水力喷射注氮压裂工艺及参数设计计算

HYDROJET INJECTING NITROGEN FRACTURING TECHNOLOGY AND ITS PARAMETERS DESIGN

针对常规水力压裂技术在低压、低渗和能量衰竭地层应用中,常会出现压裂液滞留及返排率低等问题,提出了水力喷射注氮压裂方法,并论述了该方法的特点及施工流程。在分析水力喷射注氮压裂井筒流动压降基础上,结合水力喷射参数及喷嘴组合优选原则和具体实例给出了工艺参数设计方法和计算步骤。计算结果表明,对于同一喷嘴组合而言,地面油管压力随着油管排量的增加而增加,但会随着井口氮气干度的增加而降低;对于不同喷嘴组合,都有其所适用的油管排量和井口氮气干度范围,可用于指导施工时参数设计;水力喷射注氮压裂存在一个最优油管泵注排量,该排量可以满足设计中所有的井口氮气干度要求,文中算例的最优油管施工排量为2.5-3.0 m^3/min;最后分析了水力喷射注氮压裂相对于常规液氮压裂所具有的优势。分析和计算的结果可以为水力喷射注氮压裂现场应用以及参数设计提供参考。

According to the problems of fracturing fluid retention and low flowback rate in conventional hydraulic fracturing of low pressure,low permeability and energy decline formation,hydrojet injecting nitrogen fracturing technology was put forward and the characteristics and process of this new treatment were introduced. Based on the analysis of wellbore pressure drop in hydrojet injecting nitrogen fracturing well,and combining with the selected principles of jet parameters and nozzle combination,the parameters design method and wellhead pressure prediction was presented. It was shown that for the same nozzle combination and certain tubing stream flow rate,wellhead pressure increased with the growth of tubing flowrate and decreased with the growth of wellhead nitrogen volume fraction. For different nozzle combinations,there are specific tubing flowrate and wellhead nitrogen volume fraction range which could meet the principles of parameters design. For certain depth,an optimal tubing stream flow rate range existed,which could satisfy different surface nitrogen volume fraction. In this case,the flow rate range was 2. 5~ 3. 0m3/ min. At last,the advantages of hydrojet injecting nitrogen fracturing technology were analyzed. This study could provide theoretical reference for field application and parameters design of hydrojet injecting nitrogen fracturing.