8/16/2023 0 Comments Drawdown testThese observations are eliminated from the regression by assigning weights of 0 to minimize their effects on estimates of well-loss coefficients. These anomalies result primarily from the analytical model not simulating wellbore storage. Transmissivity can be adjusted manually to best explain late-time drawdowns during each step, while visually ignoring anomalies from unsteady flow rates and wellbore storage. Transmissivity estimates are improved with the flow-normalized drawdown plot, because effects of transmissivity on drawdowns are isolated from well-losses (Figure 1). Were improved in the workbook, Pumping_StepDrawdown-2019.xlsm. Well-loss model and parameter estimation techniques Measured s/Qstep depart from straight lines at the beginning of each stepĭrawdowns were analyzed with a flow-normalized drawdown plot in a previouslyĪnd Kuniansky, 2002). Separately because of non-linear, well losses. T = 35.3 / Slopein field units of ft²/d, ft, and gpm. Slope (T/L²) estimated from flow-normalizedĮquation for transmissivity simplifies to, Q CONVERT converts flow to consistent units, e.g. T = 2.303 Q CONVERT / 4 / π / Slope or 0.1832 Q CONVERT Interpretation differs from Cooper-Jacob ( 1946) because discharge is incorporated in the estimated slope. Line, where transmissivity is inversely proportional to the slope ( Lee,ġ982). Transformed data theoretically should plot in a straight Figure 1.- Example of transformed drawdown (s) and flow-rate (Q) data and interpreted slope of s/Q that is inversely proportional to transmissivity. Drawdown ( s) and flow-rate ( Q) data are transformed by plotting drawdowns divided by flow rates ( s/Qstep) against flow-weighted, dimensionless times (Figure 1). The 2019 workbook accounts for linear and non-linear well losses while using graphical techniques to better estimate transmissivity ( Odeh and Jones, 1965). Transmissivity and well-loss coefficients can be estimated from step drawdown data with the workbook, Pumping_StepDrawdown-2019.xlsm. Pumping, during each step, and during recovery so that drawdowns can be Greater discharge rates are pumped during subsequent steps, where three to fiveĭischarge rates typically are tested. Water levels to change minimally at the end of each step ( Halford and Pumping rates are constant during steps which are of sufficient Holding these applicators at a lower angle will reduce coating thickness down to about half of the maximum value.A step-drawdown test is a single-well test that isįrequently conducted after well development to determine well efficiency and correctly (2) A = appropriately sized metering rod B = appropriately sized ACCU DYNE Applicator TM, held at a 45° angle, which applies the maximum possible yield for each coating gate. (1) Wet film thicknesses are approximate, and will vary slightly depending on coating viscosity, percent solids, and substrate absorptiveness. To determine dry film weight, multiply table values by percent solids. WFT,Ĭoating weights are based on a coating density of 1 g/cm 3 (8.345 lb/gal). Please email or call us for advice on your specific application. A Universal Blade Applicator can produce any wet film thickness from 0 to 5 mils or 0 to 25 mils, depending on the design chosen and how it is adjusted. Additionally, many alternative coating thicknesses can be produced with special order metering rods. The following table shows the wet film thicknesses, coverage, and wet film weights that can be produced with our stock metering rods and ACCU COAT Applicators™. Even when the drawdown method does not directly emulate a planned production process, it may be a useful pre-production test to screen materials or drying and curing methods. The tools described in this section open up a variety of test options. For best results, tests should be performed on a Diversified Drawdown Platform™ or a similar flat surface. Drawdowns allow easy evaluation of wettability, opacity, color match, gloss, tack strength, drying weight, dye uniformity, degree of pigment dispersion, and other attributes. Since most coating properties are thickness-dependent, it is imperative that the optimum thickness be determined for each application. The drawdown test is a fundamental laboratory technique which is used to evaluate interactions between flat surfaces (such as film, foil, and paper) and a myriad of inks, coatings, paints, suspensions, adhesives, colloids, powders, etc. Note: drawdown is shown at accelerated speed.
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