鄂尔多斯盆地延长组7段页岩全组分定量生烃模拟及原油可动性评价

页岩油和致密油是中国目前油气勘探的热点,页岩生烃模拟实验可为此类油气资源勘探提供重要数据。以鄂尔多斯盆地延长组7段（长7段）页岩为例,利用金管-高压釜模拟生烃装置,系统研究了Ⅱ型有机质在与"生油窗"对应的成熟度范围（Easy R_o 0.7%~1.6%）内生烃产物中的气体烃（C_1-5）、轻烃（C_6-14）、重烃（C₁₄₊）、各族组分,以及生烃残渣的地球化学特征。发现长7段页岩在生油期可同时生成2.35~103.91 mL/g的气体烃和10.83~88.24 mg/g的轻烃。重烃的生成高峰对应的Easy R_o约为1.0%,与其中的饱和烃、芳烃和非烃的高峰产率对应的成熟度非常接近。重烃中沥青质的产率在Easy R_o约1.35%后开始下降,说明沥青质在此后才开始大量裂解与固化。而对原油物性影响很大的轻重比（气体烃+轻烃）/重烃]及气油比气体烃/（轻烃+重烃）]随成熟度增加而不断增大,其增速分别在Easy R_o为1.05%~1.15%之后明显变快。在生油过程中,长7段页岩残渣HI值和H元素的大量减少、干酪根固体碳同位素的变重均发生在Easy R_o约1.00%之前。干酪根碳同位素的变化相对较小,在鄂尔多斯盆地可以作为母源指标。通过对生烃产物中6种常见生物标志物成熟度参数的对比,证实多环芳烃成熟度参数中的甲基菲指数（MPI）和甲基菲比值（F1）在整个生油窗内都与成熟度有很好的线性相关性,可用于鄂尔多斯盆地母源为长7段页岩的原油成熟度判识。生烃产物的各地球化学特征变化节点、以及成熟度指标可用于鄂尔多斯盆地长7段页岩油或相关致密油资源的可采性评价。

Q uantitative full-component hydrocarbon-generating simulation and crude oil mobility evaluation of shale in 7th Member of Yanchang Formation,Ordos Basin

Shale oil and tight oil are current hot spots of oil and gas exploration, and the shale hydrocarbon-generating simulation experiment can provide important information for the exploration of these oil and gas resources. Taking the shale in 7th Member of Yanchang Formation (Chang-7 Member), Ordos Basin, the gold tube-autoclave hydrocarbon-generating simulator is used to systematically study the Type-Ⅱ organic matter, the gaseous hydrocarbon (C_1-5), light hydrocarbon (C_6-14), heavy hydrocarbon (C₁₄₊), other components of hydrocarbon-generating products in the maturity range (Easy R_o 0.7% -1.6%) corresponding to "oil-generation window", and the geochemical characteristics of hydrocarbon generation residues. It is found that in the shale of Chang-7 Member during oil-generation period, gaseous hydrocarbons of 2.35-103.91 mL/g and light hydrocarbons of 10.83-88.24 mg/g are produced simultaneously. The peak yield of heavy hydrocarbons corresponds to Easy R_o of 1.00%, closely approaching to the maturities corresponding to the peak yield of saturated hydrocarbons, aromatics and non-hydrocarbons. Moreover, the asphaltene yield of heavy hydrocarbons starts to decline after reaching the Easy R_o of 1.35%, reflecting subsequent large scale of asphaltene cracking and solidification. However, the light/heavy ratio (gaseous hydrocarbon/light hydrocarbon) and gas/oil ratio (light hydrocarbon/heavy hydrocarbon) vital for physical property of crude oil are continuously increasing as the maturity getting higher, and the increasing rates are evidently accelerated after Easy R_o of 1.05% -1.15%. During oil-generating process, the massive loss of HI and H element of shale residue and the kerogen solid carbon isotope becoming heavier occur prior to Easy R_o of 1.00%; the kerogen solid carbon isotope changes less, and can be taken as an original source index in Ordos Basin. Through comparing six kinds of common biomarker maturity parameters in the hydrocarbon-generating products, it is validated that MPI and F1 among the PAH maturity are linearly correlated to maturity in the whole oil-generating window, and can be used to identify the crude oil maturity in the shale of Chang-7 Member in Ordos Basin. The change nodes of various geochemical characteristics of hydrocarbon-generating products and the maturity indexes can be applied to the exploitability assessment for shale oil or correlative tight oil in 7th Member of Yanchang Formation, Ordos Basin.