利用地震资料进行陆相储层小层等时对比的方法研究——以绥中36-1油田为例

鉴于垂向分辨率的限制,一般认为不能利用地震资料进行陆相油藏小层对比。但是,由于主要地震反射同相轴具有年代地层意义,而且地层等时对比是相对的,因此,在一定条件下,利用地震资料可以进行陆相薄互层储层小层对比。文中以绥中36-1油田为例,总结了利用地震剖面开展小层对比的基本规则。根据地震不整一边界类型、地震相特征、砂体叠置关系变化可以确定小层等时界面,并且等时界面可以从波峰等时渐变到波谷;同相轴分叉时,只有分析清楚分叉的原因,才能得到小层等时追踪;在地层下切部位,追踪下切谷底部同相轴;地层凸起时,追踪凸起部位的地震同相轴;此外,遇到断层时,通常遵循正断层下降盘小层厚度应该等于或者大于上升盘小层厚度的原则。显然,合理地利用地震资料进行小层对比可以提高陆相油藏小层对比的准确性。

Research on isochronic subzone correlation of non-marine reservoir by seismic data: a case study in SZ36-1 oil-field, Bohai Bay Basin

Seismic data could not be used to correlate subzones in a non-marine reservoir,in general, as a result of the limitation of the vertical resolution. Because the major seismic reflections have chronostratigraphic significance, and the isochronic correlation is relative, the seismic data may help us to correlate subzones of a nonmarine reservoir under certain conditions. The authors generalized the basic rules for isochronic correlation by using seismic reflection profile in the SZ36-1 oil field. Isochronal horizons can be obtained through recognizing types of seismic Unconformity boundary, the features of seismic facies and the relations of sandbody overlapping. Meanwhile an isochronal horizon may gradually change from peak to trough of a waveform in horizontal direction. Moreover, only the causes of branching for a reflection are clarified while a reflection becomes branching in waveshape, an isochronic pursuit of subzones could be conducted. The subzone traces the reflection from the bottom of an incised valley as underlying strata are truncated down, and tracks the reflection from the top of a rise high as an underlying strata lift. In addition, it is a principle to follow that the formation thickness of upfauhed block is greater than or equal to the downdip block in correlation of subzones as facing faults. Obviously, the accuracy of isochronic correlation for subzones can be improved according to a series of rules mentioned above through reasonable interpretation of seismic data in non-marine reservoir.