利用地震分频处理技术预测河流相储层——基于精细储层预测调整海上高含水油田开发方案实例

CR油田是经历了33年生产历史的海上老油田,目前已进入特高含水期,采出程度超过40%。对该油田进行综合评价,确定其剩余潜力,对海上同类油田开发有借鉴意义。CR油田主力油层段是河流相沉积,且砂岩厚度远小于地震分辨能力,因此采用分频处理技术研究储层分布特征。该技术采用高次连续的边部衰减函数来拟合地震离散数据,解决了短时窗频谱分析的关键问题,在保证灵敏度的同时,成功避免了吉布斯效应。处理结果清晰显示出了河道砂岩体的走向和相互关系;同时结合岩心分析结果进行了储层沉积微相研究。将这些成果用于精细储层地质建模并结合生产历史拟合开展数值模拟研究,在剩余油分布预测和增产措施优化分析方面取得了较好的效果。精细储层预测对于海上老油田开发方案调整非常重要,关键是预测目标要明确,对储层目标体特征的认识要清楚,技术方法选择要得当。

Prediction of fluvial-facies reservoirs using a technique of seismic frequency demultiplication: a case of adjusting development plan for an offshore oilfield with high water cut based on fine reservoir prediction

As an old offshore oilfield with a production history over 33 years,CR has reached a stage of very high water cut,with its recovery more than 40%.Making a comprehensive evaluation to determine its residual oil potential may helpful to development of other similar offshore oilfields.The dominated reservoir of CR oilfield is fluvial channel sands,and their thicknesses are far smaller than that of seismic resolution,so a technique of seismic frequency processing is needed to analyze reservoir distribution.By using a continuous high-order attenuation function to fit discrete seismic data,this technique has a resolved a key problem to analyze frequency spectrum in short time windows,and has successfully avoided the Gibbs' effect with a sensibility ensured concurrently.The results of processing clearly show strikes of the channel sands and their relationships,and are also used to analyze depositional microfacies of the reservoir in combination with core data.These results have been applied to fine geological modeling of reservoir and numerical simulation of reservoir with a production history match,leading to better effects in predicting distribution of remaining oil and optimizing stimulation measures.Therefore,the fine reservoir predication may be very important to adjusting development plan of old offshore oilfields,but the key points are to determine clear predication targets,to understand target reservoirs sufficiently and to select suitable techniques.