Unconventional Acidification Of Carbonate Reservoirs

Acidizing technology is widely applied among carbonate reservoir stimulation processes, and the selection and design of acid fluid system is the key. But conventional acidizing treatment with normal acid fluid systems remains divers problems such as rapid reaction, heavy corruption and inability of forming productive wormholes. Focus on that, this paper designs a total unconventional acid fluid system named HR, which contains characteristics such as smooth reaction, long action and deeply etching ability. An unconventional way of carbonate reservoir acidizing treatment has been come up with according to the key technology, the acid fluid system. What kind of work has this paper done are listing as follow for demonstrating the unconventional treatment’s advantages:(1) Analysis of HR fluid system’s main body structure has been conducted by NMR and other micro analytical methods, and its pH curve has been drawn. Low rapid reaction and chelation mechanism of HR fluid system have been discussed from both theoretic and experimental scales to prove fluid system’s characteristics. And the main reaction mechanism between HR fluid system and carbonate reservoir has been made clear.(2) properties of HR fluid system has been evaluated by experimental methods, then compared with other conventional acid systems. Effects of pH value, temperature and rotational speed on carbonate reservoir dissolving capacity have been discussed; measured the chelation capacity of HR fluid system on different iron elements and result in a priority of other conventional chelate agent; core flood experiments are conducted to evaluate the capacity of forming etched wormholes from different acid systems, and in the end HR fluid system shows the best performance; under high temperature condition HR fluid system behaves as a good corrosion inhibiter.(3)According to the properties of HR fluid system this paper suggests relative treatment processes for carbonate reservoir unconventional acidizing. By establishing a mathematic model describing carbonate reservoir etched wormhole propagation suitable for HR fluid system, calculation models for relative flied treatment parameters are suggested.(4)Simulate the optimum injection rate of HR fluid system under different reservoir conditions and flied production bump pressure requirement. And according to those conditions this paper makes a best fluid systems select of a certain pH value. Complete an optimum injection rate template of HR fluid system and provide a guidance of flied unconventional carbonate reservoir acidizing technology.According to this paper’research, a new way of carbonate reservoir acidizing has been suggested. Coming up with a new unconventional acid system called HR fluid system, now there is a new method to acidize carbonate reservoir, which can come over some problems by using conventional acidizing technology. And this could make a difference on carbonate reservoir acidizing technology’s development in some degree.