Bissau Exploration Co.

Fully mapped and evaluated very large prospects are identified on the Shelf edge with a ‘Neocomian fault block’ present in the early Cretaceous and a buried hill observed in the mid Cretaceous sediments. In the basin there are three stratigraphic intervals of interest.
There is a large Barremian deep water fan, sand waves in the Aptian and large channel complexes in the Albian section. All the basinal plays have an AVO expression and for the Barremian prospect the Class I AVO response is coincident with impedance anomalies and a large Vp/Vs ‘low’. For the Aptian and Albian prospects there are pronounced Class II AVO responses. Every prospect has resource numbers measured well in excess of 500 MMbbls and for the Barremian the resource could be over a billion barrels.

Guinea Bissau Block 4B Summary and Active Sales Process

Bissau Exploration Company (“BEC” or the “Company”) is a UK private company set up to specifically focus on the exploration opportunity present in Block 4B, in Guinea Bissau. In 2017 BEC signed a joint venture agreement with Petroguin – Guinea Bissau’s National Oil Company – and in 2018 the Bagre PSC was officially awarded to the Company. BEC has 100% paying interest which covers PetroGuin’s 10% carried position.
BEC was asked to take on block 4B as a direct result of the work GeoPartners had performed in Bissau, initially driving seismic acquisitions in the country, and then with their partners TGS, acquiring the giant JAAN 3D survey.
For any enquiries relating to JAAN data please contact TGS direct. A link to GeoPartners – a sister company to BEC – is provided here: GeoPartners Ltd. and their history in the MSGBC basin and seismically focussed activities elsewhere in Africa can be found on this website.
The Bagre PSC covers the block 4B of c. 3,000 sq km in the deep water of the MSGBC basin. Importantly, it is directly on trend to the Sangomar field in Senegal and the area under license has been a major site of sediment transport from the African Shield in the east to the Atlantic Ocean in the west. The carbonate shelf edge that defines the Sangomar structure can be mapped running due south through block 4B and thereby offering prospective opportunities in similar settings as the Sangomar and the Fan discoveries in Senegal.


The presence of major east – west canyons, from at least the Neocomian to present day, is encouraging for the delivery of good quality sands into the basin rather than re-worked carbonate detritus as found in the Fan wells further to the north. The location and persistence of these canyons can be seen on a map of the present-day sea floor and the seismic line below shows how the features are stacked one on top of another. This history of sediment transport makes block 4B unique in the MSGBC, and this has been used to make a regional interpretation which is supported by a study of the Petroleum System.

Seismic data courtesy of TGS 
Detailed mapping on block, including AVO studies, has resulted in a large shelf, fault block/buried hill prospect under c. 1km of water and a very large submarine fan in c. 3km of water. The fan has good additional, shallower targets with class II AVO anomalies.
BEC is now actively looking divest the Bagre concession to a deep-water operator in preparation for an exploratory well. For contact details on the divestment see below, for anything else regarding Bissau Exploration Company please contact Mark Groves Gidney at  or on +44 7956 503969.

Summary of Prospectivity post 3D acquisition and interpretation

Fully mapped and evaluated very large prospects are identified on the Shelf edge with a ‘Neocomian fault block’ present in the early Cretaceous and a buried hill observed in the mid Cretaceous sediments. In the basin there are three stratigraphic intervals of interest. There is a large Barremian deep water fan, sand waves in the Aptian and large channel complexes in the Albian section. All the basinal plays have an AVO expression and for the Barremian prospect the Class I AVO response is coincident with impedance anomalies and a large Vp/Vs ‘low’. For the Aptian and Albian prospects there are pronounced Class II AVO responses. Every prospect has resource numbers measured well in excess of 500 MMbbls and for the Barremian the resource could be over a billion barrels.

To establish the prospectivity, BEC has utilised ‘best in class’ independent contractors to undertake bespoke work such as an Atlantic Ocean reconstruction of this pivotal part of the African margin, a comprehensive data basing and review of source rocks and their maturity across the MSGBC including a 3D Trinity migration model, and inversion and AVO work of the basinal plays where well calibration is limited. BEC also studied the sediments on the Shelf using RMS slices and they display features not readily apparent on regular seismic data. Reports from these contractors, including Wealden, Integrated Geochemical Interpretation (IGI), Down Under Geophysics (DUG) and Wessex Geoscience are all available via a data room.

