塔里木盆地氦气地球化学特征及有利勘探区

Geochemical characteristics of helium and favorable exploration areas in the Tarim Basin,China

基于对塔里木盆地多个构造单元天然气中氦气相对含量及同位素组成特征,结合地质背景与典型富氦气藏分析该盆地氦气地球化学特征及有利勘探区。研究表明:塔里木盆地富氦天然气显示良好,总体上台盆区富氦天然气显示优于前陆区;塔里木盆地氦气以壳源成因为主;该盆地天然气中氦气相对含量与氮气相对含量具有一定的正相关关系,氮气相对含量高的气藏中氦气相对含量一般较高。塔里木盆地氦气勘探普查可以重点关注氮气相对含量高的气藏。氦在地质体中可能主要以水溶形式发生运移,富集成藏与地层水关系密切。受到不同物质在水中分压差异影响,结合亨利定律分析,地层水在富氦天然气聚集过程中可以起到“提氦泵”的作用。良好的输导体系以及优质的氦源是富氦气藏形成的基础;塔里木盆地多个区块具有良好的富氦天然气显示,尤其是在沙雅隆起、卡塔克隆起、麦盖提斜坡、巴楚隆起等构造单元,该系列构造单元具有良好的氦源以及天然气成藏条件,有利于富氦天然气聚集,该系列构造单元是塔里木盆地氦气勘探的优先考虑区块。大顺北地区天然气勘探前景好,并且该构造单元是“十四五”海相天然气勘探重点区块,也应该加强对该区的氦气勘探普查工作。

Based on the relative content and isotopic composition characteristics of helium in natural gas of multiple structural units in Tarim Basin,combined with geological background and typical helium rich gas reservoirs,the geochemical characteristics and favorable exploration areas of helium in the basin are analyzed.The results show that helium rich natural gas in the Tarim Basin is well displayed,and the helium rich natural gas in platform area is better than that in foreland area.The helium in the Tarim Basin is mainly of crust origin.There is a positive correlation between the relative content of helium and nitrogen in the natural gas of the Tarim Basin,to a certain extent.When the relative content of nitrogen in the gas reservoir is high,the relative content of helium is also high.The general survey of helium exploration in Tarim Basin can focus on the gas reservoirs with high relative content of nitrogen.Helium may migrate mainly in the form of water-soluble in geological bodies,and its accumulation,possibly,are closely related to formation water.Influenced by the difference of partial pressure of different substances in formation water,combined with the Henry's law analysis,formation water can play the role of“helium pump”in the process of helium-rich natural gas accumulation.Good transport system and high-quality helium source are the basis for the formation of helium rich gas reservoirs.Many blocks in Tarim Basin have good helium rich natural gas display,especially in structural units such as the Shaya Uplift,Katake Uplift,Maigaiti slope and Bachu Uplift.This series of structural units has good helium source and natural gas accumulation conditions,which is conducive to the accumulation of helium rich natural gas.This series of structural units is the preferred block for helium exploration in the Tarim Basin.The Shunbei area has a good prospect for natural gas exploration,and this structural unit is a key block for marine natural gas exploration during the“14th Five-Year Plan”.Therefore,helium exploration and general survey in this area should be strengthened.