油页岩地质类比资源评价体系的建立

Establishment of Assessment System for Oil Shale Resources Based on Geological Analogy

松辽盆地晚白垩纪青山口组和嫩江组蕴藏着丰富的油页岩资源,已查明4处超大型中浅层油页岩矿床,盆地油页岩资源整体呈现“局部查明程度高、整体认识程度低”的特征.本文采用以地质类比法为主、统计算法为辅的统计类比法估算油页岩潜在资源量.在松辽盆地嫩江组探明的超大型矿床——吉林松南油页岩含矿区的类比刻度区内,以松辽盆地油页岩成矿富集条件为理论依据,优选出控制油页岩成矿富集的3个一级和6个派生二级地质因素来建立类比参数库,并提出“多态”定性变换原则处理类比参数.采用特征因子法确定刻度区与预测区的相似类比系数概率分布函数,并构建了油页岩资源体积丰度概率分布函数,从而利用蒙特卡罗法和组合抽样法计算不同置信水平下的油页岩潜在资源量.提出利用“高概率值波动剧烈”选取原则评价概率区间上合理的油页岩潜在资源量,把100％～85％概率区间的资源量作为松辽盆地嫩江组油页岩资源评价的合理值区间.结果显示,松辽盆地嫩江组中浅层油页岩在合理概率下的潜在资源量分别为2867.2×108 t（100％）、3356.2×108 t（95％）、3834.0×108 t（90％）、4307.7×108 t（85％）,合理概率区间上的平均资源量为3591.3×108 t.验证分析表明,统计类比法对大范围低勘探程度的预测区资源估算更为准确,填补了中低勘探盆地油页岩在资源评价方面的不足,可以为其他同类型沉积盆地的能源或矿产资源评价起到借鉴作用.

The Songliao basin contains rich resources of oil shales in the Upper Cretaceous Qingshankou （K2qn）and Nenjiang （K2 n） formations,which has been identified 4 super-large deposits of middle-shallow oil shales.Oil shale resources present the characteristics of higher exploration in the local and lower recognition in the global region.We adopt a statistical analogy with the predominance of geological analogy and statistical algorithms to assess potential resources of oil shales,We selected a super-large deposit of oil shales as the calibrated region in southern Songliao basin of Jilin Province.Based on the metallogenic and enriching mechanisms of oil shales,main geological parameters are optimized to establish the data base of geological analogy.Those parameters are reset by a principle of qualitative transformation with multi-state.Moreover,an approach of characteristic factor is utilized to calculate the probability distribution function of analogical coefficients between the calibrated and predicted regions.Methods of monte-carlo and composite sampling are used to estimate potential resources of oil shales at different level of probability,based on constructed probability distribution function of volume abundance for oil shale resources.In this study,we firstly propose the principle of ＂ high probability value with remarkable fluctuation＂ to select a reasonable probability range of potential resources.Oil shale resources from the probability range of 100％ to 85％ are taken as a reasonable result of resource assessment in the Nenjiang Formation of the Songliao basin.Our results show that potential resources of oil shales from the middle-shallow Nenjiang Formation are 296.72 gigaton （100％）,335.62 gigaton （95％）,383.40 gigaton （90％）,and 430.77 gigaton （85％） （avg.359.13 gigaton）.Therefore,we establish a promising assessment system for predictive resources of wide range and low exploration,aiming at the insufficient approach of resource assessment in the middle-low exploration basin.Our technique may be utilized to attempt to assess the energy or mineral resource in the sedimentary basin of other same types.