The Effect of an Outcrop Joint Pattern on Sandstone Reservoir Models

Chris Townsend

An outcrop sandstone joint pattern from Whinney Hill, Blackburn, England has been added to heterogeneous fluvial reservoir models in order to determine their effect on a) effective permeability and b) ECLIPSE simulations. Experimental design techniques were used for efficient result generation. Three separate studies have been carried out and can be summarised as follows:

1) Joints were added deterministically to heterogeneous fluvial reservoir models and showed that they had a small but significant effect. Little change to the effects of the sedimentary description parameters occurred (compared to un-fractured models).

2) Joints were added to 18x18x0.9 m grid blocks of homogeneous sandstone (30 & 300mD k_matrix) in order to calculate new k_eff. The joint description parameters were varied to determine their influence on k_eff. The results show that upscale block size and shape, in-situ stress direction, joint sampling box size and minimum joint length were the most important parameters for determining k_effy (models were set up to maximise the effect of k_effy).

3) Jointed models were built by varying 4 of the important description parameters. These were added to 4 fluvial reservoir models and ECLIPSE simulations were run. In-situ stress direction and stress direction-stress magnitude interaction were found to be the most important parameters. Other parameters and interactions were found to be important but these were dependent upon sedimentary architecture.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California