METHOD AND APPARATUS TO ISOLATE A FORMATION ZONE

摘要

A method and apparatus are disclosed which allow isolation of a plurality of zones for treatment particularly sand fracturing. The lowermost barrier can be pumped through tubing (12) and anchored in cased or open holes. In the preferred embodiment, the pumped plug (20) has a visco-elastic member (74) which contains a particulate aggregate mixture (87), such as described in U.S. Patent 5,417 285. The visco-elastic material is subjected to a force which change its shape in that the material obstructs the wellbore. The shape change also accomplishes dehydration of the material within the visco-elastic enclosure by virtue of fluid displacement, resulting from a volume reduction, hardening it so that a plug using the visco-elastic material is formed. Thereafter, a packer (14) on the rubing string (12) is set to isolate the zone for sand fracturing. The process can be repeated without tripping out of the bole as additional plugs are pumped through tubing and the process is prepared. At the conclusion of the fracturing, the various plugs, which are of simple and economical construction, can be readily milled out