On 4 and 19 July 2015, members of The AAPG Student Chapter University of the West Indies (UWI) – St. Augustine campus (Trinidad), along with students from UWI Mona campus (Jamaica) and University of Trinidad & Tobago (UTT), embarked on a planned wellsite visit to an active onshore drilling rig at the La Fortune Anticline within the Oropouche Oilfield, Trinidad.

Since 2007, the Oropouche Oilfield has been operated by API Petroleum Company Limited under a Farmout Agreement with state-owned oil company Petrotrin. Since that time, API Petroleum has has acquired 3D Seismic data across the Oropouche Oilfield with Petrotrin and has embarked on a drilling campaign.

API Petroleum Director Fawwaaz Hosein stated that API Petroleum is establishing itself as a model independent onshore oil production company in Trinidad & Tobago, pursing aggressive production targets by increasing efficiency, conducting exploration, adapting cutting-edge methods and technology and recruiting personnel with an exploration appetite. Hosein said he was delighted to host the AAPG Student Wellsite Visit, stating that it was an excellent opportunity for students to understand the many moving parts of the oilfield and the spectrum of challenges faced (apart from geological challenges) in the search for oil.

API Petroleum contracted rig services from Sadhna Petroleum Services Company Limited, a local service company that also supported the goal to help expose next-generation explorationists to drilling operations.

The trip leader, Xavier Moonan, current treasurer for AAPG Latin America & Caribbean Region, and immediate past president of the Geological Society of Trinidad and Tobago (GSTT), gave attendees insight into:

• Geology of the Nariva Fold and Thrust Belt
• Geology of the La Fortune Anticline
• Seismic Interpretation
• HSE awareness
• Drilling Operations
• Mudlogging Geology
• Wellsite Geology

Students viewed logging data from the AO-117 and AO-118 wells being drilled and had the opportunity to interpret and correlate the data with surrounding wells. For most attendees, this was the first time viewing raw logging data. After viewing the data, students received a brief overview of the geology of the Early Miocene Retrench sandstones, the primary reservoir for the Oropouche Oilfield.

Attendees learned how the Early Miocene Retrench sandstones were deposited as deep water turbidites in the Trinidad area. At the time of deposition, numerous SW-NE trending folds formed as a result o fthe southeasterly directed oblique collision of the Caribbean Plate with the northern margin of South America. The oblique collision uplifted much of Trinidad’s Northern Ranges and the Coastal Ranges of Venezuela, generating a narrow unstable shelf which periodically collapsed, sourcing the Retrench turbidite reservoirs.

The group viewed structure maps and net oil sand maps for the WSW-ENE trending La Fortune Anticline, presented by API Consultants Shiraz ‘Murf’ Rajab, and Victor Young On, who pointe out the numerous thrust faults and associated tear faults that occur within the Oropouche oilfield. Young On stated that even after drilling 118 wells in this field, his team continues to find new reservoirs and new thrust faults.

After undergoing an HSE orientation, attendees proceeded to the wellsite, where they interacted with mud engineers, drilling engineers and operation managers and observed their routine work on an active drilling rig. Attendees gathered at site’s center of operations, affectionately called the “Dog House,” where the driller and Moonan explained the operations occurring on the rig floor. After witnessing pipe tripping and a directional survey, students received a thorough explanation and viewed of the mud circulating system.

Baroid mud engineer Zephrine Tristan explained the role of the centrifuge and the physical addition of barite as key processes in altering the mud weight, which is crucial in maintaining wellbore stability and keeping back reservoir pressures. Attendees witnessed the use of the mud balance to calculate mud weight, collected drill cuttings at the shale shakers and learned the importance of lag-time to calculate the depth from which the rock cutting originated. They also viewed the mud pumps and their associated sensors and learned about the effect of increasing and decreasing the flow rate.

After leaving API Petroleum and Sadhna Petroleum Services Company Limited, Moonan led attendees accompanied to the OAS Marl Quarry at the La Fortune Anticline. This visit was planned for the 19 July trip as well, but inclement weather made the outcrop inaccessible. The outcrops were composed of over 95% marl punctuated by thin layers of clay.

Attendees observed features of the area structures, specifically the complex folding of the anticline. They gained insight into distinguishing between tectonic and sediment deformation, as well identifying folds, thrust faults, fault gouge/zones at an outcrop level. The complex faulting observed at the outcrop can be used perfectly as an analogue for the larger structures being tested by the drill bit by API Petroleum.

Ultimately, students who attended the trips were able to get firsthand experience of life on a drilling rig, which far superseded the classroom theory on drilling rig operations.

API Petroleum Limited, in pursuing and supporting continued geological research has since donated drill cuttings from these wells (AO-116, AO-117 & AO-118) to the GSTT and the University of the West Indies. API Petroleum Subsurface Intern Stefon Harrypersad is currently examining these drill cuttings as part of his analysis of the Retrench turbidites towards his final year thesis titled Subsurface mapping of the Early Miocene Retrench Sands of the Oropouche Oilfield for his BSc. Geology (UWI, Mona Jamaica).

The AAPG Student Chapter sincerely thanks API Petroleum Limited for facilitating these rig visits, allowing students to gain hands-on wellsite experience. The AAPG UWI Student Chapter, the AAPG Latin America & Caribbean Region and the GSTT recognize the invaluable experience provided by API Petroleum Limited and are hopeful that many other companies within Trinidad & Tobago and the Region will provide similar opportunities for students in the future.

We wish to also thank Sadhna Petroleum Services Limited, the AAPG Latin America & Caribbean Region, the GSTT and Trip Leader Xavier Moonan for hosting and coordinating these fantastic wellsite visits. As geoscience students, it was a most fulfilling experience and a major milestone in our petroleum geoscience careers.