微地震监测技术在页岩气水平井重复压裂中的应用

随着美国页岩气的开发成功，页岩气在我国油气资源里占比越来越重。在实际开发过程中，由于分段射孔位置选择不当，或井筒出现套变异常段，或受限于工艺、材料、工具等作业多方的诸多因素影响，部分页岩气水平井改造效果欠佳。为促使这类页岩气水平井重获高产，实现良好的经济效益，行之有效的手段是采取重复压裂工艺。页岩气重复压裂主要面临水平段长、级数多、施工规模大、液体效率低等困难，工艺成功的关键在于精确封堵低压区、低产区，在未改造区域和未完全改造区域开启新的裂缝。通过微地震监测技术可以准确分析分析新开启裂缝的扩展区域，缝长、缝宽等参数，进而可以实时优化调整排量、砂量、暂堵材料投送时机、暂堵材料用量等施工参数。在重复压裂中应用微地震监测技术，可有效提高重复压裂的效率，增加整个水平段均匀改造程度，压后产量是重复压裂之前产量的4~5倍，这对页岩气水平井老井高效开发具有重要意义。

Application of microseismic monitoring technology to repeated fracturing of shale gas horizontal wells

Shale gas is becoming a more and more important natural resource in China after its successful development in the United States. In many filed practices, well stimulation results are unsatisfactory because of improper selection of perforation locations, casing deformation, and the limitations of stimulation processes, materials, and tools. Re-fracturing is a promising technology to re-stimulate such shale gas wells for achieving higher production rate and profit. Re-fracturing of shale gas wells usually faces the challenges of long horizontal section, multiple stages, large pump scale, and low fluid efficiency. The key to a successful re-fracturing job is to accurately identify and block the low-pressure, low-production areas and to create new fractures into the initially unstimulated and poorly-stimulated areas. Microseismic monitoring technology can be used to predict fractured area, fracture length, and fracture width using the distribution of event points. Such information are important for adjusting fluid pump rate, sand pump rate, the delivery time and amount of temporary plugging materials in a real time manner. Using microseismic monitoring technology in re-fracturing operations can effectively improve the stimulation efficiency and results of horizontal sections. After re-fracturing, the production of a well can be increased up to 4-5 times of that before re-fracturing, thus the re-fracturing technology has great significance for the efficient development of relatively old horizontal shale gas wells.