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综合油气产能、原油性质、天然气组分和同位素组成资料,结合研究区地质背景探讨了塔中隆起西北地区深部奥陶系天然气藏的分布特征及运聚模式,认为研究区目的层油气分布具有“外气内油”及“羽状破碎带富气”的特征,提出“垂向输导运移-侧向差异聚集”的天然气运聚成藏模式.研究结果表明:塔中隆起西北地区深部天然气通过塔中Ⅰ号断裂及左旋走滑断裂垂向运移至塔中隆起西北地区奥陶系储层后,一方面优先聚集于外部1~5号走滑断裂末端高孔渗羽状破碎带,导致在羽状破碎带油气产能、气油比、硫化氢质量分数、干燥系数、原油含蜡量异常高,分别可达199 442m~3/d,7 875 m~3/m~3,40 000×10-6,0.96,16.1%;原油密度异常低,低至0.77g/cm~3;天然气富集重碳同位素,最重值为-39.1‰;另一方面在不整合面、走滑断裂、高孔渗“孔缝洞”储层的侧向输导下,自北东向南西方向运移聚集,随着远离塔中Ⅰ号断裂带,气侵程度逐渐减弱,油气相态由凝析气藏向油藏过渡,气油比、天然气产能、干燥系数、硫化氢质量分数、原油含蜡量逐渐减小,分布范围分别为79~7 875m~3/m~3,1 198~199 442m~3/d,0.72~0.96,10×10-6~40 000×10-6,2.0%~16.1%,原油密度从0.77g/cm~3逐渐增大至0.89g/cm~3,甲烷碳同位素从-39.1‰逐渐变轻为-54.9‰.综合分析认为研究区深部或超深部天然气资源勘探潜力巨大,尤其是深大通源断裂附近的应力破碎带岩溶储层发育区,可作为深部天然气的优先勘探目标.
Based on the data of oil and gas productivity, crude oil, natural gas and isotopic composition, combined with the geological background of the study area, the distribution and transport of Ordovician natural gas reservoirs in the northwestern part of the Tazhong Uplift are discussed. The distribution of hydrocarbon in the target layer of the study area is characterized by The characteristics of “oil in the outer gas” and “plume” in the “feather-shaped crust” put forward a model of “gas migration and accumulation with lateral diversion” and “vertical transport and accumulation of lateral differences.” The results show that: In the mid-uplift, deep natural gas in the northwestern part of China migrated vertically to the Ordovician reservoir in the northwestern part of the Tazhong uplift through the Tazhong Ⅰ and left-lateral strike-slip faults. On the one hand, Permeability fractures lead to unusually high oil and gas productivity, oil-gas ratio, hydrogen sulfide content, drying coefficient and crude oil wax content in the pinnate zone, up to 199 442 m 3 / d and 7 875 m 3 / m ~ 3,40 000 × 10-6,0.96,16.1%; crude oil density is unusually low, as low as 0.77g / cm ~ 3; natural gas is enriched in heavy carbon isotope, the heaviest value is -39.1 ‰; on the other hand, Integrated surface, strike-slip fracture, high porosity and permeability “hole hole” reservoir lateral transport, from the north-east to the west-south migration As the gas moves away from the fault zone of Tazhong Ⅰ, the degree of gas invasion gradually decreases, and the hydrocarbon phase transitions from the condensate gas reservoir to the reservoir. The gas-oil ratio, natural gas productivity, drying coefficient, hydrogen sulfide content, wax content And the distribution range is 79 ~ 7 875m ~ 3 / m ~ 3,1 198 ~ 199 442m ~ 3 / d, 0.72 ~ 0.96,10 × 10-6 ~ 40 000 × 10-6,2.0% ~ 16.1 %, The density of crude oil gradually increases from 0.77g / cm ~ 3 to 0.89g / cm ~ 3, and the carbon isotope of methane decreases gradually from -39.1% to-54.9% .A comprehensive analysis shows that the exploration potential of natural gas in the deep or ultra-deep part of the study area Huge, especially in the stress-disrupted karst reservoir area near the deep-Datong source fault, can be the preferential exploration target for deep natural gas.