Dalhousie University – Petroleum Geoscience Field Methods – Trinidad

Summary Report

Submitted to:

Offshore Energy Research Association of Nova Scotia (OERA)

to fulfill requirements of the Graduate Student Research Travel Program

Submitted by:

April 2013

Darragh O’Connor

Basin and Reservoir Laboratory

Department of Earth Sciences

Dalhousie University

Alex Hurley

Department of Oceanography

Dalhousie University

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Table of Contents

Introduction 2

Benefits and Outcomes of Travel and Significance to Nova Scotia 4

Benefits 4

Outcomes – Darragh O’Connor 8

Significance to Nova Scotia – Darragh O’Connor 8

Outcomes – Alex Hurley 10

Significance to Nova Scotia – Alex Hurley 12

Trip Itinerary 14

*Front cover image: sketch of a scarlet ibis, the national bird of Trinidad and Tobago

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Introduction

The Petroleum Geology Field Methods course at Dalhousie University is a collaborative course with

students from Atlantic Canadian Universities, the University of the West Indies (UWI), and professionals

from both Trinity Exploration & Production and Petrotrin. The course focuses on collaboration between

students and professionals in order to define associations between offshore and onshore geology

through field-based and laboratory outcrop, core, and log analyses (Fig. 1). The course is comprised of

three sections: pre-trip literature review of Caribbean geology involving reports on relevant petroleum

systems elements, field and laboratory exercises on the Island of Trinidad, and a presentation post trip.

Students are encouraged to work collaboratively with Trinidadian professionals in order to learn the

application methods of classroom taught concepts.

The course emphasizes the importance of onshore analogues for offshore petroleum systems that are

relevant for offshore Nova Scotia. Trinidad provides an overview of the effects of compressional and

extensional tectonics in the development of petroleum systems. This is best viewed through fluvial-

estuarine, shelf margin delta, and deepwater depositional system outcrops, along with the occurrence

Figure 1: Left – A group of Dalhousie University students, UWI students, Trinity E&P employees, and trip organizer Grant

Wach along the beach at Cedros Bay. At this location deltaic sequences and abandonment deltaic lobes were described.

Right – Dalhousie University students with Petrotrin employees outside the Petrotrin core laboratory. Students described

and interpreted offshore core to gain insight on the similarities between offshore and onshore geology

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of mud volcanoes and oil seeps (Fig. 2). Subsurface data from offshore Trinidad, provided by Trinity

Exploration & Production and Petrotrin, allows students to build a framework for understanding

subsurface geology. Overall, the combined teams and new datasets provide opportunities for students

to conduct petroleum geosciences research on analogues relevant to offshore Nova Scotia geology.

The following topics are introduced in both the laboratory and field:

Basin tectonics and structural setting

Caribbean tectonics and seismicity

Trinidad structural evolution

Source rock, maturation, and overpressure

Source rock, fluid migration, and trap formation

Petroleum biodegradation

Mud volcanoes, shale tectonics, petroleum migration

Oil and gas generation in the northern and southern basins

Depositional systems and modern day analogues

Figure 2: Left – Active petroleum seeps in the city of San Franado, found near the backyard of a family residence. These

oil seeps appear as hydrocarbons travel from depth to surface through interconnected fault systems.

Right – An active mud volcano near Piparo, located in central Trinidad. The mud volcano demonstrates the overpressure

of a petroleum system, often associated with active tectonism.

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Accommodation space and basin fill

Mechanisms for sediment transport and settling rates

Micropaleontology

Modern fluvial and deltaic systems

Margin delta and slope reservoir characterization

Outcrop and core descriptions, gamma ray and permeability readings

Resource evolution of modern oil sand open pits

Health, safety, and environmental lectures

A unique component to the course is the addition of industry instructors (e.g. Petrotrin, BP, and Trinity

E&P) who assist in field and laboratory exercises. Their expertise in Trinidadian geology gave us and

Dalhousie and other students from Atlantic Canadian universities an excellent opportunity to develop

the necessary training for future careers in the petroleum industry.

