共查询到20条相似文献，搜索用时 15 毫秒
1.
Predicting the future performance of horizontal wells under varying pumping conditions requires estimates of basic aquifer parameters, notably transmissivity and storativity. For vertical wells, there are well-established methods for estimating these parameters, typically based on either the recovery from induced head changes in a well or from the head response in observation wells to pumping in a test well. Comparable aquifer parameter estimation methods for horizontal wells have not been presented in the ground water literature. Formation parameter estimation methods based on measurements of pressure in horizontal wells have been presented in the petroleum industry literature, but these methods have limited applicability for ground water evaluation and are based on pressure measurements in only the horizontal well borehole, rather than in observation wells. This paper presents a simple and versatile method by which pumping test procedures developed for vertical wells can be applied to horizontal well pumping tests. The method presented here uses the principle of superposition to represent the horizontal well as a series of partially penetrating vertical wells. This concept is used to estimate a distance from an observation well at which a vertical well that has the same total pumping rate as the horizontal well will produce the same drawdown as the horizontal well. This equivalent distance may then be associated with an observation well for use in pumping test algorithms and type curves developed for vertical wells. The method is shown to produce good results for confined aquifers and unconfined aquifers in the absence of delayed yield response. For unconfined aquifers, the presence of delayed yield response increases the method error. 相似文献
2.
Dennis E. Williams 《Ground water》2013,51(5):745-751
Recent developments in subsurface intake systems for ocean desalination plants are considering use of angled wells (slant wells) completed in permeable materials beneath the ocean floor. Conventional drawdown equations for vertical or horizontal wells are inadequate to properly describe the drawdown distribution in the vicinity of slant wells. Using the principle of superposition combined with standard well hydraulics, universal drawdown equations (UDE) are presented which calculate the drawdown distribution in the vicinity of production wells with inclination angles ranging from 0° (horizontal wells) to 90° (vertical wells). The method is computationally simple and other than the normal assumptions for standard well equations, it only requires that the calculated drawdown represent the drawdown which would be measured in a fully penetrating observation well. Solutions using the UDE are developed for confined, unconfined and semi‐confined (leaky) aquifers and compared with analytical equations for vertical and horizontal wells, and with a numerical model for slant wells. The UDE is also applied to pumping test data from the Dana Point slant well project in Southern California. 相似文献
3.
The solutions of constant‐head and constant‐flux tests are commonly used to predict the temporal or spatial drawdown distribution or to determine aquifer parameters. Theis and Thiem equations, for instance, are well‐known transient and steady‐state drawdown solutions, respectively, of the constant‐flux test. It is known that the Theis equation is not applicable to the case where the aquifer has a finite boundary or the pumping time tends to infinity. On the other hand, the Thiem equation does not apply to the case where the aquifer boundary is infinite. However, the issue of obtaining the Thiem equation from the transient drawdown solution has not previously been addressed. In this paper, the drawdown solutions for constant‐head and constant‐flux tests conducted in finite or infinite confined aquifers with or without consideration of the effect of the well radius are examined comprehensively. Mathematical verification and physical interpretation of the solutions to these two tests converging or not converging to the Thiem equation are presented. The result shows that there are some finite‐domain solutions for these two tests that can converge to the Thiem equation when the time becomes infinitely large. In addition, the time criteria to give a good approximation to the finite‐domain solution by the infinite‐domain solution and the Thiem equation are investigated and presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
GREGORY B. DAVIS 《水文科学杂志》2013,58(2):133-141
ABSTRACT A borehole partially penetrating a confined aquifer and pumped at a constant rate is modelled, taking account of water stored within the casing of the borehole. A solution for drawdown in the Laplace transform domain is obtained. The proportion of aquifer water in well discharge is numerically evaluated, tabulated as a function of time and compared with results for a fully penetrating well. Modification of the fully penetrating well theory, for application to partially penetrating wells, was found to give comparable results to the more complete analysis for a partially penetrating well both at early and late times. A previous estimate of the time of pumping before sampling (ts) to minimize casing storage effects, based on the fully penetrating well theory, was confirmed by the partially penetrating well analysis and in fact was shown to be a conservative estimate (or overestimate) of the pumping time required when sampling from a partially penetrating well. 相似文献
5.
