SRC has been taking the lead in pioneering exploration research in areas of oceanic crust since 2013, where studies in the Gulf of Guinea highlighted the potential for generation of hydrocarbons from source rocks on oceanic crust, and the significant role of crustal deformation in the formation of hydrocarbon traps above oceanic crust. The Oceanic Crust Exploration Project began as a collaboration between Steve Lawrence (SRC) and Dr Chris Cornford (IGI Limited) in 2013, with field work to the island of Fuerteventura.
As exploration extends into deeper waters there is an ever increasing need to improve our understanding of the sedimentary, tectonic and thermal conditions operating on oceanic crust. SRC, in association with IGI and Bridgeporth, is undergoing research under the Oceanic Crust Exploration Projects, designed to answer the key questions surrounding exploration on oceanic crust viz. source rock occurrence, thermal history and structural development (see ‘Technical Notes’ below). The first of these projects is aimed at the West African passive margin of the South Atlantic (OCEP – ‘West Africa’) for which the review/database has already been completed and available for licensing as follows:
- Review of biostratigraphy of 15 DSDP/ODP sites
- Review and data-basing of geochemistry data from 51 DSDP/ODP sites
- Review of thermal history and thermal calibration using DSDP data
- Examination and sampling/analysis of Mesozoic sections exposed on Fuerteventura (Canary Is.) and Maio (Cape Verde Is.)
The ongoing interpretation phase of the project will use these results and incorporate the interpretation of public domain geophysical data to:
- Synthesise the stratigraphy of the Distal Domain to ascertain the context of organic-rich intervals (ORIs)
- Evaluate the geochemistry of the ORIs as commercial source rocks
- Investigate lithospheric/crustal structure to provide critical control for structural interpretation and basin modelling
- Determine thermal (maturity) history of source rocks by 1D and 2D basin modelling extending from transitional crust to oceanic crust leading to a recognition of areas favourable for successful exploration on oceanic crust along the West Africa Margin
The initial database compilation and review has been completed, with the creation of biostratigraphic and geochemical databases for interpretation as part of the research has been completed and is available to license from SRC. A technical seminar to present the interim results of the research study was held in London in July 2018, with presentations by SRC, IGI and Weston Stratigraphic project team. Selected slides from the seminar and details of interim deliverables of the research are available on request, please contact SRC.
Accompanying Technical Notes
Here we provide a flavour of SRC/IGI’s ongoing investigations into oceanic crust exploration and early results obtained:
- Source Rocks
- Thick ORIs are developed in DSDP core-holes in the Jurassic, Aptian, Albian, Cenomanian-Turonian and Coniacian not restricted to OAEs.
- Geochemistry indicates that ORIs are dominantly oil-prone and represent good commercial source rocks.
- Thermal History
- Source rocks can be thermally mature on oceanic crust despite perceived ‘cool’ history. DSDP data show anomalously high maturity levels at several locations.
- DSDP data show evidence for ‘hotter in past’ thermal history on oceanic crust. This can be attributed to anomalously high heat flow and/or additional burial (now ‘missing section’). We are investigating this scenario offshore Morocco by obtaining new thermal history data (AFTA/VR) from DSDP 415, 416 & 370 and in the eastern Gulf of Guinea where there is an extensive thermal history database. Results will be presented at the PESGB-HGS Africa Conference in October 2019.
- Structural Development/Tectonic History
- Cretaceous and Tertiary post-break-up uplift has been demonstrated along vast tracts of the West African margin. New evidence suggests that uplift has extended into deep-water over transitional and oceanic crust offshore Morocco and eastern Gulf of Guinea (see Bray & Lawrence @ Geol. Soc. Workshop, October 2018 and Chris Cornford Conference, April 2019).
- Sub-lithospheric processes dominate current thinking on the thermal and deformational history of oceanic crust despite growing evidence for lithospheric deformation involving re-activation of oceanic crustal fabric.
- We are investigating a tectonic explanation for deformation and uplift using new seismic data offshore Morocco (see Lawrence GeoExpro article June 2019) and studies on Fuerteventura and Maio. These ideas were presented at the PESGB-HGS Africa Conference in October 2019, and a copy of the presentation is available below.
Collaboration with Geoex Limited
SRC cooperates with Geoex to help plan and promote Geoex’s various multi-client seismic projects. Our role has been to provide insights into the regional geology and prospectivity of the various areas in which Geoex has acquired multi-client 2D and 3D surveys and to assist Geoex in the promotion of the multi-client data and provision of data rooms for interested companies.