Middle and Lower Miocene Petroleum Systems in the Lower Congo Basin, Block 14, Angola

By

Frederico Domingos¹, Pedro Chicato², Augusto Salomao²

(1) Sonangol DPP, Luanda, Angola (2) Cabinda Gulf Oil Co, Luanda, Angola

 The Benguela Belize - Lobito Tomboco (BB-LT) complex is located in the northern portion of Block 14, offshore Angola. The field consists of seven Middle to Lower Miocene oil pools with oil quality ranging from intermediate to light (~24-37 API). Depths of the pools range from 5,700’ to 10,036’. The subsurface data set consists of a high quality/resolution 3D seismic survey, 14 wellbore penetrations, 9 DST's, 7 cored sections and full suites of logs.

The reservoirs are composed of high quality turbidite sands deposited in a middle bathyal slope valley/incised canyon environment. Reservoir quality sands are found as vertically stacked and nested channel complexes that both erode and aggrade preexisting sediments. The turbidite complexes are typically 500-2000m wide, 10-60m thick, and composed of intercutting sand rich turbidite channels, shale-rich mudflows, debris flows and slumps. Seismically, they display characteristics of laterally stacked sand-prone channels; meanders, differential compaction, and exhibit AVO signatures.

Traps consist of channels draped over broad four-way structural highs or in normal fault trap geometry and are likely controlled by Aptian salt movement and subsequent late stage extensional faulting. Regionally, the channel systems lie beneath highstand shales, providing a high quality seals both laterally and vertically.

The main source rocks are a combination of Iabe and Lower Malembo with the onset of peak oil generation at 13 Ma and 5 Ma. Deep penetration normal faults may provide migration pathways into the Miocene channels. All Miocene sands in trap position have encountered hydrocarbons of various quality and quantity.