通道压裂中流动通道形态影响因素实验研究

Experimental study of influencial factors on flow channel morphology in channel fracturing

通道压裂是低渗透致密油气藏高效、低成本开发的关键技术,其关键是在水力裂缝中形成供油气流动的畅通通道网络,但目前针对通道压裂支撑剂铺置形态、流动通道特征研究尚处于起步阶段。通过大型平板裂缝可视装置,开展通道压裂支撑剂动态输送实验研究,分析纤维、压裂液、支撑剂、泵注排量和脉冲时间对支撑剂输送和流动通道形态的影响。实验结果表明:纤维和压裂液决定能否在支撑裂缝中获得流动通道,而泵注排量和脉冲时间对流动通道形态有较大影响,而支撑剂密度和粒径对流动通道形态几乎无影响;胍胶分子链缠绕在纤维表面,使得纤维网状结构范围增大、强度增强,两者共同提高了携砂液脉冲段在输送过程中的稳定性;流动通道类型可以分为3类,且流动通道形态受到泵注排量和脉冲时间乘积的控制。当脉冲单元注入参数为2.5~5.0 L时,形成的高速通道形态最优,支撑裂缝导流能力最大。

Channel fracturing is the key technology to develop low and ultra-low permeability reservoirs with high efficiency and low cost. The key of channel fracturing is to create the unimpeded channel network in the fractures for oil and gas flow. However,researches on the proppant shape and channel characteristics in channel fracturing are in the initial stage. A large-scale visual slot equipment was used to simulate the proppant transport process in the channel fracturing. The effects of fiber,fracturing fluid,proppant,pumping velocity and pulse time on proppant transport and flow channel were studied.The experimental results show that the fiber and fracturing fluid determine whether the flow channel can be formed within the propped fracture,and the pump velocity and pulse time have a great influence on the flow channel morphology. The proppant density and size have less influence on the flow channel morphology. The molecular chain of guar gum is wound on the fiber surface,which makes the range of fiber network increase and the strength enhance. The fiber network and molecular chain together improve the stability of the slurry pulse in the transportation process. The flow channels can be divided into three categories and the flow channel morphology is controlled by product of pump velocity and pulse time. When the injection parameter of pulse unit is 2.5-5 L,the flow channel morphology obtained is optimal and the conductivity of propped fracture is the largest.