DR HASLEY VINCENT
Success in exploration for oil and gas resources is vital to establish an oil and gas industry and maintain significant levels of production. The hydrocarbon industry in TT has been fortunate, with several exploration successes during its history. These successes have had the single largest impact on the volume of crude oil produced relative to alternative measures of increasing production, such as enhanced oil recovery.
The process of exploration for oil and gas resources involves assessing various hydrocarbon play parameters to determine the likelihood of finding new accumulations that can be recovered commercially, given existing technology.
Industries are built on successful outcomes, though the chances of these are typically less than one in five, depending on the maturity of the hydrocarbon play and the quality of geophysical and geological workflows used.
Crude oil production in TT is currently at a mature stage, having been in continuous decline for the past 44 years, since peak production was attained in 1978.
The intent of the current administration is to ensure that crude oil continues to play a significant role in the country’s primary energy mix, and this can only be achieved if the production decline rate is minimised or reversed.
Exploration drilling can achieve this through the discovery of new fields, deeper reservoirs or bypassed resources.
As TT embarks upon a competitive bidding round for land acreage, it is timely to review past exploration successes and the positive impact they had on oil production over the span of the industry.
Phase I – The land era (1908-1957)
Commercial oil production began in 1908, with production from oil wells in the Point Fortin area.
This marked the beginning of the oil industry and the start of the first phase of commercial exploration. Crude production increased steadily till 1940 with the discovery of numerous fields in what is known as the Southern Basin, including Goudron, Guayaguayare, Point Fortin, Palo Seco and Forest Reserve.
The early 1940s saw the first decline in production, which recovered by the early 1950s, when the highest production for that period was recorded in 1954 at approximately 65,000 barrels of oil per day.
This recovery was due to increases in annual drilling footage and the discovery of several additional land fields by 1957, including Moruga East-North-West, Rock Dome, Inniss and Navette. These new fields had an immediate impact on crude oil production.
Production to this time was exclusively from land-based operations, which included submarine reservoirs from highly deviated land wells at Point Ligoure. By the end of this phase, 84 per cent of the fields across land areas had been discovered, which included the largest-producing fields known in the Southern Basin area (eg Palo Seco, Forest Reserve, Penal-Barrackpore).
Phase II – The marine era (1954-1969)
The second phase of discoveries spanned an interval from 1954-1969.
This phase saw the highest rate of exploration drilling known in the industry, peaking at 60 exploration wells in 1960, and included wells off the west, south and east coasts of Trinidad (eg Soldado, North Marine, South Marine, Galeota).
Several important discoveries occurred offshore during this exploration phase beginning with the High Seas 1 well, which was the first exploration well to be drilled in marine waters off the islands. This well resulted in the Soldado field discovery in 1955 and was followed by additional discoveries in the northern Soldado area and wider Gulf of Paria.
As in phase one, these discoveries had an immediate impact on total crude oil production, with an increase attributed primarily to development of the Soldado acreage, which at the time was operated by Trinidad Northern Areas Ltd.
The period ended with a production peak of 183,000 barrels of oil per day in 1968, which was the highest rate up to that date: this would also be the highest rate that will ever be produced from land fields.
Apart from the new fields discovered in phase one to 1957, land exploration was not very successful during this period, with only one new field area added (Erin, in 1963, is part of the Palo Seco Field).
While the earlier discoveries contributed to peak land production in 1968, the lack of exploration success coincided with the beginning of a production decline that would continue to the present day.
Phase III –East coast summit (1968-1999)
The third phase of discoveries ran from 1968-1999 and is characterised by a relatively high volume of exploration drilling, with an average of 17 exploration wells per year over the period.
The year 1976 saw the highest number of exploration wells drilled at this time, with new wells in the north coast (eg Maracas 1, LL9-1, KK4-3), east coast (Red Snapper 1, Pelican, Ibis 1, Dolphin 1, Barracuda 1, Emerald 1) and Gulf of Paria (Couva Offshore 1, Manicou 1).
