Slug Test Method Research Articles

The Application and Analysis of Slug Test on Determining the Permeability Parameters of Fractured Rock Mass

Based on the proposed calculation method for determining the different dip angle fracture permeability coefficients derived from the well flow vibration equation and the self-developed slug test system, research on the slug test in a field in fractured rock mass was carried out based on the underground water sealed cavern project of the National Huangdao Petroleum Reserve. The formation lithology of the test site was granite gneiss, and the fractures were not developed, which is conducive to the research of slug tests on fracture permeability. On the basis of obtaining the geological information of boreholes by using the self-developed slug test system, comparative research on the segmented slug test and conventional water pressure test was carried out. The test results show that the proposed slug test method and self-developed test system has good accuracy and applicability for determining the fracture permeability coefficient, equivalent permeability coefficient and rock mass permeability coefficient tensor, which is more convenient and efficient than other test methods.

Estimation of 3D hydraulic conductivity distribution of unconfined aquifer using the geostatistical method and its relation to water quality and flooding in Upper Citarum River

The 3D distribution of hydraulic conductivity in the unconfined aquifer is needed to understand the interaction between groundwater and Citarum River, which may relate to water contamination and flooding. In this study, it was estimated using the geostatistical method. The data used are the hydraulic conductivity parameter from thirteen large-diameter dug wells determined using the slug test method. Further analysis was conducted using groundwater and Citarum River physical parameters, i.e. total dissolved solids, pH, and temperature. The results show that the hydraulic conductivity of the unconfined aquifer in the Upper Citarum River ranges from 8.34 x 10−7 to 2.19 x 10−5 m/s. The area with relatively high hydraulic conductivity, i.e. Ciparay and Solokan Jeruk Sub-districts, will have a greater possibility of groundwater or river water contamination depending on their interaction. Meanwhile, the area with relatively flat topography and low hydraulic conductivity, i.e. Majalaya and Baleendah Sub-districts, will be more susceptible to flood. Therefore, the mitigation of water contamination and flooding in the Upper Citarum River should consider the 3D hydraulic conductivity distribution, e.g. by monitoring the groundwater quality in some dug wells located in high hydraulic conductivity area and installing recharge or injection well to eliminate the artificial runoff.

Educational interactive LabVIEW simulations of field hydraulic conductivity tests below water table

AbstractVisual artifacts used in graphical designs of the mechanisms of groundwater flow problems are very influential in learning and teaching. The merits of the classical methods of problem‐solving using only mathematics become much less superior to those linked with interactive graphics. In this study, an interactive educational LabVIEW program is designed to graphically simulate the constructional and mathematical procedures of the two widely used field methods in groundwater engineering, the Ernst auger‐hole method, and the Bouwer–Rice slug test method, for field measurements of the hydraulic conductivity of soils below the water table. The simulations included the basic constructional steps in carrying out the auger hole and the slug test field methods. Virtual geometric wells, boreholes, and pipes are graphically and interactively designed to conduct the required field tests. The simulations of the program enabled the students to get acquainted with what should be done in the field to measure soil hydraulic conductivity and enhanced understanding of how to perform a field test. Students were able to try different field hydrological parameters, and by successively changing any hydrological field parameter, they were able to visualize graphically and interactively its influence inside the classroom. This particular step improved the student's practical standards. Conditions of validity of each field test are completely fulfilled by the program. Results of the interactive program are found to be visually interesting and extremely accurate, which made this educational program quite interesting in teaching and learning.

Comparison of slug test methods to determine conductivity of Holocen aquifer, Dan Phuong area

Two different slug test methods including: i) slug test using the standard slug rod and ii) pneumatic slug test are conducted in different well/depth in Danphuong field site for a comparative analysis. These methods are examined at least 3 times for each well to estimate hydraulic conductivities by using Hvorslev. The results show correlation between two slug test methods is very hight with R2 = 0,93. Slug tests methods have several advantages and also disadvantage compare to each other. Practical considerations of performing the tests in real life settings are also considered in the method comparison. The slug-rod method meets 7/10 criterions while pneumatic slug test satisfy 8/10 criterions.

