The Distribution and Seismic Prediction of Beach-bar Sandbodies in Narrow and Elongate Faulted Basin — a Case from Second Segment of Shahejie Formation in Chezhen Depression.

Xia (Violet) Luo, Mingyou Tan, and Yingge Zhang
Houston, TX

The distribution of beach-bar sandbodies in narrow and elongate faulted basins are different from those in open basins. This study combined sedimentological and seismic reflection characteristics analysis to predict favorable exploration targets in beach-bar complex in one of these basins. We classified beach-bar sand bodies in the basin into “rework-dominated” and transport-dominated types based on their genetic characteristics, and established sedimentary model for each type. The reworked type beach-bars are characterized by strong wave action with weaker offshore current transportation, while the transport-type beach-bars are characterized by strong offshore current transportation with weaker wave action, as indicated by the grain sensitive analysis, a measure of local hydrodynamic conditions. The reworked beach bar sand bodies are the dominating facies in the area. Based on the established facies sequences, the seismic reflection characteristics and attributes related to these two types of sand bodies were analyzed. We found that single (for instance, amplitude) attribute can reflect the thickness changes of reworked-type beach-bar sand bodies, while double (for instance, amplitude and frequency) attributes can be used to recognize the transport-type. This paper discussed methods in seismic prediction of sedimentary microfacies including the paleotopography recovering, attributes reconstruction, linear regression of frequency division, and frequency spectrum analysis. The prediction technique can distinguish beach and bar sand bodies and zone of less than 5m in thickness, The adoption of this innovative technology can improve the accuracy of beach bar sand body prediction by 20% ~ 25%, and the success rate of reservoir prediction from 60% ~ 75% to 85% ~ 90% .

AAPG Search and Discovery Article #90152©2012 AAPG Southwest Section Meeting, Fort Worth, Texas, 19-22 May 2012