RARE-GAS CONSTRAINTS ON HYDROCARBON ACCUMULATION, CRUSTAL DEGASSING AND GROUNDWATER-FLOW IN THE PANNONIAN BASIN
RARE-GAS CONSTRAINTS ON HYDROCARBON ACCUMULATION, CRUSTAL DEGASSING AND GROUNDWATER-FLOW IN THE PANNONIAN BASIN
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DOI：
10.1016/0012-821x(91)90133-3
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发表时间：
1991-07-01
影响因子：
5.3
通讯作者：
DEAK, J
中科院分区：
文献类型：
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作者：
BALLENTINE, CJ;ONIONS, RK;DEAK, J
在匈牙利潘诺尼亚盆地的Hajduszoboszlo和Ebes的垂直叠置气藏序列中测量了He、Ne和Ar的同位素组成和丰度。天然气储层的深度范围为727至1331米，以甲烷为主，总岩石体积约为1.5立方公里。主要物种丰度和稀有气体同位素组成随深度有系统变化：CO2和N2分别从0.47%和1.76%增加到14.1%和30.5%，Ar-40/Ar-36和Ne-21/Ne-22从727 m处的340和0.02990系统地增加到1331 m处的1680和0.04290。幔源氦成分在2%~ 5%之间，其余为壳源放射性氦。Ar和Ne同位素的变化是由于地下水中大气来源的组分与地壳产生的放射成因Ar和Ne混合而引起的。大气来源的Ar-40和Ne-21分别占Ar-40和Ne-21总量的85%和97%，在727 m处下降到1331 m处的18%和68%。最深的样品被证明有大气衍生和放射性成分接近空气饱和水和放射性生产率。最浅的样品显示出显着的分馏的He/Ar和Ne/Ar比的大气衍生和放射成因的稀有气体成分，但很少或没有分馏的He/Ne比。这表明，稀有气体的扩散分馏相对不重要，并且稀有气体在CH 4和H2O相之间的溶解度分配控制了观察到的稀有气体元素丰度。Hajduszoboszlo气田中大气衍生和放射成因稀有气体组分的总丰度限制了与天然气相互作用的地下水的最小体积，以及脱气并提供放射性稀有气体的地壳数量。无论是盆地沉积物还是盆地形成以来的基底杂岩，放射性物质平衡都不能用稳态生产来解释。研究结果要求放射性成因稀有气体在区域尺度上以其生产率储存，并以最小的分馏作用输送到近地表。供应源自大气的稀有气体所需的最小地下水体积将占据约1000立方公里的岩石体积（假设盆地平均孔隙度为5%），比储层体积大670倍。地下水和Hajduszoboszlo碳氢化合物之间的相互作用比碳氢化合物形成和迁移模型中通常设想的规模更大。
The isotopic composition and abundances of He, Ne and Ar have been measured in a sequence of vertically stacked gas reservoirs at Hajduszoboszlo and Ebes, in the Pannonian Basin of Hungary. The gas reservoirs occur at depths ranging from 727 to 1331 m, are CH4 dominated and occupy a total rock volume of approximately 1.5 km3. There are systematic variations in both major species abundances and rare gas isotopic composition with depth: CO2 and N2 both increase from 0.47 and 1.76% to 14.1 and 30.5%, respectively, and Ar-40/Ar-36 and Ne-21/Ne-22 increase systematically from 340 and 0.02990 at 727 m to 1680 and 0.04290 at 1331 m. A mantle-derived He component between 2 and 5% is present in all samples, the remainder is crustal-radiogenic He. The Ar and Ne isotope variations arise from mixing between atmosphere-derived components in groundwater, and crustally produced radiogenic Ar and Ne. The atmosphere-derived Ar-40 and Ne-21 decreases from 85 and 97% of the total Ar-40 and Ne-21 at 727 m to 18 and 68% at 1331 m. The deepest samples are shown to have both atmosphere-derived and radiogenic components close to the air-saturated water and radiogenic production ratios. The shallowest samples show significant fractionation of He/Ar and Ne/Ar ratios in atmosphere-derived and radiogenic rare gas components, but little or no fractionation of He/Ne ratios. This suggests that diffusive fractionation of rare gases is relatively unimportant and that rare gas solubility partitioning between CH4 and H2O phases controls the observed rare gas elemental abundances.The total abundance of atmosphere-derived and radiogenic rare gas components in the Hajduszoboszlo gas field place limits on the minimum volume of groundwater that has interacted with the natural gas, and the amount of crust that has degassed and supplied radiogenic rare gases. The radiogenic mass balance cannot be accounted for by steady state production either within the basin sediments or the basement complex since basin formation. The results require that radiogenic rare gases are stored at their production ratios on a regional scale and transported to the near surface with minimal fractionation. The minimum volume of groundwater required to supply the atmosphere-derived rare gases would occupy a rock volume of some 1000 km3 (assuming an average basin porosity of 5%), a factor of 670 greater than the reservoir volume. Interactions between groundwater and the Hajduszoboszlo hydrocarbons has been on a greater scale than often envisaged in models of hydrocarbon formation and migration.