How do you characterize oil and gas reservoirs?

Reservoir characterization refers to the process of unfolding all the features of the hydrocarbon-bearing reservoir, which necessitates the utilization of the most accurate measurements from multiple sources to enhance its lifetime performance. In essence, the rock is studied by considering all the characteristics of the reservoir that are pertinent to its ability to store and facilitate fluid flow, covering exploration to field development plans. An improved understanding of the intricate geology of the reservoir allows for more effective well placement and better long-term field production management.

Comprehensive understanding of reservoir properties fluid behaviour, geometry & future performance. It aims to unravel basic properties like porosity, permeability, lithology & saturations thus helping in determining the in-place for resource assessment & FDP planning. It also delves in phase behaviour, rock-fluid interactions & other parameters. Thus helping in optimising the production strategies from primary recovery to advanced EOR techniques. Structural & statigraphical relationships will further help in deciding exact well placement & maximise recovery. Continuous monitoring of reservoir performance will validate the models, define the production forecasts and help in inform decision process.

1. Geological Methods to understand surface geology, outcrops along with deposition environment & stratigraphy. 2. Geophysical techs like gravity, magnetic & electromagnetic surveys that provide sub-surface imaging. 3. Core analysis to understand properties like lithology, porosity & permeability. 4. Well logs like GR, SP, resistivity, neutron & sonic logs aiding in proper well correlation and fluid content in formation. 5. Reservoir simulation to know the flow behaviour, reservoir behaviour to strategise development. 6. Production / Rate transient analysis that include PTA, RTA, DCA, M. Balance for understanding extent and vulnerabilities occurring.

Imbibing reservoir characterization into reservoir simulation models poses challenges in data integration, capturing reservoir heterogeneity accurately, and managing model complexity. Diverse datasets demands meticulous validation to ensure accuracy, while accurately representing reservoir heterogeneity requires capturing variations in properties like porosity & permeability. Balancing model complexity with computational efficiency is crucial, as complex models can strain computational resources. Parameterizing models with precise rock & fluid properties and calibrating them to match observed reservoir behavior are critical. Managing uncertainties inherent in characterization data and simulation models is essential for reliable predictions.

For an RE, reservoir characterisation is the ultimate end point. Because now the person has clear insights of reservoir thus helping in enabling development strategies. Accurate reservoir model indicate better confidence at production forecasts, thus enabling RE to aggressively develop the field. High confidence in well placement intersection zones at greater contact and max. production rates. EOR methods that can be planned will be studied better considering field scale implementation if required helping in understanding the effectiveness of its application. Reservoir characterisation however is a continuous process as knowing every pore scale is not practical.

Best practices in reservoir characterization involve an integrated approach, combining geological, geophysical, and engineering data. Quality data acquisition, multidisciplinary collaboration, and advanced interpretation techniques ensure accuracy. A robust geological model, built on detailed analysis, captures reservoir heterogeneity. Utilizing advanced interpretation and modeling techniques, including continuous monitoring and updating, enhances accuracy over time. Thorough risk and uncertainty management and transparent documentation facilitate informed decision-making. These practices enable effective reservoir management, optimized production strategies, and maximized hydrocarbon recovery.