Driller's Logs Research Articles

Improved Imaging of the Large‐Scale Structure of a Groundwater System With Airborne Electromagnetic Data

AbstractWorking with airborne electromagnetic (AEM) data acquired in the Kaweah Subbasin in the Central Valley of California, USA, we developed a new approach for imaging the bedrock surface and the confining Corcoran Clay layer. Our approach, which incorporated the prior knowledge of the targets for the improved imaging, included multiple L2‐norm and Lp‐norm inversions as well as an interpolation process. The major improvement in imaging the targets was made in the Lp‐norm inversion step by incorporating prior knowledge. For the Corcoran Clay, pairs of resistivity and driller's logs at two wells guided the selection of the primary resistivity model and were used to increase the accuracy of the estimated Corcoran Clay thickness. The bedrock surface was poorly constrained by well data in the existing groundwater model, appearing as a flat surface. Acquired AEM data covered most of the area, so we had higher confidence in the obtained map of the bedrock surface at depths ranging from 15 to 160 m. There was relatively good agreement between the location of the Corcoran Clay in the AEM data (depth ranging from 50 to 130 m and thickness ranging from 3 to 25 m) and the existing groundwater model, with both depth and thickness showing ∼15% relative difference. The AEM data provided information about the continuity of the Corcoran Clay that is challenging to capture in the well data. The locations of the bedrock and Corcoran Clay were used in a structurally constrained inversion to improve the imaging of the smaller‐scale resistivity structure.

Developing an Approach for a Three-Dimensional Hydrogeologic Framework to Find Water in Northern Ghana

The purpose of this study was to develop an approach for constructing a three-dimensional hydrogeologic framework using borehole driller logs. The ultimate goal is to increase drilling success rates via a better understanding of the regional hydrogeologic framework in northern Ghana. Groundwater development has increased in northern Ghana, but drilling successful boreholes is difficult due to complex geology and limited aquifer characteristic information. An approach was developed to construct a three-dimensional hydrogeologic framework of the basin using 900 borehole logs from World Vision International’s Ghana Integrated Water, Sanitation, and Hygiene Project, located in northern Ghana. The study’s approach consists of: evaluating potential software programs; collecting borehole drilling logs; data QA/QC; data standardization and normalization; analysis for trends and correlations; and creation of a three-dimensional hydrogeologic framework and two-dimensional cross sections. This approach can be used and adapted by others working to provide groundwater in developing countries.

Bouse Formation in the Bristol basin near Amboy, California, USA

Limestone beds underlain and overlain by alluvial fan conglomerate near Amboy, California, are very similar in many respects to parts of the Bouse Formation, suggesting that an arm of the Pliocene Bouse water body extended across a wide part of the southern Mojave Desert. The deposits are north of the town of Amboy at and below an elevation of 290 m, along the northern piedmont of the Bristol “dry” Lake basin. The Amboy outcrops contain the Lawlor Tuff (4.83 Ma), which is also found in an outcrop of the Bouse Formation in the Blythe basin near Buzzards Peak in the Chocolate Mountains, 180 km southeast of Amboy. Bouse exposures near Amboy are ∼3.4 m thick, white, distinctly bedded, with limestone and calcareous sandstone as well as stromatolite mounds; we interpret these as nearshore deposits. The Bouse at Amboy contains ostracodes, diatoms, and mollusks that indicate saline lake or estuarine environments with an admixture of fresh-water forms. Along with wading bird tracks and a spine from a marine fish, these fossils suggest that the deposits formed in saline waters near a fresh-water source such as a perennial stream. Beds of the outcrop dip southward and are 113 m above the surface of Bristol Playa, where similar age sediments are buried 270+ m deep, indicating significant faulting and vertical tectonics in this part of the Eastern California Shear Zone during the past 5 m.y. Confirmation of the Bouse Formation at Amboy strengthens previous assignments to the Bouse Formation for mudstones in driller logs at Danby “dry” Lake, California, and suggests that areally extensive arms of the Bouse water body were west of the Blythe basin. The Bristol basin arm of the lower Bouse basin probably was restricted from the main water body by narrow passages, but Bouse sediment there is similar to that in the Blythe basin, suggesting generally similar water chemistry and environmental conditions. Examining the degree to which Bouse deposits in the western arms differed from Bouse deposits in the Blythe basin offers an approach to test whether the southernmost Bouse water body was deposited in an estuarine or lacustrine setting.

