What is a well step drawdown test?
A Step-Drawdown Test is an accelerated pumping test for a single well, designed to estimate the aquifer characteristics and performance of a pumped well under three successively higher pumping rates or steps under controlled flow. The test is suitable for a design production rate of 35 gallons per minute (gpm) or less.
What is the draw down at the pumping well?
Drawdown is a term applied to the maximum lowering of the groundwater table caused by pumping or artesian flow (Figure D60). It is measured as the difference between the initial level of water in a well before pumping, and the static, or stabilized, level of water after a long period of pumping.
How do you calculate pressure drawdown?
∆P= Pressure drawdown = SBHP – Pwf Example: If SBHP = 200 bar, and Pwf = 80 bar; therefore the Pressure drawdown (∆P) = 200 – 80 = 120 bar. The amount of pressure drawdown dictates the amount of flow into the wellbore or production. The higher the pressure drawdown is, the higher the production rate.
How do you calculate pump drawdown?
Subtract the measurements you collect as the pump is running from the static water level. The difference is the drawdown. For example, if the static water level is 1 foot below the top of the casing and the water level after one hour is 3 feet below the top of the casing, the drawdown at one hour of pumping is 2 feet.
What is pumping test method?
A pumping test consists of pumping groundwater from a well, usually at a constant rate, and measuring the change in water level (drawdown) in the pumping well and any nearby wells (observation wells) or surface water bodies during and after pumping (see Figure 1).
What is pressure draw down?
Pressure drawdown is the difference between the reservoir pressure and the flowing wellbore pressure, which drives fluids from the reservoir into the wellbore. The difference between reservoir and flowing wellbore pressure is called pressure drawdown, and this has the greatest impact on the production rate of a well.
What is the pressure drawdown?
The differential pressure that drives fluids from the reservoir into the wellbore. The drawdown, and therefore the production rate, of a producing interval is typically controlled by surface chokes.
How do you calculate drawdown capacity?
Therefore, for any given tank, drawdown equals the volume of air at cut-in minus the volume of air at cut-out. Stated as a mathematical formula, taking into consideration the total volume of a pressure tank, it looks like this: Drawdown = P1V / P2 – P1V / P3 where, P1 is the pre-charge pressure.
How is water drawdown measured?
Calculate the drawdown by subtracting the static level from the pumping level. saving well testing data. Also listed are some ways that you can use well drawdown measurements. Operating records should contain information about the static and pumping levels of a well, plus other important data.
What is the maximum pumping rate in a step drawdown test?
Pumping Rates Pumping rates used in a step-drawdown test should encompass the maximum design pumping rate for the well (Qmax). The following table shows one possible scheme for the pumping rates in a step-drawdown test consisting of four steps: Step Rate 1 0.5Qmax 2 0.75Qmax 3 Qmax 4 1.25Qmax Well Loss Equation
What is a step drawdown test in a well?
In a step-drawdown test, the discharge rate in the pumping well is increased from an initially low constant rate through a sequence of pumping intervals (steps) of progressively higher constant rates. Each step is typically of equal duration, lasting from approximately 30 minutes to 2 hours (Kruseman and de Ridder 1994).
How do you calculate the drawdown of a pump?
The total drawdown is the sum of the drawdown from the forma- tion and the drawdown from the pump equipment, total drawdown = s f + s w = C f Q + C w Q 2. The step- drawdown test runs the pump at several flow rates by adjusting the downstream resistance to flow. Different drawdowns are observed as the drawdown ʻsettles intoʼ a steady value.
What is a step-drawdown test?
A step-drawdown test is a single-well test that is frequently conducted after well development to determine well efficiency and correctly size the production pump. Pumping rates are constant during steps which are of sufficient duration, about 1–4 hours, for water levels to change minimally at the end of each step ( Halford and Kuniansky, 2002 ).