Benefits and Outcomes of Travel and Significance to Nova Scotia

Benefits

Trinidad is an exceptional location for the study of petroleum geoscience. The island offers remarkable

outcrop which clearly demonstrates petroleum system elements of source, seal, reservoir, trap, and

migration; all of which are required in forming an effective petroleum system. The thick reservoir and

seal packages of deltaic deposits (Fig. 3); the active overpressure shown through mud-volcanoes; the

over mature Northern Range organic rich source rock; the large number of faults indicating tectonic

activity; and the many oil seeps are examples of petroleum systems elements on the island of Trinidad.

In order to better understand the formation of petroleum system elements, the trip involved studying

modern wetlands and deltaic systems. Researching modern depositional systems, we were able to use

present day deposition models as keys to decipher and understand the formation of outcrop.

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Aside from containing world-class outcrops and modern depositional analogues, Trinidad has a number

of other benefits in the study of petroleum geoscience. These benefits are:

1. The island is approximately 4700 km2, or about half the size of Cape Breton Island. This allows

for daily trips to be completed from the lodge to points of interest, all within reasonable time.

The longest period spend travelling from point to point was approximately two hours.

2. The island is a current hydrocarbon producing nation. Many of the rock formations seen on the

coast extend far into the subsurface of offshore Trinidad. The Trinidadians have learned to

exploit their well exposed onshore geology to aid in understanding and producing of offshore

subsurface reservoirs. This connection between onshore and offshore geology is a vital point of

proof when teaching and learning about petroleum system elements. Observations are made on

outcrop, then interpretations on how they formed, theories are conceived on how these would

produce hydrocarbons, and then offshore platforms are seen producing from these same

Figure 3: A collaborative effort amongst

Dalhousie students and Trinity E&P and

Petrotrin employees to try and piece

together the depositional history of this

outcrop. The outcrop is part of a known

deltaic sequence which often forms

both reservoir and sealing units. Both

of these petroleum system elements

are seen here: gray sediments are fine

grained silts and sand producing sealing

units and yellow sediments are clean

sands which produce hydrocarbon

reservoirs. A fault also highlights the

past tectonic influence on this system.

This deltaic system is an analogue for

the depositional systems of the sable

field offshore Nova Scotia.

Fault trace

Reservoir

Seal

Seal

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reservoirs. These same procedures are being used to aid in describing reservoirs offshore Nova

Scotia.

3. There is a strong connection between academic, industrial, and governmental groups in Trinidad

with Dalhousie University, in part to close ties between Grant Wach and geologists of Trinidad.

This connection gives students the opportunity to meet and learn from Trinidadian geologic

professionals. The University of West Indies is a current member of the Atlantic Association of

Universities, again connecting Dalhousie University to UWI. Trinity Exploration & Production

often collaborates in field participation by sending a number of young geologists, engineers, and

chemists, as well as experienced managers, to both learn from and teach us. Petrotrin, the

petroleum company of Trinidad and Tobago, invited all Dalhousie University course participants

to study offshore core and to learn from some of the World’s top biostratigraphers. Trinidad is

known to be one of the founding nations in biostratigraphy, giving students a unique

opportunity to meet the founding fathers of modern petroleum geoscience biostratigraphers.

4. Hydrocarbon production is clearly integrated into the Trinidadian culture. The mesh of

hydrocarbons and culture is shown in political relations, national monuments, employment and

the economy, and day to day life. A national monument in Trinidad is Naparima Hill, located in

the city of San Fernando. Culture and petroleum are tied together once again as the hill is the

only outcrop of the petroleum systems source rock, known as the Naparima Hill Formation.

The economy also shows a clear cooperative relationship between fishing and petroleum

exploration. While standing on beaches, both fishing boats and oil producing platforms can be

seen in the water. Both industries appear to thrive, without significantly impacting the other.