Gaussian setting time for solute transport in fluvial systems

Gaussian setting time is the time scale at which solute plumes converge to their asymptotic Gaussian shape. This study estimates the Gaussian setting time using a high‐resolution hydrofacies model of a typical fluvial system, with an instantaneous point source in the mobile phase. Monte Carlo simulations are augmented by a time‐nonlocal transport model to forecast plume shape at late time. Analysis of plume spatial moments indicates that convergence to Fickian transport is affected by molecular diffusion and the thickness of low‐permeability floodplain layers. These layers can cause non‐Gaussian tailing to persist at late time because the low‐permeability lenses are elongated in the horizontal, so that most particles escape vertically by diffusion. A simple empirical setting time formula is developed, which can be fitted using data from driller's logs that characterize the thickness of the low‐permeability lenses. The empirical formula may be useful for predicting setting time in fluvial aquifers similar to those considered in this study. For such aquifers, the plume will often exit the region prior to the setting time, so the asymptotic Gaussian model will not be a useful predictor of plume shape.

Estimación de las propiedades de flujo de agua de agua subterránea a escala regional en la cuenca de Bengala en India y Bangladesh

Quantitative evaluation of management strategies for long-term supply of safe groundwater for drinking from the Bengal Basin aquifer (India and Bangladesh) requires estimation of the large-scale hydrogeologic properties that control flow. The Basin consists of a stratified, heterogeneous sequence of sediments with aquitards that may separate aquifers locally, but evidence does not support existence of regional confining units. Considered at a large scale, the Basin may be aptly described as a single aquifer with higher horizontal than vertical hydraulic conductivity. Though data are sparse, estimation of regional-scale aquifer properties is possible from three existing data types: hydraulic heads, 14C concentrations, and driller logs. Estimation is carried out with inverse groundwater modeling using measured heads, by model calibration using estimated water ages based on 14C, and by statistical analysis of driller logs. Similar estimates of hydraulic conductivities result from all three data types; a resulting typical value of vertical anisotropy (ratio of horizontal to vertical conductivity) is 104. The vertical anisotropy estimate is supported by simulation of flow through geostatistical fields consistent with driller log data. The high estimated value of vertical anisotropy in hydraulic conductivity indicates that even disconnected aquitards, if numerous, can strongly control the equivalent hydraulic parameters of an aquifer system.

Mise-à-la-masse and smoke tests for mapping vadose zone karst

Roughly 20% of the United States is underlain by limestone or dolomite. Shallow karst, riddled with cavities and fractures enlarged by dissolution, poses a costly problem for engineers and developers. Nearly every conceivable geophysical method—microgravity, ground-penetrating radar, electromagnetics, seismic reflection, refraction tomography, seismic surface waves, resistivity, spontaneous potential, and induced polarization—has been conscripted in the war against damage caused by subsidence. In this paper, we will discuss two unusual methods that we have tested for mapping the extent of shallow karst: smoke tests and mise-a-la-masse resistivity. Both methods presuppose at least one borehole intersecting a cavity. Given the highly irregular nature of karst networks, the discovery of a cavity though drilling is sufficient to alert engineers that the site poses a potential problem, but little else can be determined using just the driller's log from a single borehole. The two methods we discuss provided a s...

In search of clay deposit in a dual geological environment in the South-Southern part of Nigeria.

The presence of clay deposits in the south-southern part of Nigeria was investigated using the electrical resistivity methods. The Vertical Electrical Sounding (VES) was adopted for the investigation using the Schlumberger electrode arrangement. Resistivity soundings were collected from several locations which were evenly distributed within the study area. Models were generated for computer iterative technique. Borehole data were also collected using spontaneous potential logging method as well as driller's log in some selected sites within the study area so as to correlate surface measurement with borehole records. Analysis based on five depth related resistivity contour maps as well as sellected cross sectional profiles confirm the existing dual regional geological environment of the area. Finally, it was established that the quantity of clay deposits is more in the sedimentary environment than basement complex area. Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp. 443-456

Determination of water table using electrical sounding technique: A case study of Afuze Edo State, Nigeria

