In this paper, we will introduce the performances, research's process and a case study of ultra-high temperature fracturing fluid. The ultra-high temperature well is a carbonate formation with 205°C, located in HuaBei Oilfield, East China. The temperature of NiuDong carbonate formation is more than 200°C in HuaBei Oilfield in East China, acid-fracturing is an important stimulation for NiuDong reservoir. As known, the guar fracturing fluid is usually used less than 177°C because of guar molecule's performances, so we develop a ultra-high temperature polymer as pad fluid of acid-fracturing to stimulate the NiuDong carbonate, the polymer is a novel structural terpolymers which can be cross-linked by crosslinking agent and broken by APS. The structure of thickener is a key factor to increase the high temperature resistance of polymer, so a novel molecular structural polymer with C-C bond backbones and C=C bond monomers is developed for the ultra-high temperature fluid, and the hydration group with C-C, C-S, C-N is also added in the side chains with the purpose of decreasing the dissolution time of the polymer. An organic zirconium crosslinking agent with amide groups is selected to crosslink the polymer fluid, and the cross-linking time is controlled. After cross-linked, the network structures of gel fluid like the uniformed petals in the scanning electron microscope, so the viscosity is very high. Under the conditions of 200°C, 170s−1 and shearing120 minutes, the residual viscosity is more than 130mPa.s, The evaluated tests show that carrying proppant of polymer fluid are good, low interfacial tension and low residues. The ultra-high temperature polymer fracturing fluid has been successful used in a Well of NiuDong sag. Ultra-high temperature polymer fracturing fluid provides a selection for the formation with more than 200°C.

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