Reservoir Surveillance Techniques for Mature Fields
Written by Dr.Nabil Sameh
1. Introduction
Mature oil and gas fields represent a significant portion of global petroleum production, with many reservoirs currently producing beyond 60–70% of their expected life. These assets often face challenges such as declining reservoir pressure, increasing water cut, reduced productivity, and uncertainties in remaining reserves. Effective reservoir surveillance is therefore critical to maximize recovery, extend field life, and ensure economic viability.
Reservoir surveillance encompasses a systematic set of measurements, analyses, and monitoring methods designed to evaluate dynamic reservoir behavior. It provides vital data for reservoir management, well interventions, enhanced oil recovery (EOR) strategies, and production optimization.
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2. Objectives of Reservoir Surveillance in Mature Fields
The key objectives of surveillance programs include:
1. Tracking Reservoir Pressure and Saturation Changes
Monitoring pressure depletion and its impact on recovery efficiency.
Identifying gas-oil and water-oil contact movement.
2. Understanding Production Performance
Differentiating between reservoir-related and wellbore-related problems.
Diagnosing reasons for productivity decline.
3. Evaluating Recovery Processes
Assessing the efficiency of waterflooding, gas injection, and EOR methods.
4. Optimizing Reservoir Management
Improving field development strategies by integrating static and dynamic data.
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3. Types of Reservoir Surveillance Data
Reservoir surveillance relies on a combination of static and dynamic data:
Static Data: Core analysis, well logs, geological models.
Dynamic Data: Pressure measurements, production rates, fluid composition, and time-lapse seismic data.
Dynamic data are more critical in mature fields as they reveal changes in reservoir behavior over time.
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4. Reservoir Surveillance Techniques
4.1 Well Testing
Pressure Transient Tests (PTA): Provide information about reservoir permeability, skin factor, and boundaries.
Interference Tests: Evaluate reservoir connectivity between wells.
Buildup/Drawdown Tests: Assess near-wellbore conditions and reservoir depletion.
4.2 Production Logging Tools (PLT)
Diagnose multiphase flow profiles in producing wells.
Identify zones contributing water, gas, or oil.
Evaluate effectiveness of water shutoff or stimulation operations.
4.3 Tracer Tests
Chemical or radioactive tracers injected to track fluid movement.
Detect high-permeability channels, breakthrough times, and waterflood sweep efficiency.
4.4 Time-Lapse (4D) Seismic
Provides areal surveillance of reservoir saturation and pressure changes.
Monitors movement of water front and gas cap expansion.
Effective for offshore fields with complex reservoir heterogeneities.
4.5 Reservoir Pressure Monitoring
Permanent downhole gauges (PDG) and quartz gauges.
Enable continuous pressure and temperature monitoring.
Critical for tracking reservoir energy over time.
4.6 Fiber Optic Monitoring (Distributed Acoustic and Temperature Sensing – DAS/DTS)
Real-time surveillance of production and injection wells.
Identifies flow distribution along horizontal or multilateral wells.
4.7 Surveillance of Injectors
Injection profiling tools measure distribution of injected fluids.
Allows correction of conformance issues during waterflood or gas injection projects.
4.8 Surface and Subsurface Flow Monitoring
Multiphase flow meters provide real-time well test data.
Integrated with digital oilfield platforms for surveillance automation.
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5. Surveillance Strategy for Mature Fields
Developing an effective strategy involves:
1. Baseline Data Collection
Establish initial conditions before implementing recovery or EOR methods.
2. Regular Monitoring
Well testing and PLT should be scheduled periodically.
3. Integration of Surveillance Data with Reservoir Models
Dynamic reservoir models updated with surveillance data for better forecasting.
4. Optimization of Field Development
Surveillance findings drive well placement, workover design, and EOR implementation.
5. Digital Oilfield Implementation
Using IoT sensors, cloud platforms, and AI for real-time monitoring and predictive analytics.
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6. Challenges in Surveillance of Mature Fields
1. Economic Constraints – Mature fields often have reduced budgets; cost-effective techniques are required.
2. Complex Well Completions – Multilateral and horizontal wells complicate PLT interpretation.
3. Data Integration Issues – Combining geological, geophysical, and engineering data remains challenging.
4. Aging Infrastructure – Deteriorating well integrity and facilities hinder accurate data acquisition.
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7. Case Study Example (Generalized)
In a Middle East carbonate field under waterflood for more than 30 years:
Tracer tests revealed early water breakthrough in specific zones.
4D seismic showed unswept oil in flank areas of the reservoir.
Permanent downhole gauges allowed continuous pressure monitoring.
Integration of these surveillance techniques led to targeted infill drilling and selective water shutoff, resulting in incremental recovery of 5% OOIP and significant economic benefit.
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8. Emerging Trends in Reservoir Surveillance
1. Digital Twin Applications – Real-time models that update dynamically with field data.
2. Machine Learning in Surveillance Data Interpretation – Automated anomaly detection in pressure and production data.
3. Nano-Tracers – New generation tracers offering better resolution for fluid pathways.
4. Autonomous Reservoir Monitoring Systems – Self-powered sensors for long-term data collection.
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9. Conclusion
Reservoir surveillance is the backbone of effective reservoir management, particularly in mature fields, where production decline, water cut, and reservoir uncertainties challenge operators. The integration of traditional techniques (well testing, PLT, tracer analysis) with modern methods (4D seismic, fiber optics, digital twins, and AI) has revolutionized surveillance programs.
A robust surveillance strategy not only enhances hydrocarbon recovery but also ensures efficient utilization of resources, prolongs field life, and reduces operational risks. As mature fields continue to dominate global oil supply, innovative and cost-effective surveillance techniques will play a critical role in securing future energy demands.
Written by Dr.Nabil Sameh
-Business Development Manager at Nileco Company
-Certified International Petroleum Trainer
-Professor in multiple training consulting companies & academies, including Enviro Oil, ZAD Academy, and Deep Horizon
-Lecturer at universities inside and outside Egypt
-Contributor of petroleum sector articles for Petrocraft and Petrotoday magazines
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