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Frederick L. Paillet

Publications and source records attributed to Frederick L. Paillet.

At least 37 records · Page 2Linked to original sources
USGS2001

Use of advanced borehole geophysical techniques to delineate fractured-rock ground-water flow and fractures along water-tunnel facilities in northern Queens County, New York

Advanced borehole geophysical methods were used to assess the geohydrology of crystalline bedrock along the course of a new water tunnel for New York City. The logging methods include natural gamma, spontaneous potential, single-point resistance, mechanical and acoustic caliper, focused electromagnetic induction, electromagnetic resistivity, magnetic susceptibility, borehole-fluid temperature and conductance, differential temperature, heat-pulse flowmeter, acoustic televiewer, borehole deviation, optical televiewer, and borehole radar. Integrated interpretation of the geophysical logs from an 825-foot borehole (1) provided information on the extent, orientation, and structure (foliation and fractures) within the entire borehole, including intensely fractured intervals from which core recovery may be poor; (2) delineated transmissive fracture zones intersected by the borehole and provided estimates of their transmissivity and hydraulic head; and (3) enabled mapping of the location and orientation of structures at distances as much as 100 ft from the borehole. Analyses of the borehole-wall image and the geophysical logs from the borehole on Crescent Street, in northern Queens County, are presented here to illustrate the application of the methods. The borehole penetrates gneiss and other crystalline bedrock that has predominantly southeastward dipping foliation and nearly horizontal and southeastward-dipping fractures. The heat-pulse flowmeter logs obtained under pumping and nonpumping conditions, together with the other geophysical logs, indicate five transmissive fracture zones. More than 90 percent of the open-hole transmissivity is associated with a fracture zone 272 feet BLS (below land surface). A transmissive zone at 787 feet BLS that consists of nearly parallel fractures lies within the projected tunnel path; here the hydraulic head is 12 to 15 feet lower than that of transmissive zones above the 315-foot depth. The 60-megahertz directional borehole radar logs indicate the location and orientation of two closely spaced radar reflectors that would intersect the projection of the borehole below its drilled depth. Subsequent excavation of the tunnel past the borehole allowed comparison of the log analysis with conditions observed in the tunnel. The tunnel was found to intersect gneiss with southeastward dipping foliation; many nearly horizontal fractures; and a southeastward dipping fracture zone whose location, character, and orientation was consistent with that of the mapped radar reflectors. The fracture zone produced inflow to the tunnel at a rate of 50 to 100 gallons per minute. All conditions indicated by the logging methods were consistent with those observed within the tunnel.

New York↗
USGS2001

An evaluation of borehole flowmeters used to measure horizontal ground-water flow in limestones of Indiana, Kentucky, and Tennessee, 1999

