Exploration Technique: Stress Test
|Exploration Technique Information|
|Exploration Group:||Downhole Techniques|
|Exploration Sub Group:||Well Testing Techniques|
|Parent Exploration Technique:||Well Testing Techniques|
|Information Provided by Technique|
|Stratigraphic/Structural:||Fracture distribution and ambient tectonic stresses|
|Hydrological:||Fluid flow direction|
A stress test begins with collecting downhole images of the borehole walls. The images are analyzed by geologists for rock type, hydraulic characteristics, and fracture location and orientation. Hydraulic fracturing stress tests are sometimes conducted following the analysis and designed to measure and characterize the formation stress fields. The main purpose of conducting stress tests are to locate planes in the borehole of shear and normal stresses to predict how the well will respond to hydraulic fracturing. After hydraulic fracturing has been conducted the stress fields within the well can be more accurately defined and further hydraulic fracturing may take place.
Stress tests are used mainly during EGS projects. Determining the ambient state of stress in the formation is important for defining fracture patterns and fluid transport direction.
Stress tests begin with imaging of the borehole walls in areas of interest. The images are analyzed for fracture orientation, distribution, and size. Natural fractures, drilling induced tensile wall fractures, and borehole breakouts are identified. Then a hydraulic fracturing plan can established based on the data. After hydraulic fracturing is conducted borehole images are taken again and analyzed.
Stress tests normally begin with imaging of the borehole walls for analysis of fracture patterns and indications of stress zones. After a visual analysis hydraulic fracturing is conducted and the borehole walls should be imaged again to analyze how the well responded and determine any zones where permanent permeability might be established.
Stress tests are expensive and in very hot geothermal environments where the rock becomes plastic fractures might close up soon after the hydraulic fracturing.
- Judith M. Sheridan,Stephen H. Hickman. 2004. In situ stress, fracture, and fluid flow analysis in Well 38C-9: an enhanced geothermal system in the Coso geothermal field. In: Twenty-Ninth Workshop on Geothermal Reservoir Engineering. Twenty-Ninth Workshop on Geothermal Reservoir Engineering; 2013/01/01; Stanford, California. Stanford, California: US Geological Survey; p. 9
- U.S. Geological Survey. Borehole Imaging of In Situ Stress Tests at Mirror Lake Research Site [Internet]. 2013. U.S. Geological Survey. [cited 2013/10/16]. Available from: http://water.usgs.gov/ogw/bgas/toxics/ml_bips.html
|Page||Area||Activity Start Date||Activity End Date||Reference Material|
|Stress Test At Coso Geothermal Area (2004)||Coso Geothermal Area||2004||2004|