Seismic Expression of Upper Morrow Sands, Western Anadarko Basin
Jens R. Halverson
In the western Anadarko basin, the Lower Pennsylvanian upper Morrow sands are both a prolific and an elusive exploration target. Initial production from some of these sands can reach over 1,000 BOPD, yet an offset well just 350 m away from a good producer can miss the sand entirely. High-resolution seismic data and seismic facies mapping techniques have been used to detect the sands before drilling.
One-dimensional merged log modeling, two-dimensional log interpolation modeling, color seismic inversion processing, and seismic facies mapping techniques were applied to two upper Morrow sand fields in the Texas Panhandle--the Lear and Darden fields. The sands reach an isopach thickness of 10-15 m at a depth of 2,500-3,000 m. the Morrow sands are within a thin-bed regime and below the turning point, where there is a correlation between the amplitude of the reflection and the thickness of the sand. The velocity and density contrasts of the shales and sands are of sufficient magnitude to produce a good acoustic impedance contrast and make the sands detectable on good signal-to-noise ratio seismic data. The comparison of geologic isopach mapping and geophysical seismic facies mapping sh ws an excellent correlation in the delineation of the upper Morrow sands.
The use of seismic stratigraphy methods should substantially increase exploration and development success when high-resolution seismic data and advanced interpretation techniques are used.
AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.