Study On The Displacement Mechanism Of Expending Solvent-Steam Assisted Gravity Drainage (ES-SAGD)

A number of shortcomings and problems showed up as SAGD come into the late stageof the exploiting. For example SAGD spend a lot of energy and consumes large amounts ofwater and fossil fuels. And the using rate of energy of SAGD is very low. The proposal ofthe solvent-assisted SAGD solved the problems that conventional SAGD encountered in theexploiting. The advantages of SAGD and VAPEX method were combined in the oilextraction with the solvent-assisted SAGD. By the joint injection of the solvent and steamon the basis of the recovery rate of SAGD, the recovery rate can be improved further andthe energy consumption can be decreased, which is meaningful to the increase of theproduction of the oilfield and the energy conservation and emission reduction.Then the indoor experiments of the viscosity reduction of the heavy oil were carriedout with the heavy oil in Liaohe Oilfield, the rule of viscosity reduction of the heavy oil wasobtained then. The results of the experiment showed that the viscosity reduction ratio willincrease linearly as the injection ratio of the solvent goes up at the same temperature. At thesame injection ratio of the solvent, the viscosity of the solvent-oil mixture will decreasegreatly with the increase of temperature, but the difference of the viscosity reduction ratio isquite small. In the three solvents, the viscosity-reducing effect of n-pentane is best, followedby n-hexane, isohexane is the worst.The regular SAGD method was simulated firstly in the numerical method on the basisof the geological data of the reservoir in the SAGD experimental area of the dual horizontalwells in Liaohe Oilfield. The evaluations about the influence of the dryness, the temperatureand the injection rate of the injected steam to the development effect have been made on thefoundation of the conceptual model.Finally, the solvent-assisted SAGD technology was simulated in numerical method, which exploring the oil driven mechanism, the extended features of the steam chamber wereobtained. And the solvents were filtered, the result showed that the oil displacement effectof n-pentane is the best. Then the optimization of injection parameters was made, thereasonable injection parameters were determined, in which the dryness of the injected steamis0.7, the temperature of the steam is280degree centigrade, the injection rate is160m3/d,and the injection ratio is0.1. With the reasonable injection parameters, the final recoveryratio is74.91%, which is14%higher than conventional SAGD.