基于地质知识库的致密砂岩气藏储层建模——以苏里格气田苏X区块为例

摘要

The tight sandstone gas reservoirs in Sulige Gas Field are characterized by unclear understanding of effective reservoir,lack of suitable modeling methods and low effective reservoir drilling rate of horizontal wells.Based on logging curves correlation of 169 wells in Su X block and geological understanding of braided river,the reservoir geological knowledge database was established,and combined with 3D image training,a new 3D multiplepoint geostatistics modeling method was put forward.The results show that the width,thickness,length and width-thickness ratio of braided river point bar are 200-450 m,3-10 m,450-1 000 m,45 ∶ 1-55 ∶ 1,respectively,and the width of single braided river is 1 000-2 500 m.By using the geological knowledge database in the process of 3D image training,the geological model is more suitable to display the proportion between braided river and point bar,and reflects the overlap and migration characteristics of braided river sedimentary systems.Multi-point geostatistics method could apply 3D training image to 3D geological modeling of braided river,and presents a structure of "sand pack sand" in effective reservoir.Horizontal well drilling results confirm that the geological model could accurately predict the effective sandbodies and guide the geo-steering of the horizontal well in tight sandstone gas reservoir.This study will play a certain reference role to tight sandstone gas reservoir modeling.%针对苏里格致密砂岩气藏有效储层规模认识不清、致密气藏三维地质建模方法欠缺和水平井有效储层钻遇率低等问题,利用苏X区块169口并储层砂体解剖、实钻井对比分析与辫状河地质认识,建立储层地质知识库,再利用基于目标法建立三维训练图像,最后利用多点地质统计学建模方法建立三维地质模型.结果表明,苏里格致密砂岩气藏的辫状河砂体中,心滩有效储层规模参数为:宽度200～450 m、厚度3～10m、长度450～1 000 m、宽/厚45∶1～55∶1,单一辫状河道宽度1 000～2 500 m;将以上储层地质知识库应用于三维训练图像中,体现了辫状河道与心滩规模的比例关系,及其在三维空间上的叠置迁移特征;多点地质统计学方法能够将辫状河三维训练图像成果应用到三维地质建模中,使地质模型更符合辫状河地质认识和致密砂岩气田有效储层的“砂包砂”二元结构.水平井实钻证实,地质模型能够准确预测井间有效砂体规模、指导致密砂岩气藏的水平井地质导向.以上建模方法对国内外类似致密砂岩气藏储层建模具有借鉴意义.