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thickness and type of formation being tested along with any geological features such as <br /> natural fractures, a fault, or a pinchout that should be anticipated to impact the test. <br /> Wellbore and Reservoir Data Needed to Simulate or Analyze the Falloff Test <br /> • Wellbore radius, rw-from wellbore schematic <br /> • Net thickness,h - See Appendix,page A-15 <br /> • Porosity, � - log or core data <br /> • Viscosity of formation fluid, µf- direct measurement or correlations <br /> • Viscosity of waste, µwaste - direct measurement or correlations <br /> • Total system compressibility, ct-correlations, core measurement, or well test <br /> • Permeability, k-previous welltests or core data <br /> • Specific gravity of injection fluid, s.g. -direct measurement <br /> • Injection rate, q -direct measurement <br /> Design Calculations <br /> When simulation software is unavailable the test periods can be estimated from empirical <br /> equations. The following are set of steps to calculate the time to reach radial flow from <br /> empirically-derived equations: <br /> 1. Estimate the wellbore storage coefficient, C (bbl/psi). There are two equations to <br /> calculate the wellbore storage coefficient depending on if the well remains fluid filled <br /> (positive surface pressure) or if the well goes on a vacuum (falling fluid level in the well): <br /> a. Well remains fluid.filled: <br /> C=V" Cwaste where, Vw is the total wellbore volume, bbls <br /> Cwaste is the compressibility of the injectate, psi` <br /> b. Well goes on a vacuum: <br /> C= Vu where, Vu is the wellbore volumeper unit length, bbls/ft <br /> P'g <br /> 144-gc <br /> p is the injectate density, psi/ft <br /> g and gr are gravitational constants <br /> 2. Calculate the time to reach radial flow for both the injection and falloff periods. Two <br /> different empirically-derived equations are used to calculate the time to reach radial flow, <br /> tradial flows for the injectivity and falloff periods: <br /> a. Injectivity period: <br /> 200000+12000s)-C <br /> tradial,Jlow � k,h hours <br /> IU <br /> b. Falloff period: <br /> A-3 <br />