Static Temperature Survey
Exploration Technique: Static Temperature Survey
|Exploration Technique Information|
|Exploration Group:||Downhole Techniques|
|Exploration Sub Group:||Well Testing Techniques|
|Parent Exploration Technique:||Well Testing Techniques|
|Information Provided by Technique|
|Thermal:||Extrapolate the true temperature of the formation the well penetrates|
|Low-End Estimate (USD):|| 0.2525 centUSD |
2.5e-10 TUSD / foot
|Median Estimate (USD):|| 0.3535 centUSD |
3.5e-10 TUSD / foot
|High-End Estimate (USD):|| 0.7575 centUSD |
7.5e-10 TUSD / foot
Due to the time constraints imposed by the economics of commercial drilling and utilization of geothermal wells, temperature logs are taken in a well during or soon after circulation of drilling fluids has taken place. During drilling operations the drilling mud and circulation of fluids cause the temperature in the well to be influenced by these external fluids, so temperatures in the well may not be at equilibrium. It can take days to several months for a well to reach its static temperature. In many cases waiting for the well temperature to reach static conditions may take too long so the static or “true” temperature of the well can be extrapolated using various numerical methods. The estimation of true formation temperature is affected mainly by the duration of fluid circulation, the process of heat transfer during drilling, and the drilling technology used.
In a geothermal well static temperature surveys are conducted to find the static or true temperature of the formation.
In order to get temperature measurements that are as close to the static temperature as possible the well must be closed off for some time so that the circulation of fluid is mitigated as much as possible. There are a number of numerical simulators that attempt to reproduce the complete thermal history taking into account the drilling fluid column and surrounding formation. These simulators can be useful for estimating the static temperature without needing to wait for the well to reach equilibrium conditions. The most common numerical method for estimating static formation temperature in the geothermal industry is the line source solution known as the Horner method. Other methods used are the Spherical and radial heat-flow method, and numerical simulations.
Static temperature surveys are expensive and can take a lot of time so they are seldom conducted. Alternatively temperature logs are recorded during the well warm-up phase and used to estimate what the stabilized formation temperature will be.
- Stephen Prensky. 1992. Temperature Measurements in Boreholes: An Overview of Engineering and Scientific Applications. The Log Analyst. 33(3):313-333.
- G. Espinosa-Paredes,A. García-Gutiérrez. 2003. Estimation of static formation temperatures in geothermal wells. Energy conversion and management. 44(8):1343-1355.
- Blue Mountain Geothermal Area
- Chena Area
- Coso Geothermal Area
- Fish Lake Valley Area
- Fort Bliss Area
- Glass Buttes Area
- Hot Pot Area
- Kilauea East Rift Geothermal Area
- Kilauea Summit Area
- Lake City Hot Springs Area
- Lassen Volcanic National Park Area
- Long Valley Caldera Geothermal Area
- Maui Area
- Medicine Lake Area
- Molokai Area
- Newberry Caldera Area
- Reese River Area
- Rio Grande Rift Geothermal Region
- San Andreas Geothermal Region
- Steamboat Springs Area
- U.S. South Region
- Vale Hot Springs Area
- Wister Area