Low-density and Strength Cement Slurry for Fractured Formation

The Yanchang formation in the E’nan block is the naturally fractured pay zone into which losses of cement slurry and hence the contamination of the reservoir often took place. To solve this problem, a low-density high strength high toughness cement slurry was formulated, based on the principle of low density, loss prevention and toughness improvement, to effectively seal the reservoir formation. An innovative epoxy-nanometer liquid silica cement slurry with low density high strength high toughness cement slurry was formulated with the synergy of several additives; a self-developed light-weight agent, a waterborne epoxy emulsion and a nanometer liquid silica that were carefully selected. The density of the cement slurry is 1.65 g/cm³. Performance evaluation of the cement slurry showed that the filter loss of the cement slurry can be controlled within 40 mL/30 min, the thickening time of the cement slurry has reasonable time range. The set cement has high compressive strength, the elastic modulus of the set cement is less than 7.0 GPa. The set cement has good elastic and plastic mechanical properties, and low contamination to the reservoir. Using this technology, low density, high strength and toughness enhancement were achieved. Later stage reservoir fracturing of wells cemented with this cement slurry can be easily performed. The application of this technology has ensured the successful exploration and development of the Paleozoic natural gas in E’nan area.