COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Pwfa — Pwf — APskin • From the previous equations, it can be seen that the adjusted bottomhole pressure is directly dependent on a single point, the last injection pressure recorded prior to shut-in. Therefore, an accurate recording of this pressure prior to shut-in is important. Anything that impacts the pressure response, e.g., rate change, near the shut-in of the well should be avoided. Determination of the Appropriate Fluid Viscosity • If the wastestream and formation fluid have similar viscosities, this process is not necessary. • This is only needed in cases where the mobility ratios are extreme between the wastestream, (k/µ)µ„ and formation fluid, (k/µ)f. Depending on when the test reaches radial flow,these cases with extreme mobility differences could cause the derivative curve to change and level to another value. Eliminating alternative geologic causes, such as a sealing fault, multiple layers, dual porosity, etc., leads to the interpretation that this change may represent the boundary of the two fluid banks. • First assume that the pressure transients were propagating through the formation fluid during the radial flow portion of the test, and then verify if this assumption is correct. This is generally a good strategy except for a few facilities with exceptionally long injection histories, and consequently, large waste plumes. The time for the pressure transient to exit the waste front is calculated. This time is then identified on both the log- log and semilog plots. The radial flow period is then compared to this time. • The radial distance to the waste front can then be estimated volumetrically using the following equation: 0.13368•Vwasteinjected rwaste plume — where, Vwaste injected = cumulative waste injected into the completed interval, gal rwaste plume=estimated distance to waste front, ft h = interval thickness, ft =porosity, fraction • The time necessary for a pressure transient to exit the waste front can be calculated using the following equation: 126'73- u,, 'Ct 'Vwaste injected tty = ;r•k-h where, tw=time to exit waste front, hrs Vwasteinjeoted =cumulative waste injected into the completed interval, gal h= interval thickness, ft A-13