Seismic
Inversion Techniques as Aids in Basin Modeling
R. Jonk and R. Saltzer
ExxonMobil Upstream Research Company, P.O Box 2189, Houston TX 77008
The challenge for generating a basin model is the estimation of rock properties at a regional scale for the full range of lithologies. To date, the application of
seismic
data
obtained through 2D and 3D surveys are the primary means for developing the spatial and temporal distribution of rock properties required for modeling thermal and pressure evolution of basins. Firstly, mapping of
seismic
reflections and establishment of age-control provide a framework for the stratigraphic and structural evolution of a basin,
seismic
facies of intervals provides a first-order approximation of the bulk rock properties (e.g. sand-prone versus shale-prone intervals). Secondly,
seismic
surveys provide spatial coverage of basins at resolutions appropriate for basin modeling applications that cannot be obtained by other means.
There are however, gaps in the conventional use of
seismic
data![Next Hit](/images/arrow_right.gif)
to populate model properties. Detailed mapping of
seismic![Next Hit](/images/arrow_right.gif)
reflections and inferred environments of deposition from
seismic![Next Hit](/images/arrow_right.gif)
facies is itself complex and as a result
seismic![Next Hit](/images/arrow_right.gif)
interpreters generally restrict such detailed efforts to reservoir-prone intervals where well-penetrations aid in increasing confidence in the
interpretation![Next Hit](/images/arrow_right.gif)
. Away from reservoir-prone intervals, detailed
interpretation![Next Hit](/images/arrow_right.gif)
in fine-grained strata is often lacking and confidence diminishes due to fewer well-penetrations and the non-unique character of
seismic![Next Hit](/images/arrow_right.gif)
facies. To further add to the difficulty, the fluid flow properties of shales and mudstones are more poorly understood than their coarser-grained counterparts, and it is the distribution and properties of these that largely control the thermal and pressure evolution and petroleum accumulation in the subsurface.
We propose that inversion of
seismic
data![Next Hit](/images/arrow_right.gif)
(angle stacks) provides a relatively rapid method for generating basin-scale volumes of relevant rock properties such as clay content and porosity. This presentation will review the rock physics relationships between these properties and the elastic (
seismic![Next Hit](/images/arrow_right.gif)
) parameters focusing on the sedimentary rocks that are dominated by clay mineral grains (i.e. shales and mudstones).
In addition, rock property prediction methods that are suited for different
data![Next Hit](/images/arrow_right.gif)
density and quality will be discussed. As a conclusion, the workflow of generating seismically-derived basin-scale volumes of flow properties (permeability and capillary entry pressure) from porosities and clay contents (calibrated to well log
data![Top](/images/arrow_up.gif)
and sample measurements) is explained. These are the parameters ultimately used as inputs in modeling a basin's thermal, pressure and fluid flow evolution.
AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands