Understanding the Transition Between Limestone and Dolomite to Estimate the Hydrocarbon Volume of Carbonate Reservoirs

Abstract

Abstract

The hydrocarbon volume in the reservoir is used to appraise reservoir quality and the economics associated with reservoir field development. For seismic-based reservoir characterization, porosity and saturation information derived from seismic inversion are often used to provide an estimate of the amount of hydrocarbon volume.

In general, porosity and saturation estimations from seismic data are based on a rock physics transformation. However, using a traditional rock physics transformation, there is no satisfactory method of choosing a model parameter to describe the geological events of carbonate reservoirs in order to define porosity and saturation. Porosity reduction in carbonate rocks can be related to mechanical compaction, recrystallization, cementation and dolomitization. Pores in dolomites are preserved to greater depths of burial than the pores in limestone because of the greater mechanical and chemical stability of dolomite. Dolomite loses porosity more slowly with burial than most limestones, therefore understanding the transition between limestone and dolomite is an important issue when interpreting the seismic signatures of a carbonate reservoir.

This paper presents a workflow to compute quantitative estimates of porosity and saturation of carbonate reservoirs, along with associated uncertainties. The main components used in this workflow are a geological-based rock physics model to describe the transition between limestone-dolomite and Bayesian statistics.

We demonstrate this workflow using seismic and well data from a producing carbonate reservoir in North America showing the expected risk associated with a geological model and confidence associated with the prediction to constrain economic models for development decisions.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016