This level of exploration drilling would not be matched to the present date. Much of the exploration activity at this time was still focused on finding crude oil, which distinguished this phase from later years, when natural gas gained prominence.
Several significant discoveries were made in the east and north coast areas, beginning with the exploration programme of Pan American Trinidad oil company, which led to consecutive oil, condensate and natural gas discoveries in the east coast (eg Teak, Poui, Samaan, Cassia).
Others included the first discovery of natural gas to the west of Tobago in the Orchid and Poinsettia fields (1971 and 1975 respectively) and this was followed by the Chaconia and Hibiscus discoveries in the same area.
Phase three had an immediate impact on production, with first oil from the Teak field (east coast) occurring three years after its discovery in 1969. East-coast fields would be the primary contributor to the industry’s peak oil production by 1978 (then operated by Amoco oil company), with 60 per cent of total production in that year (Soldado contributed 19 per cent and land, 21 per cent).
This phase of exploration drilling would later have a profound impact on the natural-gas developments that occurred during Phase IV exploration.
Phase IV – The natural gas era (1994-2022)
The fourth phase of successful exploration activity occurred from 1994 to the present, and saw the beginning of LNG exports in 1999.
The establishment of a market for gas led to an increased importance of natural gas relative to crude oil. The beginning of this phase was marked by the lowest drilling footage in the history of the industry, with 98,085 ft drilled in 1994.
Not surprisingly, these low drilling rates coincided with a low quantity of exploration drilling relative to earlier exploration phases. There was an average of seven exploration wells per year over the period, with a maximum of 16 in 2019. The increased importance of LNG saw a focus on finding natural gas resources primarily in the north and east offshore areas.
Despite the lower count of exploration wells, there was a high rate of exploration success that immediately affected natural gas volumes, leading to its peak production of approximately 4.3 bcf/d by 2010. There was a lesser impact on total crude oil production with the addition of crude oil and condensate from the southern Columbus Basin and the Angostura oil field.
Successful exploration wells were few on land, with most finding associated gas resources. These included the Central Block discoveries (Carapal ridge/ Baraka) and the 2019-2021 discoveries by Touchstone within the Ortoire block (Coho, Royston, Cascadura, Chinook).
Significant gas reserves were added rather than crude oil, the production of which continued to decline from the peak of 230,000 barrels of oil per day in 1978 to 60,000 barrels of oil per day in 2021. Fluctuations in production were characteristic of this period, likely attributed to drilling activity (eg 1994) and smaller-scale initiatives such as the lease operatorship and farmout programmes on land. These served to retard the rate of production decline, at best.
Summary
Failed wells are an intrinsic part of the search for new and bypassed oil and gas resources because of the numerous unknowns that exist within the subsurface. The occurrence of dry holes or unsuccessful wells should not lead to premature termination of an exploration programme. The discovery well of the Teak field that led to peak oil production in 1978 was the ninth to be drilled within Amoco's east coast acreage, with the previous eight being dry holes.
The industry in TT is fortunate to have several examples of successful exploration campaigns dating back to the earliest years of production. Geoscientists, resource managers and government administrators of today have easy access to data, technology and workflows that can replicate such successes. As practitioners within an industry that contributes approximately 40 per cent of the country’s GDP, we remain hopeful that in the near future, the current administration would engage with the available expertise to examine the exploration potential of basins around TT in keeping with their resolve to increase crude oil production. This is critical to kickstart the exploration process that will lead to a Phase V in oil production, whether that be on land, Gulf of Paria or below the waters of the Atlantic Ocean and Caribbean Sea.
Dr Hasley Vincent contributed to this article for the Geological Society. He has doctorate in sedimentology and stratigraphy from Dalhousie University, Canada, and has spent over 20 years in various managerial and geoscience roles at the Ministry of Energy, BG, BP and Heritage. He is now a primary geological consultant with Basins-tt Ltd.
Vincent has been a part-time lecturer at UWI, St Augustine, and is a longstanding member of the GSTT. https://thegstt.org/