亨利定律与壳源氦气弱源成藏——以渭河盆地为例

发布时间：2018-05-09 16:38

本文选题：氦气 + 成藏　；参考：《天然气地球科学》2017年04期

【摘要】：壳源氦来自地质体中铀钍等氦源元素的放射性衰变,其生成速度极其缓慢,不存在集中的生气高峰,相对常规油气为典型的弱源气。其常以甲烷或二氧化碳气藏的伴生气产出,因稀有性而低丰度(0.1vol%)即可成矿,且成藏与地下水关系密切。为研究其弱源成藏机理,总结了前人关于氦气、氮气和甲烷亨利系数和溶解度的研究成果,以渭河盆地为例,通过模拟计算探讨了亨利定律在氦气运移和成藏中的关键作用。根据亨利定律,稀溶液中气体溶解度受控于气体的分压和亨利系数。与载体气相比,氦气的亨利系数高,且高低温下相差较大,特别是在氦源岩和气藏中的分压差别显著,造成两处的溶解度差异显著,使以溶解态运移的弱源氦气能够脱溶成藏。综合分析认为:①氦气在深部氦源岩处分压大、温度高,能溶解于水而运出;②运移至浅部遇到天然气等载体气藏时,在气水界面,氦气分压极低而脱溶进入气藏,载体气则溶解进入水中,好似载体气将氦气从水中"置换"出来。这种作用使气藏附近形成溶解氦低浓度漏斗,水溶氦不断向气藏附近迁移而进入气藏,大大提高了氦气运聚系数;③氦气进入气藏后,由于盖层中氦气分压低而难溶于水,不易扩散,利于保存。研究结果明确了氦气在氦源岩"运得出"、遇气藏"脱得出"、进气藏"保得住"的高运聚系数富集机制,为氦气资源勘查提供了理论依据。
[Abstract]:Crustal helium comes from radioactive decay of helium source elements such as uranium and thorium in geological bodies. The rate of formation is extremely slow and there is no concentrated gas peak. Compared with conventional oil and gas, it is a typical weak source gas. It is usually produced by associated gas of methane or carbon dioxide gas reservoirs, and is low in abundance (0.1volr) because of rarity), and the accumulation is closely related to groundwater. In order to study the mechanism of weak source reservoir formation, the previous research results on Henry's coefficient and solubility of helium, nitrogen and methane are summarized. Taking the Weihe Basin as an example, the key role of Henry's law in helium migration and accumulation is discussed through simulation calculation. According to Henry's law, the solubility of gas in dilute solution is controlled by the partial pressure of gas and Henry's coefficient. Compared with carrier gas, the Henry coefficient of helium gas is higher, and the difference between high and low temperature is great, especially the difference of partial pressure in helium source rock and gas reservoir is obvious, which results in the significant difference of solubility between the two places, which makes the weak source helium gas transported in dissolved state can be dissolved into reservoir. The comprehensive analysis shows that the ratio 1 helium gas in the deep helium source rock has a high disposal pressure and high temperature, and can dissolve in water and migrate out of the gas reservoir to the shallow gas carrier gas reservoir, and at the gas-water interface, the helium partial pressure is very low and the desolation enters the gas reservoir. Carrier gas dissolved into the water, like carrier gas from the helium gas out of the water. This effect causes the formation of dissolved helium low concentration funnel near the gas reservoir and the continuous migration of water dissolved helium into the gas reservoir, which greatly increases the helium accumulation coefficient and the helium accumulation coefficient after entering the gas reservoir, which is difficult to dissolve in water due to the low helium content in the caprock. It is not easy to spread and is easy to preserve. The results show that the accumulation mechanism of high accumulation coefficient of helium gas in helium source rock, gas reservoir and reservoir is determined, which provides a theoretical basis for the exploration of helium gas resources.
【作者单位】：中国地质调查局西安地质调查中心;中国矿业大学(北京)地球科学与测绘工程学院;中国地质调查局资源评价部;
【基金】：国家自然科学基金面上项目(编号:41572131) 中国地质调查局矿产资源调查评价项目(编号:121201011000150014)联合资助
【分类号】：P618.13

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