Sensitivity of the response of well-aquifer systems to different periodic loadings: A comparison of two wells in Huize, China

Groundwater well can be used as a seismograph or as strainmeter, since the well water level is sensitive to seismic waves and other crustal strains through mechanical coupling between rock and groundwater. The use of the groundwater level in monitoring tectonic strain, however, is hindered by the enigmatic response discrepancy among wells (different responses may be recorded by even closely clustered wells). Therefore, understanding the factors that control the sensitivity of well-aquifer systems in response to different periodic loadings is important. In this paper, we analyzed two closely located wells that show no response to seismic waves and respond differently to earth tides and barometric pressure. We discuss these wells’ sensitivity of response to periodic loadings by using the spectrum, barometric response function, tidal response, and slug test methods. Our results show that the different response characteristics are due to the differences in permeability and confinement of the well-aquifer systems. Well-aquifer systems with a low permeability cannot record coseismic responses, even if they can record clear tidal and barometric signals. In addition, periodic loading signals in shallow aquifers will be easily masked by the interference from the surface, for example rainfall or pumping, which diminishes the signal-to-noise ratio of the tectonic activity. Thus, the hydrogeological and tectonic settings are the two key factors that should be considered in choosing a suitable monitoring well location for tectonic strain monitoring.

The influence of land-cover changes on the variability of saturated hydraulic conductivity in tropical peatlands

Understanding the movement of water through peat is essential for effective conservation and management strategies for peatlands. Saturated hydraulic conductivity, Ks, describes water movement through the peat profile. However, the spatial variability of Ks in tropical peatlands and the effects of land conversion on peat characteristics are poorly understood. Utilizing the slug test method, we estimated hydraulic conductivity in tropical peatlands in West Kalimantan, Indonesia, at three depths (0.75, 3.5, and 5.5 m) across four different land-cover types (undrained forests, recently burned forests, early seral communities, and oil palm (Elaeis guineensis Jacq.) plantations). We found strong spatial autocorrelation among measurements collected at our 19 study sites and evaluated the relationship between hydraulic conductivity and land-cover types, peat properties, and depth of measurement with a hierarchical linear model. Hydraulic conductivity varied greatly (c. 0.001–13.9 m d−1). The best approximating model for estimating Ks contained depth, forest cover, a depth and forest cover interaction, and the von Post degree of decomposition (Ks ~ depth + forest + depth × forest + von Post). Parameter estimates indicated that Ks was greater in forested than non-forested sites and decreased with increasing depth and decomposition stage. There was no evidence that Ks differed among the non-forested sites or was related to other physical and chemical peat properties. Our results suggest that Ks should be measured directly in tropical peatlands rather than estimated as a function of peat properties. Additionally, the strong spatial dependence suggests that similar research designs should examine the sample data for spatial dependence and, if necessary, incorporate hierarchical models.

Comparison of specific-yield estimates for calculating evapotranspiration from diurnal groundwater-level fluctuations

Methods that use diurnal groundwater-level fluctuations are commonly used for shallow water-table environments to estimate evapotranspiration (ET) and recharge. The key element needed to obtain reliable estimates is the specific yield (Sy), a soil-water storage parameter that depends on unsaturated soil-moisture and water-table fluxes, among others. Soil-moisture profile measurement down to the water table, along with water-table-depth measurements, can provide a good opportunity to calculate Sy values even on a sub-daily scale. These values were compared with Sy estimates derived by traditional techniques, and it was found that slug-test-based Sy values gave the most similar results in a sandy soil environment. Therefore, slug-test methods, which are relatively cheap and require little time, were most suited to estimate Sy using diurnal fluctuations. The reason for this is that the timeframe of the slug-test measurement is very similar to the dynamic of the diurnal signal. The dynamic characteristic of Sy was also analyzed on a sub-daily scale (depending mostly on the speed of drainage from the soil profile) and a remarkable difference was found in Sy with respect to the rate of change of the water table. When comparing constant and sub-daily (dynamic) Sy values for ET estimation, the sub-daily Sy application yielded higher correlation, but only a slightly smaller deviation from the control ET method, compared with the usage of constant Sy.