This work investigated water-bearing formation and determined the water table in Afuze, a major town in Edo state, Nigeria, using electrical sounding techniques with the schlumberger electrode configuration The ABEM SAS 300B Terrameters was used in this work to carry out Resistivity soundings from several locations which were evenly distributed within the study area. The value of the apparent resistivities got, were computed manually and with computer and plotted on log-log graph, all of which are shown in this work. The interpretation was done qualitatively and quantitatively by comparison of resistivity curve type and curved matching techniques respectively. Models were generated for computer iterative technique and Borehole data were also collected using spontaneous potential logging method as well as driller's log in some selected sites within the study area so as to correlate surface measurement with borehole records. Analysis based on three depth related resistivity contour VES, as well as selected cross sectional profiles confirm the existing dual regional geological environment of the area. Finally, it was established, from The result obtained that the water bearing formation at Afuze was mainly sand and was found at depth between 32.6m-50m. Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp. 457-464

High-resolution simulation of basin-scale nitrate transport considering aquifer system heterogeneity

Nitrate contamination presents a growing threat to many groundwater basins relied upon for drinking water. This study combines geostatistical techniques, parallel computing of flow simulation, and particle tracking to develop realistic nitrate loading and transport scenarios. The simulation scenarios are patterned after the rapidly urbanizing Llagas groundwater subbasin in the south San Francisco Bay area of California. In the Llagas subbasin, groundwater is the sole municipal water supply. A key component of this study is the development of a highly resolved model of the heterogeneity in the aquifer system using a new geostatistical technique for simulating hydrofacies architecture that can incorporate uncertain or “soft” data, such as well driller logs. Numerical simulations of nitrate transport indicate the degree to which a heterogeneous conceptual model can account for dispersion relative to a conventional homogeneous model assuming typical dispersivity coefficients. The heterogeneous model transport results are found to be consistent with observed nitrate contamination patterns and depth distribution as well as groundwater-age trends with depth. The model provides a realistic test-bed for prediction of future nitrate concentrations, including the time frame for potential nitrate impacts to deep wells, given that geochemical data indicate that denitrification is not likely to occur.

SUBSURFACE SEQUENCE DELINEATION AND SALINE WATER MAPPING OF LAGOS STATE, SOUTHWESTERN NIGERIA

A subsurface sequence delineation and saline water mapping of Lagos State was carried out. Ten (10) deep boreholes with average depth of 300 m were drilled within the sedimentary basin. The boreholes were lithologically and geophysically logged. The driller's lithological logs aided by gamma and resistivity logs, showed that the area is underlain by clays, sandy/silty clays, clayey sands and sands with shale and limestone in places. The resistivity logs delineate saline water at shallow depth at Lekki wells I and II, Lakowe and Akodo with fresh/saline water interface at depths ranging from 8 - 15m. Confined saline water was delineated at deep levels at Eredo and Akodo. Saline seawater incursion has extended in land to within 2.5 - 12.5km from the coastline. KEY WORDS: Subsurface Sequence, Saline Water Mapping Global Jnl Geological Sciences . Vol.2(1) 2004: 111-123

Palynology and paleoecology of strata associated with the Ohoopee river dune field, Emanuel county, Georgia

Fourteen auger holes were drilled through ancient dunes near the Ohoopee River in Emanuel County, Georgia. Driller's logs and sieve analyses show that the wind‐blown sands of the dune field overlie a layer of coarse sand and gravel, which in turn overlies clayey Late Tertiary strata. Clay‐rich sediment recovered from two of the holes contained diatoms, sponge spicules, and other siliceous marine microfossils, while clay analyses from seven other holes revealed the presence of the clay mineral attapulgite (a variety of palygorskite). Twenty‐two sediment samples collected from six of the drill holes contained sufficient organic material to warrant palynological analysis. Eighty‐one taxa of pollen, spores, and algal cysts were used along with the diatoms, clay analyses, and stratigraphy to indicate probable ages and environments of deposition of the sediments. Both the diatoms and the attapulgite indicate marine depositional conditions. Overlying the marine units, but below the eolian sands we found rare occurrences of the extinct or extirpated genera Casuarinidites, Sciadopitys, Pterocarya, and Momipites. We believe these support a Late Tertiary age interpretation for the clayey strata. The presence of taxa such as the Cyrillaceae, Nyssa, Sphagnum, Myriophyllum, and Pseudoschizaea in the uppermost Tertiary units indicates that these sediments accumulated in freshwater wetlands. Our interpretation of the depositional history is that Late Tertiary marine strata accumulated first, probably during the Miocene. As sea level dropped fluvial and paludal conditions led to the accumulation of freshwater swamp/marsh sediments and probable stream sands or gravels later in the Tertiary. Exposure of the Inner Coastal Plain during the Pleistocene resulted in the formation of dunes that migrated over the Tertiary strata at the site of deposition.

