鄂尔多斯盆地长7_(3)亚段页岩油可动烃资源量评价方法

Research on evaluation method of movable hydrocarbon resources of shale oil in the Chang 7_(3) sub-member in the Ordos Basin

鄂尔多斯盆地长7_(3)亚段发育一套富有机质泥页岩夹薄层粉—细砂岩的细粒沉积,具有整体生烃、普遍含油的特征。明确不同类型细粒沉积的含烃量、赋存状态、烃类组分等,对于该类型页岩油资源潜力分析和甜点优选具有重要意义。基于CY1井长7_(3)亚段岩心系统测试分析,运用多粒级多极性分步抽提方法,对黑色页岩、暗色泥岩、粉砂岩、细砂岩等4种细粒沉积岩石类型开展可动烃研究,评估了盆地长7_(3)亚段页岩油的可动烃资源量。结果表明,多粒级多极性分步抽提分析不同类型细粒沉积在不同粉碎条件下(1 cm^(3)、0.5 cm^(3)、150目)的含烃量及其组分,单位抽提量大小顺序为细砂岩>黑色页岩>粉砂岩>暗色泥岩,步骤1、步骤2抽提可溶有机质以轻质—中质组分为主,属于可动烃;步骤3和步骤4抽提可溶有机质为不可动烃。实验结果表明长7_(3)亚段黑色页岩、暗色泥岩、粉砂岩和细砂岩的可动烃量分别为3.35 mg/g、1.45 mg/g、3.28 mg/g和4.48 mg/g。对城80井区220 km^(2)长7_(3)亚段页岩油可动烃资源量进行评价,初步评价结果为(0.37~0.51)×10^(8) t。鄂尔多斯盆地长7_(3)亚段页岩油有利分布面积约为1.5×10^(4) km^(2)。通过类比分析,评价其可动烃资源量为(25~35)×10^(8) t,该类型页岩油有望成为盆地石油勘探新的接替领域。

A set of fine-grained sediments of organic-rich shale interbedded with thin layer silt and fine grained sandstones developed in the Chang 7_(3) sub-member of the Ordos Basin.It has the characteristics of overall hydrocarbon generation and general oil-bearing.It is of great significance to clarify the hydrocarbon content,occurrence state and hydrocarbon components of different types of fine-grained sediments for the potential analysis and sweet spot selection of this type of shale oil resources.This study is based on the systemical core testing and analysis of the Chang 7_(3) sub-member of Well CY1,movable hydrocarbon research on four fine-grained sedimentary rock types is carried out,including black shale,dark mudstone,siltstone and fine-grained sandstone,by using multi-granular multi-polar sequential extraction methods,and the movable hydrocarbon resources of shale oil in the Chang 7_(3) sub-member is evaluated in the Ordos Basin.The research results show that the hydrocarbon content and its components of different types of fine-grained sediments under different particle size crushing conditions(1 cm^(3),0.5 cm^(3),150 mesh)are analyzed by multi-particle multi-polar sequential extraction.The unit extraction amount of hydrocarbon is fine-grained sandstone>black shale>siltstone>dark mudstone.The soluble organic matter extracted by step 1 and step 2 is mainly light-medium components and belongs to movable hydrocarbons.Soluble organic matter extracted by steps 3 and 4 is immobile hydrocarbon.Based on the above test methods,the movable hydrocarbon of black shale,dark mudstone,siltstone and fine sandstone in the Chang 7_(3) sub-member are 3.35 mg/g,1.45 mg/g,3.28 mg/g and 4.48 mg/g,respectively.The movable hydrocarbon resources of 220 km^(2) shale oil in Cheng 80 well block in the Chang 7_(3) sub-member were evaluated.The preliminary evaluation results were(0.37-0.51)×10^(8) t.The distribution area of shale oil in the Chang 7_(3) sub-member in the Ordos Basin is about 1.5×10^(4) km^(2).Through analogy analysis,it is estimated that its movable hydrocarbon resources are(25-35)×10^(8) t.This type of shale oil is expected to become a new replacement area for oil exploration in the basin.