud losses occurred in the Well G21X3. The procedure of using the selfsolidifying LCM is the same as that of the compound LCMs, and is easy to operate. This technology is widely applicable, and has broad prospects of application.