Well Rehabilitation via the Ultrasonic Method and Evaluation of Its Effectiveness from the Pumping Test

Abstract

The exploitation of groundwater reserves, especially for drinking purposes, is becoming increasingly important. This fact has created the need to maintain wells in the best possible functional condition. However, wells are subject to an ageing process during intensive use, which entails an increase in up-to-date resistances in the well itself and its immediate surroundings (the skin zone). This causes a decrease in the efficiency of the well (a decrease in the pumped quantity, a decrease in the specific yield, an increase of the drawdown in the well, and creation of the skin zone). The increased hydraulic gradient in the skin zone causes an increase in the inflow rate to the well, thereby inducing the movement of fine material towards the casing. This material can clog the well casing and injection ports, which is compounded by an increase in chemical and biological plugging of the skin zone. In cooperation with the company sonic technologies, GmbH. (Sailauf, Germany), an experimental ultrasonic technology-based well rehabilitation assembly was developed and successfully tested. This article describes the prototype development of the ultrasonic device, including its incorporation into the rehabilitation set and a demonstration of its pilot deployment in the MO-4 pumping well in Czech Republic with an evaluation of the rehabilitation effects using the authors’ software (Dtest_ULTRA). Based on visual inspection and the results of hydraulic and geophysical analysis, the high efficiency of the tested technology was demonstrated in virtually all monitored parameters, where an improvement in the range of 25–55% compared to the original condition was identified.

INV-FLOW: New Possibilities to Evaluate the Technical Condition and Function of Extraction Wells

“…Agarwal [35] solved the equation of unsteady radial flow to a real well in cylindrical coordinates, considering additional resistance (skin effect) and the actual well volume (wellbore storage) [35,36] at the beginning of the pumping test. Using Algorithm 368 [37], Equation (6) was derived in [38][39][40][41] for the slope of the first straight line of the pumping test (s D * ) as a function of the skin factor, W (coefficient of additional resistance), and the dimensionless wellbore storage, C D [24,36], which precedes, in groundwater hydraulics, the standard Cooper-Jacob section-the Cooper-Jacob straight line [38] (Figure 3).…”

“…Agarwal [35] solved the equation of unsteady radial flow to a real well in cylindrical coordinates, considering additional resistance (skin effect) and the actual well volume (wellbore storage) [35,36] at the beginning of the pumping test. Using Algorithm 368 [37], Equation ( 6) was derived in [38][39][40][41] for the slope of the first straight line of the pumping test (sD * ) as a function of the skin factor, W (coefficient of additional resistance), and the dimensionless wellbore storage, CD [24,36], which precedes, in groundwater hydraulics, the standard Cooper-Jacob section-the Cooper-Jacob straight line [38] (Figure 3). 𝑠 * = 0,166 𝑊 + 0.1908 (𝑙𝑜𝑔 𝐶 ) + 0.2681 (6) where sD * is the dimensionless drawdown for the first straight line (-), W is the coefficient of additional resistance (skin factor) (-), and CD is the dimensionless wellbore storage (the wellbore storage effect occurs at early pumping times, during which the water withdrawn is not derived from the aquifer but from the water volume originally stored in the well casing [36,39]).…”

Effective water well rehabilitation using a combined ultrasonic-mechanical method

“…increased demands on electrical power to be delivered and larger power lines and radiators required. The resulting size of the unit may then become an important issue, as heavy equipment will be needed to manipulate it, such as a crane for lowering the ultrasound generator into the well and a truck with a 20 kW electrical generator to power the ultrasound excitation source (Kahuda et al 2021).…”

Evaluation of Well Improvement and Water Quality Change before and after Air Surging in Bedrock Aquifers

“…When a well is developed and used for a long time, the casing inside the well becomes corroded or various substances become deposited on the screen, causing clogging that degrades well performance. Well clogging is caused by decreasing amounts of water pumped in the same drawdown in the well, and it also increases the hydraulic gradient and flow velocity around the well [2,3]. Subsequently, the specific yield of the well (well efficiency), which is defined as the ratio of the pumped quantity to the drawdown, decreases [4].…”