Frequently Asked Questions

Q. I have drilled a cluster of ten wells in an area and they have been shut in since they were drilled and completed. How can I evaluate these wells without drilling a new well and taking and evaluating a core sample?  How many wells should I test?

A. Use WellDog’s Critical Gas Content™ reservoir evaluation services to judge gas saturation levels and gas content in the field.  With the resultant information, you can make well-informed decisions regarding which wells to permit and which wells to produce.  WellDog’s services can be performed in any wellbore that has been completed (either open hole or with perforations) and that contains reservoir fluid.

A detailed view of all wells provides the best data to support field operations decisions and reservoir production optimization strategies.  And with WellDog’s volume pricing options, you can finally afford to do so.

However, if you’d like to limit the number of wells tested, we suggest that you test at least a representative sample.  Variability in a reservoir is difficult to estimate, and is not a standard characteristic.  Our experience shows that you need to test at least one well out of a three- or five-well pod in order to create even a rudimentary view of trends in reservoir properties.

A. You may be nearly at production — or you may never get there. Answering this critical question is a key part of what WellDog’s TopSide Solutions™ service provides.

Our service gives you two very important reservoir parameters (in addition to gas content): the critical desorption pressure of methane in your seam, and the saturation of methane in your seam.  By comparing the critical desorption pressure to your reservoir pressure during water production, you can determine if you are nearly at production.  If you are unable to effectively reduce your reservoir pressure below the critical desorption pressure, you may have an uneconomic field.

The good news is that even for a well that has been producing only water, WellDog’s CDP services can still be used to determine how far a well is from reaching a gas production state. This allows you to make an informed abandonment decision, or to show your stakeholders that continued dewatering is a good idea.  The gas content data that WellDog also provides as part of the  service will help you answer the longer-term question of "will dewatering be worth the effort?."

Q. How does the detector determine gas content?

A. By analyzing solution gas levels (as well as other physical and chemical properties) in reservoir fluids and correlating them to gas content via an adsorption isotherm that is representative of the coal. WellDog’s patented detector uses Raman Spectroscopy to measure partial pressure in wellbore fluid. These partial pressure measurements are then used, in conjunction with an industry standard or seam-specific adsorption isotherm, to determine the critical desorption pressure and gas content of the individual coal seams.

For more detailed information on Raman Spectroscopy please see the Raman Spectroscopy Technical Brief.

Q. When do I need to calibrate the WellDog measurement for reservoir fluids?

A. WellDog automatically calibrates for most known coalbed reservoir properties, including pressure, temperature and general water quality.  If you are working in an area in which the solution gas levels may be affected by unusual compounds in the wellbore fluids, or if you have serious problems with wellbore fluid contaminants such as coal fines, drilling fluids and completion or stimulation residuals, then you may need to run a custom calibration.  Some customers also run custom calibrations when they desire the highest levels of accuracy for coal seams that are primary development targets.

Q. How long does the WellDog Reservoir Analysis Service take?

A. Typically, we are in and out of your well location within 3 hours. Data is sent via satellite communications directly to the WellDog Data Analysis and Interpretation Center for immediate processing; in cases where geology is more complicated, we may run multiple tests and so require more time at the well site.  Preliminary results are usually available within hours of leaving the wellsite and final analyses are available within three business days.

For more detailed information about what WellDog does while on location please see the Operational Overview.

Q. I have a well completed in multiple zones.  Can you help me determine characteristics of all the seams?

A. Yes. By completing your seams from the bottom to the top, and using retrievable bridge plugs to isolate the zones along the way, we can quickly analyze the critical desorption pressure, required drawdown, and gas content of all of your target zones in just one wellbore.

In any case, please contact us for help in developing a successful testing program - call 307-742-6340.