气田开发过程中地下水环境保护方案初探

Discussion on Groundwater Environment Protection Scheme during Gas Field Exploitation

区域地下水环境的保护是气田开发过程中环境保护工作的重点之一。通过现场调查和统计分析得知,外部污染源是影响当地地下水环境的主要因素,农田径流污染源是外部的主要污染源,以COD_(Cr)计其排放量分别约占外部污染源排放总量的67%,而钻井液漏失、天然气窜层、钻井废水排放等钻井作业是内部的主要污染源,其COD_(Cr)排放量约占内部污染源COD_(Cr)排放总量的62%,因而钻井作业的污染防治应是项目内部地下水污染防治工作的重点。根据地下水环境质量现状分析及变化趋势分析可知由于气田的开发建设,气田区地下水水质已受到一定程度的影响,特征污染物表现为COD_(Cr)、氨氮、氯化物、硝酸盐氮。为保护气田区地下水环境,分施工期和运营期两阶段设计了地下水环境保护方案,采取源头控制的清洁生产,至末端控制的污染治理并提出了突发污染事故应急预案,为气田的可持续开发提供指导。

The regional groundwater Protection is one of the priorities of the environment protection in the gas field exploitation process. The result of site investigation and statistical analysis indicates that agricultural runoff, as a primary external pollutant sources, play an important role in groundwater pollution. CODCr emission from agricultural runoff accounts for 67% of the total external pollutant sources. While the discharge of drilling activities, such as drilling fluid leakage, natural gas cross-flow, and drilling wastewater, is the main internal pollutant sources. It accounts for 62% CODCr of the total internal sources of pollution. Thus, pollution prevention during drilling activities should be emphasized during the gas field exploitation project. Based on the analysis of environmental quality status and change tendency, results indicated that due to the exploitation activities, water in gas field has been polluted to some degree. Special pollutants are CODCr, ammonia-N, chloride and nitrate-N. To protect groundwater environment of gas field, protection scheme of construction period and operation period are presented, pollution source control of clean production and pollution treatment at terminal control was adopted and the emergency plan of sudden pollution accidents were proposed, which provide guidance for sustainable development of gas field.