--> Capturing Fracture Uncertainties in Reservoir Simulation of a Giant Mature Fractured Carbonate Field, Oman

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Capturing Fracture Uncertainties in Reservoir Simulation of a Giant Mature Fractured Carbonate Field, Oman

 

Wei, Lingli1, Simon Price1, Martin De Keijzer2, Salah Al Dhahab1 (1) Shell International Exploration and Production, Rijswijk, Netherlands (2) Nederlandse Aardolie Maatschappij (NAM), Assen, Netherlands

 

Significant hydrocarbon volumes still remain in the mature giant fractured carbonate fields of the Middle East. Recovering the remaining reserves in these geologically complex reservoirs requires detailed understanding of matrix and fracture heterogeneity at and below the inter-well scale (typically metre to 10s metre areally).

Surface (outcrop) and subsurface (seismic, BHI, cores etc) data provide the input con­straint for a range of plausible 3D fracture models, extending beyond areas of well control. The range of a priori estimates of many fracture parameters is still, however, too broad for optimal re-development of these complex fields.

This paper describes the workflow developed and applied for such a field in Oman. The method involves the description of the fracture system using a number of key geometrical

(e.g. density) and non-geometrical (e.g. porosity) parameters. Along with other matrix and dynamic parameters, a priori estimates of each parameter are made and then historical field production data are used to narrow the uncertainty range. The narrowed uncertainty ranges significantly improve the economic evaluation of alternative re-development options and allow for a more focused data collection and surveillance programme to target remaining uncertainties.

The focus of this paper is:

      1. How to implement a range of geologically realistic static fracture models in reservoir simulations (nested, multi-scaled fracture systems with multi-scaled vertical connectivity);

      2. How to determine and model fracture porosity and fracture permeability uncertainties;

      3. How to incorporate historic production data to narrow down the uncertainties; and

      4. Which types of historic data are useful for narrowing down different fracture uncertainties.