The constant-head pumping tests are usually employed to determine the aquifer parameters and they can be performed in fully or partially penetrating wells. Generally, the Dirichlet condition is prescribed along the well screen and the Neumann type no-flow condition is specified over the unscreened part of the test well. The mathematical model describing the aquifer response to a constant-head test performed in a fully penetrating well can be easily solved by the conventional integral transform technique under the uniform Dirichlet-type condition along the rim of wellbore. However, the boundary condition for a test well with partial penetration should be considered as a mixed-type condition. This mixed boundary value problem in a confined aquifer system of infinite radial extent and finite vertical extent is solved by the Laplace and finite Fourier transforms in conjunction with the triple series equations method. This approach provides analytical results for the drawdown in a partially penetrating well for arbitrary location of the well screen in a finite thickness aquifer. The semi-analytical solutions are particularly useful for the practical applications from the computational point of view. 相似文献
6.
Ferenc Székely 《Ground water》2013,51(5):762-767
The vertical variation of drawdown around pumping wells generates an induced flow in the observation wells. A set of governing equations is presented to couple the drawdown variation and the vertical flux distribution in observation wells. A numerical example is performed to justify the governing equations and to verify the solution methods used by the simulation software WT. The example analyzes the effect of skin loss, wellbore storage, and vertical segmentation on the drawdown and induced flow in observation well during pumping. The evaluation of the Fairborn pumping test involves a vertically homogeneous and anisotropic water table aquifer, uniform well‐face drawdown conditions in the pumping well and simulation of the drawdown evolution in the observation well with and without the effect of induced flow. The computer calibrations resulted in small differences between the measured and simulated drawdown curves. 相似文献
7.
《Ground Water Monitoring & Remediation》2008,28(2):75-80
In a recent field study, the performance of four production wells was evaluated. The intake of a vertical turbine test pump was set below the top of the screened interval of the wells due to anticipated drawdown. Water level sounding tubes were welded to the well casing at various depths in each well. Drawdown data collected at various depths were used to evaluate the vertical head distribution in the wells under various pumping stresses. A direct relationship was observed between the head loss and the location of the pump intake in the production wells. A vertical head profile developed, suggesting that the location of the pump intake controlled the location of water production from the aquifer. The head loss in the wells observed during pumping was directly proportional to well discharge and annulus size between the well casing and the vertical turbine pump shaft. The pressure differences that developed in the wells created increased drawdown in water level sounding tubes installed deep in the wells compared to the total drawdown observed in the production wells. Certain implications should be considered based on the evaluation of the data obtained from this study. Because water management decisions are made using well test data, the quality of the data is crucial. In instances where well performance is evaluated using water level data collected from water level sounding tubes that are located close to a pump intake (in this case deep in the well), it should be recognized that well performance could be underestimated. 相似文献
8.
Shabbir A. S. Sayed 《Ground water》1984,22(2):148-153
In order to understand the flow pattern around a pumping well partially penetrating a vertically extensive aquifer, a specially designed pumping test was carried out in Pakistan. In this paper salient features of the test have been described. The spatial distributions of drawdown have been shown graphically. Some of the preliminary conclusions made from the drawdown pattern include:
- • The distance beyond which the flow is likely to be horizontal increases with decrease in the degree of aquifer penetration.
- • In equidistant observation wells open at different depths, (1) the drawdowns tend to merge at larger times, provided the observation point is located within the screened section of the aquifer; (2) the less the depth of penetration is, the earlier the drawdowns start merging; and (3) the initial rate of drawdown near the aquifer top is slow but catches up with time to exceed those at deeper points.
9.
