Study of Heat Transfer During Steam Injection and Effect of Surfactants on Steam Mobility Reduction

摘要

A system of differential equations describing the temperature distribution in the insulation and the heat frontal movement in a cylindrical core during steam injection is derived and solved in Laplace space. The real-time solution is obtained by using the Stehfest algorithm. The solution shows that movement of the heat front is strongly dependent on the heat transfer coefficients at the inner and outer boundaries. Experimental results of steam injection are shown at pressures varying from 0.11 to 1.42 MPa (16 to 206 psia). The apparent thermal conductivity of the insulation as a function of temperature was obtained by comparing experimental data with an analytic solution. When the pressure of the steam zone changed during a run, it was found that changes of volumetric heat content in the heated core and the insulation may be treated as though they were changes in heat injection rate. The method of succession of steady states can also be used to approximate the heat frontal movement for cases of variable pressure. For displacements using Kaydol as the in-place oil, the initial oil saturation had little effect on irreducible oil saturation. A method for approximating the steam swept volume is presented using an adjustment to the Marx and Langenheim equation and a new definition of the critical time. The steam mobility can be reduced by alternate injection of steam and surfactant slugs. The steam mobility decreased with an increase of surfactant concentration and with an increase in the slug sizes of the surfactant solutions. The number of surfactant slugs required to obtain the maximum mobility reduction was found to be a function of surfactant concentration and backpressure. The addition of nitrogen in the injected steam further reduced the steam mobility, with very little effect seen at concentrations of nitrogen above about one mole percent. 90 refs., 86 figs., 21 tabs. (ERA citation 11:055744)