Use of Image Logs for Detecting Fractures and Resolving Structure in the Monterey
The Monterey Formation in California is a prolific producer from fractured systems and is often structurally complex. Resisitivity image logs are very useful in identifying and understanding the structure and fractures in the Monterey. Detailed analysis of the bedding dips are interpreted and are displayed in Strucview which is a model for displaying the structure and faulting of the bedding dips along the well path in a 2D cross section. Examples of fractures observed in resistivity image logs include open and healed natural fractures and drilling induced fractures. Valuable information obtained from the interpretation includes fracture location, orientation, type (i.e. open or healed), and classification (i.e. lithologically bound, continuous, or partial). Detailed interpretation by hand picking the discrete fracture traces with borehole images that are calibrated to a known resistivity allows you to quantify fracture attributes (i.e. aperture, porosity, density, and trace length) from them. The behavior and occurrence of the fractures observed in borehole images can be compared with fractures observed in Monterey outcrops. Methods used to analyze interpreted data include stereoplots, dipvector plots, and Strucview analysis. Borehole images are an effective way of understanding the structure and fractures in the Monterey.
AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009