Vertical wells with radial extension at the well bottom can improve the rate of water production. No study has yet investigated the effects of the transient state and anisotropy in directional hydraulic conductivities on the wellbore flux rate for this type of well. This study derives a semianalytical transient drawdown solution for constant-head pumping at a fully penetrating well radially extended at the bottom of a confined, anisotropic aquifer by applying Laplace transform and separation of variables as well as conducting a Fourier analysis. The results of this new solution indicate that transient and steady-state wellbore flux rates can be increased by a factor of two for greater radial extension of the well. Compared with an isotropic aquifer (a ratio of vertical and horizontal hydraulic conductivities equal to one), an anisotropic aquifer with the ratio less than one may produce a higher transient wellbore flux rate and lower steady-state wellbore flux rate. Moreover, the time required to achieve the steady-state wellbore flux rate can be substantially affected by anisotropy of the aquifer. 相似文献
10.
The Laplace domain solutions have been obtained for three-dimensional groundwater flow to a well in confined and unconfined wedge-shaped aquifers. The solutions take into account partial penetration effects, instantaneous drainage or delayed yield, vertical anisotropy and the water table boundary condition. As a basis, the Laplace domain solutions for drawdown created by a point source in uniform, anisotropic confined and unconfined wedge-shaped aquifers are first derived. Then, by the principle of superposition the point source solutions are extended to the cases of partially and fully penetrating wells. Unlike the previous solution for the confined aquifer that contains improper integrals arising from the Hankel transform [Yeh HD, Chang YC. New analytical solutions for groundwater flow in wedge-shaped aquifers with various topographic boundary conditions. Adv Water Resour 2006;26:471–80], numerical evaluation of our solution is relatively easy using well known numerical Laplace inversion methods. The effects of wedge angle, pumping well location and observation point location on drawdown and the effects of partial penetration, screen location and delay index on the wedge boundary hydraulic gradient in unconfined aquifers have also been investigated. The results are presented in the form of dimensionless drawdown-time and boundary gradient-time type curves. The curves are useful for parameter identification, calculation of stream depletion rates and the assessment of water budgets in river basins. 相似文献
11.
When a fully penetrating well pumps an ideal unconfined aquifer at steady state, the water table usually does not join the water level in the well. There is a seepage face inside the well, which is a key element in evaluating the well performance. This problem is analyzed using the finite-element method, solving the complete equations for saturated and unsaturated flow. The seepage face position is found to be almost independent of the unsaturated zone properties. The numerical results are used to test the validity of several analytic approximations. Equations are proposed to predict the seepage face position at the pumping well for any well drawdown, and the water table position at any distance from the pumping well for any in-well drawdown. Practical hints are provided for installing monitoring wells and evaluating well efficiency. 相似文献
12.
A new finite layer method (FLM) is presented in this paper for transient flow analysis in layered radial two-zone aquifer systems. A radial two-zone system is an aquifer configuration in which a circular aquifer with finite radius is surrounded by a matrix possessing different permeability and storage properties. The aquifers can be pumped from fully or partially penetrating wells of infinitesimal radius. The trial function for drawdown is obtained through the use of piecewise linear correction functions in the present method. The trial function can satisfy the continuity conditions of flow and possess an appropriate continuity of C(0) at the two-zone interface. On the basis of Galerkin's method and the continuity condition of flow, the finite layer formulation is derived. The proposed method can cope with the anisotropy and layered heterogeneity in radial two-zone aquifer systems. Several numerical examples are presented to verify the validity of the present method through comparison with the analytical solution and the numerical results based on the finite difference method, in which a test of three-dimensional (3D) flow to a partially penetrating well in anisotropic two-zone aquifers is included. Furthermore, an additional application in simulating the two-zone flow in aquitard-aquifer systems is presented to demonstrate the applicability of FLM in modeling flow in more complex aquifer systems. 相似文献
13.
