陵水凹陷中央峡谷水道砂体构型地震响应正演模拟及有利分布区预测

Forward simulation on seismic response of channel sand body architecture in central canyon of Lingshui sag and favorable zone prediction

以琼东南盆地陵水凹陷中央峡谷水道为例,通过正演模拟方法对复合水道内部砂体构型的叠置样式及地震响应特征开展了系统分析,并联合地震储层反演、时频三原色切片技术进行了有利砂体分布区预测。研究表明,单一水道砂体的地震响应具有中等连续的强反射特征;尺寸较大时,砂体边缘为强振幅反射,砂体内部为弱振幅反射;复合水道内部砂体可划分为垂向孤立式、垂向叠合式、垂向切叠式、侧向孤立式、侧向叠合式和侧向切叠式等6种叠置构型样式,不同叠置构型样式的水道砂体具有不同的地震响应特征。基于水道砂体构型地震响应特征正演模拟结果,按照地震相特征将研究区2个主要气组水道砂体划分为6类,并利用地震时频三原色切片分析技术对研究区晚期水道体系2气组有利砂体分布区进行了预测,结果表明2气组有利砂体分布区位于未遭受下切水道改造的区域,其中中段W1井区、W5井区、WW1井区北部及峡谷水道侧翼水道改造较弱,砂体厚度大,圈闭及物性条件好,是最有利的I类水道砂体发育区,而东北部(未钻探区域)发育多个厚度较大、含气性较好的Ⅰ、Ⅱ类水道砂体,是未来勘探潜力区。

The study case is the channels in central canyon of the Lingshui Sag,Qiongdongnan Basin.Systematic analysis was conducted on superimposition patterns of sand body architecture in these composite channels and their seismic response characteristics by the forward simulation method,and favorable sand body zones were predicted in combination with seismic-reservoir inversion and time-frequency tricolor slicing technology.It is indicated that the seismic response of single channel sand body has intermediate-continuous strong reflection characteristics;and the margin has strong amplitude reflection and the inner part,weak amplitude if the sand body is large.The sand bodies in composite channels could be classified into six patterns of superimposition architectures;namely,vertical isolation,vertical superimposition,vertical cutting superimposition,lateral isolation,lateral superimposition,and lateral cutting superimposition.The channel sand bodies with diverse superimposition architecture patterns have different characteristics of seismic response.Based on forward simulation results of seismic response characteristics of channel sand body architecture,the channel sand bodies in two main gas reservoirs in the study area could be divided into six types by seismic facies characteristics,and favorable sand bodies in these two gas reservoirs in late-stage channel system were predicted by seismic time-frequency tricolor slicing analytical technology.The result shows that favorable sand bodies in these two gas reservoirs occur in the area that was not reconstructed by incised channels;the sand bodies are thick with good trapping and reservoir quality by weak channel reconstruction in central W1,W5,northern WW1 well fields and the limbs of canyon channels.They are the most favorable zones of sand body occurrence in I-type channel.There are many channel sand bodies as I and II types channel ones that are thick with high gas content in northeastern undrilled area.They are potential exploration ones in future.