Block 4B Summary

Technical Summary post 3D

Regional Introduction

Reconstruction of the Central Atlantic margin, with the associated accommodation issues caused by the Vema Wedge, shows a very good fit to the North and South American Plates with the Demerara Plateau sitting immediately south of Guinea Bissau, prior to the opening of the ocean. This means prior to opening the Neocomian shelf edge identified in the MSGBC has a natural extension to the same aged shelf edge currently located in Guyana and Suriname, as shown on the map below.

Similarities with the prolific Guyana plays associated with the Berbice Canyon running into an embayment along the Neocomian margin are clear. In the MSGBC the Geba River can be seen to have carried sediment from the Neocomian to the present day into an embayment mapped predominantly in Block 4B. Whilst the Demerara petroleum system is Turonian/Cenomanian in age and the Block 4B area is noticeably older, BEC believes there is undoubtably a very similar aged set up to Guyana in the MSGBC. The presence of embayments on the African margin has set up the perfect conditions for anoxic conditions and the accumulation of oil prone source rocks.


Barremian

The largest prospect in Block 4B is the Barremian fan which is clearly identified with discrete feeder channels cutting across the shelf, individual sand lobes with truncation away from the carbonate shelf edge and injectite deformation. The average size of the main lobes is 450 sq km (the total fan area is 650 sq km) and the individual lobes measure some 50m in thickness.

Detailed AVO screening shows the fan to have an AVO Class I anomaly with the top sand considered a hard event within soft, organically rich shales. This work has been tested by forward modelling with an analogue and Vp/Vs and impedance mapping. Prior to undertaking this work the sand lenses were blocked and de tuned so that any amplitude variation due to thickness changes could be addressed.

With the size of the fans and thickness of the sand lenses any resource numbers calculate in excess of a billion barrels. With no basinal well control and no way to calibrate the seismic response there is a risk, at the depth of burial, that no good poroperms exist. Nevertheless, there are many examples of early hydrocarbon emplacement preserving reservoir quality and there is no doubt the Barremian fan would have been charged early on in its burial history. By using an analogue more deeply buried than the Barremian fan, BEC can illustrate the preservation of good reservoir, and this is supported by the presence of injectites which would not occur in a carbonate cemented sand zone.

The source rocks for the Barremian are the interbedded distal equivalents to the sand fan and the ‘soft’ seismic signature is consistent with an organic rich shale. Age equivalents are seen in the DSDP 367 and these are organically rich.

Lower Cretaceous basinal souce potential – IGI study on MSGBC


Seismic data courtesy of TGS 
Aptian

Lying above but not necessarily coincident with the Barremian fan, are Aptian sand wave and contourite stratigraphic traps that are mappable off the 3D and they have distinct Class II AVO anomalies. The contourites lie in the north of the basin whilst the sand waves are in the south, away from the main east to west channels delivering sediment across the platform and basin. These two different sedimentary features are clear on the maps below.
The Aptian sand filled traps are most likely charged with oil from the interbedded shales as well as from the underlying Barremian. This stratigraphic section consists of black shales in the Atlantic basin and they are mature for oil. These source rocks have been drilled elsewhere in the MSGBC and they are of a high quality.
The traps in the Aptian are difficult to map directly off the 3D but the AVO anomalies are clear so mapping the brightening on the Fars provides the prospect definition. The location and size of the traps are shown below.
Albian
The Albian in Block 4B is abnormally thick which is not a surprise upon viewing the feeder channels on the Shelf. The channels feed directly into distributary channel systems and associated fans in the basin, and these are clear on the seismic and the maps below. Channel switching exists and therefore sand continuity is likely to be significant and the AVO anomalies provide great encouragement.

Shelfal Neocomian Fault Block

The stratigraphic section under the main unconformity on the shelf edge in Block 4B is deemed to be Neocomian in age and as such the control on the exact type of sediments to be drilled is poor as no drilling to date has gone below the Barremian. Based on regional geology BEC expects the Neocomian and underlying Jurassic to be shelfal carbonates although strong evidence of progradation and some channelling is observed. Basic inversion work performed by DUG highlighted areas of reservoir karstification within the structural closure.

