Forward
Seismic
Modelling of Exhumed Clastic Intrusions to Improve Understanding of Architecture and Impact of Large-Scale Injectites in the Subsurface
Abstract
Seismic
forward modelling integrates reservoir petrophysical properties with outcrop architectural geometries, and is therefore crucial in applying subseismic-scale detail and understanding to
seismic
-scale
interpretation
of hydrocarbon reservoirs. Here, four synthetic
seismic
sections have been constructed using outcrops from the Karoo Basin, South Africa and physical rock properties from a North Sea Tertiary discovery, Northern North Sea. The synthetic
seismic
was then compared to
seismic
data
from the North Sea, after which several sets of different geometries were identified as being common throughout both
data
sets. The integration of outcrop panels, well log
data
, forward
seismic
modelling and subsurface
seismic
sections allows these common types of
seismic
expression to be related back to the original outcrop
data
. A model was created for a detailed understanding of the injectite geometry at outcrop scale based on six “injectite morphologies”: Type 1 low-angled bowl, Type 2 Anastomosing injectite, Type 3 Bifurcated injectite, Type 4 Abrupt step, Type 5 Composite intra-bowl injectites and Type 6 Vertical dykes. In reflection
seismic
data
, the identification of injectites can be ambiguous, which impacts the construction of geological models. The integrated approach here has developed recognition criteria that will help to discriminate between clastic injectites and the parent sands. Furthermore, the results helps to bridge the gap between outcrop and
seismic
data
by indicating that injectite architecture is largely scale invariant, which permits outcrop-scale knowledge to be used in
seismic
scale
interpretation
. Injectites are increasingly being identified in the subsurface, and the specific targeting of clastic injectite complexes as hydrocarbon reservoirs, meaning the approach taken in this study could be used in many other basins around the world to reduce uncertainty in the role of injectites.
AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015