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minimize the wellbore storage period • The condition of the well,junk in the hole, wellbore fill or the degree of wellbore damage (as measured by skin) may impact the length of time the well must be shut-in for a valid falloff test. This is especially critical for wells completed in relatively low transmissibility reservoirs or wells that have large skin factors. • Cleaning out the well and acidizing may reduce the wellbore storage period and therefore the shut-in time of the well • Accurate recordkeeping of injection rates is critical including a mechanism to synchronize times reported for injection rate and pressure data. The elapsed time format usually reported for pressure data does not allow an easy synchronization with real time rate information. Time synchronization of.the data is especially critical when the analysis includes the consideration of injection from more than one well. • Any unorthodox testing procedure, or any testing of a well with known or anticipated problems, should be discussed with EPA staff prior to performing the test. • If more than one well is completed into the same reservoir,operators are encouraged to send at least two pulses to the test well by way of rate changes in the offset well following the falloff test. These pulses will demonstrate communication between the wells and, if maintained for sufficient duration, they can be analyzed as an interference test to obtain interwell reservoir parameters. Site Specific Pretest Planning 1. Determine the time needed to reach radial flow during the injectivity and falloff portions of the test: • Review previous welltests, if available • Simulate the test using measured or estimated reservoir and well completion parameters • Calculate the time to the beginning of radial flow using the empirically-based equations provided in the Appendix. The equations are different for the injectivity and falloff portions of the test with the skin factor influencing the falloff more than the injection period. (See Appendix, page A-4 for equations) • Allow adequate time beyond the beginning of radial flow to observe radial flow so that a well developed semilog straight line occurs. A good rule of thumb is 3 to 5 times the time to reach radial flow to provide adequate radial flow data for analysis. 2. Adequate and consistent injection fluid should be available so that the injection rate into the test well can be held constant prior to the falloff. This rate should be high enough to produce a measurable falloff at the test well given the resolution of the pressure gauge selected. The viscosity of the fluid should be consistent. Any mobility issues (k/µ) should be identified and addressed in the analysis if necessary. 3. Bottomhole pressure measurements are required. (See Appendix,page A-2 for additional information concerning pressure gauge selection.) 5