Chemical Tracers-2

Harnessing Chemical Tracers for Enhanced Oil and Gas Reservoir Surveillance

?Introduction: Tracing the Path to Enhanced Recovery

Tracer technology has revolutionized the oil and gas industry's approach to understanding and optimizing reservoirs. Tracers have become indispensable tools for reservoir characterisation, well connectivity analysis, and enhanced oil recovery (EOR) strategies by offering a window into the complex interactions within sub-surface formations.

For oil and gas scientists and engineers, navigating the enigmatic world of subterranean reservoirs presents a constant challenge. Just like detectives piecing together clues, they rely on various tools to understand fluid flow, reservoir properties, and wellbore integrity.?

The Essence of Tracer Technology

Tracers, essentially identifiable parts of a mass that can be tracked through a system, have become indispensable in revealing well-to-well connectivity, fluid pathways, and reservoir heterogeneities. Their journey, significantly diluted before detection, provides direct proof of communication within the reservoir's connected pore space, offering insights into reservoir flows and efficiencies.

Types and Classifications

• Functionality-Based: Partitioning vs. Passive Tracers: Partitioning tracers interact with the reservoir and provide insights into oil saturation; passive tracers do not interact but provide distinct insights.
• Carrier Fluid-Based: Differentiated into water and gas tracers, each suited for specific recovery operations such as improved oil recovery (IOR) or enhanced oil recovery (EOR)
• Radioactivity Consideration: Choice between radioactive and non-radioactive tracers based on safety, solubility, stability, detection, and environmental impact.

Water Tracers: Enhancing Waterflooding Performance

Water tracers, particularly halogenated benzoic acids, have gained prominence due to their conservative behavior, excellent stability, and affordability. These tracers are pivotal in investigating and optimizing water-flooding performances, with passive water tracers providing insights into injection water dynamics and partitioning inter-well water tracers offering data on oil/water interactions.

Gas Tracers: Mapping Gas Movement

Gas tracers, including perfluorocarbons and sulfur hexafluoride (SF6), have been instrumental in tracking gas movement within reservoirs. Their stability and detectability make them suitable for wide-ranging applications, from evaluating gas injection strategies to assessing reservoir heterogeneities.

Applications Across the Reservoir Lifecycle

Tracer technology's flexibility allows for its application across various stages of the reservoir lifecycle, from drilling to production optimization. Innovative uses include:

• Single Well Chemical Tracer Tests (SWCTT): This method assesses oil saturation near wellbores, providing valuable data for enhanced oil recovery (EOR) strategies.
• Waterflooding Strategy Optimization: Inter-Well Tracer Tests (IWTT): Employed to evaluate fluid movement and connectivity between wells, IWTTs are crucial for optimizing reservoir models, and wells to improve sweep efficiency and improving recovery techniques.
• Partitioning Interwell Tracer Tests (PITT): PITTs specifically target the determination of residual oil saturation (SOR) between wells, offering insights crucial for evaluating EOR potentials.

Enhancing Fracture Diagnostics with Tracers

The integration of tracer technology into hydraulic fracturing operations represents a significant leap forward in optimizing unconventional oil and gas extraction processes. Tracers, both chemical and radioactive, have been deployed to diagnose the extent and efficacy of fractures, providing invaluable data for improving well performance and resource recovery.

Tracers in the Fracking Process

• Diagnostic Tool: Tracers are used as a diagnostic tool to assess the clean-up efficiency of fracking fluids and evaluate the contribution of each fracture stage to total hydrocarbon production.
• Types of Tracers: Various tracers, including gas, oil-based tracers, have been utilized to gain insights into proppant distribution, fracture height, volume, and the overall success of the stimulation efforts.

Field Applications and Advancements

Recent advancements have seen the deployment of hydrocarbon (HC)-based tracers in emulsion forms within stimulation fluids. These tracers are designed to optimize stimulation design and maximize production in future wells. Unlike radioactive tracers, HC-based tracers offer a longer lifespan and do not pose issues during the well's short or long-term shut-in phases, making them a preferred choice for environmental and operational reasons.

Key Lessons and Insights

• Operational Insights: Tracer tests in fracking operations have provided detailed information on fracture volume, connectivity, and the efficiency of hydraulic fractures.
• Safety and Environmental Considerations: The shift from radioactive to HC-based tracers reflects the industry's focus on safety and environmental sustainability.
• Optimization of Stimulation Designs: The data obtained from tracer tests are instrumental in refining fracturing fluid compositions and injection protocols, leading to more effective fracture creation and hydrocarbon recovery.

Stay tuned for our upcoming posts, where we'll dive deeper into the? role of chemical tracers in the? topics of?

• Inflow measurement
• Acid Stimulation Performance Monitoring
• Core invasion studies

further unravel their significance in enhancing oil and gas recovery processes.

References

• Insightful studies and field case reviews from SPE Kuwait Oil and Gas Show and Conference, OnePetro.

Sources and Further Reading:

• Tracerco: Fuel Marking - Insight into fuel marking programs.
• ScienceDirect, Elsevier B.V.: Articles on chemical tracers in environmental and oil and gas applications.
• American Chemical Society (ACS): Publications on the use of isotopic and chemical tracers in environmental science.