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APPENDIX <br /> Pressure Gauge Usage and Selection <br /> Usage <br /> • EPA recommends that two gauges be used during the test with one gauge serving as a <br /> backup. <br /> • Downhole pressure measurements are less noisy and are required. <br /> • A bottomhole surface readout gauge (SRO)allows tracking of pressures in real time. <br /> Analysis of this data can be performed in the field to confirm that the well has reached <br /> radial flow prior to ending the test. <br /> • The derivative function plotted on the log-log plot amplifies noise in the data, so the use <br /> of a good pressure recording device is critical for application of this curve. <br /> • Mechanical gauges should be calibrated before and after each test using a dead weight <br /> tester. <br /> • Electronic gauges should also be calibrated according to the manufacturer's <br /> recommendations. The manufacturer's recommended frequency of calibration, and a <br /> copy of the gauge calibration certificate should be provided with the falloff testing report <br /> demonstrating this practice has been followed. <br /> Selection <br /> • The pressures must remain within the range of the pressure gauge. The larger percent of <br /> the gauge range utilized in the test, the better. Typical pressure gauge limits are 2000, <br /> 5000, and 10000 psi. Note that gauge accuracy and resolution are typically a function of <br /> percent of the full gauge range. <br /> • Electronic downhole gauges generally offer much better resolution and sensitivity than a <br /> mechanical gauge but cost more. Additionally, the electronic gauge can generally run for <br /> a longer period of time, be programmed to measure pressure more frequently at various <br /> intervals for improved data density, and store data in digital form. <br /> • Resolution of the pressure gauge must be sufficient to measure small pressure changes at <br /> the end of the test. <br /> Test Design <br /> General Operational Considerations <br /> • The injection period controls what is seen on the falloff since the falloff is replay of the <br /> injection period. Therefore, the injection period must reach radial flow prior to shut-in of <br /> the well in order for the falloff test to reach radial flow <br /> • Ideally to determine the optimal lengths of the injection and falloff periods, the test <br /> should be simulated using measured or estimated reservoir parameters. Alternatively, <br /> A-1 <br />