In November 2017, United Oil & Gas agreed to farm-in to the Tullow Oil operated Walton Morant licence, offshore Jamaica, at a 20% equity level. The Walton Morant licence extends for over 32,000km2, and with numerous plays and prospects already identified across three separate basins, the opportunity provides United with exciting access to high-risk / high-reward frontier exploration.
In May 2018, the acquisition of 2,250km2 of 3D seismic data was successfully completed. This was the first ever 3D survey completed in Jamaica, and was focussed on the high-graded Colibri lead.
A Joint Venture farm-down effort is currently underway, with the aim of bringing in an additional partner for potential exploration drilling in 2021.
Walton Morant Licence, offshore Jamaica and location of the Colibri Prospect in the Walton Basin.
The Colibri Prospect
Although offshore Jamaica is a true Frontier Basin, there is compelling evidence that a working petroleum system is present.
11 wells have been drilled to date (9 onshore, 2 offshore), with the most recent in 1983. None of these appear to have tested valid structures, yet all bar one contained hydrocarbon shows.
Since getting into the licence in 2014, Tullow have bought the existing 2D seismic data, shot and interpreted a further 3,650km of 2D seismic, and conducted extensive fieldwork and dropcore studies, with ~$20m spent to date.
This work has served to increase the confidence in the presence of a working petroleum system, has high-graded the preferred plays, and led to the identification of numerous structures, including the robust Colibri prospect which is in an optimal location to test the offshore Jamaica petroleum system, and which has been further supported by the recent identification of an active thermogenically derived offshore oil seep to the south of the structure. Colibri has been estimated to hold gross meancase prospective resources of over 200mmbbls.
Given the size of the Walton Morant licence (>32,000km2), it is perhaps not surprising that numerous follow-up structures have been identified. These would be significantly de-risked given success at Colibri.
.. Identified structures, Walton Morant Licence, offshore Jamaica
Walton Morant Play Elements and Stratigraphy
- Oil-prone source rocks have been identified in the Eocene and in the Cretaceous, with migrant oil identified in onshore wells and outcrop samples, and two positive offshore seep surveys. This provides good evidence of the presence of regional source rocks.
Maturity and Migration
- Extensive maturity modelling suggests significant oil would have been expelled from Eocene kitchens in both the Walton and Morant basins. Preferred lead (Colibri) has been selected on the basis of its position in relation to migration routes out of an identified Eocene kitchen.
- On the Caribbean plate, reservoir has often been cited as an issue due to the distance from major continental clastic input and the high proportion of volcanics in the region, which tend to downgrade reservoir quality.
- However, there is good evidence from field-mapping and from plate reconstructions that during the Eocene, Jamaica was receiving sediment from the continental Maya-Chortis block.
- Guy’s Hill Fm: a fluvio-deltaic- shallow marine succession in stacked parasequences onshore, with thicknesses >300m gross, and porosities of ~20%. A potential correlative in the offshore Arawak well maintained porosities of 14%, despite 4000m overburden. Depositional models suggest this reservoir should be widely developed across the Walton and Morant Basins.
- Shales and marls of the Chapelton Fm directly overlie the Guys Hill Fm reservoir. These are tight and provide good regional seals.
- A large number of structures have been identified in both the Walton and Morant Basins
- There has been recent transpressional activity across the region, and although many of the structures are large, identifying ones that have not been reactivated and which don’t rely on closure against through-going faults is key
- Colibri is a good first test of the play as it appears to satisfy these requirements. Given success at Colibri, the entire basin would be de-risked