鄂尔多斯盆地天环坳陷北部山1-盒8段地层水地球化学特征及成因

Geochemical Characteristics and Genesis of Formation Water in Shan 1st to He 8th Member in Northern Tianhuan Depression,Ordos Basin

通过对天环坳陷北部地区山1-盒8段地层水水文地球化学特征等研究,揭示地层水成因,为该区下一步气水关系研究和天然气勘探开发提供基本依据。研究表明,天环北部地层水矿化度较高,偏酸性,离子组成以Cl-、K++Na+和Ca2+为主,水型为氯化钙Ⅳ型和Ⅴ型水,反映所处环境有利于气藏的聚集和保存。地层水特征参数中除变质系数较大外,钠氯系数、钙镁系数和脱硫系数均较小,反映了山1-盒8段地层水浓缩和变质程度较深,地层封闭条件优越,是良好烃类聚集区。此外,通过对比水体环境中各离子组分的富集和损耗状态,分析认为研究区山1-盒8段地层水成因与蒸发浓缩作用、水-岩相互作用和流体混合作用等有密切关联,属于原始沉积成因水且经历了较强浓缩变质作用。

Based on the study of hydro-geochemical characteristics of formation water of Shan 1st to He 8th member in northern of Tianhuan Depression,the genesis of formation water is speculated,which provides a basic reference for the further study of gas-water relationship and the exploration and development of natural gas.The formation water show high salinity and weak acidity.Cl-,Na++K+and Ca 2+are predominant among ion component.The calcium chlorideⅣ-type andⅤ-type water are major.The environment is conducive to the accumulation and preservation of natural gas.Other than high metamorphism coefficient in chemistry,the formation water in Shan 1st to He 8th member had low sodium-chloride ratio,magnesium-calcium ratio and coefficient of desulfurization,the formation water therein has deep concentration and metamorphism and the sealing conditions of formation are good,which is conducive to hydrocarbon accumulation.In addition,the enrichment and loss of ion in the formation water were studied and results show that the formation water in the study area is related to evaporation,concentration effect,water-rock interaction effect and fluid mixing effect.The formation water is original sedimentary water,which has experienced intensive condensation and metamorphism effect.