致密油油藏空气泡沫调驱机理实验

以长庆某致密油井区取心样品、注入水与地层水、优选的空气泡沫体系等为基础，利用一维长岩心驱替实验装置开展了致密油储层基质与裂缝岩心分别注入纯泡沫液、空气与空气泡沫的注入能力实验，揭示在实际储层条件下，空气泡沫体系无法直接进入致密油基质岩心，但由于泡沫剂受到储层吸附，消泡后的纯泡沫液与气体可以顺利注入致密油基质岩心实现稳定驱替。设计并开展了基质渗透率级差为10、基质与裂缝双重发育的三管并联岩心驱替实验，明确了空气泡沫封堵裂缝调驱机理。泡沫流体主要进入裂缝岩心并有效封堵裂缝，部分泡沫消泡后形成的泡沫液与空气进入并驱替基质中的剩余油，最终空气泡沫驱残余油饱和度比水驱降低了21.12%，驱油效率提高了32.89%，改善水驱后开发效果明显；为避免暴性水淹的低效阶段，应在含水90%以前尽早转入空气泡沫驱，提高采油速度与经济效益。

Experimental Study on Profile-Controlling Mechanisms of Air Foam Flooding in Tight Oil Reservoirs

Based on the coring samples, injection water and formation water, optimized air foam, etc, from a typical tight oil block in Changqing oilfield, the 1D long core flooding system is utilized to carry out the experiments of injection capacity of pure foaming liquid, air and air foam into the core matrix and fracture. The experimental results indicate that under the real formation conditions, the air foam is not able to be injected into the tight core matrix directly, but because some of the foaming surfactant is absorbed by the reservoir rock, the defoamed liquid and air are able to flow into the tight core matrix and realized the stable displacement. According to the actual formation characteristics, three-core parallel flooding experiment is designed which include two matrix cores with permeability difference of 10 and one fractured core and the profile-controlling mechanisms by air foam are analyzed and determined. The air foam majorly flows into the fractured core and plugs the fractures, a part of defoamed liquid and air flow into the matrix cores to displace the waterflooded residual oil.Finally, the residual oil saturation of air foam flooding is 21.12% lower than that of waterflooding, and the oil displacement efficiency is 32.89% higher, which indicates encouraging performance following waterflooding. In order to avoid the inefficient production phase of ultra high watercut, it is recommended to convert to air flooding as early as possible before the water cut reaches 90%, so as to enhance oil rate and economic performance.