A&D marketing for the oil and gas industry



Offshore / Exploration

Envoi has been engaged by London-listed (Dublin-based) United Oil & Gas Plc, to assist in their search for partners to help accelerate the exploration of their large, 22,400 km² 100% operated Walton Basin and Morant Basin Licence, located offshore southern Jamaica. United initially farmed into the acreage for a 20% interest in 2017 by funding 3D seismic when Tullow were the operator. Tullow exited the country in 2020 as part of a new corporate strategy and shift away from frontier exploration. Their 80% interest and operatorship were acquired by United due to the high potential and prospectivity unlocked by the new 3D seismic acquired following United’s involvement in the block.

Only 11 exploration wells have ever been drilled in the entire country (comprising an area of around 258,137 km² including all the offshore areas), all between 1955 and 1983. Of these, the majority (9 wells), are onshore with just 2 wells drilled offshore. Hydrocarbon shows were observed in these wells despite not having tested valid structures, as is evident on the latest data. Prior to United joining the licence, Tullow combined and reprocessed various vintages of pre-existing 2D seismic and acquired 3,650 km of new infill 2D data in 2016 and 2017. This helped further delineate and unlock the potential of the Walton Basin in the west, and Morant Basin in the east of the acreage and led to the new 3D survey acquired over the Walton Basin ‘sweet spot’ after United’s entry, in 2018.

Onshore fieldwork and well core analysis studies have confirmed mature Eocene and Cretaceous oil-prone source rock potential, with migrated oil identified in onshore wells and outcrop samples as well as onshore and offshore seeps. These include Late Cretaceous (Cenomanian-Turonian) aged organic shales exhibiting TOCs up to 8% with maturity. Modelling also suggests significant oil potential exists in mature Cretaceous source kitchens in both the Walton and Morant basins while shallower Palaeogene shales with TOCs up to 15% could also locally be deep enough to be mature.

The large Colibri Prospect is interpreted on 3D to contain karstified Upper Cretaceous rudist and shoaling grainstone carbonates developed on a prominent palaeo-horst. Gravity data is consistent with a carbonate reservoir with at least 20% porosity and there are good indications that it is laterally consistent. A structurally-conformant, prominent low velocity anomaly is observed on 3D PSDM seismic data at Colibri and also supports the presence of porosities of >20%. Amplitude supported prospects have also been defined on the new 3D in the Walton Basin, with Upper Eocene-Oligocene carbonates as the reservoir targets. Eocene clastic reservoirs include fluvio-deltaic and marine sandstones, eroded from the Maya-Chortis continental remnant. These are found across onshore Jamaica in outcrop with depositional modelling indicating their distribution offshore in both basins and encountered in both offshore wells to the west of the Walton Basin. Eocene targets identified include a series of tilted fault block closures mapped on the 2D in the Morant Basin. Extensive shales, marls and tight limestones create effective seals across the two basins. An independent Prospective Resources Audit completed by Gaffney Cline & Associates in December 2020 estimates that the11 prospects & leads evaluated for the audit contain combined total unrisked mean prospective recoverable resources in excess of 2.4 Billion bbls STOOIP. Of this, 406 MMbbls is attributable to the Colibri Prospect alone, with an upside of 966 MMbbls STOOIP. Additional leads identified on older 2D seismic data could hold another 4.8 Billion bbls of mid-case unrisked prospective recoverable resources.

United is offering a material interest in return for funding the upcoming work programme (est. cost US$3 million) to complete the obligations for the current First Exploration Period, for which a 2 year extension to January 2026 has been granted. This is designed to significantly de-risk the prospectivity of the licence area through acquisition of a piston coring survey over features of interest, together with seismic reprocessing to improve structural and reservoir imaging. Further equity would be available in return for a commitment to fund United’s share of drilling costs (a well to test the large 3D-defined Colibri in 750 metres of water is estimated likely to cost c. US$ 30 million dry hole) in the subsequent Second Exploration Period of the licence.