黔西松河井田煤层群合层分段压裂影响因素及参数优化

Influencing factors and parameter optimization of staged fracturing in thin and medium coal seam group in Songhe mine in western Guizhou

目前薄至中厚煤层群煤层气井普遍存在"前期产能高但周期短、衰减快且幅度大、后期恢复困难"的生产特征。针对这一现象,以黔西松河井田为例,通过对示范井组工程效果从煤储层赋存特征、合层分段改造效果及影响因素进行对比分析,并对施工参数进行优化和工程试验。分析认为:合层分段压裂仍是多煤层煤层气开发主要途径,其效果受层间兼容性和开发方式影响;投球暂堵合层改造受层间跨度、有效射孔厚度、施工参数及固井质量影响大。基于影响因素分析,提出施工参数优化措施,即施工排量6～8m3/min,前置液占比40%～50%,单孔流量0.2～0.3m3/min和前置段塞加砂方式,优化方案经后期工程验证取得较好的试验效果,对类似地质条件煤层群发育区煤层气合层开发层段组合、施工参数优化有较好的借鉴意义。

At present,the CBM wells in thin and medium coal seam group show commonly the characteristics of“high production capacity but short period,fast attenuation and large attenuation amplitude in the early stage,difficult recovery in the late stage”.Aiming at this phenomenon,Songhe mine in western Guizhou was taken as example to conduct comparative analysis of the engineering effect of demonstrative well group from the characteristics of coal reservoir occurrence,the reformative effect and influencing factors of staged fracturing,optimization of the construction parameters and engineering tests were carried out.The analysis showed that the staged fracturing of the combined layers is the main way for CBM development in multi-seam,the reformative effect is influenced by interlayer compatibility and development mode;ball sealer staged fracturing is affected greatly by interlayer span,effective perforation thickness,construction parameters and cementing quality.Based on the analysis of influencing factors,measures for optimization of construction parameters were proposed,that is:construction displacement of 6–8 m3/min,prepad liquid proportion of 40%–50%,single hole flow of 0.2 to 0.3 m3/min,sand plug of front segment,the optimization scheme has been proved to have good trial effect by later engineering,it has good reference significance for parameter optimization of staged fracturing for CBM development in similar geological condition of thin and medium coal seam group.