PALYNOLOGY AND PALEOECOLOGY OF STRATA ASSOCIATED WITH THE OHOOPEE RIVER DUNE FIELD, EMANUEL COUNTY, GEORGIA

Abstract Fourteen auger holes were drilled through ancient dunes near the Ohoopee River in Emanuel County, Georgia. Driller's logs and sieve analyses show that the wind‐blown sands of the dune field overlie a layer of coarse sand and gravel, which in turn overlies clayey Late Tertiary strata. Clay‐rich sediment recovered from two of the holes contained diatoms, sponge spicules, and other siliceous marine microfossils, while clay analyses from seven other holes revealed the presence of the clay mineral attapulgite (a variety of palygorskite). Twenty‐two sediment samples collected from six of the drill holes contained sufficient organic material to warrant palynological analysis. Eighty‐one taxa of pollen, spores, and algal cysts were used along with the diatoms, clay analyses, and stratigraphy to indicate probable ages and environments of deposition of the sediments. Both the diatoms and the attapulgite indicate marine depositional conditions. Overlying the marine units, but below the eolian sands we found...

Abstract: Using a Geographic Information System to Determine the Chicot Aquifer System Surficial Confining Unit's Thickness and Location of Sand Lenses, Southwestern Louisiana 

ABSTRACT The Chicot aquifer system in southwestern Louisiana has a surficial confining unit that is undifferentiated from overburden material near the surface. This confining unit is composed of fine sand, silt, and clay, through which recharge flows to the underlying aquifer units. The thickness of the confining unit was mapped suing water-well and petroleum-well data from federal and state agency databases, and supplemental information from previous publications. thicknesses were estimated from 128 petroleum-well geophysical logs, 260 water-well geophysical logs, and 1,705 water-well driller's logs. Although an abundance of petroleum-well geophysical logs are available from southwestern Louisiana, logging commonly did not start at or near the ground surface, which rendered the logs unusable. Water-well driller's logs vary in quality, and those used were complied from paper-files of more than 10,000 well records. Thickness values from driller's logs were not used if the values did not match thickness values from other nearby geophysical and driller's logs. The thickness of the confining unit was estimated using kriging, and interpolation method. Kriging can handle spatial variability, smooth out random noise, and mitigate the impact of hot spots where there is a great quantity of data. Universal kriging was used instead of ordinary kriging because the data were highly correlated in a particular direction. The distribution of shallow domestic wells completed in sand lenses within the Chicot surficial confining unit was compared to the distribution of sand lenses obtained from the log data. This provided independent corroboration of areas where sufficient water is available for rural domestic use. End_of_Record - Last_Page 5-------

Borehole Flowmeter Application in Fluvial Sediments: Methodology, Results, and Assessment

AbstractIn many situations, inadequate design or performance of ground‐water remediation systems is the result of underestimation of aquifer hydraulic heterogeneity, and in particular, the vertical variation of hydraulic conductivity which plays an important role in contaminant migration. Described herein are applications of the electromagnetic (EM) borehole flowmeter to fluvial sediments in Louisiana and South Carolina. The direction of natural vertical flow in the test aquifers was defined easily, and short pumping tests enabled the calculation of hydraulic conductivity profiles for each test well. The results correlated well with other information obtained independently, including natural gamma logs, driller's logs and a hydraulic conductivity profile based on grain size analysis. Large variations in hydraulic conductivity over short vertical and horizontal distances were documented. Tests in gravel‐packed wells suggested that flowmeters produce misleading data for a variety of reasons in such situations. Among other things, an annulus of high permeability around a well screen allows flow to bypass the meter, and the phenomenon is amplified by high pumping rates. The resulting error is displayed as an erroneous high permeability zone at the top of the well screen. This observation deserves further study. In its present form the EM flowmeter is awkward to handle on a routine basis. However, none of the present design flaws preclude its effective use.

