化学驱储层内驱油剂性能及其变化规律

Oil Displacement Agent Properties and Its Variation Regulation in Chemical-flooding Reservoir

三元复合驱化学驱油剂在储层内滞留和由此引起的色谱分离现象等问题是石油科技人员十分关心的问题。依据矿场实际需求,以大庆喇嘛甸油田储层地质和流体为研究对象,首次在18 m长含天然油砂人造岩心上开展了强碱三元复合驱过程中储层内驱油剂性能及其变化规律实验研究。结果表明,与聚合物相比较,碱和表面活性剂相对分子质量小,不可及孔隙体积较小,波及体积较大,滞留量较大,突破时间较晚,导致三者间出现色谱分离现象,进而减弱三元复合驱油的协同效应。在强碱三元复合体系注入过程中,当注入段塞尺寸达到0.482数0.543 PV时,整个岩心长度区域内油水界面张力可以达到10-2m N/m数量级,局部区域可以达到10-3m N/m。三元复合体系在岩心内传输运移过程中,因聚合物分子线团尺寸受到孔隙剪切作用而减小,溶液黏度从注入端到采出端逐渐减小,采出端黏度损失率高达69%。后续水驱结束时,岩心内残余油饱和度和表面活性剂滞留量从注入端到采出端逐渐减小,出口端处残余油饱和度58%,表面活性剂滞留量0.6462 mg/g。

As for alkali-surfactant-polymer system, the problem of the chemical flooding agent retention in reservoir and the resulting chromatographic separation phenomenon, is the hot-button issue among petroleum science and technology personnel. According to field actual demand, the oil displacement agent properties and its variation regulation in reservoir was researched during the course of alkali-surfactant-polymer flooding with strong base at artificial core containing natural sands with the length of 18 m, based on the geological and fluid characteristics in reservoir of Daqing Lamadian oilfield. The results showed that, comparing with polymer, the relative molecular mass of surfactant and alkali is smaller, so the inaccessible pore volume was smaller, their swept volume was larger, their liquid retention was larger and their breakthrough time was later, which led to chromatographic fractionation phenomenon among the three parts, and weakened their synergistic effect in oil displacement process. During the injection process of alkali-surfactant-polymer composite system, when the injected slug size was up to 0.482-0.543 PV, the interracial tension could reach to a magnitude of 10-2 mN/m within the whole length of the core and reach to a magnitude of 10-3 mN/m in the local area. During the transmission and migration process of alkali-surfactant-polymer composite system in theartificial core, the polymer molecular coil dimension decreased due to the pore shear effect, the viscosity of the system gradually reduced from injection side to produced end, as a result, the viscosity loss rate of produced end was as high as 69%. At the end of succeeding water flooding, the residual oil saturation and the retention of surface active agent in the core gradually reduced from injection side to produced end, and the residual oil saturation was of 58% and the retention of surface active agent was of 0.6462 mg/g at the produced end.