Risk, Uncertainty and Priorities - Quantitative Models
I. Lerche, S. Cao, S. Mallory, K. Petersen, and A. Lowrie
1
Introduction
Quantitative basin analysis has three major components: (i) determination of
the spatial and temporal dynamic evolution of the sediments in relation to
evolving basinal structure, and with respect to the spatial variations of lithologic
and diagenetic fabrics; (ii) determination of the thermal history of sedimentary
units in relation to their burial histories; (iii) determination of the hydrocarbon
generation, migration and accumulation histories of all hydrocarbons generated
in the basin, so that the relative timing of hydrocarbon evolution can be assessed
in relation to the development of traps and their seals, and in relation to the continued integrity of sealed traps after hydrocarbon emplacement. In this way a
better appreciation can be obtained of potential hydrocarbon sites in a basin. On
the path to achieving such an evaluation of hydrocarbon site determination, four
major concerns have to be addressed in relation to the output from any basin
analysis model. The concerns are: (i) resolution; (ii) sensitivity; (iii) uniqueness;
(iv) precision. These four factors are controlled to a greater or lesser extent by
three overriding inputs: (i) intrinsic assumptions; (ii) parameter values; (iii)
quality, quantity and sample spacing of data.
A detailed analysis of the evaluation of basins taking into account the three input factors and the four output concerns has been given elsewhere (Lerche 1989,
1990) for dynamical, thermal and hydrocarbon assessments. Every case history
investigated should be evaluated for its rugged stability (or lack thereof) in relation to the points made above.
Thus the development of quantitative basin analysis can be separated into
three stages: the first stage of model development concentrates on the construction and use of mathematical and numerical models of basinal evolution; the
second stage is uncertainty and sensitivity in which the main aim is to examine
the stability of model results in relation to the uncertainties and rages of variations in assumptions, parameters and input data; the third stage, and the one we
are dominantly concerned with here, is related to the uncertainties and sensitivities of the models used, as in stage two above.
The purpose, then, is to provide quantitative probability measures to outcomes of model calculations in order to have objective, reproducible estimates
I. Lerche, S. Cao, S. Mallory, K. Petersen, and A. Lowrie
1
Introduction
Quantitative basin analysis has three major components: (i) determination of
the spatial and temporal dynamic evolution of the sediments in relation to
evolving basinal structure, and with respect to the spatial variations of lithologic
and diagenetic fabrics; (ii) determination of the thermal history of sedimentary
units in relation to their burial histories; (iii) determination of the hydrocarbon
generation, migration and accumulation histories of all hydrocarbons generated
in the basin, so that the relative timing of hydrocarbon evolution can be assessed
in relation to the development of traps and their seals, and in relation to the continued integrity of sealed traps after hydrocarbon emplacement. In this way a
better appreciation can be obtained of potential hydrocarbon sites in a basin. On
the path to achieving such an evaluation of hydrocarbon site determination, four
major concerns have to be addressed in relation to the output from any basin
analysis model. The concerns are: (i) resolution; (ii) sensitivity; (iii) uniqueness;
(iv) precision. These four factors are controlled to a greater or lesser extent by
three overriding inputs: (i) intrinsic assumptions; (ii) parameter values; (iii)
quality, quantity and sample spacing of data.
A detailed analysis of the evaluation of basins taking into account the three input factors and the four output concerns has been given elsewhere (Lerche 1989,
1990) for dynamical, thermal and hydrocarbon assessments. Every case history
investigated should be evaluated for its rugged stability (or lack thereof) in relation to the points made above.
Thus the development of quantitative basin analysis can be separated into
three stages: the first stage of model development concentrates on the construction and use of mathematical and numerical models of basinal evolution; the
second stage is uncertainty and sensitivity in which the main aim is to examine
the stability of model results in relation to the uncertainties and rages of variations in assumptions, parameters and input data; the third stage, and the one we
are dominantly concerned with here, is related to the uncertainties and sensitivities of the models used, as in stage two above.
The purpose, then, is to provide quantitative probability measures to outcomes of model calculations in order to have objective, reproducible estimates