摘要
以贵州松河区块煤层气井产出水跟踪测试数据为依据,系统研究了该区产出水化学特征及其地质意义.认为煤层气井产出水地球化学性质与产能之间关系密切,可用产能响应指数来反映煤层气井的产能水平.研究结果表明:煤层气井产出水Na~+和HCO_3~-含量高,Ca~(2+),Mg~(2+)和SO_4~(2-)含量低,是煤层气藏富集的表现.特征离子K~+和Cl~-异常高,随排采时间的增加逐渐减小,暗示产出水受到了压裂液的污染,δD偏重,表现出明显的D漂移特征,则是煤层水的典型特征,总体指示产出水具有煤层水混合压裂液的特征.Na~+,K~+,Cl~-在井网空间分布表现出低部位为高值,分别在3g/L,160mg/L,5g/L以上,高部位为低值,分别在2g/L,100mg/L,3g/L左右,是高部位水往低部位运移的结果,而HCO_3~-表现出高部位值大,在900mg/L左右,低部位值小,在600mg/L左右,推测为低部位CO_2向高部位运移的结果,存在"气水分异"现象.
Based on the produced water tracking test data of CBM wells in Songhe block of Guizhou province,chemical characteristics and geological significance of the produced water in this area were systematically studied.It is found that there is a linkage between the geochemical properties of CBM produced water and production capacity,and the production capacity response index can be used to reflect the CBM production capacity.The results show that the produced water in CBM wells has higher content of Na~+and HCO_3~-and lower content of Ca~(2+),Mg~(2+)and SO_4~(2-),which is the performance of CBM reservoir enrichment.The concentrations of K~+and Cl~-of characteristic ions are abnormally high and decrease with the increase of drainagetime,suggesting that the produced water is contaminated by fracturing fluid.The value ofδD is biased showing obvious D drift features,which is the typical characteristic of coal seam water.On the whole,the produced water is characterized by mixed coal seam water with fracturing fluid.As a result of the migration of high position water to the lower part,the spatial distribution of Na~+,K~+,Cl~-shows higher accumulations in the lower part of the well network,which are 3g/L,160mg/L,5g/L respectively,and lower concentrations in the higher part,which are 2g/L,100mg/L,3g/L or so,which is the result of the migration of high position water to lower part.In contrast,the content of HCO-4is high in the higher position at about900mg/L,and low in the lower position at about 600mg/L.It is speculated that this may be caused by the migration of CO_2 from the lower to the higher part,which leads to the phenomenon of gas and water differentiation.
引文
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