| Acid fracturing transformation technology is not only one of the leading technologies of the carbonate reservoir development wells for stable production, but also has become the essential and important means for exploration wells to discover oil or gas or ascertain the deposits of them. The technology has already drawn much attention from home and abroad, which provides a strong protection for discovering oil and gas, verifying the yield, stabilizing and enhancing oil recovery ratio, and exploiting oil and gas resources economically and efficiently. In high temperature conditions about 170℃~ 180℃, if the viscosity of gelling acid is not enough, the penetrating deep cracks can not effectively be formed because of its bad herm tolerance. Under the condition of ambient temperature and 170s-1, the viscosity of gelling acid is generally 20mPa ? s. At about 150℃, the viscosity of gelling acid is only 6 ~ 8mPa ? s, and acid effective distance is leaded to less than 60m. Therefore, it is needed to further enhance the viscosity of gelling acid. At present, in the aspect of the acid fracturing improvement of the deep reservoir at high temperature (such as reservoir temperature higher than 170℃, zones more than 4000 meters in depth), the basic research, the optimal design and the match of the chemical agent have to be studied further. When acidification polymerized in aqueous solution, such problems as low effective concentration of gelling agent, a product of lower molecular weight, properties of instability and inconvenience in transportation and use will occur. In this thesis, 2 - acrylamido--2 - methylpropane sulfonic acid, N, N - dimethyl acrylamide, acrylic acid methyl ester are used as materials, and with the inverse emulsion polymerization method and oil-soluble redox initiator system, gelling agent is synthesized. The mechanism and kinetics of emulsion polymerization of the gelling agent are studied. Through experiments, it is discussed the effect of the initiator concentration, emulsifier, reaction temperature, monomer concentration, polymerization rate and the copolymer molecular weight. The gelling agent with emulsion state has properties such as low viscosity, good stability and low freezing point; and with good acidresistivity, thermo tolerance, shear resistance. Besides, it is able to be dissolved into the acid system directly, and is compatible with the commonly used acid additives, as well as its low costs. During the in-situ experiment of the emulsion system, by adding 3% -4%( mass fraction) to 25% (volume fraction)hydrochloric acid, it can quickly be tackified to form a stable performance of the gelling acid system. By mixing gelling agent with a certain concentration of hydrochloric acid and adding the corresponding gelling made of corrosion inhibitors( such as acid), the acid viscosity is enhanced, and the internal fluid convection speed and the proliferation speed are effectively lessened, thus the reaction rate of the acid and the rock is delayed. The gelling acid is made by adding 25%( mass fraction) hydrochloric acid to gelling agent. At 170℃, 170s-1 after having been sheared for one hour, the viscosity of the gelling acid is still greater than 25mPa.s; through experiments, including the gelling acid system's rheology testing, and its general performance testing, fracture conductivity and reaction kinetics of the gelling etching acid and carbonate core are being researched, then the acid-rock reaction kinetic equation is attained. It exerts an influence on a larger theoretical and practical significance, which lays the foundation of numerical simulation for the acid fracturing and enhances the effect of combination acid fracturing improvement of carbonatite which is at high temperature, in deep level. |
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