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170000•C•eo.>4-s <br /> trad"'flow > k.h flours <br /> IU <br /> The wellbore storage coefficient is assumed to be the same for both the injectivity and <br /> falloff periods. The skin factor, s, influences the falloff more than the injection period. <br /> Use these equations with caution, as they tend to fall apart for a well with a large <br /> permeability or a high skin factor. Also remember,the welltest should not only reach <br /> radial flow, but also sustain radial flow for a timeframe sufficient for analysis of the <br /> radial flow period. As a rule of thumb, a timeframe sufficient for analysis is 3 to 5 times <br /> the time needed to reach radial flow. <br /> 3. As an alternative to steps 1 and 2,to look a specific distance"L" into the reservoir and <br /> possibly confirm the absence or existence of a boundary, the following equation can be <br /> used to estimate the time to reach that distance: <br /> 948.0' 'c, • Lbo"d" <br /> tboundary — k hours <br /> where, Lboundary=feet to boundary <br /> tboundary=time to boundary, hrs <br /> Again,this is the time to reach a distance"L" in the reservoir. Additional test time is <br /> required to observe a fully developed boundary past the time needed to just reach the <br /> boundary. As a rule of thumb, to see a fully developed boundary on a log-log plot, allow <br /> at least 5 times the time to reach it. Additionally, for a boundary to show up on the <br /> falloff, it must first be encountered during the injection period. <br /> 4. Calculate the expected slope of the semilog plot during radial flow to see if gauge <br /> resolution will be adequate using the following equation: <br /> 162.6•q•B <br /> msemilog — k•h <br /> P <br /> where, q=the injection rate preceding the falloff test, bpd <br /> . B = formation volume factor for water, rvb/stb (usually assumed to be 1) <br /> Considerations for Offset Wells Completed in the Same Interval <br /> Rate fluctuations in offset wells create additional pressure transients in the reservoir and <br /> complicate the analysis. Always try to simplify the pressure transients in the reservoir. Do not <br /> simultaneously shut-in an offset well and the test well. The following items are key <br /> considerations in dealing with the impact of offset wells on a falloff test: <br /> • Shut-in all offset wells prior to the test <br /> • If shutting in offset wells is not feasible, maintain a constant injection rate prior to and <br /> during the test <br /> • Obtain accurate injection records of offset injection prior to and during the test <br /> A-4 <br />