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The coexistence of people and the petroleum industry in day to day events is obvious in

Trinidad. Many areas of the island have natural oil seeps, in which biodegradation results in a

tar-like hydrocarbon product bubbles from the ground. The most extensive example of this is

Pitch Lake which is the largest natural deposit of asphalt in the world. Although the lake is mined

for its tar-asphalt, many people still bathe in the lake for both pleasure and potential health

benefits from the sulphuric rich water. Stollmeyers Quarry is an open pit oil sands mine located

directly along the highway and next to a commonly visited beach (Fig. 4). There have been no

negative effects to the beach or surrounding area.

The benefits of studying petroleum geoscience in Trinidad are clear. The island is relatively small; it

contains all of the essential elements of a petroleum system; there is current production of

hydrocarbons both onshore and offshore; there is a strong academic-industrial-governmental

connection in understanding petroleum geoscience; the deltaic outcrops are analogues for offshore

Nova Scotia; and exploration and production of hydrocarbons is simply part of the Trinidadian culture.

These are all benefits that may not be as accessible elsewhere in the world.

Figure 4: Students from Dalhousie

University and young professionals

from Trinity E&P work together in order

to define the geometrical features of

this oil bearing channel sandstone. It

was concluded that the oil was held in a

series of stacked channels which were

approximately 100 m in width and 25 m

in thickness. This exercise helped

students conceptualize the

architectural elements and geobodies

that comprise reservoirs which form

from channel deposits. These channels

could be analogous to the Late Triassic

Eurydice Formation offshore Nova

Scotia.

Remaining oil sand

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Outcomes – Darragh O’Connor

The major outcome from studying in Trinidad is clarity that outcrop can be an effective indicator used

for characterizing subsurface offshore geology. Understanding the complexity and heterogeneity of

easily accessible outcrop can give insight into the character of offshore geology, which could in turn aid

in the understanding of potential viable petroleum systems. Wach and Vincent (2005) explain that the

Sable gas project, offshore Nova Scotia, is partly composed of fluvial wave and tide deltaic systems from

the Mid-Jurassic to Early-Cretaceous. Having both wave and tide influence in the system makes it

difficult to determine the subsurface baffle and barrier heterogeneities of the feeding channel systems,

in turn resulting in potential bypassed hydrocarbons. A problem arises in that Nova Scotia contains no

outcrop with similar characteristics to its own offshore, so no reservoir model can be built. However,

they continue by explaining that outcrop and producing fields of Trinidad are analogous to the Sable gas

project. Applying the fluvial and estuarine outcrops (the Morne L’Enfer Formation) of Trinidad to Nova

Scotia can help in accurately describing the complex architectural elements and geobodies of the Sable

gas project geology. The Morne L’Enfer Formation is broken into a lower and upper member. The lower

member was deposited in fluvial to estuarine channels of a deltaic system. Following a marine

transgression and regression, the upper member was deposited in a tidally-influenced delta. This change

in deposition style marks a decrease in basin accommodation. This progradation cycle and change of

deposition style can be used as an analogue to comprehend the offshore reservoirs of Nova Scotia.

Significance to Nova Scotia – Darragh O’Connor

Although Nova Scotia has no outcrop with similar characteristics to offshore field developments, the

province does have an abundance of Triassic outcrop which could be similar to the underexplored

deepest regions of Nova Scotia’s offshore. Work currently being completed at Dalhousie University, by

Darragh O’Connor, focuses on describing the Triassic rift- and syn-rift outcrop along the Minas Subbasin

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and Chedabucto Bay, as well as offshore core and log information from the Orpheus Graben, east of

Cape Breton (Fig. 5). This work looks to describe the reservoir quality and architectural elements of

onshore and offshore Triassic basin sediments using a variety of classic techniques (core and well log

description, logging outcrop sections, photogrammetry) and modern tools (Ground Penetrating Radar,

LiDAR, handheld permeability and radioactive measuring devices). Combining these techniques will

allow for an assessment to be made between onshore and offshore Triassic sediments of Nova Scotia.

