Study On Mechanism And Heavy Oil Recovery Enhanced By Chemical Flooding

With fewer reserves of conventional crude oil, the huge heavy oil resources willplay a vital role in the energy structure in the future, whose exploitation has becomean important subject for future energy development. In this paper, recovery andmicroscopic mechanism of polymer flooding and viscosity reducer flooding wascompared through the selection and the performance evaluation of polymers andviscosity reduction system indoor, which can provide the necessary basis forconventional heavy oil exploitation.The polymer screened was a sulfonic acid anionic hydrophobically associatingpolyacrylamide that contained benzenes and part of the amides substituted and theCAC measured by different methods was150~200mg·L-1.The polymer had high viscosity and was resistant to salt and temperature. Whenconcentration was1500mg·L-1, the polymer viscosity increased to315.2mPa·s; theloss rate of viscosity at the degree of mineralization of19334mg·L-1was only54.79%;60℃, the residual viscosity was196.7mPa·s. The reason was that dense networkstructure by the intermolecular association that is less susceptible to salt appeared.After indoor simulation of porous medium shear the viscosity loss rate was81.82%because of the part of the loss of molecular weight, shear resistance was in general.The system of anion reducing agent XJ and nonionic drop mixed system agentOP-10has good viscosity, temperature resistance, salt resistance and emulsifyingproperties. For the0.3%XJ+0.2%OP-10viscosity reducer system,60℃, viscosityreduction rate can reach more than95%;180℃, viscosity reduction rate remainedwas more than90%; the viscosity solution formation water prepared had goodviscosity reducing effect. The dispersed emulsion by0.3%XJ+0.2%OP-10system hadsmall and uniform oil particle, whose distribution range was5~20μm and was lessthan the reservoir pore throat average radius of13.81~31.06μm. The concentration ofXJ was determinated by two-phase titration method, and the concentration of OP-10was determinated by cobalt thiocyanate colorimetry. The adsorption of oily sandreached its saturation value of16.28mg·g-1in the complex system. The ultimate recovery rate of water flooding experiment was only41.1%; therecovery rate of polymer flooding after water flooding increased by18.55%, and thetotal recovery rate reached57.18%; under the optimum experimental conditions: aone-time injection of0.3PV0.3%XJ+0.2%OP-10solution, the recovery rate ofviscosity reducer flooding after water flooding increased by18.67%, and the totalrecovery rate reached56.7%. After water flooding large presence of residual oil wasin unswept areas, and the film and lump was in swept areas; mechanism of polymerflooding was to increase the sweep area by increasing the viscosity of displacingagent and the pull effect on the oil film and blind-residual oil; recovery rate ofviscosity reducer flooding mainly relyed on transport of large oil particles afterdeformation and emulsification to reduce the flow resistance, and boosting function ofdispersed oil particles to oil film and the remaining oil stripping by drawing canenhance recovery efficiency. Polymer flooding mainly depended on increasing sweeparea and viscosity reducer flooding mainly relyed on enhancing oily recoveryefficiency, so that recovery rates was silimar.