南川页岩气田压裂工艺改进及应用

The Improvement and Application of Fracturing Technology in the Nanchuan Shale Gas Field

  • 摘要: 页岩储层具有低孔隙度和特低渗透性特征,必须进行大规模体积压裂改造以形成人工缝网。南川页岩气田开发已经形成相对完善的压裂工艺技术体系,但随着甜点储量规模化生产,亟需深入研究并进一步改进压裂工艺。从南川页岩气田不同井网储量动用、射孔方式、投球暂堵、加砂模式等方面提出了页岩气压裂工艺改进思路和方法,并通过现场应用效果评价了改进工艺的可行性。系统总结了压裂工艺改进措施:鉴于井网关系和开发目标的差异,对不同类型井组的压裂改造区域进行差异化控制;超深穿透射孔方式为深层高应力页岩储层压裂提供了重要的工艺基础,满足了电动压裂设备数量和压力等级的限制;借鉴重复压裂及加密井压裂工艺中的投球暂堵技术,优化了投球数量与时机,抑制了主裂缝过度延伸;精细化压裂,支撑剂体系趋于完善,形成了“初始小粒径远输前缘铺置+中段中粒径主流通道支撑+尾段大粒径缝口收尾”三级连续加砂模式。改进后的压裂工艺现场应用效果显著,在统计的现场投球暂堵中,封堵有效率79.8%,在超深穿透工艺下,为更多加砂和注液提供了压力窗口;提高了加砂强度和小粒径占比,显著提升了裂缝导流能力和支撑效果,压后日产气量从3.30×104 m3提高至8.46×104 m3。研究结果表明,通过综合应用差异化压裂设计、超深穿透射孔技术、优化投球暂堵以及精细化三级加砂模式,可显著提升南川页岩气田的压裂改造效果和经济效益,为南川页岩气田有效开发提供了技术保障。

     

    Abstract: Due to the low porosity and extremely low permeability of shale reservoirs, they must undergo large-scale volume fracturing to create an artificial fracture network. The development of the Nanchuan Shale Gas Field has already formed a relatively mature fracturing technology system. However, with the large-scale production of sweet spot reserves, there is an urgent need for in-depth research and further improvement of fracturing technology. Improvement ideas and methods for shale gas technology were proposed for the Nanchuan Shale Gas Field. They involve the utilization of reserves in different well patterns, perforation methods, temporary plugging with ball injection, and sand addition modes. The feasibility of these improvements was evaluated through on-site application effect assessment. Fracturing technology process improvements were summarized systematically. In view of the difference in well pattern and development objectives, the fracturing modification area of different types of well groups was controlled differently. The application of an ultra-deep penetration perforation provided a crucial technological foundation for fracturing in deep and high-stress shale reservoirs, meeting limitations on the number of electric fracturing devices and pressure levels. Repeat fracturing and temporary plugging with ball injection during tight well fracturing resulted in the optimization of the quantity and timing of ball injection to suppress excessive extension of the main fracture. The fracturing process was refined, and the proppant system was improved, leading to a three-stage continuous sand addition mode featuring “long-distance transport placement of initial small particles at front edge + main flow channel support by medium particles in middle section + fracture closure by large particles in tail section.” The improved fracturing technology demonstrated significant on-site application effects. After statistically analyzing the on-site temporary plugging with ball injection, the effective plugging rate was 79.8%. The ultra-deep penetration technology provided a pressure window for more sand addition and fluid injection which increased the sand addition intensity and the proportion of small particles, the fracture conductivity and support effect were significantly enhanced. As a result, the daily production after fracturing increased from 3.30×104 m3 to 8.46×104 m3. It has demonstrated that the integrated application of differentiated fracturing design, ultra-deep penetration perforation technology, optimized temporary plugging with ball injection, and a refined three-stage sand addition mode can significantly enhance the fracturing stimulation effect and economic benefits of the Nanchuan Shale Gas Field. This provides strong technical support for the efficient development of the Nanchuan Shale Gas Field.

     

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