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4. Use two pressure gauges during the test with one gauge serving as a backup, or for verification in cases of questionable data quality. The two gauges do not need to be the same type. (See Appendix, page A-1 for additional information concerning pressure gauges.) 6.0 Conducting the Falloff Test 1. Tag and record the depth to any fill in the test well 2. Simplify the pressure transients in the reservoir • Maintain a constant injection rate in the test well prior to shut-in. This injection rate should be high enough and maintained for a sufficient duration to produce a measurable pressure transient that will result in a valid falloff test. • Offset wells should be shut-in prior to and during the test. If shut-in is not feasible, a constant injection rate should be recorded and maintained during the test and then accounted for in the analysis. • Do not shut-in two wells simultaneously or change the rate in an offset well during the test. 3. The test well should be shut-in at the wellhead in order to minimize wellbore storage and afterflow. (See Appendix, page A-3 for additional information.) 4. Maintain accurate rate records for the test well and any offset wells completed in the same injection interval. 5. Measure and record the viscosity of the injectate periodically during the injectivity portion of the test to confirm the consistency of the test fluid. 7.0 Evaluation of the Falloff Test 1. Prepare a Cartesian plot of the pressure and temperature versus real time or elapsed time. • Confirm pressure stabilization prior to shut-in of the test well • Look for anomalous data, pressure drop at the end of the test, determine if pressure drop is within the gauge resolution 2. Prepare a log-log diagnostic plot of the pressure and semilog derivative. Identify the flow regimes present in the welltest. (See Appendix, page A-6 for additional information.) • Use the appropriate time function depending on the length of the injection period and variation in the injection rate preceding the falloff (See Appendix, page A-10 for details on time functions.) 6