This work is similar to that used in Trinidad to better constrain the complexity and heterogeneity of

offshore hydrocarbon producing fields. However, the extent of Triassic outcrop in Nova Scotia, and the

amount of data for offshore Triassic sediments, is limited compared to petroleum system equivalent

sediments of Trinidad.

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Outcomes – Alex Hurley

The majority of the field seminar involved observing and interpreting sedimentological and depositional

environments at outcrop. Caroni Swamp, a modern tide and wave dominated delta that is a tropical

equivalent to a temperate saltmarsh (Fig. 6). Caroni Swamp allowed us to ground truth the depositional

environments previously interpreted at outcrop as well as observe the earliest formation of source rock

from mangrove ecosystems for type II kerogen.

0 150 Km

65° 60°

45°

Figure 5: The upper imagine shows areas of Late Triassic sediment from both onshore and offshore Nova Scotia. There are three major

areas of study, of which two are onshore and one offshore. What is distinctive and similar about all three sample locations is the red

colour of the rock. Lower left – capturing LiDAR data of the Triassic Wolfville Formation along the Minas Subbasin coastline. The data

can be used to render a 3D reconstruct of the channel complex system which is well studied in the area. Lower central – The Late

Triassic Chedabucto Formation which outcrops along the western edge of the Orpheus Graben. The formation consists is sandstone-

mudstone dominated with minor clast supported conglomeratic units. This area has been poorly studied in the past. Lower right –

Eurydice Formation core from the Eurydice P-36 well located in the Orpheus Graben. The core is dominated by fine grained material

with minor fine grained sand intervals.

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The field exercise trip along consisted of travelling by boat on a channel (No. 9 Drain) where the deepest

areas (the thalweg) reached an approximate depth of 12 meters (40ft). The dominant mechanism of

sediment transport is by suspended load, which is best explained as to the transport of fine grained

sediment with the appearance of a "puff of smoke". Secondary bed load transport through traction

currents causes the formation of geological features such as sand waves, mega ripples, and point bars.

Suspended load transport means that relatively low amounts of energy are required to suspend and

transport these sediments. Once the suspended sediment is transported to the ocean, it falls out of

suspension and deposits forming the delta front and prodelta, at a rate of approximately 60 to 100 cm

Figure 6: Satellite image of the Caroni Swamp located in Trinidad. The trip began at the Boat Launch and followed the No. 9 Drain to the west. The first stop was at the mouth of the River into the Gulf of Paria. This is where sediment fell out of suspension, causing a relative shallowing of water depth. The second stop was located on the inner lake of Caroni Swamp. Here we were able to view the areas fauna.

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per 100 years (Fig. 7). It is important to note that where this deposition occurs, the depth becomes

significantly shallow, relative to the depths further inland. Observation of sediment grain size in outcrop

is useful as it allows for interpretation of depositional environments, are determined by studying

present day sediment transport and deposition.

Potential source material for hydrocarbons can also be observed at Caroni Swamp in the form of

mangroves trees. Mangrove trees, like most green plants, contain cellulose, which provides their

physical structure. This cellulose is refractory, meaning that it is difficult for organisms (e.g. bacteria) to

break down. The remaining refractory material is then buried, undergoing increases in pressure and

temperature until the proper requirements are met to create hydrocarbons.

Significance to Nova Scotia – Alex Hurley

Current research by Alex Hurley (M.Sc. candidate) of Dalhousie University shows how the sediment

particle density is fundamental for determining the rate of sedimentation because particle density

affects settling velocity. In the Caroni Swamp, the dominant mechanism of sediment transport is

suspended load, which transports fine grained sediments. Once these fine grained sediments leave an

Figure 7: (Top and Bottom) Cross sections of coastal profiles from mangrove/back barrier to prodelta/shelf region (modified from Pothier and Wach, 2011).

