鄂尔多斯盆地张家滩页岩气区三维盆地模拟

Three-dimensional basin modeling study on Zhangjiatan shale gas area in Ordos Basin

相对于常用的多因素叠加法和概率体积法,对页岩气有利区选取和资源评价的三维盆地模拟可以将关键地球化学数据和储集物性等参数在时间和空间上更合理的结合,进而对页岩含气的空间非均质性和聚集过程进行刻画。通过实验数据分析认为,鄂尔多斯盆地张家滩页岩有机质含量高、成熟度适中、储集物性好并且天然气显示良好,具有较大的页岩气资源潜力。利用翔实的地质背景资料、地球化学数据、储集物性参数和现场含气量测试数据等对张家滩页岩的地史(沉积史和构造史)、热史(热流史和热成熟史)和生排烃史进行了三维盆地模拟。解释了目前张家滩页岩埋藏深度与成熟度分布不匹配的原因,预测了该层页岩气的空间分布,获得了该层页岩气的成分、吸游比(吸附气和游离气体积之比)、地质资源量和可采资源量等关键资源评价参数。盆地模拟研究认为张家滩页岩有机质转化率约为20%,平均排烃效率约为80%。目前张家滩页岩气主要以吸附态分布在富县以西地区,地质资源量约为0.15×10^(12) m^3。通过实测孔隙度、成熟度和现场含气量解吸等实验数据对模拟结果的校正表明,三维盆地模拟结果与实测数值吻合性好,可靠性较高。综合研究认为,三维盆地模拟是一种可靠的页岩气资源评价方法,在我国地质资料翔实的研究区具有广阔的应用前景。

Three-dimensional basin modeling which combines geochemical and reservoir parameters can make a very good simulation of the heterogeneity of shale gas distribution and the process of its accumulation.Geochemical analysis implies that Zhangjiatan shale in Ordos Basin has a high TOCcontent with a moderate organic maturity.Production data also demonstrate the shale has a great potential of gas generation.Solid geological background materials,geochemical data and reservoir parameters were applied in the simulation of the geological evolution history,geo-thermal history and hydrocarbon generation and expulsion history of the shale.The distribution of shale gas was predicted by the three-dimensional basin modeling,and gas constitution,adsorb to free gas ratio,resource and reserve of the shale gas were also calculated.It was speculated that the organic conversion of the shale is about 20%and about 80% of the hydrocarbon that had been generated was expelled out of the source rock.Basin modeling result manifests that most of the shale gas is distributed to the west of Fuxian in adsorbed phase with a geological resource of 0.15×10^12 m^3.Calibration on porosity,maturity and gas content verified that the basin modeling is solid.It was concluded that the three-dimensional basin modeling is a reliable way in shale gas resource evaluation especially in well researched areas in China.