Application of 4-D Integrated Technologies to a Submarine-fan Channel System in the Niger Delta Basin: Insights Into the Reservoir Heterogeneity and Its Controls on the Fluid Flow During Development

Abstract

The submarine-fan channels' reservoir heterogeneity has been the focus of intense studies in recent years because of their significant impacts on field development. Using integrated well logs and 3-D seismic data from a subsurface field in the Niger delta basin, the current study attempts to characterize the previously undocumented spatial distribution of shale barriers/baffles and permeability contrast within a submarine-fan channel system. In combination with 4-D seismic data that provides direct evidence for fluid flow, an effort has further been made to examine how the submarine-fan channels' reservoir heterogeneity controls the fluid flow during development. Results from this study will provide significant guidance on the deployment of development strategies and prediction of remaining oil within a submarine-fan channel system. The integrated investigation from well logs and 3-D seismic data shows that a submarine-fan channel system is highly compartmentalized by the extensively developed shale barriers among multi-episodic channel complexes, except that erosional holes occur locally at the severely channel-downcutting positions. Within a channel complex, inclined shale baffles are developed locally on the stacking boundaries of individual channels, exhibiting a discontinuous bowing shape in plane view. The characterization of permeability shows that the middle part of the channel system displays a generally weak vertical permeability contrast with an overall higher permeability, despite a severe vertical permeability contrast for the whole channel system. In plane view, a channel complex shows a severe planar permeability contrast, manifested as relatively high-permeability streaks along the channel axis. The 4-D seismic responses have validated that the injected water mainly sweeps along different channel complexes forming a dominant parallel-flow in cross sections, as a result of the vertical impediment by the extensively developed shale barriers and the generally weak vertical permeability contrast; whereas at the localized erosional-holes parts can form a cross-flow in cross sections. Within a channel complex, the planar fluid-flow pathways can display multiple-strips like due to the lateral impediment by inclined shale baffles. Additionally, the injected water sweeps preferentially along the relatively high-permeability streaks, forming unevenly or evenly waterflooding patterns depending on the positions of injector-producer wells.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017