Thickness Trends and Structure of Berea Sandstone (Mississippian) in Washington County, Ohio: ABSTRACT

The Berea Sandstone has been a drilling target for hydrocarbon production in Ohio for over 100 yr. Although extensively produced, the Berea still rewards the driller with new commercial production. Due to its shallow depth and low cost of completion, the Berea has undergone a renaissance in interest in recent years. This paper presents the results of a study of more than 3,500 geophysical and driller's logs in Washington County in southeastern Ohio. Structure contours show major trends, such as the Burning Springs anticline and the Cambridge arch, trending almost north-south. In the western third of the county, structural trends change, however, to a more complex, less continuous pattern with a predominant northeast-southwest trend. Isopach trends delineate a system of ch nnel sands trending roughly east-west with sandstone thicknesses ranging from 0 to greater than 25 ft (8 m). Both structures and thalwegs are relatively narrow and thickness changes rapidly, both parallel to and normal to the thalweg. Although no new interpretations of Berea structure End_Page 244------------------------------ or depositional environment is intended, this study graphically shows that even in a mature province, low-cost, closely spaced data can indicate new minor structures and delineate new areas for profitable and productive testing with the drill. End_of_Article - Last_Page 245------------

Breaks in Resistivity Sounding Curves as Indicators of Hard Rock Aquifers

In a previous paper (Nordic Hydrology, Vol. 12, 1981), the authors have discussed the inadequacies in the technique of resistivity method for location of sites for constructing deep water walls in hard rock areas. It was pointed out that the water bearing fracture zones in the bed rock could not be identified by merely considering geoelectrical parameters such as layer resistivity. An empirical study based on the correlation of minor irregularities or deviations – “BREAKS” – in the normally smooth sounding curves with the actual driller's logs reveals that under normal geo-electric conditions these water bearing zones (hard rock aquifers) are indicated in the curve by a perceptible lowering of apparent resistivity and hence could be used as a guide for locating well sites. As such breaks may also be caused by other conditions such as lateral inhomogeneities, certain methods for distinguishing them are discussed.

Mud Pulse MWD Systems Report

Summary Measurement-while-drilling (MWD) systems, using mud pulse telemetry, are now available to the industry. The most popular sensor package is for directional drilling measurements. Accuracy of such measurements has been proved under field conditions and has resulted in considerable savings in rig time. This acceptance and usage has increased the demand for other sensors, for improved drilling efficiency, kick detection, and formation evaluation. Introduction The acronym MWD currently is used by the industry to describe telecommunications between the bottom of the drillstring and the surface. MWD at the surface is not new. Since the beginning of the drilling industry in the mid-1800's it has been a standard practice to record the time required to drill each foot of hole. A correlationtype log may be made by comparing the drilling time with the cuttings returned from downhole to establish the tops and bottoms of different formations. This driller's log was the sole logging method used by the industry until 1927, when the first electrical logs were developed. As early as 1932, attempts were made to make these downhole electrical measurements during the drilling process. Such efforts used an insulated cable inside the process. Such efforts used an insulated cable inside the drillpipe and were termed logging-while-drilling. Intended to replace the conventional logs, these electrical alternatives were not very successful for both technical and economical reasons. After the sudden increase in oil prices during the 1970's, renewed efforts were made by prices during the 1970's, renewed efforts were made by many companies to refine such methods. During this period, there was no standard industry nomenclature for period, there was no standard industry nomenclature for this procedure. In various companies it was called MWD for measurement-while-drilling, LWD for logging- while-drilling, or DHLWD for downhole-logging-while- drilling. In most instances, the information obtained is not intended to replace conventional well logs and often is nothing more than a few measurements taken intermittently on hole angle and direction. More descriptive terms might be downhole-measurements-made-while-drilling (DHM-MWD) or downhole-mud-pulse-telemetry-measurements (DHMPTM). These terms might better differentiate measurements made at the surface while drilling from downhole measurements telemetered to the surface while drilling. The entire industry has adopted the term MWD, although this generally refers only to downhole measurements telemetered to the surface while drilling. The need for intermittent directional measurements (unlike the need for continuous information, as obtained by conventional wireline logs) may be another reason that MWD seems to be an accepted term for these new procedures. As the market matures it may develop a new procedures. As the market matures it may develop a new terminology, but for now it seems to be MWD. Other sensors and devices for improving dulling efficiency and safety, as well as providing correlation-type logs, are being added by most companies. The MWD directional methods show a considerable advantage over older techniques, since lost rig time for wireline surveying or other means to determine hole angle and direction in deviated wells can be very costly. These immediate savings have caused MWD directional services to find a ready market. Basic Types of Mud Pulsers Mud pulse telemetry types currently available include:1. Negative pressure pulses generated by a bypass valve from inside the drillstring to the annulus (Fig. 1a). JPT P. 2301

