CO_2相态变化在干法压裂中的应用——以锦125井为例

The phase change of carbon dioxide in fracturing engineering

CO_2干法加砂压裂对低压、低渗透、强水锁/水敏储层的压裂改造效果十分明显,但CO_2的相态变化复杂,压后放喷易形成水合物。因此,笔者根据CO_2相态变化曲线图,研究了CO_2在干法加砂压裂中各阶段的相态变化,证实了CO_2干法加砂压裂能够在三低气井中应用。同时,笔者结合CO_2水合物的形成机理和数学模型,形成了CO_2水合物预测图版,预测了CO_2形成水合物的压力、温度。基于以上研究,笔者提出从井口加入乙二醇预防井口附近水合物的产生。本论文以锦125井为例,该井泵注液态二氧化碳580 m3和砂量56 m3开展干法压裂,压后采用降压、升温、加入抑制剂等方法排液288.8 m3,顺利完成了试气压裂作业。

Fracturing with carbon dioxide is effective to low-pressure, low-permeability,strong water-locked and water-sensitive reservoirs. However, the phase change of CO2 is so complex and it is easy to form a hydrate after the pressure is released. Therefore, the author studied the phase change of fracturing with carbon dioxide in each stage, and confirmed that fracturing with carbon dioxide can be applied in the three low-gas wells. At the same time, a prediction map of CO2 hydrate is formed by the author combined with the formation mechanism and mathematical model of CO2 hydrate. So the pressure and temperature of CO2 hydrate formation are predicted. Based on the above research, it is proposed to prevent the formation of hydrate near the wellhead by adding ethylene glycol from the wellhead. Taking Jin-125 well as an example, this well was injected 580 m3 liquid carbon dioxide and 56 m3 sand in fracturing engineering.And we use antihypertensive, heating, adding inhibitor and other methods to drained 288.8 m3 liquids and completed the gas fracturing-test operation successfully.