Experimental Study On Layers Subdivision And Enhanced Oil Recovery Of Complex Fault Block Reservoir

There being characteristics such as many and small fault blocks,serious heterogeneity of intra-bed and inter-bed in complex fault block reservoir,the effect of water flooding is becoming worse and worse by means of general water injection. In many cases,That is because the injected water tends to break through early in permeability layer and water cut rises fast, and also because low permeability layer has a poor sweep efficiency due to a higher Threshold pressure. What is worse, with water flooding going on, conflicts between layers become more and more serious, and economic benefit gets worse and worse. Making use of methods of modern physical simulation, technology of monitoring oil saturation, this paper did some research on factors,such as permeability ratio,strata combination,areal heterogeneity,well pattern,which have influencing on effect of water flooding and chemical flooding and distribution of remaining oil. The results show that for vertical heterogeneity reservoir, With the permeability ratio increasing,fluid diversion rate of low permeability layer trended to decrease and effect of water flooding became worse. When permeability ratio and injection intensity were maintained at a constant, With the number of small layers increasing, the fluid diversion rates of high and low permeability presented descend trend,while the fluid diversion rates of the middle permeability layer indicated continuously increasing trend. Moreover, oil recovery of water flooding remained almost unchangeable in high permeability layer, but increased gradually in the low permeability layer. In general,oil recovery of water flooding of combined Layer fell firstly and then increased.However, Injecting fluid diverting agent or displacing agent after water flooding,the fluid absorption(or fluid diversion rate)of middle and low permeability layers became larger significantly,and the oil recovery became greater subsequently. In many cases,the remaining oil mainly distributed in middle and low permeability layer after water flooding and chemical flooding. Fluid Diverting Agent or displacing agent could make more succeeding fliud enter low permeability layer. That is to say, it further improved sweep efficiency. However, it depended upon reasonable choices such as chemical agent type, slug size and its combinations in order to do less chemical harm to low permeability layer. For areal heterogeneity reservoir, the more serious areal heterogeneity , the worse effect of water flooding. Nevertheless, the effect of water flooding and chemical flooding would be further improved by means of Horizontal well or increasing the number of injection well. What is more,Enhanced oil recovery by chemical flooding could increase by 10 percent more or less after water flooding. Sweep efficiency increased rapidly at the initial stage of water flooding and then became steady. However,sweep efficiency rose by a big margin at the stage of chemical flooding, and remained almost unchanged at the stage of succeeding water flooding. After water flooding and chemical flooding,remaining oil greatly distributed in both sides far away from the mainstream line,the low permeability zone and the zone that injection-production well systems were imperfect.