塔里木盆地轮探1井下寒武统超深层油气相态演化定量模拟

Quantitative simulation of phase evolution for ultra-deep oil and gas from Lower Cambrian strata of Well Luntan-1 in the Tarim Basin

轮探1井位于塔里木盆地塔北隆起轮南低凸起,钻遇并揭示下寒武统玉尔吐斯组优质烃源岩,并在8 260 m深的吾松格尔组白云岩储层发现超深层轻质油,展现了塔里木盆地超深层油气良好的勘探前景。已有研究表明轮探1井轻质油主要来源于寒武系烃源岩,但对于该井烃源岩生烃过程及其深层油气相态物性预测还没有进行系统研究。鉴于此,采用盆地模拟和相态模拟相结合的方法,选择适用的相态动力学模型,定量模拟了轮探1井玉尔吐斯组烃源岩生烃与油气相态物性演化特征,通过与轻质油实际相态物性特征对比,对吾松格尔组轻质油来源与生成阶段进行了预测。研究结果表明:轮探1井玉尔吐斯组烃源岩在晚加里东期—早海西期以生成正常油为主,具有较低的气油比和较高的黏度、密度;燕山期—喜马拉雅期以生成轻质油—凝析油气为主,具有更高的气油比和更低的黏度、密度。轮探1井吾松格尔组轻质油藏的相态物性特征与玉尔吐斯组烃源岩在晚喜马拉雅期生成的烃类流体吻合,表明该轻质油的形成阶段为晚喜马拉雅期。综合研究认为,轮探1井轻质油是玉尔吐斯组烃源岩处在相对封闭且热演化程度较高(1.00%<R_(O)<1.50%)的地质条件下的生烃产物,进一步说明特定的地质条件和热演化阶段是烃源岩生成轻质油的关键。轮探1井在落实玉尔吐斯组烃源岩存在和良好资源潜力的同时,也进一步证实塔里木盆地深层—超深层良好的轻质油勘探前景。

Well Luntan-1(LT-1),located in the Lunan Low-uplift of Tabei Uplift,the Tarim Basin,drilled and revealed the high-quality source rocks of Lower Cambrian Yuertusi Formation,and successfully found ultradeep light oil and gas in the 8260-meter-deep dolomite reservoirs of Wusongar Formation.It shows a good prospect for ultra-deep oil and gas exploration in the platform of Tarim Basin.Previous research shows that the light oil from Well LT-1 is mainly derived from the Cambrian source rocks,however,there has been no systematic study on the generation history of the source rocks as well as the phase characteristics and physical properties of the generated oil and gas.In this paper,we quantitatively simulated the hydrocarbon generation history and its staged phase characteristics of the Yuertusi source rocks in Well LT-1 using a combined method of basin modeling and phase simulation after selecting an appropriate phase kinetic model.Then,we predict the generation stage of the light oil from the Wusongar dolomite reservoirs by comparing the real and the modeled phase-physical properties.The results show that the Yuertusi source rocks of Well LT-1 mainly generated normal oils in the Late Caledonian-Early Hercynian period,with low gas-oil ratios but high viscosity and density.The light oilcondensates were generated in the Yanshan-Himalayan period with much higher gas-oil ratios(GORs)but lower viscosity and density.The phase characteristics and physical properties of the light oil from the Wusongar dolomite reservoirs have coincided with the hydrocarbon fluids generated by the Yuertusi source rocks during Late Himalayan period.Comprehensive analysis shows that the light oil in Well LT-1 was derived from the Yuertusi source rocks at the stage of very closed condition and specific thermal maturation(1.00%<R_(O)<1.50%),further supporting that specific geological and thermal conditions are the key to form light oils in source rocks.The drilling of Well LT-1 in the Tarim Basin further verified the good resource potential of Yuertusi source rocks and confirmed a good prospect of the deep and ultra-deep exploration for light oil and gas in the basin.