煤层气开采产出水特征及处理措施

煤层气产出水造成的污染是煤层气开发带来的主要环境问题之一。根据产出水的排采时间,将气井产出水分为压裂返排液和生产排采水2种,介绍了产出水的水质和水量变化特征。总体来看,不同区域气井产水量变化很大,并呈逐渐递减趋势,不同气井产出水水质变化也较大,矿化度、COD、氨氮、悬浮物和氟化物为主要特征因子。目前,国内煤层气开采产出水大多经井场蓄水池沉淀后外排,水质与行业和地方标准的差距较大,提出应统一排放标准,根据区域地形特点和水质、水量变化情况,采取针对性的产出水处理对策。建议根据区块开发条件,分别采用自然蒸发、散排和集中排放等方式;在确保去除悬浮物、氨氮和COD基础上,增加深度处理工艺,使氟化物以及部分区块超标的硫化物、铁离子等污染因子得到有效处理;根据矿化度大小,采用不同的处置措施;有条件的地区可将处理后的产出水用于后续气井压裂用水、农田灌溉和绿化用水等。 

WATER FEATURES AND TREATMENTS DURING CMB MINING

Water pollution coming from mining CBM which is a major environmental issue can be classified as two types, fracturing return water and production discharge according to production time. Water volume and quality vary with location, generally showing a descending trend, with mineralization degree, COD, ammonia nitrogen, floats and fluorides as its chief indicators. In Chinas practice, water from CMB mining is discharged after settling down, but quality is much different from local standards, which shall be unified. Water shall be treated according to regional terrain, water quality and volume. This paper suggests applying natural evaporation, decentralized and centralized discharging based on allowable conditions. Besides removal of floats, ammonia nitrogen and COD, further processing needs to be done to treat fluorides, sulfides and iron ions. Treatments vary with mineralization degrees. Water after processed, if allowable, may be used for fracturing liquid, agricultural irrigation or sprinkling plants.