HART, BRUCE, New Mexico Bureau of Mines, Socorro, NM

ABSTRACT: 3-D Seismic Based Definition of Fracture-Related Production Trends in Tight Gas Mesaverde Sandstones, San Juan Basin

Conventional (p-wave) 3-D seismic data, integrated with log and production data, are proving themselves to be useful for detecting fracture-swarm sweet spots in tight Mesaverde sandstones in the San Juan Basin. Analysis of production data shows that several of the >4O0 wells within the seismic survey area have mu& higher cumulative production (>10 BCF) than the majority (typically 3-4 BCF). Analysis of horizon attributes, including a variety of curvature attributes, indicates- that the best producers penetrated fracture-swarm sweet spots associated with small-offset faults. Excluding these wells, cumulative production trends follow depositional trends, suggesting that net sandstone is an important factor controlling production. Net sandstone can be predicted seismically, and can influence production either by defining reservoir storage capacity or fracture density.

This work has defined some key factors that need to be considered when undertaking similar studies. The key element is that good-quality seismic data are essential for identifying fracture swarms and defining reservoir properties. Noisy data can make horizon attribute-based detection of subtle structures problematic. Post-stack processing ("data enhancement", e.g., trace mixing, fan filtering) can only partly remedy noisy data. Stratigraphic complexity also adversely affects the interpreter's ability to detect subtle structural details. Even survey orientation plays an important role. If the acquisition geometry parallels the fracture orientation, it may be difficult to distinguish between acquisition artifacts and seismic attribute trends that are related to fractures. Good quality digital logs and production data are also important.

AAPG Search and Discovery Article #90915©2000 AAPG Rocky Mountain Section, Albuquerque, New Mexico