Refinement of Bouwer‐Rice Baildown Test Analysis

AbstractThe recoverability of light nonaqueous phase liquids (LNAPL) in the subsurface can be estimated using LNAPL transmissivity. LNAPL transmissivity is analogous to aquifer transmissivity in that it represents the volume of LNAPL that flows through a unit width of a porous medium for a unit gradient in a unit time. Methods for estimating LNAPL transmissivity from baildown test data have been modified from the Bouwer and Rice (1976) slug test method by Lundy and Zimmerman (1996) and Huntley (2000). The primary assumptions when estimating LNAPL transmissivity with the Bouwer‐Rice method include, a quasi‐steady‐state model for recharge to the well (the model assumes steady‐state radial flow to the well with rate dependent well drawdown and no storage effects) and that the ratio of change in LNAPL drawdown to change in LNAPL thickness at the well (ds/db) is constant. This ratio will be referred to as the j‐ratio. Rather than having to meet boundary conditions for a predetermined j‐ratio value, each baildown test provides the data to estimate the j‐ratio value that is unique to that data set. This calculation methodology in turn results in the Bouwer‐Rice method being applicable to a wider range of baildown tests where it is not required for the potentiometric surface or LNAPL/water interface to remain constant.

Measurement of streambed hydraulic conductivity and its anisotropy

A method is described for the measurement of streambed hydraulic conductivity. Unlike permeameter methods, this method applies straight and l-shaped standpipes directly to streambeds for measurements of in-situ hydraulic conductivity in the vertical (K v ) and horizontal (K h ) directions, as well as in other oblique directions (K s ). This method has advantages in determination of K v values over grain-size analysis, permeameter tests, or slug test methods. Also unique to this method is that it provides K s values of a streambed. The measured results can be used to construct a hydraulic conductivity ellipse and to evaluate the anisotropy of streambed sediments. Field examples from the Republican River, Nebraska, demonstrated the usefulness of this method in the determination of streambed hydraulic conductivity and anisotropy along or across a river channel. Results indicate that the K h is about three to four times larger than K v , whereas K s values are larger than K v but smaller than K h .

Estimation of hydraulic conductivity in large-diameter, hand-dug wells using slug-test methods

To demonstrate the viability of using slug-test-analysis techniques to interpret recovery data in large-diameter, hand-dug wells, 37 wells representing a range of hydraulic conductivity and located in unconfined and weathered chalk and marl and confined alluvium in North-Central Texas were tested. Recovery data were analyzed by means of a numerical model, two semiempirical methods developed especially for interpreting recovery data from large-diameter hand-dug wells, and different slug-test-analysis methods that have different shape factors describing well geometry. Most hydraulic-conductivity values estimated by slug-test methods are within an order of magnitude of values that are estimated by using a numerical model or methods derived specifically for hand-dug wells. Because of the unique geometry of hand-dug wells (diameters on the same order as well lengths), care must be taken to ensure that the proper shape factors are used with slug-test methods. Because of the substantial well storage in hand-dug wells, considerable time may be required to lower the water level to the desired position, especially if pump capacity is limited. This pumping time results in a noninstantaneous withdrawal of water from the aquifer, which violates one of the assumptions of slug-test-interpretation methods. However, in low-permeability environments, reasonable results can still be attained if water removed from the well sources from well storage or if recovery time is considerably longer than pumping time.

Spatial and Temporal Variability of Hydraulic Conductivity in Active Reattachment Bars of the Colorado River, Grand Canyon