Inadequacies in theTechnique of Resistivity Method for Location of Waterwell Sites in Hard Rock Areas

Large scale exploratory work for groundwater in hard rock region of South India has been carried out by the authors during the last ten years, using electrical resistivity method. The standard methods of data interpretation were found to be inadequate in locating water well sites and determining the existence and depth of occurrence of water bearing fractures and joints. Wenner and Schlumberger type vertical electrical sounding (VES) curves were interpreted by matching against theoretical model curves and also by inverse slope method. The interpreted results were correlated with the actual driller's logs. No satisfactory correlation could be observed either between the geoelectrical interpreted layer boundaries and the layer boundaries from the wells or between the resistivity in the hard rock and the water yield. A more pragmatic approach to the problem is desirable to minimize the failures of wells in hard rock terrain.

Well‐Water Quality Changes Correlated with Well Pumping Time and Aquifer Parameters—Fresno, Californiaa

ABSTRACTGround‐water chemical quality in alluvial valleys can be stratified, which can cause well‐water quality to vary with pumping time, especially after a pump shutdown of several hours. These changes in chemical quality could have public health implications for automatically controlled high‐capacity municipal water wells that pump directly into the distribution mains.For a large number of municipal wells, the shapes of the curves for the change‐in‐specific electrical conductivity and the NO3‐N content of well water during the first 96 minutes of constant rate pumping are reported after a 24‐hour shutdown as compared with “steady‐state” quality. The variables recovery‐transmissivity, well specific capacity, type of well construction, and equivalent specific yield of aquifer computed from driller's logs of the bore holes were considered in the analysis.The results showed that well‐water quality vs. time curves vary in shape and are related mainly to the well depth and the depth to the perforations. The “steady‐state” specific electrical conductivity and NO3‐N values were significantly correlated to each other and inversely to recovery‐transmissivity and equivalent specific yield. The specific capacity of wells was related to the recovery‐transmissivity and to type of well construction.

Uniqueness of a model of steady-state groundwater flow

The main objective of this study was to investigate some of the methods and conditions necessary to determine bounds on values of the hydrogeologic parameters which characterize a model of steady-state areal near-surface groundwater flow. The basic tool selected to accomplish the research objectives was the optimization approach to determining the parameters. With this approach the parameters are calculated by minimizing some selected objective function composed of a measure of the difference between observed and computed heads. Several methods were investigated for possible use, and modifications of the ones by Coats et al. and Yeh and Tauxe were selected for comparison. The results of application of the Coats et al. method to several test problems and a field area indicate that occasional large errors may occur even when the input data (water levels and constraints on parameters) are very good, and that when the data are subject to various errors, as is the case for the Truckee Meadows data, the method is unreliable. Application of a modified version of the Yeh and Tauxe method to test problems and Truckee Meadows, Nevada, yielded much better results than did the method of Coats et al. There is no unique set of parameters which produce a distinct minimum error (defined as the sums of squares of the differences between computed and observed hydraulic heads) for the Truckee Meadows data. The apparent minimum error occurs for transmissivity which is constant throughout the valley. This appears to conflict with the geological and driller's log evidence that show the existence of zones of differing average hydraulic conductivity (and presumably transmissivity). However, some of the parameters can be changed over a large range and the error is not materially affected. Thus, the system is not well determined by the “optimum” parameters and other combinations of parameters, including combinations that satisfy the geological constraints, yield solutions that are almost as good. The failure of the water-level data to provide a definite optimum solution which conforms to the geological evidence may be due at least in part to the basic methods normally used to construct water-level maps. By changing the positions and configurations of contours within logical limits, it would be possible to turn recharge or discharge areas into adjacent zones of differing transmissivity and vice versa. Data collection and use of a reliable parameter estimation method are complementary. Early, preliminary computation of parameters in a study would indicate areas where data are contradictory or inadequate and where additional critically placed data should be collected. Repeated application of this process should result in a more efficient expenditure of time and money than occurs for the more traditional approach where the model is applied at a late stage in the study.