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 3.30×10
4 m
3 to 8.46×10
4 m
3. 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.