基于压裂液滤失驱油作用的油井压裂方法及实践效果

Fracturing Method for Oil Well Based on the Displacement of Filtrated Fracturing Fluid and Its PracticalEffect

卢祥国 曹 豹 谢 坤 何 欣 王珂昕

LU Xiangguo CAO Bao XIE Kun HE Xin WANG Kexin

聚合物压裂液在大庆油田压裂施工中取得了较好的增油降水效果。为了探索聚合物压裂增油机理，开展了压裂液驱油效果和滤失距离评价实验，从滤失和驱油角度分析了聚合物压裂液压裂增油作用机理，提出“驱 油+压裂”提高油井压裂效果的方法，并在低渗透油藏油井进行了现场试验。结果表明，与胍胶溶液和聚合物凝胶溶液相比，聚合物溶液中分子聚集体尺寸较小，与岩心孔隙尺寸配伍性较好，滤失性较强，驱替过程中波及区域较大，驱油效果较好。与聚合物压裂液相比，聚/表二元体系驱油效果并未明显增加。滤失压裂液扩大波及体积作用明显强于提高洗油效率作用。随压裂液段塞尺寸和注入压差增加，压裂液滤失量增大，波及体积扩大，驱油效果提高。在相同渗透率和注入压差下，滑溜水溶液和聚合物溶液滤失速率更高，滤失能力更强；在同等滤失时间下，滑溜水溶液和聚合物溶液滤失距离较大，但滑溜水溶液驱油效果较差。聚合物压裂液良好的滤失性及驱油作用是大幅提高压裂施工增油效果的主要机理，可提高裂缝两侧基质内难动用原油的采出程度。基于聚合物压裂液滤失及驱油机理，提出了“驱油+压裂”（先驱油后造缝）方法。与常规压裂和“压裂+驱油”（边造缝边驱油）方法相比，该方法压裂液滤失量较大，扩大波及体积效果较好，增油效果更佳，对进一步提高油井压裂施工增油效果具有重要意义。

Polymer fracturing fluid has achieved good effect of increasing oil production and lowering water cut in Daqing oilfield. In order to explore the mechanism of polymer fracturing，the evaluation experiments of oil displacement effect and filtration distance of fracturing fluid were carried out. The mechanism of polymer fracturing was analyzed from the perspective of filtration and displacement. The method of“oil displacement+fracturing”was proposed to improve the fracturing effect of oil well，and the field test was carried out in oil well of low permeability reservoir. The results showed that compared with agar solution and polymer gel solution，the polymer solution had smaller molecular aggregate size，better compatibility with core pore size，and stronger filtration capacity，which could achieve larger sweep volume and better displacement effect. Compared with polymer fracturing fluid，the displacement effect of polymer and surfactant binary system was not significantly improved，which indicated that the effect of expanding the sweep efficiency of filtration fracturing fluid was obviously stronger than that of improving the displacement efficiency. With the increase of slug size and injection differential pressure，the filtration rate of fracturing fluid increased，and the sweep volume and the oil displacement effect were enhanced. Under the same permeability and injection differential pressure，the fluid loss rate and the filtration capacity of polymer solution and slickwater solution were higher，and the filtration distance was larger under the same filtration time，but the oil displacement effect of slickwater solution was lower. The good filtration and oil displacement effect of polymer fracturing fluid were the main mechanisms to greatly improve the oil production effect of fracturing operation，which could improve the oil recovery in the matrix near both sides of the fracture. Based on the filtration and oil displacement mechanism of polymer fracturing fluid，the“oil displacement+ fracturing”（fracturing after displacing）method was proposed. Compared with conventional fracturing and“fracturing+oil displacement”（fracturing with displacing），it could achieve better oil increase effect with higher filtration loss and sweep efficiency of fracturing fluid. The method could be of great significance to further improve the oil production effect of fracturing operation for oil well.