Summary

This paper shows an example of a geocellular facies model constructed for a shale gas play in the Horn River Basin, Canada. It shows that traditional techniques of identifying lithofacies within a sequence stratigraphic framework can be utilized to setup the framework for constructing a geocellular model. Relationships between elastic parameters and lithofacies allow us to obtain low-resolution larger-scale 3-dimensional geobody geometries and facies relationships from inverted seismic data. These help constrain variograms and allow propagation of geocellular facies models away from well control, both vertically and laterally. Lithofacies are tied to distinct porosity, permeability and water saturation distributions and thus the resulting geologic model can be used to evaluate in-place resources, assist in well planning and ultimately help understand recovery factors and influence well spacing and infill drilling during development stages of the field.

Introduction

Constructing geocellular models of oil and gas accumulations is a well-established component of reservoir evaluations. These models serve to define the 3-dimensional distribution of the resource in the exploration phase and allow for well planning in the field development phase. Ultimately the fluid flow simulations of such geocellular models provide predictions of production over the life of the field and allow us to define EUR, Recovery factor and to plan for infill drilling of unswept compartments during the mature phase of field development.

However, in so-called resource plays, defined here as hydrocarbon accumulations over relatively large basinal areas in relatively low permeability rocks that lack a clear trap and fluid contact definition, the construction of geocellular models is virtually non-existent. This is due to

  • the lack of a clear definition of what constitutes a hydrocarbon accumulation in these plays making it difficult to define the scale and resolution at which a model would need to be constructed for meaningful evaluations, and

  • production of a resource play depends on horizontal drilling and artificial fracturing techniques, the effect of which has not yet been integrated in fluid flow simulators. Finally, there is uncertainty in regard to the flow mechanisms that deliver free and adsorbed gases through rocks with absolute permeabilities less than about 1 microdarcy into the well bore that prohibits the use of traditional reservoir simulators for modeling and history matching production. Hence there is little perceived value of a geologic model for predicting production time-scale flow.

URTeC 1578553

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