Print this pageIntegrating High-Resolution Aeromagnetic and 3-D Multiazimuth P-Wave Surveys for Natural Fracture Detection
GWILLIAN, WILLIAM J., DOE/METC, VELLO A. KUUSKRAA, and
DAVID 
DECKER
Tight gas reservoirs house a vast resource of natural gas, in excess of 1,000 Tcf of gas. The ability to find and map open, natural fractures in advance of drilling represents the major challenge for future development of these low permeability reservoirs. To further the development of fracture detection technologies, a joint R&D and field demonstration effort involving DOE/METC, Barrett Resources and Advanced Resources International was established.
The technical approach is to start with the use of low cost regional reconnaissance methods to locate subtle basement structures that cause overlying sediments to fracture. High-resolution aeromagnetic data (2,500 mi{2}) were acquired to delineate basement geometry. Remote sensing imagery analysis was used in conjunction with 400 line-miles of 2-D seismic to provide consistency of interpretation. The integrated geologic study revealed that the basin structural fabric was dominated by a series of large northwest trending reactivated basement features. Northwest aligned natural gas production trends confirmed the importance of basement features for causing natural fractures and high productivity fairways.
In April 1996, a 4.5 mi{2} 3-D multiazimuth P-wave reflection study was acquired to target subsurface fracture sets. The 3-D survey is full-azimuth, full-offset designed to evaluate P-wave azimuthal anisotropy. For offset amplitude variation with azimuth processing, we identified the fast velocity and therefore open fracture orientation as N30 degrees W consistent with the integrated geologic prediction. Mapped amplitude anomalies have been interpreted as subsurface open fracture clusters. A six-well program, starting in October 1996, is being located to target the amplitude anomalies and will be used to verify commercial viability of this newly developed natural fracture detection technology.