Reservoir geological model

To derive a reservoir geological model various methods and techniques are employed mainly the analysis of core material, wireline logs, high resolution seismic and outcrop studies. These data gathering techniques are further discussed in Sections 5.3 and 2.2. 

Bryant, I.D. Flint, S.S. (1993) Quantitative clastic reservoir geological modelling problems and perspectives. In The Geological Modelling of Hydrocarbon Reservoirs and Outcrop Analogues (Eds Flint, S.S. Bryant, I.D.). Spec. Publ. Int. Ass. Sediment., 15, 3-20. 

To a large extent the reservoir geology controls the producibility of a formation, i.e. to what degree transmissibility to fluid flow and pressure communication exists. Knowledge of the reservoir geological processes has to be based on extrapolation of the very limited data available to the geologist, yet the geological model s the base on which the field development plan will be built. 

Having gathered and evaluated relevant reservoir data it is desirable to present this data in a way that allows easy visualisation of the subsurface situation. With a workstation it is easy to create a three dimensional picture of the reservoir, displaying the distribution of a variety of parameters, e.g. reservoir thickness or saturations. All realisations need to be in line with the geological model. 

At the development planning stage, a reservoir mode/will have been constructed and used to determine the optimum method of recovering the hydrocarbons from the reservoir. The criteria for the optimum solution will most likely have been based on profitability and safety. The model Is Initially based upon a limited data set (perhaps a seismic survey, and say five exploration and appraisal wells) and will therefore be an approximation of the true description of the field. As development drilling and production commence, further data is collected and used to update both the geological model (the description of the structure, environment of deposition, diagenesis and fluid distribution) and the reservoir model (the description of the reservoir under dynamic conditions). 

Pawar R.J., Zhang D., et al. Preliminary geologic modeling and flow simulation study of C02 sequestration in a depleted oil reservoir. NETL Carbon Sequestration Conference Proceedings. 

FIGURE 3.6 Point-bar geologic model showing the influence of a sequence of rock textures and structures in a reservoir consisting of a single point-bar deposit on horizontal permeability, excluding effects of diagenesis. (Modified after Ebanks, 1987.)... 

Lindsay, N.G., Murphy, F.C., Walsh, J.J. and Watterson, J, 1993. Outcrop studies of shale smears on fault surfaces. In S. Flint and A.D. Bryant (Editors), The Geological Modelling of Hydrocarbon Reservoirs and Outcrop Analogues. Int. Assoc. Sediment., 15 113-123. 

The fundamental question asked when evaluating an exploration prospect is how much hydrocarbon resource is in place To answer this question, the conventional reservoir engineering approach is to compute the probable reservoir hydrocarbon pore volume, i.e. the size and extent of the hydrocarbon container , from estimates of reservoir rock and fluid properties. Uncertainties in the geological model, source rock characteristics, trapping mechanisms and seal rock effectiveness, and the presence of sufficient reservoir rock for commercial hydrocarbon production, are often represented as a singlevalued probability of success. 

This element of the mass balance model refers to the efficiency with which the generated hydrocarbons migrate to and are trapped within the reservoir. Components of this element include the trapping mechanisms identified from the geological model as well as characterization of the reservoir seals. As discussed previously, structure often plays little or no role in the accumulation of hydrocarbons in a BCGS, so evaluation of the seals is especially critical to an accurate evaluation. Key components and data requirements include ... 

The fields chosen as the petrophysical and reservoir engineering analogue for exploration prospects in the Bossier tight gas sand play are the Dew/Mimms Creek Fields. Note that, rather than using these fields as the geological analogue, specific geological models were developed for each exploration prospect, especially in the deeper parts of the basin. 

Geological Modelling and Reservoir Simulation 151 to zero, the set of equations... 

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