少井条件下的复杂岩性储层地质建模技术——以渤海湾盆地石臼坨凸起A油田为例

Reservoir modeling of complex lithologies with sparse wells:A case from A oilfield in Shijiutuo uplift,Bohai Bay Basin

钻井揭示渤海湾盆地石臼坨地区沙河街组一段、二段储层垂向岩性为复杂的碎屑岩和碳酸盐岩混杂堆积,总体物性为低孔、特低渗,储层厚度大但隔夹层不发育,且横向变化快,内部非均质性严重。勘探评价阶段由于海上油气田评价井数量有限,储层认识难度大。针对此类储层的精细表征,单井上通过元素俘获谱测井技术识别储层复杂岩性,并结合核磁共振测井技术完成不同岩性储层的渗透率优化解释,在此基础上根据岩性和物性特征划分储层岩相。同时结合地层切片演绎技术和井点岩性分布进行扇三角洲沉积期次划分,从而搭建精细地层格架。以地层格架为单元,利用地震多属性分析技术预测扇体的空间展布范围,并通过确定性建模和随机模拟相结合的方法多级约束建立储层岩相模型,最终通过相控随机模拟的方法得到定量的储层物性空间分布。该套建模技术合理表征了石臼坨地区古近系复杂岩性储层的空间分布特征。所建立的地质模型在确保等时性的同时,细化了储层层系,明确了优质储层的分布特征,提高了勘探评价阶段古近系中深层复杂岩性储层预测的精度。

The 1st and 2nd Member of Shahejie Formation reservoir in Shijiutuo uplift of Bohai Bay Basin are complex in vertical lithology because of the nature of mixed elastics and carbonates. The reservoirs feature in low porosity and super- low permeability,large thickness but underdeveloped barriers and baffles with quick lateral variance, and strong internal heterogeneity. As there are limited appraisal wells available in offshore oilfield during the exploration and evaluation stage, it is difficult to understand the reservoirs. In order to finely describe these reservoirs, element capture spectroscopy logging was used to identify the complex reservoir lithology in single well, and nuclear magnetic resonance logging tech- nique was used to optimize permeability interpretation of different lithologies. Then the reservoir lithofacies were divided according to the identified lithologies and petrophysics. By combining seismic attribute slice analysis with lithology distri- bution of wells, we identified different sedimentation stages of fan deltas and established a stratigraphic framework. By taking the stratigraphic framework as units, we predicted spatial extent of sandbody through seismic multi-attribute analy- sis and finished the lithofacies model with multilevel constraints by integrating deterministic modeling with stochastic simulation. Finally, we established the reservoir physical parameter modeling by using the lithofacies model as constraint.