Three borehole flowmeters and hydrophysical logging were used to measure ground-water flow in carbonate bedrock at sites in southeastern Indiana and on the west-central border of Kentucky and Tennessee. The three flowmeters make point measurements of the direction and magnitude of horizontal flow, and hydrophysical logging measures the magnitude of horizontal flowover an interval. The directional flowmeters evaluated include a horizontal heat-pulse flowmeter, an acoustic Doppler velocimeter, and a colloidal borescope flowmeter. Each method was used to measure flow in selected zones where previous geophysical logging had indicated water-producing beds, bedding planes, or other permeable features that made conditions favorable for horizontal-flow measurements. Background geophysical logging indicated that ground-water production from the Indiana test wells was characterized by inflow from a single, 20-foot-thick limestone bed. The Kentucky/Tennessee test wells produced water from one or more bedding planes where geophysical logs indicated the bedding planes had been enlarged by dissolution. Two of the three test wells at the latter site contained measurable vertical flow between two or more bedding planes under ambient hydraulic head conditions. Field measurements and data analyses for each flow-measurement technique were completed by a developer of the technology or by a contractor with extensive experience in the application of that specific technology. Comparison of the horizontal-flow measurements indicated that the three point-measurement techniques rarely measured the same velocities and flow directions at the same measurement stations. Repeat measurements at selected depth stations also failed to consistently reproduce either flow direction, flow magnitude, or both. At a few test stations, two of the techniques provided similar flow magnitude or direction but usually not both. Some of this variability may be attributed to naturally occurring changes in hydraulic conditions during the 1-month study period in August and September 1999. The actual velocities and flow directions are unknown; therefore, it is uncertain which technique provided the most accurate measurements of horizontal flow in the boreholes and which measurements were most representative of flow in the aquifers. The horizontal heat-pulse flowmeter consistently yielded flow magnitudes considerably less than those provided by the acoustic Doppler velocimeter and colloidal borescope. The design of the horizontal heat-pulse flowmeter compensates for the local acceleration of ground-water velocity in the open borehole. The magnitude of the velocities estimated from the hydrophysical logging were comparable to those of the horizontal heat-pulse flowmeter, presumably because the hydrophysical logging also effectively compensates for the effect of the borehole on the flow field and averages velocity over a length of borehole rather than at a point. The acoustic Doppler velocimeter and colloidal borescope have discrete sampling points that allow for measuring preferential flow velocities that can be substantially higher than the average velocity through a length of borehole. The acoustic Doppler velocimeter and colloidal borescope also measure flow at the center of the borehole where the acceleration of the flow field should be greatest. Of the three techniques capable of measuring direction and magnitude of horizontal flow, only the acoustic Doppler velocimeter measured vertical flow. The acoustic Doppler velocimeter consistently measured downward velocity in all test wells. This apparent downward flow was attributed, in part, to particles falling through the water column as a result of mechanical disturbance during logging. Hydrophysical logging yielded estimates of vertical flow in the Kentucky/Tennessee test wells. In two of the test wells, the hydrophysical logging involved deliberate isolation of water-producing bedding planes with a packer to ensure that small horizontal flow could be quantified without the presence of vertical flow. The presence of vertical flow in the Kentucky/Tennessee test wells may preclude the definitive measurement of horizontal flow without the use of effective packer devices. None of the point-measurement techniques used a packer, but each technique used baffle devices to help suppress the vertical flow. The effectiveness of these baffle devices is not known; therefore, the effect of vertical flow on the measurements cannot be quantified. The general lack of agreement among the point-measurement techniques in this study highlights the difficulty of using measurements at a single depth point in a borehole to characterize the average horizontal flow in a heterogeneous aquifer. The effective measurement of horizontal flow may depend on the precise depth at which measurements are made, and the measurements at a given depth may vary over time as hydraulic head conditions change. The various measurements also demonstrate that the magnitude and possibly the direction of horizontal flow are affected by the presence of the open borehole. Although there is a lack of agreement among the measurement techniques, these results could mean that effective characterization of horizontal flow in heterogeneous aquifers might be possible if data from many depth stations and from repeat measurements can be averaged over an extended time period. Complications related to vertical flow in the borehole highlights the importance of using background logging methods like vertical flowmeters or hydrophysical logging to characterize the borehole environment before horizontal-flow measurements are attempted. If vertical flow is present, a packer device may be needed to acquire definitive measurements of horizontal flow. Because hydrophysical logging provides a complete depth profile of the borehole, a strength of this technique is in identifying horizontal- and vertical-flow zones in a well. Hydrophysical logging may be most applicable as a screening method. Horizontal- flow zones identified with the hydrophysical logging then could be evaluated with one of the point-measurement techniques for quantifying preferential flow zones and flow directions. Additional research is needed to determine how measurements of flow in boreholes relate to flow in bedrock aquifers. The flowmeters may need to be evaluated under controlled laboratory conditions to determine which of the methods accurately measure ground-water velocities and flow directions. Additional research also is needed to investigate variations in flow direction with time, daily changes in velocity, velocity corrections for fractured bedrock aquifers and unconsolidated aquifers, and directional differences in individual wells for hydraulically separated flow zones.

