--> ABSTRACT: Predictive Modelling of Water Breakthrough in a Fractured Carbonate Gas Reservoir, by Lex Rijkels, Stephen J. Bourne, Alexander Weber, and Franz Brauckmann; #90906(2001)

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Lex Rijkels1, Stephen J. Bourne1, Alexander Weber2, Franz Brauckmann2

(1) Shell International Exploration and Production B.V, Rijswijk, Netherlands
(2) BEB Erdgas und Erdoel GmbH, Hannover, Germany

ABSTRACT: Predictive Modelling of Water Breakthrough in a Fractured Carbonate Gas Reservoir

This paper describes a Permian evaporite carbonate gas field that has been plagued by severe water problems since it was put on production in the mid-80s. The surprising pattern of water encroachment was the result of a heterogeneous natural fracture network in combination with a highly permeable streak The complex interaction between fractures, matrix and the highly permeable streak required an integrated, geomechanical model for the fractures to explain and predict the field behaviour.

Geological and flow data were used to validate and constrain this predictive field-wide fracture model. First, the stress distribution around seismically visible faults was calculated assuming homogeneous, isotropic, linear elastic rock mechanical properties, and frictionless faults. Second, the calculated stress field was used to simulate the growth of discrete fracture networks, which were constrained by statistically comparing fracture orientation and connectivity with that derived from core, BHI, PLT, mud loss, and well test data. Finally, the fracture networks were upscaled dynamically to the grid of a dual-permeablity simulator, enabling field-scale multi-phase reservoir simulation. The flow model obtained this way matched historical production data from all wells. It also explained the source of water breakthrough and the inflow profile seen on PLTs. Integrating seismic, borehole, well test and production data to constrain and validate such a field-wide model considerably reduced the uncertainty in the final predictions. The integrated, predictive fracture model is presently used to investigate future field development scenarios.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado