Cavitation: A Possible Key to the Jail?

Randal L. Billingsley
Advanced Resources International, Inc, Denver, CO

A completion procedure designed around the process of wellbore cavitation may be a useful tool for extending gas production into deep, overpressured Cretaceous shales of the Rocky Mountain area. Strong shows and wellbore instability are often observed when drilling through overpressured shales to deeper objectives. Minor shale production has been established in the Green and Wind River Basins through the practice of perforating shows. Post appraisal of one such productive well indicates the process of cavitation may be a factor in the productivity of a highly overpressured shaly zone. If so, then understanding the conditions under which the process can be induced and its reservoir impact will be critical to consistently establishing commercial production.

Cavitation, the process of completion by generating a cavity at depth in the objective interval, has been successfully employed in other settings. Adapting cavitation to deep, geopressured gas shales may unlock new volumes of gas from extremely low permeability settings. Technical barriers to making this technique commercially viable include identification of favorable conditions and the practical aspects of safely performing the procedure at great depths and pressures. A detailed understanding of the mechanical characteristics and insitu stresses acting upon the target formation will most likely be required for success.

The challenge for Operators in the Rockies will be to identify suitable targets and improved technologies in order to capture the next lower level of the resource pyramid. Cavitation of overpressured Cretaceous shales should be evaluated as a strategy for extending production deeper into more hostile conditions.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005