KTSI
WHY RUN RECORDERS
Recorders are run into a well to monitor the pressure & temperature at, or as close as possible to, the producing formation during a Flow & Build-Up test. When downloaded, this data is used for analysis in determining things like Reservoir Pressure, Skin and Permeability. The permeability of a rock is basically how easy it is to move a fluid through it and we measure by using a pressure drop or buildup over a time period. Skin is a further restriction to the flow right at the wellbore and can be caused by a finer material like drilling mud causing the flow to be slowed down even more.
Static gradients are done primarily to determine Liquid Levels & Bottom-Hole Pressure/Temperature. Engineers like to compare Liquid Levels & Pressures from Initial Gradients to Final Gradients after a Production test – this really helps with an in-depth analysis.
STATIC GRADIENT PROCEDURES
When performing a static gradient, please try to keep all your stops going in the same direction (the reporting program only knows how to draw straight lines). When making the gradient stops, please try to make at least 2 stops in either Gas or Liquid (depending on a high or low liquid level in the Tubing or Wellbore). This will eliminate the need to use an 'Assumed' gas or liquid gradient,
and provide more accurate results.
*please note that this information is not intended to be used to supersede a customers request, as we will ultimately do the job they ask us to do.
Recommended Gradient (This can be used in the reverse, if the gradient is started from MPP or the set depth)
Stop 1 (Surface) - 5 minutes
Stop 2 - 5 minutes
Stop 3 - 5 minutes
Stop 4 - 5 minutes
Stop 5 - 5 minutes
MPP minus 90 m (295 ft) - 5 minutes
MPP minus 60 m (195 ft) - 5 minutes
MPP minus 30 m (95 ft) - 5 minutes
MPP (or as close as possible) - 10 minutes (or 2.25 hrs if shut in for less than 14 Days
& is to be AER acceptable)
MPP plus 10 m (30 ft) - 5 minutes
RECORDER RETRIEVAL
When performing a reverse gradient after latching recorders, pull up to the next stop after confirming a successful latch. Also, when performing a Gradient on the way out of the hole,
please base your Gradient stops on the bottom of the recorders, not the bottom of the pulling tool
(if it was zero'd to GL or CF). This difference is quite noticeable when the recorders are in liquid and affects calculation of the formation gradient.
ELECTRONIC MEMORY
RECORDERS
CALIBRATIONS:
AER Directive 40 (section 8.3) states: “The service companies are required to maintain adequate calibration history on each gauge, and be prepared to submit this data to the AER upon request. However, the date of last calibration is required on every pressure test report”.
This is VERY important.
Oil and Gas Conservation Regulations (Section 11.110) states:
"The operator of a well shall use instruments that meet the following requirements:
1. any dead weight gauge that is used to calibrate wire line instruments for taking subsurface pressure measurements must be certified annually by a calibration laboratory accredited by the Standards Council of Canada through the Calibration Laboratory Assessment Service of the National Research Council of Canada or another calibration laboratory certified as meeting ISO/IEC 17025 standards;
2. the calibration shall be obtained using an approved dead weight gauge at a minimum frequency
(i) within 3 months prior to use in any survey,
(ii) twice after repairs or abnormal stresses, and
(iii) once annually under the necessary conditions to check temperature sensitivity."
PROGRAMMING: This too is important. We have seen quite a few recorders that have not been programmed for the same sample rates. True, the recorders do track time-wise, but when the filtered data table is included in the final report, it “appears” that one recorder quits before the other (sometimes a few pages before the other). It is recommended to have standard programs for gradients and/or extended tests saved into the recorder software. It would be advisable to create a company/station standard for the different tests, so all operators could program with the click of a button, rather than trying to recall how they programmed the previous recorder.
AER REQUIRMENTS
Initial subsurface pressures are required on productive oil & gas wells as follows:
· Gas Wells – on all productive wells, within the first 3 months of production (one well per pool per section)
· Oil Wells – on all productive exploratory, discovery, development or step-out wells; prior to any sales or production, other than test production (one well per pool per quarter section).
Annual pressure surveys must be conducted by year end (December 31) for oil & gas pools,
as specified in the annual survey schedules.
25% of the producing well count in oil pools based on a quarter section.
25% of the producing well count in gas pools based on a full section.
For both the Initial & Annual tests, the AER requires that the well be “Stable” in order to be
an acceptable pressure survey.
There is a 2 kPa/hr rule for Stability:
Flow & Build-Up: If the well has been shut in for less than 14 days (336 hrs), then the pressure must not change more than 2 kPa per hour (12 kPa total) over the last 6 hours of the test in order for the measured pressure to be AER acceptable. If the pressure changes more than the allowed 2 kPa/hr, then a Buildup or Falloff Analysis may be needed.
Static Gradient: Technically, the same 2 kPa/hr rule applies, but the AER has given a bit of a cushion for gradients. If the well has been shut in for less than 14 days (336 hrs), then the final stop (MPP or as close as possible), has to be a minimum 2 hrs (2.25 hrs is recommended).
During this time, the well must not build more than 2.5 kPa per hour or a 5 kPa total over a 2 hour duration.
If the well has been shut in for more than 14 days (336 hrs), then the pressure build rate is not an issue, and a 10 minute stop at MPP is adequate.