AbstractGround water/surface water interaction in rivers is dependent on the hydraulic conductivity of sediments lining the streambed. This study was designed to determine the temporal and spatial variability of the hydraulic conductivity of active sedimentary deposits lining the streambed of the Colorado River in the Grand Canyon. These reattachment bars form aquifers and create return‐current channels that are critical for supporting terrestrial and aquatic ecosystems. Monitoring wells were placed in five separate reattachment bars over a 200 mile long reach of the Colorado River below Glen Canyon Dam. Hydraulic conductivity was measured in all wells with the pneumatic slug test method. There is no significant difference in hydraulic conductivity among the five reattachment bars in the Grand Canyon. Hydraulic conductivity is bimodally distributed within a reattachment bar because of differing sizes of sediments deposited under different eddy velocities. A major controlled release of water from Glen Canyon Dam in March 1996 redistributed the sediments in the reattachment bars and compressed sediments deposited during previous floods. Hydraulic conductivity was significantly lower in these sediments after the flood due to the increased effective stress from the newly deposited sediment. A year later, after the sediments had drained and some deflation had occurred, hydraulic conductivity of sand deposits returned to values similar to pre‐flood values, whereas fine‐grained sediments that compressed weren't able to elastically respond.

Mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer : Hinsby, K; Bjerg, P L; Andersen, L J; Skov, B; Clausen, E V J HydrolV136, N1/4, Aug 1992, P87–106

Mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer : Hinsby, K; Bjerg, P L; Andersen, L J; Skov, B; Clausen, E V J HydrolV136, N1/4, Aug 1992, P87–106

Spatial variability of hydraulic conductivity of an unconfined sandy aquifer determined by a mini slug test

The spatial variability of the hydraulic conductivity in a sandy aquifer has been determined by a mini slug test method. The hydraulic conductivity ( K) of the aquifer has a geometric mean of 5.05 × 10 −4 m s −1 , and an overall variance of 1n K equal to 0.37 which corresponds quite well to the results obtained by two large scale tracer experiments performed in the aquifer. A geological model of the aquifer based on 31 sediment cores, proposed three hydrogeological layers in the aquifer concurrent with the vertical variations observed with respect to hydraulic conductivity. The horizontal correlation length of the hydraulic conductivity has been determined for each of the three hydrogeological layers and is found to be small (1–2.5 m). The asymptotic longitudinal dispersivity of the aquifer has been estimated from the variance in hydraulic conductivity and the horizontal correlation length, to be in the range of 0.3–0.5 m compared with a value of 0.42 m obtained in one of the tracer tests performed.

A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer

A new and efficient mini slug test method for the determination of local hydraulic conductivities in unconfined sandy aquifers is developed. The slug test is performed in a small-diameter (1 inch) driven well with a 0.25 m screen just above the drive point. The screened drive point can be driven from level to level and thereby establish vertical profiles of the hydraulic conductivity. The head data from the test well are recorded with a 10 mm pressure transducer, and the initial head difference required is established by a small vacuum pump. The method described has provided 274 spatially distributed measurements of a local hydraulic conductivity at a tracer test site at Vejen, Denmark. The mini slug test results calculated by a modified Dax slug test analysing method, applying the elastic storativity in the Dax equations instead of the specific yield, are in good accordance with the results from two natural gradient tracer experiments performed at the test site. The original Dax, the Bouwer and Rice, and the Chirlin analysing methods all led to an underestimation of the effective hydraulic conductivity by a factor of more than 2, when compared with the tracer tests. In contrast the spherical flow model of Karasaki et al. overestimated the results of the tracer tests by approximately a factor 1.4. The Dax and the Cooper et al. methods, assuming only radial flow to the partially screened well, yielded a better approximation of the horizontal hydraulic conductivity, than the Chirlin method, which also considers axial flow. This fact is suggested to be a result of aquifer anisotropy, as a significant higher horizontal than vertical hydraulic conductivity may suppress the significance of the axial flow component.

Hydraulic properties of groundwater systems in the saprolite and sediments of the wheatbelt, Western Australia

