Pressure Temperature Log

Exploration Technique: Pressure Temperature Log

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Activities (13)
Areas (13)
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Exploration Technique Information
Exploration Group:	Downhole Techniques
Exploration Sub Group:	Well Log Techniques
Parent Exploration Technique:	Well Log Techniques
Information Provided by Technique
Lithology:
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
Cost Information
Low-End Estimate (USD):	0.600.6 TUSD 0.6 MUSD 0.6 kUSD 60 centUSD / foot
Median Estimate (USD):	1.481.48 TUSD 1.48 MUSD 1.48 kUSD 148 centUSD / foot
High-End Estimate (USD):	2.502.5 TUSD 2.5 MUSD 2.5 kUSD 250 centUSD / foot
Time Required
Low-End Estimate:	1.23 days0.00337 years 29.52 hours 0.176 weeks 0.0404 months / job
Median Estimate:	1.46 days0.004 years 35.04 hours 0.209 weeks 0.048 months / job
High-End Estimate:	2.39 days0.00654 years 57.36 hours 0.341 weeks 0.0785 months / job

Pressure Temperature Log:

After a well is drilled to a desired depth a tool is lowered into the hole that measures temperature and pressure (and often flow) at depth. This information is plotted onto a log and allows production specialists or reservoir engineers to estimate the capacity of a well given the temperature and pressure profile.

Other definitions:Wikipedia Reegle

Introduction

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.

Use in Geothermal Exploration

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.

Field Procedures

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.

Data Access and Acquisition

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.

Best Practices

Allowing the well to reach equilibrium with the surrounding formation is going to provide the most accurate reservoir temperature (Blackwell, et al., 2010).

Potential Pitfalls

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).

References

Blackwell, et al., 2010, http://smu.edu/geothermal/publications/SMU_SECO_CM709_TexasGeothermalReport.pdf

Page	Area	Reference Material
Pressure Temperature Log At Alum Area (DOE GTP)	Alum Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Colrado Area (DOE GTP)	Colado Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Fish Lake Valley Area (DOE GTP)	Fish Lake Valley Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Flint Geothermal Area (DOE GTP)	Flint Geothermal Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Fort Bliss Area (DOE GTP)	Fort Bliss Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Glass Buttes Area (DOE GTP)	Glass Buttes Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Maui Area (DOE GTP)	Maui Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Mccoy Geothermal Area (DOE GTP)	McCoy Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Silver Peak Area (DOE GTP)	Silver Peak Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Soda Lake Area (DOE GTP)	Soda Lake Geothermal Area	GTP ARRA Spreadsheet
Pressure Temperature Log At Steamboat Springs Area (Combs, Et Al., 1999)	Steamboat Springs Geothermal Area	Slimhole Handbook- Procedures And Recommendations For Slimhole Drilling And Testing In Geothermal Exploration
Pressure Temperature Log At Vale Hot Springs Area (Combs, Et Al., 1999)	Vale Hot Springs Geothermal Area	Slimhole Handbook- Procedures And Recommendations For Slimhole Drilling And Testing In Geothermal Exploration
Pressure Temperature Log At Wister Area (DOE GTP)	Wister Geothermal Area	GTP ARRA Spreadsheet

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Pressure Temperature Log

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Exploration Technique: Pressure Temperature Log