四川盆地水化学特征标准剖面的建立及其与天然气成藏的关系

为了深入研究气田的气水关系特征，根据斯蒂夫水化学相图理论方法，以判别不同地层水化学特征差异为理论基础，基于四川盆地各含油气构造4 000余件地层水水质全分析资料，建立了该区上白垩统灌口组-中三叠统雷口坡组的地层水斯蒂夫相图标准剖面，解决了各构造流体的归属性问题。研究发现：新场、洛带地区上侏罗统蓬莱镇组气藏的地层水水化学相图与其他区域同组地层水的化学相图不能对比，却与下伏上三叠统须家河组水化学相图相似，从油气成藏角度推断认为川西地区蓬莱镇组气藏的聚集形成，存在受下伏深源气沿裂缝垂向上升补给气源的可能；地层水的演化特征与油气成藏具有极为密切的关系，在今后的油气勘探开发过程中，可利用水化学相图作为寻找天然气矿藏的指示标志之一；该区某些蓬莱镇组气藏开发气井的地层水呈现深部碳酸盐岩地层（雷口坡组）水化学相图特征，可视为深部碳酸盐岩地层作为烃源岩参与浅层气藏形成的证据之一。

Relationship between hydro-chemical characteristics and gas pooling in the Sichuan Basin

In order to thoroughly study the gas-water relationship at gas fields,we introduced the theoretical method of Steve hydrochemical facies to identify the differences of chemical properties of water in different strata.We collected water quality analysis data of more than 4000samples from different strata with oil-bearing structures in the Sichuan Basin.These data were used to build the standard section of Steve hydrochemical facies for the formation water in the upper Cretaceous Guankou Formation-Middle Triasic Leikoupo Formation in the study area.These standard sections were successfully applied to determine the origin of fluids in each structure.The hydrochemical facies of the formation water in the Penglaizhen Formation gas reservoir in the Xinchang and Luodai areas can not be correlated with those of the same strata in other areas.However,they are similar to those of the underlying Xujiahe Formation.This indicates that the deep-sourced gas possibly have migrated vertically upward along fractures and contributed to gas accumulation in the Penglaizhen gas reservoir in the western Sichuan Basin.The evolution characteristics of formation water are closely related to hydrocarbon accumulation,thus hydrochemical facies can be used as an indicator of gas reservoirs in future exploration and development.The formation water in some wells produced from the Penglaizhen gas reservoirs show some similar features in hydrochemical facies like that in the deep carbonate reservoirs(the Leikoupo Formation),which indicates that the deep carbonate as source rocks have contributed to gas accumulation in the shallow reservoirs.