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|
|Hydrological:||Permeability of the well|
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.
An injectivity test is a method for testing a wells permeability. Injectivity tests can be useful indicators of the likely productivity of a well.
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.
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.
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.
- 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
- Hagen Hole. 2008. Geothermal Well Completion Tests. In: Petroleum Engineering Summer School; 2008/06/09; Dubrovnik, Croatia. N/A: N/A; p. N/A
- Chena Geothermal Area
- Dixie Valley Geothermal Area
- Fenton Hill HDR Geothermal Area
- Long Valley Caldera Geothermal Area
- Newberry Caldera Area
- Raft River Geothermal Area
- Reese River Area
- Steamboat Springs Area
- Vale Hot Springs Area