Pre-Pliocene Prospectivity Study: Onshore Azerbaijan
- The executive companies: Geology Institute, BP and STATOIL ALLIANCE
- The year of publication: April 1995
- Code: EXT 67373
- Volumes: total 2. Volumes with appendixes in same amount: 1
The largely Pliocene "Productive Series" succession of Azerbaijan produces 99% of the hydrocarbons found in the South Caspian Basin to date. However, although exploration efforts have concentrated almost exclusively on the Productive Series, there is minor production in onshore Azerbaijan from the succession beneath the Productive Series (for example from Maastrichtian flysch and from the Maykop Suite (Oligocene - Early Miocene) sands). It has been a long-held belief of many Azeri geoscientists that considerable potential for hydrocarbon discoveries exists in the Pre-Pliocene succession. In order to test this, we visited numerous outcrops in eastern Azerbaijan in order to sample and study potential source and reservoir rocks and to develop structural models. We also reviewed the Pre-Pliocene exploration effort to date. This, in combination with the outcrop data, enabled potential play fairways to be identified and a hierarchy of prospective regions to be presented.
It is clear from both outcrop and well data that there are several horizons in the Pre-Pliocene succession which contain reservoir quality sediments, leading to the recognition of several potential play fairways. These include horizons within the Eocene, Oligocene - Miocene, Late Cretaceous and Early Cretaceous successions. Particular attention has been placed on the potential of the Gobustan region. Here Tertiary and perhaps even Mesozoic sediments are most likely a potential play beneath the imbricate stack of the southern Greater Caucasus, although burial cementation may occlude porosity. At outcrop, potential Cretaceous and Early Tertiary reservoirs (e.g. the Kululin Sandstone and sands within Maykop Suite) contain a high degree of cementation, and individual beds are laterally discontinuous. The best reservoir quality sands seen in Gobustan were those of the Chokrak Horizon (Miocene) (close to where they produce oil at Umbaki). However, their thickness and areal distribution is thought likely to be limited.
Structural cross-sections across Eastern Azerbaijan suggest that anticlinal traps may exist in the autocthon beneath the thrusts of the Greater Caucasus. However, their existence is still the subject of agreement on a structural model for the region. In any case, it seems likely that these traps will be at considerable depth and difficult to recognise on seismic. A simpler option is to explore the existing structures of the Apsheron Peninsula, Kura Valley and southern Gobustan to greater depths in order to test the Maykop Suite, Chokrak Horizon and deeper reservoirs.
A subject of ongoing research is the probable source rock for potential Pre-Pliocene plays. Geochemical analysis of samples collected during field work indicates that the sediments of the Maykop Suite (and especially the lower part) form the best present-day source rocks. Sediments of parts of the Diatom Suite and Middle Jurassic succession also display reasonable present-day source quality. Potential reservoirs within the Tertiary succession may receive a charge from a Maykop Suite source rock. Autocthonous Mesozoic reservoirs may require a Jurassic source rock.
(i) Executive summary
(ii) Contents List
2. GEOLOGICAL OVERVIEW
3. HYDROCARBON EXPLOITATION
4. PRE-PLIOCENE PROSPECTIVITY OF GOBUSTAN
5. FUTURE DIRECTIONS FOR HYDROCARBON EXPLORATION
6. SELECTED BIBLIOGRAPHY
- APPENDIX 1: The Joint GIA and the BP and Statoil Alliance Pre-Pliocene Prospectivity Field Trip
- APPENDIX 2: Pre-Pliocene Prospectivity Field Trip Guide
- APPENDIX 3: Pre-Pliocene Prospectivity Field Trip - Biostratigraphic Data
- APPENDIX 4: Summary of "Mesozoic and Cenozoic Phases of Tectonic Movements of the Eastern Caucasus" by Academician E.Sh. Shikhalibeily.