The issue of data quality is something that everyone needs to pay attention to. Bad data can cause bad results such as incorrect diagnostic analysis, incorrect interpretation of down hole dynamometer card shape, wrong rod and gearbox loading, etc. If your pumping unit, stroke length, pump size, etc. are wrong, the results that you will get from a program such as RODDIAG or RODSTAR will not be correct. Fortunately, XDIAG with its built-in expert knowledge can warn you about the possibility of bad input data or can even correct the data for you.
One of the most common errors is caused by a load cell that is off and is reading either too high or too low as compared to the true loads. XDIAG and XSPOC can successfully detect and correct this error. This allows you to get good results even though the original data was not correct. However, another problem we have run across in many cases is bad position data due to a malfunctioning or incorrectly set position transducer in a Rod Pump Controller. This often occurs when the "top of stroke" setting that some POCs require you to set is either done incorrectly or has changed because the unit's stroke length or pumping speed was changed. This typically causes the surface dynamometer card to be rotated either to the left or to the right as compared to the true data. This in turn causes a rotation or tilt on the downhole dynamometer card that can result in misinterpretation of the pump condition. The following Figure shows an XDIAG output screen that is an example of this problem. This can be corrected at the POC by setting the top of stroke correctly.