Abstract

According to the requirements of rapid setting at low temperatures and long-term performance during high-temperature production on cementing for heavy oil thermal recovery wells, this study proposes the application of aluminate cement to cementing of heavy oil thermal recovery wells. Against the background of operation conditions in Liaohe Oilfield, the strength decline mechanism of the conventional silicate cement stone added silica sand were evaluated by simulating the high-low temperature circulating humid environment that the cement sheath of the heavy oil thermal recovery well faced with. Then, through laboratory experiments, the research compounded a kind of mineral clinker based on aluminate cement, prepared fluid loss agent J73S and retarder SR compatible with aluminate cement and designed a new-type thermostable aluminate cement slurry system with an applicable density range of 1.70g/cm3~1.90g/cm3 and temperature range of 30°~80°. Moreover, the hydration product and the thermostable mechanism of the modified aluminate cement slurry were analyzed through this simulation. According to the results, with the crystalline transforming at high temperatures, the strength of conventional silicate cement with silica sand substantially declines under the condition of multi-cycle high-low temperature circulation, therefore it cannot satisfy the cementing requirement of thermal recovery wells effectively. The thermostable aluminate cement slurry system features excellent engineering performance: the slurry density difference is lower than 0.02 g/cm3, the fluid loss is less than 50 ml, the thickening time is adjustable from 60 min to 300 min, the 24h strength is up to 14 MPa, and the compressive strength of cement slurry can still reach 25 MPa after two rounds of high-temperature testing. In addition, the SiO2 in the additives massively participate in the hydration reaction, endowing the modified aluminate cement slurry with favorable thermostable performance and long term stability. The application of the cement slurry system to cementing for heavy oil thermal recovery wells of Liaohe Oilfield exhibits a smooth operation process and excellent cementing quality, so it can efficiently satisfy the cementing operation requirement of heavy oil thermal recovery wells efficiently.

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