The Importance of Halokinesis from Deep Water Reservoir Development — From Exploration Model from the Miocene Offshore Angola

Lars Seidler¹, Andrew Wakelin¹, and Andre Da Costa^2
1Maersk Oil, Copenhagen, Denmark
²Maersk Oil Angola, Luanda, Angola

The deepwater trend of Angola offshore is strongly influenced by halokinesis, with salt structures controlling trap formation, fluid migration pathways, heat flow and reservoir distribution. This study addresses how salt controls the confinement and orientation of slope turbidite channels and fans, including depocenter formation. The results can be used for reservoir prediction and characterization of reservoir risk adjacent to salt structures, and in particular for sub-salt plays where imaging is poor. A 40 km long section of a Miocene slope channel system is examined from a region with minor salt influence into a salt province. Along the channel system from proximal to distal a significant change in both width and thickness is observed, suggesting varying degrees of erosion, bypass and deposition. Proximally the channel style is characterized by deep incision with small levees and seismic facies indicating low net-to-gross. This zone is dominated by strong erosion and bypass. As the channel approaches a large salt diapir it diverts around the salt indicating syn-sedimentary salt movement. Turbidites do not reach the salt body, and partially pond behind it. The seismic facies indicate higher net-to-gross in this further down-slope region, whilst down-dip of the salt diapir, the channel system shows a marked change to become distributary with thick sands present. This region is dominated by deposition and is characterised as an intraslope basin, most likely controlled by salt evacuation.

We will present prediction criteria for estimating net-to-gross relative to the distance to salt and also present a model with different reservoir styles observed around the salt.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery