--> Abstract: The Effect of Hydrodynamics on Capillary Seal Capacity; #90063 (2007)

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The Effect of Hydrodynamics on Capillary Seal Capacity

 

Manzocchi, T.1, B. Palananthakumar1, C. Childs1 (1) University College Dublin, Dublin, Ireland

 

Water drive is an efficient mechanism in oil production. However, it has been suggested that hydrodynamic effects can be effectively ignored in the evaluation of seal capacity over geological timescales. It is argued that, for the relatively low water flow rates which occur naturally, the relative permeabilities to water of trapped oil columns are low enough that viscous forces are negligible and only the capillary properties of seals need to be considered. This conclusion has largely been reached by consideration of thick top seals. When considering thin seals, e.g. fault seals, it is not clear whether pressure compartmentalisation in the water-phase can be ignored when evaluating trapped column heights.

 

To examine the effect of across-fault pressure differences on trapped column heights we have solved the two-phase flow equations in 1D for a dipping carrier. We assume an oil column is trapped on the down-dip side of the fault and allow water flow to be either up or down dip. For a constant water flow rate we solve for the stable trapped column height which provides a dynamic balance between viscous, gravity and capillary forces. Results show that for realistic fault seals, naturally occurring across fault pressure differences can be significant and can impact the column height both positively and negatively depending on the water flow direction. Our modelling also indicates that realistic hydrodynamic flow rates can also influence the column heights supported by relatively thin or high permeability top seals as well as fault seals.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California