Injectivity Test

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Exploration Technique: Injectivity Test

Exploration Technique Information
Exploration Group: Downhole Techniques
Exploration Sub Group: Well Testing Techniques
Parent Exploration Technique: Well Testing Techniques
Information Provided by Technique
Lithology:
Stratigraphic/Structural:
Hydrological: Permeability of the well
Thermal:
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Injectivity Test:
A well testing technique conducted upon completion of a well. Water is pumped into the well at a constant rate until a stable pressure is reached then the pump is turned off and the rate at which pressure decreases is measured. The pressure measurements are graphed and well permeability can be calculated.
Other definitions:Wikipedia Reegle


 
Introduction
An injectivity test is one of several well tests typically preformed on geothermal production and injection wells upon completion of drilling operations. The purpose of the injectivity test is to get an indication of the total permeability of the well. The injectivity test will provide the well with an injectivity index rating, which is usually a reliable indicator of well performance.
 
Use in Geothermal Exploration
An injectivity test is a method for testing a wells permeability. Injectivity tests can be useful indicators of the likely productivity of a well.

 
Field Procedures
A pressure element is lowered into the well and set at some depth, preferably at or near a major permeable zone; however the permeable zones may or may not be confirmed at the time of the test. Once the pressure element is in place water is pumped into the well at three or four different pumping rates. The first pumping rate is the lowest and each successive pumping rate is higher. The first pumping rate is initiated and held at a constant rate until the well pressure stabilizes. Once the pressure in the well stabilizes the next pumping rate is initiated and held constant until the pressure in the well stabilizes again. This process is repeated for three or four pumping rates. When the well pressure has stabilized after the highest pumping rate, the pump is turned off and the well is allowed to return to its natural pressure. The well pressure vs. time is recorded during the entire process. This procedure may be repeated numerous times with the pressure element at different depths for each test.

Example of an injectivity test on a production well at the Krafla Geothermal Area in Northern Iceland. The top line shows the reservoir response to the pressure increases, the bottom solid line shows the flow rate in increasing steps from the well head pump.[1]



 
Best Practices
An injectivity test is best conducted before removal of the drill rig equipment, so that the drill pump can be used for the injectivity test.[2]
 
Potential Pitfalls
An injectivity test is a good indicator of a wells productivity; however the injectivity index is not always proportional to the productivity index, so the predictions are not always completely accurate.[1]








 
References
  1. 1.0 1.1 Gudni Axelsson,Benedikt Steingrímsson. 2012. Logging, Testing and Monitoring Geothermal Wells. In: Short Course on Geothermal Development and Geothermal Wells. United Nations University Geothermal Training Programme; 2012/03/11; Santa Tecla, El Salvador. Reykjavik, Iceland: UNU; p. 20
  2. Hagen Hole. 2008. Geothermal Well Completion Tests. In: Petroleum Engineering Summer School; 2008/06/09; Dubrovnik, Croatia. N/A: N/A; p. N/A


Page Area Activity Start Date Activity End Date Reference Material
Injectivity Test At Chena Geothermal Area (Holdmann, Et Al., 2006) Chena Geothermal Area 2005 2007


Injectivity Test At Dixie Valley Geothermal Area (Benoit, Et Al., 2000) Dixie Valley Geothermal Area 1997 1997


Injectivity Test At Dixie Valley Geothermal Area (Morin, Et Al., 1998) Dixie Valley Geothermal Area 1998 1998


Injectivity Test At Fenton Hill HDR Geothermal Area (Dash, Et Al., 1983) Fenton Hill HDR Geothermal Area


Injectivity Test At Fenton Hill HDR Geothermal Area (Grigsby, Et Al., 1983) Fenton Hill HDR Geothermal Area


Injectivity Test At Long Valley Caldera Geothermal Area (Farrar, Et Al., 2003) Long Valley Caldera Geothermal Area 1999 1999


Injectivity Test At Long Valley Caldera Geothermal Area (Morin, Et Al., 1993) Long Valley Caldera Geothermal Area 1992


Injectivity Test At Newberry Caldera Area (Combs, Et Al., 1999) Newberry Caldera Area


Injectivity Test At Raft River Geothermal Area (1979) Raft River Geothermal Area 1979 1979


Injectivity Test At Reese River Area (Henkle & Ronne, 2008) Reese River Area


Injectivity Test At Steamboat Springs Area (Combs, Et Al., 1999) Steamboat Springs Area


Injectivity Test At Vale Hot Springs Area (Combs, Et Al., 1999) Vale Hot Springs Area



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