五宝场地区沙溪庙组致密砂岩储层地震预测技术

Seismic prediction technologies used for tight sandstone reservoirs of Shaximiao Formation,Wubaochang area,Sichuan Basin

五宝场地区中侏罗统沙溪庙组河道砂地震响应特征不明显,普通裂缝预测方法不适用,烃类检测符合率低,储层预测难度大。通过采用均方根振幅属性来表征河道砂体,再采用信噪比差异体对裂缝进行描述,最后通过能量比对储层含气性进行烃类检测,实现了较为精细的储层预测。应用结果表明:(1)以地震“顶峰-底谷”的反射特征为主体,利用均方根振幅属性与基于相控测井约束的阻抗反演进行联合分析,能较好表征出河道砂体的形态;(2)以断层附近的岩性变化造成的地震反射突变为特征,引入信噪比差异体,有效地降低了地球物理解释的多解性;(3)通过高低产井与高低频能量呈正相关的关系,利用叠后近道集数据进行油气检测,优选中低频能量与高频能量比值大于1.1的油气富集量化指标,获得的含气性预测结果与实钻井符合率达80%。

There is dull seismic reflection feature on the channel sandbody in Shaximiao Formation,Wubaochang area.And for sake of low coincidence in hydrocarbon detection and strong difficulty in reservoir prediction,most traditional approaches to predict fractures can not work.So,the channel sandbody was characterized by by adopting root-mean-square amplitude.And then,fractures were evaluated by S/N ratio difference.In addition,hydrocarbon detection on gas content was carried out by means of energy contrast to achieve more careful reservoir prediction.Results show that(1)with seismic reflection characteristics of both pinnacle and rock bottom as the soul,a joint analysis on impedance inversion is conducted by adopting root-mean-square amplitude and through facies-controlled logging constraint,which can characterize the pattern of channel sandbody;(2)the S/N ratio difference,which means sudden changes in seismic reflection induced from lithological variation around faults,is introduced to validly lessen an ambiguity in geophysical interpretation;and(3)because gas wells with high or low production emerge as a positive relation to high-or low-amplitude energy,oil and gas can be detected by using poststack near-trace data.And one index on behalf of hydrocarbon accumulation is selected,namely low-to high-amplitude energy vs.high-amplitude energy is bigger than 1.1.The consistency is 80%between the obtained gas-bearing content and that from actual drilling.