Hydraulic properties of deeply weathered basement rocks and variably weathered sedimentary materials were measured by pumping and slug-test methods. Results from over 200 bores in 13 catchments, and eight pumping-test sites across the eastern and central wheatbelt of Western Australia were analysed. Measurements were made in each of the major lithological units, and emphasis placed on a ubiquitous basal saprolite aquifer. Comparisons were made between alternative drilling and analytical procedures to determine the most appropriate methods of investigation. Aquifers with an average hydraulic conductivity of 0.55 m day −1 occur in variably weathered Cainozoic sediments and poorly weathered saprolite grits (0.57 m day −1). These aquifers are separated by an aquitard (0.065 m day −1) comprising the mottled and pallid zones of the deeply weathered profile. Locally higher values of hydraulic conductivity occur in the saprolite aquifer, although after prolonged periods of pumping the values decrease until they are similar to those obtained from the slug-test methods. Hydraulic conductivities measured in bores drilled with rotary auger rigs were approximately an order of magnitude lower than those measured in the same material with bores drilled by the rotary air-blast method. Wheatbelt aquifers range from predominantly unconfined (Cainozoic sediments), to confined (saprolite grit aquifer). The poorly weathered saprolite grit aquifer has moderate to high transmissivities (4–50 m 2 day −1) and is capable of producing from less than 5 to over 230 kl day −1 of ground water, which is often of a quality suitable for livestock. Yields are influenced by the variability in the permeability of isovolumetrically weathered materials from which the aquifer is derived. The overlying aquitard has a low transmissivity (< 1 m 2 day −1), especially when deeply weathered, indurated and silicified. The transmissivity of the variably weathered sedimentary materials ranges from less than 0.5 m 2 day −1 to over 10 m 2 day −1, depending on the texture of the materials and their position within the landscape. Higher transmissivity zones may occur as discrete layers of coarser textured materials. The salinity of the saprolite and sedimentary aquifers ranges from less than 2000 mgl −1 to greater than 250000 mgl −1 (total dissolved solids; TDS), depending on position within the landscape. Secondary soil salinization develops when groundwater discharge occurs from either saprolite or sedimentary aquifers.

Monitoring the deterioration of small-diameter observation wells

This research studies the problem of monitoring the deterioration of small-diameter observation wells. It considers three methods for achieving this task: visual inspection of hydrographs, on-going recording of borehole depth, and analysis of slug tests. The relative merits of these methods are judged in view of the results of a large-scale field survey. The field results indicate that while the first two methods suffer certain disadvantages, the slug test method is a rather reliable tool.

Hydraulic conductivity of deeply weathered materials in the Darling Range, Western Australia

The hydraulic conductivity (K) of unconsolidated, deeply weathered material was measured by the slug test method In 214 boreholes distributed over five distinct areas in the Darling Range of Western Australia. Most of the measurements were made in the zone 0-3 m above hard rock. Theory of the method was extended to include a layer of material with lower K about the slotted pipe. The frequency distribution of K in each area was well fitted by the log-normal function. Parameters of the linear regression of logK against the inverse Gaussian function of cumulative frequency differed significantly (P&lt;0.001) between areas. In one area of 134 ha, measurements were made in 54 boreholes located on a grid. There was a very poor correlation between values of K at the smallest separation of grid points (100 m), which suggests that there is an essentially random spatial variation of K measured by this method in this study area. Assuming log-normal frequency distributions and random spatial distributions, bulk conductivities were estimated for each area. On the basis of these investigations, it is concluded that the bulk hydraulic conductivity of the weathered material in the Darling Range is slow to moderately slow, and relatively uniform on the broad scale.

Analysis of ''Slug Test'' Or DST Flow Period Data

Abstract In recent years, there has been a great interest in the "slug test" which involves the instantaneous removal of a specific quantity of fluid from a wellbore and measurement of the resulting pressure-time response. Although a skin effect term was introduced by Jaeger, most recent studies have not considered a skin effect in analyzing slug test data. A new approach to conventional well-test analysis by Earlougher and Kersch was used to prepare type curves for the slug tech which include the skin effect. This study includes: results presented in both tabular and graphical form to aid application, a new material on the radius investigated and the time of duration of slug test, and the presentation of field example illustrating the application and important limitations of the method, as well as limitations of conventional DST analyses. The main application of the slug test method is in the analysis of pressure data for cases wherein the fluid influx into the drill pipe tends to kill the flow (sometimes even before the tester valve is closed). On the other hand, many field test have been observed wherein the phenomena of critical (acoustic velocity) flow destroys the application of the method. The slug test, as currently developed, does not consider critical flow.