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estuary, they aggregate to form larger particles, known as flocs. As the particles are aggregating they

begin to settle out of the suspension, which results in deposition in the coastal zone. The resulting

aggregates are composed of different components that have varying density, and currently measuring

the density of these particles is difficult to measure in situ without disturbance. Current methods to

measure particle density are labour intensive, time consuming and expensive. Hurley's research seeks to

establish a new method for measuring these particles in situ using commercially available

instrumentation. If the new method proves to be comparable to the labour intensive method, then

current measurements of particle density can be used to determine the deposition rates of sediment in

present day aquatic environments.

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Trip Itinerary

Day 1 Saturday February 23

Travel from Halifax – Toronto – Trinidad

Day 2 Sunday February 24

Arrive in Port of Spain (Piarco) at 6:00am

STOP 1 (8:30 - 11:00am): Asa Wright – Rain Forest Ecosystem & Overview of Caribbean and Trinidad Tectonics

STOP 2 (1:30 - 2:30pm): La Filette Bay – Petroleum Systems Field Exercise: Structural and Metamorphic Interpretation, Failed Petroleum

System, Passive Margin

STOP 3 (3:00 - 5:00pm): Maracas Bay – Swim and Late (2nd) Lunch

STOP 4 (5:30pm): Port of Spain Lookout – Overview of Trinidad Geology & Gulf of Paria

STOP 5 Arrive at PAX Guesthouse, check in (6:30pm), and dinner (7:30pm)

Day 3 Monday February 25

Depart PAX Guesthouse (7:00am)

STOP 1 (8:30am - 12:00pm): Vessigny, Guapo Bay – Sequence Stratigraphy Field Exercise: Log and Measure Section (Permeameter and Scintillometer)

STOP 2 (1:00 - 3:00pm): Stollmeyer’s Quarry – Fluvial Estuarine Channel Complexes & Compartmentalization

Field Exercise: Reservoir Characteristics

STOP 3 (4:00 - 5:00pm): Pitch Lake – Biodegradation & Migration

Return to PAX Guesthouse (7:00pm) and dinner (7:30pm) Evening Exercise: Reserve Estimates of Stollmeyer’s Quarry

Day 4 Tuesday February 26

Depart PAX Guesthouse (7:00am)

STOP 1 (10:30am – 3:30pm): Cedros Bay – Deltaic Systems, Sequence Stratigraphy & Trace Fossils

Field Exercise: Log and Measure Sections (Permeameter and Scintillometer)

Return to PAX Guesthouse (7:00pm) and dinner (7:30pm) Evening Exercise: Bonasse Log and East Field Correlation

Day 5 Wednesday February 27

Depart PAX Guesthouse (9:00am)

STOP 1 (10:00 - 12:00pm): Naparima Hill, San Fernando – Central Range, Source Rock, and Migration, Trap & Seal

STOP 2 (2:00 - 3:00PM): Piparo – Mud Volcanoes, Migration and Overpressure

Return to PAX Guesthouse (7:00pm) and dinner (7:30pm)

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Evening Exercise: Well Log and Seismic Correlation, and update/review field notes

Day 6 Thursday February 28

Depart PAX Guesthouse (7:00am)

STOP 1 (9:00 - 3:30pm): Mayaro – Shelf Margin Deltas, Active and Abandonment Phases Field Exercise: Log and Measure Sections (Permeameter and Scintillometer)

Return to PAX Guesthouse (7:00pm) and dinner (7:30pm) Evening Exercise: Mayaro Log Correlation and complete any outstanding

assignments and field notes

Day 7 Friday March 1

Depart PAX Guesthouse (8:15am)

STOP 1 (8:45 - 3:00pm): Petrotrin, Point-a-Pierre – Geological Lab & Biostratigraphy Field Exercise: Core Logging Exercise

STOP 2 (3:30 - 6:30pm): Caroni Swamp – Mangrove Ecosystems, Shelf Margin Deltas & Accommodation Space, Caroni Basin

Field Exercise: Distributary Channel Morphology

Return to PAX Guesthouse (7:00pm) and dinner (7:30pm)

Day 8 Saturday March 2

Travel from Trinidad – Toronto – Halifax