鄂尔多斯盆地胡尖山地区长7段页岩型页岩油源储特征及勘探前景

Source rock and reservoir characteristics and exploration prospects of shale type shale oil in the seventh member of Yanchang Formation in Hujianshan area in Ordos Basin

鄂尔多斯盆地三叠系延长组长7段发育一套以富有机质泥页岩为主夹砂质沉积的烃源岩层系,其中长7段源内夹层型页岩油已取得勘探突破并实现规模效益开发,但页岩型页岩油前期研究相对较少,是否具有勘探开发前景还不够明确。为此,以长7段烃源岩为研究对象,开展基于岩心分析化验、测井资料解释的烃源岩源储特征评价和矿场开发试验,用以评价胡尖山地区长7段页岩型页岩油勘探前景。长7段岩心测试分析表明,页岩主要发育粒间孔、晶间孔及有机质孔,常见层理缝及有机质收缩缝,游离态轻质油主要赋存于粒间孔及页理缝;运用多溶剂连续分步抽提方法实验结果表明,长7段页岩中游离态轻质油比例可达到54.3%。通过地球化学特征分析,长7段页岩平均TOC为14.03%、平均生烃潜量为57.73mg/g,为优质烃源岩;有机质热演化程度较高,平均R_(o)为1.08%、平均T_(max)为450℃;岩石热解可动烃含量达到4.34mg/g,表明页岩型页岩油具有良好的资源基础。研究区长7段页岩有机质类型好、有机质含量高、岩石可压裂性好,盆地内直井试油试采表明页岩含油性较好,利用岩石热解法估算该地区页岩型页岩油可动烃资源量为4.1×10^(8)t,综合认为研究区页岩具有水平井体积压裂提产的勘探开发前景。

A set of source rocks mainly composed of organic-rich shale and intercalated with sandy sediments were developed in the seventh member of the Triassic Yanchang Formation(Chang 7 member)in Ordos Basin.Among them,exploration breakthrough and large-scale beneficial development of intra-source interlayered type shale oil have been achieved.However,there is a lack of study on shale type shale oil,as well as insufficient understanding on the exploration and development prospects.As a result,source rock and reservoir characteristics have been analyzed based on core laboratory tests and well logging interpretation results,and field pilot well development has been tested to evaluate the exploration prospects of shale type shale oil in Chang 7 member in Hujianshan area.The core testing results indicate that intergranular pores,intercrystal pores,and organic matter pores are mainly observed,with common bedding fractures and organic matter shrinkage joints,and free light oil mainly occurs in intergranular pores and bedding fractures;The experimental results of multi solvent continuous stepwise extraction method show that the proportion of free light oil in Chang 7 member shale reaches up to 54.3%.The geochemical experiment results indicate that the average total organic carbon content(TOC)is 14.03%and the average hydrocarbon generation potential is 57.73 mg/g,showing a high-quality source rock;The thermal evolution degree of organic matter is relatively high,with an average R_(o) of 1.08%and an average T_(max) of 450℃;The rock pyrolysis movable hydrocarbon content is 4.34 mg/g,indicating a good resource foundation of shale type shale oil.To sum up,Chang 7 member shale in the study area has good organic matter type,high organic content,good fracability,as well as good oil-bearing property indicated by vertical well testing and production results in the basin.By using rock pyrolysis method,8 the preliminarily estimated movable hydrocarbon resources of shale type shale oil in this area are 4.1×10^(8) t.The comprehensive study shows that the shale type shale oil in the study area has exploration and development prospects by applying horizontal well volume fracturing and reservoir stimulation.