绒囊暂堵剂在深层碳酸盐岩储层转向压裂中的应用

为了明确绒囊暂堵剂在深层碳酸盐岩储层转向压裂中的适应性,选取塔里木盆地塔河油田奥陶系碳酸盐岩THX井岩心作为样品,开展了注入绒囊暂堵剂前后的岩石力学特征评价实验和绒囊注入含裂缝岩心后的封堵压力实验,然后在THX井进行了现场试验,首次评估了绒囊暂堵剂用于碳酸盐岩深井暂堵酸化的效果。研究结果表明:①绒囊注入后岩石弹性模量减小、泊松比增大、岩心弹塑性应变增大,从而提高了岩心的韧性变形能力;②封堵压力实验结果显示,绒囊暂堵后裂缝承压能力逐渐提升,在注入压力峰值后未出现"悬崖式"陡降,说明绒囊韧性封堵带已经形成且具有明显的封堵作用;③绒囊暂堵后裂缝封堵压力与裂缝宽度成负指数关系,并且随着裂缝宽度的增加,暂堵剂承压力达到稳定的时间缩短;④绒囊暂堵剂注入岩石后提升了岩石的抗变形能力,绒囊暂堵裂缝后在缝内形成憋压,当缝内净压力超过水平地应力差时强制裂缝转向,并且绒囊暂堵剂可以耐130℃高温。结论认为,绒囊暂堵剂能够满足深层碳酸盐岩暂堵转向压裂的需求。

Application of a fuzzy-ball temporary plugging agent to the diverting fracturing of deep carbonate reservoirs

To clarify the adaptability of a fuzzy-ball temporary plugging agent to the diverting fracturing of deep carbonate reservoirs, this paper selected the cores taken from Well THX in the Ordovician carbonate rocks of the Tahe Oilfield in the Tarim Basin as the research object. After the experiments were conducted for evaluating the rock mechanical characteristics before and after the injection of fuzzy-ball temporary plugging agent and for measuring the plugging pressure after the injection of fuzzy-ball temporary plugging agent into fractured cores, as well as field tests in Well THX. In addition, the application effect of the fuzzy-ball temporary plugging agent to the temporary plugging and the acidizing of deep carbonate wells was evaluated for the first time. And the following research results were obtained. First, after the injection of fuzzy-ball temporary plugging agent, the elastic modulus of rock decreases and the Poisson's ratio and the elastic–plastic strain of cores increases, so that the ductile deformation capacity of cores is improved. Second, the plugging pressure experiment results show that the bearing capacity of the fracture increases gradually after it is temporarily plugged by fuzzy balls, and no "cliff-like" steep drop occurs after the peak injection pressure, which indicates that the ductile plugging zone of the fuzzy-ball temporary plugging agent has been formed and exerted a plugging effect obviously. After the fracture is temporarily plugged by fuzzy balls, its plugging pressure is in a negative exponential relationship with its width. And with the increase of the fracture width, the time that the bearing capacity of the temporary plugging agent takes to reach the stable state decreases gradually. Fourth, after the injection of the temporary plugging agent into the rock, the deformation resistance of the rock is improved. After the fracture is temporarily plugged by fuzzy balls, pressure is built in the fracture and when the net pressure in the fracture is higher than the horizontal ground stress difference, the fracture is forced to divert. What's more, the temporary plugging agent can withstand a high temperature of 130 ℃. Therefore, it can satisfy the demand of temporary plugging and diverting fracturing in deep carbonate rocks.