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Cretaceous Prospectivity in Southern Trinidad

Krishna Persad
KPA Group of Companies

Abstract

This presentation initially outlines the geo-tectonic history of southern Trinidad and its impact on the presence and distribution of reservoirs and source horizons. Based on this framework the concept of a pre-Tertiary petroleum system is then developed and the existing well and seismic evidence for its presence and extent in the Southern Basin is then reviewed. Finally we suggest a tool that can be used in developing a play.

Most of the four billion barrels of oil extracted from Trinidad in the last hundred years has come from the youngest (mainly Plio-Pleistocene) sediments. About one and a half billion barrels of this have come from the onshore piggy-back Southern Basin and a further billion from its offshore extension westward in the Gulf of Paria. Over one billion barrels of oil and ten trillion cubic feet of gas have come from similar age sediments in the Columbus Basin, part of which extends into the south-eastern onshore extremity of Trinidad.

The vast majority of the remainder of the oil production has come from the Mid-Tertiary, Oligo-Miocene age, sediments. The reservoirs are turbidite sands in the Naparima Nariva Fold and Thrust Belt (FTB), which underlies the piggy-back Southern Basin, south of the Central Range Uplift and north of the Southern Range Anticline. These deeper Tertiary objectives are only lightly explored in parts of the proven fairway in both onshore Southern Trinidad and in the Eastern offshore. (Their prospectivity in the SWP Peninsula onshore Trinidad is discussed in a poster presentation also written by my co-author, Neil Ritson and myself.)

To date there has been no commercial production from the Cretaceous.

With regard to the mid-Tertiary and older sediments onshore, complex surface features and a paucity of good quality 3D seismic data have prevented the exploration of the imbricate thrusts known to be present within the Naparima Nariva Fold and Thrust Belt (FTB) which underlies the piggy-back Southern Basin and onshore portion of the Columbus Basin, south of the Central Range Uplift and north of the Southern Range Anticline. The Cretaceous horizons have as a result been largely un-explored due to their depth of burial and poor imaging.

Focusing on the SW Peninsula where a Cretaceous play is postulated, but where the exploration for the pre-Tertiary is, to be charitable, in its infancy, we will explore the potential for further petroleum exploration and develop a rationale for that work. We will outline the potential petroleum systems present and then suggest the use of full tensor airborne gravity (FTG) which we believe is a tool that can assist in the better delineation and exploration of the basin. Some examples of the successful application of FTG elsewhere in the world are given.

AAPG Search and Discovery Article #90203 © AAPG Geoscience Technology Workshop, Trinidad and Tobago Deep Horizon and Deep Water Frontier Exploration in Latin America and the Caribbean, March 9-11, 2014, Port of Spain, Trinidad