基于分频构形反演方法的河道砂精准预测——以华北冀中探区赵皇庄地区为例

河道砂体具有单层厚度薄、规模小、分布散、非均质强的特点,常规模型反演预测中存在模型化严重、横向分辨率低及容易破坏沉积体构造形态的问题,导致预测精度不高。本次研究利用分频构形反演方法进行河道砂的精准预测,充分考虑测井和地震的优势频带和波形变化特征,由低、中、高不同频带模型融合而成初始模型,然后在贝叶斯框架下,通过地震合成记录的约束,修正全频带的反演结果。在赵皇庄地区河道砂薄、小储层预测实践中,反演结果具有较高的纵、横向分辨率,砂体横向叠置关系和尖灭点合理、清晰,砂体平面分布规律符合曲流河沉积相砂体展布特征,预测分辨4 m以上厚度储层的符合率达到80%以上,较好支撑了该区的井位部署。所形成的基于分频构形反演的薄、小砂体精准预测方法,对类似地区或区带的地震储层预测具有一定指导意义。

Accurate prediction of channel sand based on frequency-divided configuration inversion method:A case study of Zhaohuangzhuang area in Jizhong Sag,Huabei Oilfield

Channel sand bodies have the characteristics of thin single-layer thickness,small scale,scattered distribution,and strong heterogeneity.In conventional model inversion and prediction,there are problems such as serious modeling,low lateral resolution,and easily damaging the structural morphology of sedimentary bodies,which results in low prediction accuracy.This study uses the frequency-divided configuration inversion method to accurately predict channel sand.This method fully considers the dominant frequency band of logging and seismic and waveform change characteristics,and combines the low,medium and high frequency band models to form the initial model.Then under the framework of Bayesian,the inversion result of the whole frequency band is corrected through the constraints of the seismic synthesis record.In the practice of forecasting thin and small channel sand reservoirs in the Zhaohuangzhuang area,the inversion results have higher vertical and horizontal resolutions,which better support the well placement in this area.The sand body is reasonable and clear for the horizontal stacking relationship and sharp point,and conforms to the distribution characteristics of the sediment body of the meandering river for the plane distribution.Meanwhile,the predicted rate of resolving reservoirs with a thickness of more than 4 m is over 80%.The precise prediction method of thin and small sand bodies based on frequency division configuration inversion has certain guiding significance for the prediction of seismic reservoirs in similar regions or zones.