积雪油气化探方法试验研究

油气化探取样介质主要是近地表土壤和地下潜水,而以积雪为取样介质的化探方法研究国内、外很少报道。选择西北某已知油气藏上方积雪进行了顶空气、荧光等方法的试验研究,结果表明积雪顶空气甲烷(DC₁)、荧光F360、F405等指标的应用效果良好,显示出积雪油气化探方法在油气勘探中的良好应用前景。积雪样品和土样三维荧光特征基本一致,表明积雪样品可以有效应用于油气化探中的油气属性判别。雪是"天外来客",在一定区域内,可以认为雪中烃物质分布是均一的,雪中烃物质含量背景也基本相同,不存在明显差异性。累积到一定厚度的雪对下伏微渗漏的烃起到封盖作用,有空隙间隙且有吸附性的积雪,对深部微渗漏至近地表的烃类起到了吸附、累积、富集作用。冬季近地表土壤中对烃类微渗漏起到"干扰"的微生物作用处于最小态,因而,雪样油气化探异常的干扰因素相对土样要少,这为采集和分析雪介质,并进行油气化探异常评价提供了依据。 

Experimental research on the oil and gas geochemical exploration method of snow cover

The sampling media in surface oil and gas geochemical exploration are dominated by near-surface soil and subsurface phreatic water,and snow cover is seldom used as the sampling media.An experimental study has been carried out over a known oil and gas reservoir in the Northwest China to investigate the content of the headspace hydrocarbons and the fluorescence intensity of the aromatics in the snow cover.The results show that the headspace methane(DC₁),the F360 and the F405 are effective in reflecting the existing oil and gas field,indicating that the snow-based geochemical exploration method has good application prospect in oil and gas exploration.The 3D fluorescence spectrum characteristics of both the snow cover and the surface soil are basically consistent within a certain area,suggesting that snow cover samples can be used to predict the reservoir fluid property.Compared with the surface soil,snow is "the guest from the sky",and the distribution of the hydrocarbons in the snow cover can be regarded as homogeneous,thus the background values of the hydrocarbons in the snow cover are basically homogeneous,without obvious differences from one sampling site to another.The snow cover,when developed to certain thickness,can act as the seal cap for the hydrocarbon gases migrated from the underlying layers.With its unique pores,cavities,and adsorption capability,the snow cover plays a role in adsorbing,accumulating and enriching the hydrocarbon gases migrated into the near-surface.The microbiological effect to the migrated hydrocarbons is minimized in the winter time,thus the disturbance factors of the geoche-mical anomaly obtained from the snow cover is relatively less,which provides a basis both for snow-based oil and gas geochemical exploration,and for the geochemical anomaly evaluation.