Seismic
Attribute Analysis of the Mississippian Chert at the Wellington Field, South-Central Kansas
Ayrat Sirazhiev, George Tsofias, and Lynn Watney
Mississippian chert reservoirs are highly heterogeneous, typically below seismic
resolution and, therefore, present a challenging task for
seismic
characterization. We used well and 3D PSTM
seismic
data to investigate the relationships of thickness and porosity of the Mississippian microporous cherty dolomite reservoir with post-stack
seismic
attributes at the Wellington Field, south-central Kansas. The analysis of well-log and
seismic
data revealed distinct characteristics across the NE-SW trending fault. The reservoir in the southeastern part of the field was characterized by a vertical gradational porosity reduction (from 25-30% to 4-6%), a corresponding increase in P-wave velocity (referred as a ramp-transition velocity function), variable thickness (6-20 m) and lower
seismic
amplitude and frequency content. High correlation between
seismic
amplitude and reservoir thickness, conformable with the theoretical amplitude response of a ramp-transition velocity function, was used to predict reservoir thickness in this part of the field. The reservoir in the northwestern part of the field exhibited more heterogeneous porosity distribution with no clear relationship between reservoir thickness and
seismic
attributes. Inverted acoustic impedance showed high correlation with porosity throughout the field. The porosity model predicted from inverted impedance supported the well-log and
seismic
amplitude interpretation. Wedge
modeling
determined resolution limits as 5 m (1/16λ) for predicting thickness from
seismic
amplitude and 10 m (1/8λ) for porosity prediction from model-based inverted impedance for the Mississippian reservoir characterized by vertical gradational porosity reduction. This study revisited the
seismic
response of a ramp-transition velocity function as a characterization tool for Mississippian chert reservoirs with gradational downward porosity reduction.
AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013