The progradation and channelling within the pre Barremian shelfal sediments has been investigated by undertaking RMS work. Some graphics are shown here, and they illustrate the presence of a channel system – in exactly the same location as multiple Barremian to present day channels – that appears to be a clastic package. The channel feeds the prograding package of sediments seen on the southern flank of the Neocomian High, providing  a good reservoir target within the predominantly carbonate package.
Seismic data courtesy of TGS 
Regardless of a karstic carbonate or sand reservoir, there is over 80 sq km closure with over 1 km of overburden and interestingly, where the channel fill is observed, there is a noticeable gas escape feature running to surface.
Seismic data courtesy of TGS 
In terms of a hydrocarbon charge into the Neocomian, the underlying Jurassic is part of an active petroleum system as evidenced by  oil seeps onshore Bissau and Conakry, typed to be from a Jurassic source. There is also the chance of a hydrocarbon charge coming across/up the main bounding fault or even up the dip slope. At the base of the dip slope as one enters the well documented salt basin, there are several proven source rocks in the Lower Cretaceous that have expelled billions of barrels of oil. These same source intervals are juxtaposed against the Neocomian across the main Atlantic margin bounding fault. Hydrocarbon charge, whilst not clearly controlled, is not seen as a major risk as active source rocks are present on both sides of the regionally high area.

The size of closure of the Neocomian High offers the potential for significant resources. CNOOC was planning to drill the Neocomian in the Wolverine prospect across the border in AGC waters, so the play on Block 4B is one recognised as worthy of a risked investment.

Culmination of the technical evaluation – a 3D Trinity Migration Model of Block 4B north to the proposed Atum well

IGI were contracted to deliver a 3D migration model using the regional maps with the quality control from the basin modelling developed over the last three years, tied and calibrated to the available well data. The model only covers migration from the Atlantic basin in the west as no 3D exists to the east of the block, so no mapping was possible. The maps and model cover the entire block 4B area and go northward to the Anchova/Atum structure due to be drilled in 2024. Anchova and Atum (in Blocks 2 and 4a), along with the Neocomian High mapped in block 4B, are all separate culminations along a mega regional high located on the Shelf edge. This high could be charged with oil from both the west (Barremian to Aptian mature source rocks) and from the east (where the Aptian/Albian and Cenomanian/Turonian source rocks are mature). At least three oil families have been identified in the eastern (salt) basin and expulsion is proven by the oil found at Sinapa and the giant Dome Flore and Gea accumulations, albeit there is severe biodegradation in the shallow Domes salt features.

BECs focus was on the basin to the west where the Barremian/Aptian source rocks are deemed to have generated a 2 billion barrel (in place) charge to the Barremian submarine fan. The oil is modelled to be low GOR, 36 degree API. Such a charge (with minimal migration distances) will fill the fan first and any excess oil generated migrates up onto the Shelf edge, firstly filling the Neocomian High and then spilling progressively northwards to Anchova and then Atum. A direct charge from the west into Atum is complicated by the presence of several north-south salt walls in the basin. It was one of these salt walls that the deepwater Kora well was drilled on. It is estimated from the Trinity model that a further 2 billion barrels has been expelled from the depocentre in block 4B up onto the Shelf to fill these various traps – this is in addition to anything coming from the east or from depth where the Jurassic is likely to provide a condensate charge. A summary map of the model is shown below.

Sales Process and Contact Details

Block 4B in Guinea Bissau offers a wealth of opportunity with shelfal and basinal plays and large prospects at four stratigraphic levels. Water depth is between 1,000 and 3,000m dependent upon the prospect chosen and a well needs to be committed to on or before 2026.

BEC is looking for a clean exit although BEC will consider taking risk (and reward) on the first well. Back costs are $10m for the seismic licensing and about the same for other costs including signature bonus. The fiscal terms in Guinea Bissau are some of the best in the world to encourage and reward exploration and the planned drilling in the MSGBC, including the Apus operated Atum well due in mid 2024, could de risk the shelfal plays.

A proven oil charge onto the Shelf at Atum will no doubt be a positive for the area but Atum is very shielded from a direct oil charge from the west because of salt. Any oil into Atum is most likely to have come via the shelf in block 4B where there is a large structural trap to be filled first. Clearly the Barremian submarine fan in the basin is the very first trap to be filled so this play is unique and can only be evaluated by a dedicated well in the basin.

Block 4B Sales Process

BEC has contracted Merida Energy Advisors to run a sales process for Block 4B and data rooms are currently open.

For further enquiries please or to arrange a data room visit please contact Rolf Bakker at Merida Energy Advisors at or on +44 7880 336223

Bissau Exploration have offices in London. Contact can be made with Mark Groves Gidney in the UK on +44 (0)7956 503969 ()

Bissau Exploration Company Limited (BEC), an independent UK oil company, is incorporated in England and Wales (Company Number 09586299), with registered office at 10 The Triangle, NG2 Business Park, Nottingham NG2 1AE, United Kingdom. BEC’s Block 4B JVA is partner is Petroguin (A Empresa Nacional de Pesquisa e Exploração Petroliferas, E.P.).