Cementing slurry technology for ultra-deep and ultra-high temperature fractured gas reservoir

In Shunnan well block, it is a fractured gas reservoir with great leakage risk and the set cement tends to suffer strength degradation under ultra high temperature. And consequently, the cementing quality in gas layers cannot satisfy the needs of subsequent construction. In this regard, the cementing technology of reinforced leakage control slurry was researched in this paper. Firstly, the method to prevent the degradation of slurry strength was developed by investigating the effect of fine silica dosage on the set cement strength. Then, the plugging capacity of fiber system was evaluated by using the slurry static plugging device, and the leakage control slurry technology was formed. Finally, by means of the slurry strength degradation prevention and leakage control method, the key additives were optimized and thus the high-temperature reinforced gas channeling prevention slurry system used for the well cementing in gas reservoirs was worked out. The experimental results show that when the well temperature is higher than 180 ℃, the strength of the set cement with fine silica content higher than 50% doesn’t degrade easily. To plug 1 mm fractures and 2 mm fractures, it is necessary to add 6 mm 0.6% fibers and 8 mm 1% fibers, respectively. The new slurry system has better capacity of gas channeling prevention, and its application in Shunnan well block is successful. This cementing technology of high-temperature reinforced leakage control slurry is applicable in Shunnan well block and provides the technical guarantee for the exploration and development of this block.