We jointly invert field data of flowmeter and multiple pumping tests in fully screened wells to estimate hydraulic conductivity using a geostatistical method. We use the steady-state drawdowns of pumping tests and the discharge profiles of flowmeter tests as our data in the inference. The discharge profiles need not be converted to absolute hydraulic conductivities. Consequently, we do not need measurements of depth-averaged hydraulic conductivity at well locations. The flowmeter profiles contain information about relative vertical distributions of hydraulic conductivity, while drawdown measurements of pumping tests provide information about horizontal fluctuation of the depth-averaged hydraulic conductivity. We apply the method to data obtained at the Krauthausen test site of the Forschungszentrum Jülich, Germany. The resulting estimate of our joint three-dimensional (3D) geostatistical inversion shows an improved 3D structure in comparison to the inversion of pumping test data only. 相似文献
14.
A general analytical solution for flow to a single horizontal well by Fourier and Laplace transforms
The objective of this paper is to present an analytical solution for describing the head distribution in an unconfined aquifer with a single pumping horizontal well parallel to a fully penetrating stream. The Laplace-domain solution is developed by applying Fourier sine, Fourier and Laplace transforms to the governing equation as well as the associated initial and boundary conditions. The time-domain solution is obtained after taking the inverse Laplace transform along with the Bromwich integral method and inverse Fourier and Fourier sine transforms. The upper boundary condition of the aquifer is represented by the free surface equation in which the second-order slope terms are neglected. Based on the solution and Darcy’s law, the equation representing the stream depletion rate is then derived. The solution can simulate head distributions in an aquifer infinitely extending in horizontal direction if the well is located far away from the stream. In addition, the solution can also simulate head distributions in confined aquifers if specific yield is set zero. It is shown that the solution can be applied practically to evaluate flow to a horizontal well. 相似文献
15.
The buried-valley aquifers that are common in the glacial deposits of the northern hemisphere are a typical case of the strip aquifers that occur in many parts of the world. Pumping from a narrow strip aquifer leads to much greater drawdown and much more distant drawdown effects then would occur in a sheet aquifer with a similar transmissivity and storage coefficient. Widely used theories for radial flow to wells, such as the Theis equation, are not appropriate for narrow strip aquifers. Previously published theory for flow to wells in semiconfined strip aquifers is reviewed and a practical format of the type curves for pumping-test analysis is described. The drawdown response of strip aquifers to pumping tests is distinctive, especially for observation wells near the pumped well. A case study is presented, based on extensive pumping test experience for the Estevan Valley Aquifer in southern Saskatchewan, Canada. Evaluation of groundwater resources in such buried-valley aquifers needs to take into account the unusually large drawdowns in response to pumping. 相似文献
16.
Tomas Perina 《Ground water》2021,59(3):438-442
Time-domain analytical solution for groundwater flow to a fully penetrating flowing well is derived using the same substitution technique used to re-derive (Perina 2010) the Theis (1935) equation and the approximate solution by Mishra and Guyonnet (1992) is confirmed. The exponential integral-based flowing well function is a computationally effective alternative to the original Jacob and Lohman (1952) solution in integral form. For a constant drawdown test, the ratio of drawdown at an observation well to the flowrate is equivalent to drawdown response to pumping at unit constant rate; the transformed observations can be analyzed using the Theis (1935) function. Analysis of field test shows that simultaneous fitting to measurements of flow from the test well and drawdown at an observation well results in more accurate and better resolved estimates of aquifer properties than fitting to flow observations only. 相似文献
17.
