Fractured Reservoirs - Elective I

Fractured Reservoirs - Elective I

• Fractures are three-dimensional (3D) features with heterogeneous distribution.
• Well logs (e.g., borehole micro-scanners) analyze fractures in wellbores to determine aperture and production rates.
• Fractures are crucial in tight reservoirs, not necessarily for oil storage, but for influencing flow.
• Fracture volume, although potentially small compared to reservoir volume, significantly increases matrix-reservoir interface.
• Factors influencing fracture occurrence include folding/faulting, in-situ stresses, and rock properties (porosity, bedding).
• Fractures are often concentrated in low-porosity rocks (e.g., during folding or doming).
• In reservoirs with low matrix permeability, fractures are crucial for productivity.

Fracture Detection and Analysis

• Borehole imaging and 3D seismic improve fault and fracture mapping.
• Fractures typically form parallel or perpendicular to faults (normal, reverse, oblique).
• Fracture density (number of fractures per unit length) is a key parameter corrected for orientation changes.
• Fracture orientations are correlated to geological parameters and structural events.
• Fault-related fractures are less abundant than those associated with folding.
• Recognizing faults involves identifying bedding planes.
• Natural fractures are often created by tectonic stress and are more common in brittle rocks (carbonates, igneous, metamorphic).
• Induced fractures are often long, straight cracks on opposite borehole sides.
• Fractures can be detected during drilling via massive lost circulation, sudden pressure kicks, or drilling breaks.

Fracture Geometry and Measurement

• High-resolution logs (e.g., Formation Micro-Scanner or FMI) help describe fracture geometry.
• Fracture inclination, spacing, and aperture are measurable from imaging logs.
• Electrical imaging logs offer high vertical resolution for fracture analysis.
• Acoustic imaging differs in resolution and investigation depth.

Problems related to Fractured Reservoirs

• Defining fractured reservoirs.
• Tools for detecting fractures.
• Importance of fractures.
• Fracture intensity.
• Common fracture types (Lithology).
• Fault-related fractures vs. folding-related fractures.
• Detecting fractures from induced drilling activities.
• Mud circulation limitations in fracture detection.

This quiz focuses on the critical role of fractures in fractured reservoirs, examining their influence on flow and production rates. Key concepts include fracture detection techniques and the relationship between fractures and rock properties. Test your understanding of how fractures affect reservoir productivity and the methods used for their analysis.