--> ABSTRACT: Predicting Rock Properties away from Well Control with Coupled Diagenesis and Rock Physics Models, by Lander, Robert H.; Dræge, Anders ; Bonnell, Linda; #90142 (2012)

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Predicting Rock Properties away from Well Control with Coupled Diagenesis and Rock Physics Models

Lander, Robert H.*1; Dræge, Anders 2; Bonnell, Linda 1
(1) Geocosm, Austin, TX.
(2) Statoil, Bergen, Norway.

Most rock physics approaches for interpreting seismic data rely heavily on the use of well derived data. These approaches are sensible where the properties of the rocks in the area of interest are within the range shown by the sample set. Deviation in rock compositions and textures in the area of interest, however, are to be expected in response to differences in (1) depositional composition or texture or (2) burial histories.

To address this problem in siltstones and sandstones we have developed an approach that couples process oriented diagenetic models with rock physics models. The diagenesis models take sediment depositional composition and texture (derived from analogs or depositional models) as input together with the subsequent effective stress and temperature histories (derived from basin / petroleum system models) to simulate compaction, grain dissolution / replacement, and cementation through geologic time. The associated predictions for the abundances and textural nature of pores and solid phases in turn provide input for rock physics models as well as other models for bulk physical properties such as permeability.

Our approach employs a priori diagenetic models for a number of important processes including compaction, quartz cementation, illite formation, feldspar secondary porosity, and plagioclase albitization, among others. We use an a posteriori approach that relies on analog sandstones to consider the effects of diagenetic processes for which accurate deterministic models have not yet been developed. The result of the diagenetic modeling includes prediction of petrographic modal components through geologic time including explicit simulation of intergranular, intragranular, and microporosity as well as the bulk mineralogy, density, and chemistry of the rock.

We have incorporated a modified version of the rock physics modeling scheme of Dræge et al.
(2006) into our reservoir quality models. This scheme combines a number of established rock physics models to calculate the static bulk and shear moduli of sandstones based on the physical properties, abundances, and textures of constituent solid and fluid phases. In this presentation we will review some of the model concepts, our early attempts to evaluate its performance on natural datasets, and discuss how it might be applied to exploration and production problems.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California