AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Breakthroughs in the Use of Analogues in Geological Modeling – Examples from Holocene Sabkhas of Qatar
(1) Qatar Center for Coastal Research, ExxonMobil Research Qatar, Doha, Qatar.
The use of modern depositional systems as analogous, conditioning data in geological models is well established in the oil and gas industry. Most historical analogue work has been based on surface mapping and satellite imagery of facies patterns. These images are devoid of data on origin, thickness, age, time lines, sea-level history, and pore water chemistry. Without such data it is difficult to determine how modern data should be applied to a geological or diagenetic model.
This paper presents the first results of a countrywide integration of surface sediments, ages, thicknesses, composition, and pore water chemistry in an ArcGIS model. Industrial geotechnical data from boreholes, building excavations, and offshore dredging provided data on thickness and ages of the Holocene. This is the first integration of analogue data into a geo-referenced framework, examining modern analogue data in a format similar to that of ancient rock data.
The Holocene coastal systems of Qatar and AbuDhabi have long been regarded as the most valid analogues for arid climate, carbonate ramp depositional systems. The coastlines vary in orientation to prevailing winds, sediment supply, and elevation profile. These factors create four major coastal, physiographic areas; each distinguished by variable facies types and facies proportions. Accordingly, windward, leeward, oblique and protected shoreline depositional profiles are recognized. All have a common sea-level history of a rapid rise over the last 10,000 years, followed by a highstand 4000-6000 years before present; approximately 2-4 meters above present day sea level. Comparison of sabkha features between physiographic provinces provides an insight into the variability that might be expected in an ancient sabkha.
Comparisons of depositional and diagenetic histories along the different parts of the coast provide the basis for distinction of depositional models that can be incorporated into geological models. Facies types, 3-D shapes, ordering and internal structure are derivable conditioning parameters from modern data.
We propose that the use of modern depositional systems as analogues for ancient reservoir rocks should evolve in complexity, just as geological models have. Recent advances in geological modeling resolution call for equally high-resolution conditioning data, derived from Holocene sequence stratigraphic and diagenetic models.