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The use of high energy material to stimulate production has been practiced in the oilfield since early in the industry's history. While the materials used for stimulation have progressed from explosive materials to propellants, the basic concept remains the same. A highly energetic material is burned in the wellbore and the gasses and energy released cause the rapid pressurization and breakdown of the formation. This breakdown is capable of generating multiple fractures with certain geometric properties. To investigate and confirm the generation of propellant induced fractures in low permeabililty formations, a large scale laboratory test was designed and conducted at the TerraTek, Inc. laboratories in Salt Lake City, Utah. The test was conducted on a 30"x30"x36" Colton Sandstone block that was loaded in a poly-axial stress frame to predetermined reservoir conditions. A scaled wellbore, drilled in the center of the block, contained the propellant charge. After the block was properly stressed, the propellant charge was deflagrated. The block contained several pressure probes imbedded in the block and located in the wellbore that were capable of sampling at extremely high rates (milliseconds) to capture the full response of the propellant burn. Upon completion of the deflagration, the block was removed from the test frame and cut horizontally to examine the fracture pattern generated by the propellant burn. Each half was later split along the primary fracture to examine the height growth and fracture lengths generated by the propellant stimulation. This paper discusses the test design and execution, the resulting fracture geometries and analyzes the pressure responses witnessed during the propellant deflagration. The results show laboratory verification of some propellant fracture theories and provide insight to the effects of propellant deflagration in field applications. |