《Advances in water resources》2004,27(10):981-990
The Theis equation has been widely used to study the transient movement of groundwater as a result of pumping in a confined aquifer. It is well known that the observed drawdown at early times has an obvious departure from the theoretical drawdown based on the Theis equation. The Theis equation was derived under the assumption that total stress in the aquifer was constant and the mechanical behavior of the confining unit was neglected. However, most geological formations, especially those which are well consolidated, have rigidity and therefore may bend like a plate to a certain extent. The increase in the effective stress in the aquifer due to pumping may not contribute entirely to the compression of the aquifer, but may be partially cancelled out by bending of the overlying aquitard. This means only a part of the total stress is used to compact the aquifer, or the aquifer cannot produce as much water as estimated from the Theis equation. This paper investigated the impact of the bending effect of the confining unit on drawdown. An analytical model which couples flow in the aquifer and bending of the confining unit was presented. The theory is based on elastic plates and solutions were given to the drawdown of groundwater level and deflection of the overlying formation. The drawdown estimated from the new equation was compared with that from the Theis equation. It can be concluded that drawdown from the Theis equation is less than the drawdown predicted by including the bending effect of the confining unit. Both a hypothetical example and a field pumping test in Shandong Province, China, were used to demonstrate the bending effect of the confining unit in the analysis of pumping test data. This paper demonstrated that the initial disagreement between observed drawdown and the Theis solution could be caused by the bending effect of the confining unit, a phenomenon not well addressed in traditional pumping test analysis. A quantitative understanding of this phenomenon can provide improved guidelines for analyzing drawdown data in a confined aquifer. 相似文献
18.
Walter W. Loo Klaus Franz Gary R. Holzhausen 《Ground Water Monitoring & Remediation》1984,4(4):124-130
An advanced two-way radio link (transceiver units) and data logging system have provided a powerful means of real-time series data collection and analysis. The application of this telemetry system to surface tiltmeter surveys provides significant cost savings for testing and analysis of deep, large-scale horizontal anisotropic permeability and heterogeneity determinations.
The determination of horizontal anisotropic properties requires one pumping well and eight to 10 tiltmeter monitoring stations. The validity of the depth of the test may reach 4,000 feet below land surface. With the addition of one partially penetrating observation well, the entire three-dimensional anisotropic permeability can be determined. With the addition of a fully penetrating well, the storage coefficient can be determined as well as leakage property (including vertical permeability of the confining layers). An example test case was analyzed for horizontal anisotropic permeability with remarkable success despite relatively unfavorable detection conditions.
A thorough understanding of the geology overlying the aquifer system must be made in order to assess the applicability of the surface tiltmeter survey to large-scale horizontal anisotropic permeability determinations. 相似文献
The determination of horizontal anisotropic properties requires one pumping well and eight to 10 tiltmeter monitoring stations. The validity of the depth of the test may reach 4,000 feet below land surface. With the addition of one partially penetrating observation well, the entire three-dimensional anisotropic permeability can be determined. With the addition of a fully penetrating well, the storage coefficient can be determined as well as leakage property (including vertical permeability of the confining layers). An example test case was analyzed for horizontal anisotropic permeability with remarkable success despite relatively unfavorable detection conditions.
A thorough understanding of the geology overlying the aquifer system must be made in order to assess the applicability of the surface tiltmeter survey to large-scale horizontal anisotropic permeability determinations. 相似文献
19.
Pumping test evaluation of stream depletion parameters 总被引：1，自引：0，他引：1
20.
Paul F. Hudak 《Ground Water Monitoring & Remediation》1993,13(2):113-117
Pumping test data for surficial aquifers are commonly analyzed under the assumption that the base of the aquifer corresponds to the bottom of the test wells (i.e., the aquifer is truncated). This practice can lead to inaccurate hydraulic conductivity estimates, resulting from the use of low saturated thickness values with transmissivity estimates, and not accounting for the effects of partially penetrating wells. Theoretical time-drawdown data were generated at an observation well in a hypothetical unconfined aquifer for various values of saturated thickness and were analyzed by standard curve-matching techniques. The base of the aquifer was assumed to be the bottom of the pumping and observation wells. The overestimation of horizontal hydraulic conductivity was found to be directly proportional to the error in assumed saturated thickness, and to the (actual) ratio of vertical to horizontal hydraulic conductivity (Kv /Kh ). Inaccurately high estimates of hydraulic conductivity obtained by aquifer truncation can lead to overestimates of ground water velocity and contaminant plume spreading, narrow capture zone configuration estimates, and overestimates of available ground water resources. 相似文献