准噶尔盆地沙湾凹陷二叠系凝析气藏相态识别及成因分析

近年来,我国中西部陆续发现了资源量较大的凝析气藏,准噶尔盆地沙湾凹陷周缘的多个凝析气藏也显示出深层勘探的潜力。针对沙湾凹陷凝析气藏的烃类流体特征和形成机制不清晰的科学问题,笔者等采用原油物性和地球化学分析测试,运用经验统计法来识别油气藏类型,分析油气相态特征及其来源。主要认识如下：① 沙湾凹陷二叠系主要存在带油环凝析气藏,中佳2- H井为典型带油环凝析气藏井,研究区存在风城组为烃源—断层垂向输导—温压控制的原生型和天然气气侵共同作用形成的次生型凝析气藏;② 结合P—V—T相图分析沙湾凹陷二叠系凝析气藏烃类流体C7+占比较小,挥发性油藏地层温度明显低于临界温度,地饱压差较小,黑油油藏地层流体的临界温度与临界凝析温度都较高且临界压力较小;③ 根据新光井区凝析气藏的气油比要高于13000 m3/m3,且新光1井凝析气藏属于无油环凝析气藏可判断新光1井为原生型凝析气藏;中佳2- H井凝析气藏正构烷烃损失率达到90%,且研究区存在混合来源气,证实该凝析气藏曾遭受气侵作用。笔者等提出的凝析气成因可为研究区下一步油气勘探提供参考,同时也可以为准噶尔盆地凝析气成藏的研究和资源评价提供方法支持。

Phase state identification and origin analysis of Permian condensate gas reservoirs in Shawan Sag, Junggar Basin

In recent years, condensate gas reservoirs with large resources have been discovered in the central and western regions of China, several condensate gas reservoirs around Shawan sag also show the potential of deep exploration. In this paper, the physical properties and geochemical analysis of crude oil are used, and the empirical statistical method is used to identify the types of oil and gas reservoirs and analyze the phase characteristics and sources of oil and gas. The main understanding is as follows：① There are mainly condensate gas reservoirs with oil ring in the Permian in Shawan Sag. Zhongjia 2- H well is a typical gas condensate well with oil ring. In the study area, there is a secondary condensate gas reservoir formed by the Fengcheng Formation, which is the primary type of hydrocarbon source—fault vertical transport—temperature and pressure control and natural gas invasion;② Combined with P—V—T phase diagram, it is analyzed that the proportion of hydrocarbon C7 + in Permian condensate gas reservoirs in Shawan sag is relatively small. The formation temperature of volatile reservoir is obviously lower than the critical temperature, and the ground saturation pressure difference is small. The critical temperature and critical condensate temperature of formation fluid in black oil reservoir are higher and the critical pressure is lower;③ According to the fact that the gas—oil ratio of condensate gas reservoir in Xinguang well area is higher than that of 13000m3/m3, and the condensate gas reservoir of Xinguang 1 well belongs to non- oil ring condensate gas reservoir, it can be judged that Xinguang 1 well is a primary condensate gas reservoir. The origin of condensate gas proposed in this article can provide a reference for the next step of oil and gas exploration in the study area, and can also provide methodological support for the research on condensate gas accumulation and resource evaluation in the Junggar Basin.