Integration of Sequence
Stratigraphy, 3D Seismic Data Visualisation and Quantitative Risk Assessment -
Towards a Stratigraphic Trap
Exploration Portfolio in Cooper-Eromanga Basin,
South Australia
By
Takeshi Nakanishi1, Simon C. Lang2
(1) Adelaide University, Adelaide, Australia (2) University of Adelaide, Adelaide, Australia
The future for petroleum exploration in the predominantly non-marine Cooper-Eromanga
Basin of onshore Australia, lies in the identification and appropriate risk
assessment of stratigraphic traps. Using an integrated approach of sequence
stratigraphy and 3D seismic data visualisation, a variety of stratigraphic trap
prospects were identified in the Permian and the basal Jurassic successions.
The geologic chance factors for an effective stratigraphic trap
include
reservoir, top seal, lateral seal, bottom seal within each depositional systems
tract, the seal effectiveness of the adjacent depositional systems tracts and
the appropriate spatial arrangement of these factors. To assess the chance of
geologic success, the confidence values for the existence of geologic chance
factors were estimated according to the genetic-stratigraphic interval (e.g.
lowstand, transgressive, highstand systems tracts). For probabilistic reserves
estimation, geologically reasonable ranges were estimated for each parameter
employing Monte Carlo simulation to calculate the reserves distribution.
When a series of possible exploration portfolios, including single or
multiple prospects from a prospect inventory are plotted regarding the chance of
geologic success vs. the mean value of the reserves estimate, an efficient
exploration frontier emerges. The portfolio candidates on the efficient
exploration frontier were assessed with regard to the expected net present value
(ENPV) using a simple cash flow model. The results indicate that appropriate
portfolios include multiple prospect exploration especially with lowstand
systems tract plays using multiple exploration wells. The portfolio construction
approach for stratigraphic trap
exploration should be made consistent with
conventional play types, to enable an assessment of all exploration
opportunities.