Pressure Temperature Log
(Redirected from PT Spinner Log)
Exploration Technique: Pressure Temperature Log
|Exploration Technique Information|
|Exploration Group:||Downhole Techniques|
|Exploration Sub Group:||Well Log Techniques|
|Parent Exploration Technique:||Well Log Techniques|
|Information Provided by Technique|
|Stratigraphic/Structural:||Perturbations in temperature or pressure can be indicative of faults or other structural features|
|Hydrological:||fluid cirulation, over-pressured zones, and under-pressured zones.|
|Thermal:||Temperature profile with depth|
|Low-End Estimate (USD):|| 0.6060 centUSD |
6.0e-10 TUSD / foot
|Median Estimate (USD):|| 1.48148 centUSD |
1.48e-9 TUSD / foot
|High-End Estimate (USD):|| 2.50250 centUSD |
2.5e-9 TUSD / foot
|Low-End Estimate:|| 1.23 days0.00337 years |
0.0404 months / job
|Median Estimate:|| 1.46 days0.004 years |
0.048 months / job
|High-End Estimate:|| 2.39 days0.00654 years |
0.0785 months / job
Temperature/pressure logs are used to identify certain characteristics of a geothermal reservoir. The primary goal of utilizing a temperature/pressure tool is to locate the most suitable zones of a reservoir to produce from. Temperatures change with depth, sometimes there are structural or hydrological controls that can push the temperature up or down at a specific depth, the temperature depth logging tool is able to locate these perturbations at depth. Similarly, pressures within a well can fluctuate depending on the depth, formation, or fluid circulation. A high grade geothermal resource has high temperatures and high pressures, and a temperature/pressure log is a tool to locate the best production zone within a well.
The geothermal industry relies on pressure/temperature tools to locate where the best zone for production is at depth. Most of this technology was originally used for petroleum exploration, but quickly became an obvious application for geothermal exploration. Initially the tools would be damaged due to the high temperatures encountered in a high grade geothermal system, so various tool companies designed temperature pressure tools that could survive the extreme environments encountered within a geothermal system. Uses in geothermal exploration include locating the capacity of steam entries and document the pressure and temperature profile of a well. These two parameters are very useful when estimating the capacity of a given well, and ultimately the resource.
After a well has been drilled and fluids have stopped circulating the temperature of the well is expected to equilibrate with the surrounding rocks in a matter of hours to days. Once equilibration is reached a temperature-pressure tool is lowered into the hole to take measurements as it descends into the hole. This is done at the well head.
There are a number of tools that can be used for logging temperature and pressure in a geothermal well. Data is sent up the hole to a computer and can be monitored in real time.
Allowing the well to reach equilibrium with the surrounding formation is going to provide the most accurate reservoir temperature (Blackwell, et al., 2010).
Fluids are being circulated in the hole during drilling, this cools the rocks in the immediate vicinity of the well. Taking temperature measurements too soon after drilling can cause erronerous measurements that are lower than the true formation temperature (Blackwell, et al., 2010).
Blackwell, et al., 2010, http://smu.edu/geothermal/publications/SMU_SECO_CM709_TexasGeothermalReport.pdf
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