川东北南江地区须家河组四段砂砾岩体储层预测——基于正反演结合的概率体岩相建模储层预测方法

Reservoir prediction of conglomerate bodies in the fourth member of Xujiahe Formation of Nanjiang area, northeastern Sichuan Basin: a probabilistic body lithofacies modeling-based reservoir prediction method combining forward and inverse modeling

龙涛 刘明 张玉玺 孙均

LONG Tao LIU Ming ZHANG Yuxi SUN Jun

中国石化 勘探分公司, 成都 610041

SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

川东北山前带南江地区上三叠统须家河组发育大规模典型砂砾岩含气储层，勘探程度低、潜力巨大，其中须四段是重要的含气储层，构造与岩性复杂、地球物理参数敏感性较差、多解性强，储层表征难度大，有利储层分布特征与规律认识不清。鉴于此，针对勘探初期的砂砾岩储层预测方法进行攻关研究，将地震正演、反演与序贯高斯模拟的岩相建模方法相结合，形成了正反演结合的概率体岩相建模储层预测方法，即应用地震正演确定储层边界、地震反演初步预测储层空间分布、测井与反演协同建模精细预测岩相空间概率分布，最终实现储层精细预测。研究表明：基于正反演结合的概率体岩相建模储层预测方法，以岩相建模为桥梁，将测井数据与地震反演结果相结合，实现了储层厚度定量预测；结合地震正演精细刻画的储层边界，有效提高了储层的预测精度。应用该方法精细刻画了南江地区须四段砂砾岩体储层的分布，其中有利储层主要位于砂砾岩相辫状河道，地震上表现为中—弱振幅和微幅下切的特征，砂质含量越高、泥质和砾质含量越低，地震振幅越弱，储层越好；从北向南有利储层逐渐增厚，呈条带状分布，厚度主体介于15～30 m。该研究既为目标区后续井位部署提供了可靠地质依据，又为相似区块的储层预测提供技术方法借鉴。

The Upper Triassic Xujiahe Formation in the Nanjiang area of the piedmont belt in the northeast Sichuan Basin hosts large-scale, typical conglomerate gas-bearing reservoirs. These reservoirs remain underexplored and hold significant potential. Among them, the fourth member of the Xujiahe Formation is an important gas-bearing reservoir characterized by complex structural and lithological features, low sensitivity of geophysical parameters, and strong multi-solution, making reservoir characterization highly challenging. The distribution characteristics and patterns of favorable reservoirs remain unclear. To address this, a prediction method tailored for early-stage conglomerate reservoir exploration was developed by integrating seismic forward modeling, seismic inversion, and sequential Gaussian simulation-based lithofacies modeling. The probabilistic body lithofacies modeling-based reservoir prediction method applied seismic forward modeling to determine reservoir boundaries, seismic inversion for preliminary spatial reservoir distribution prediction, as well as well-logging and inversion collaborative modeling for refined prediction of the spatial probabilistic distribution of lithofacies, ultimately achieving precise reservoir prediction. The results showed that this prediction method used lithofacies modeling as a bridge to combine logging data with seismic inversion results, enabling quantitative prediction of reservoir thickness. The combination with seismic forward modeling further refined reservoir boundaries, significantly enhancing prediction accuracy. Applying this method to the Nanjiang area, the distribution of conglomerate reservoirs in the fourth member of the Xujiahe Formation was finely characterized. The favorable reservoirs are mainly located in the braided channels of the conglomerate facies, characterized by medium to weak amplitudes and slight amplitude downcutting on seismic profiles. Reservoir quality improves with increasing sandy content and decreasing mud and conglomerate content, resulting in weaker seismic amplitudes. The favorable reservoirs gradually thicken from north to south, exhibiting a banded distribution with thickness primarily between 15 and 30 m. This study provides a reliable geological basis for subsequent well location deployment in the target area and serves as a technical reference for reservoir prediction in similar blocks.

中国石化科技部项目“川东北地区须家河组致密砂岩气高产富集规律与预测技术”(P24011)和“四川盆地及周缘资源评价”(P23221)联合资助。

https://doi.org/10.11781/sysydz2025020362