Indiana, Kentucky, Tennessee↗
USGS2001

Applications of resistivity modeling in reservoir development: examples from Balder Field, Norwegian North Sea

The massive Paleocene oil sands of the Balder Field are overlain by several thinly bedded Eocene sand-prone packages of variable facies and reservoir quality. Although these sands have been penetrated by numerous exploration and development wells, uncertainty remains as to their extent, distribution, and ultimate effect on reservoir performance. The section is geologically complex (thin beds, injected sands, shale clasts and laminae, and faulting), and also contains a field-wide primary gas cap. With a depletion plan involving both gas and water injection, geologic/reservoir characterization of the Eocene is critical for prudent resource management during depletion. With this goal, resistivity modeling and core-based thin bed reservoir description from the first phase of development drilling have been integrated with seismic attribute mapping. Detailed core description, core permeability and grain size distribution data delineate six facies and help in distinguishing laterally continuous massive and laminated sands from potentially non-connected injection sands and non-reservoir quality siltstones and tuffs. Volumetric assessment of the thin sand resource has been enhanced by I-D forward modeling of induction log response using a commercial resistivity modeling program, R,BAN. After defining beds and facies with core and high resolution log data, the AHF60 array induction curve response was approximated using the 6FF40 response. Because many of the beds were thinner than 6FF40 resolution, the modeling is considered to provide a lower bound on R,. However, for most beds this model-based R, is significantly higher than that provided by one-foot vertical resolution shallow resistivity data, and is thought to be the best available estimate of true formation resistivity. Sensitivities in STOOIP were assessed with multiple R, earth models which can later be tested against production results. In addition, water saturation height functions, developed in vertical wells and thick beds, can be validated in deviated wells with thin beds. Sand thickness models constrained by this logand core-based petrophysical analysis were used to build impedance seismic synthetic sections from which seismic attributes could be extracted and calibrated. The model-based attribute calibration was then applied to the seismic impedance 3-D cube permitting sand thickness to be mapped and reservoir geology to be modeled with significantly more detail than previously possible. These results will guide the field''s reservoir management and assist in the delineation of new targets.

Petrophysics↗
USGS2000

Flowmetering of drainage wells in Kuwait City, Kuwait

A heat-pulse flowmeter was used in six drainage wells in Kuwait City for flow profiling under both ambient and pumping conditions. The data collected were used in: (a) estimating the cross-flow among the screened intervals under ambient conditions; (b) estimating the relative transmissivity adjacent to the individual screen zones; and (c) determination of the hydraulic heads at the far boundaries of the large-scale aquifer zones. These inferences were cross-checked against known hydrogeology of the aquifer-aquitard system in the study area, and the calibration results of numerical flow modeling. The major conclusions derived from the flow measurements were: (a) the presence of natural downward cross-flow under ambient condition supported the hypothesis that the upper part of the Kuwait Group aquifer in the study area was divided into a series of permeable units (aquifers), separated by confining or semi-confining beds (aquitards); (b) the head differences between the different screened zones, derived through modeling of the flowmeter data of the wells, provided additional confirmation for the division of the upper part of the Kuwait Group aquifer into compartments in the study area; (c) flowmeter data indicated that the second and third aquifers were contributing most of the water to the well bores, compared with the uppermost (first) and the lowermost (fourth) aquifers; and (d) inflow to the wells during pumping was associated with discrete sub-intervals in the screened zones, controlled by local aquifer heterogeneity, and possibly clogging of screens and gravel pack.

Kuwait City↗
USGS1999

Lithostratigraphy, geophysics, biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifer system of eastern Collier County and northern Monroe County, Florida

In 1997, ten cores were drilled in eastern Collier County and northern Monroe County, within the limits of the Big Cypress National Preserve. These cores represent a continuation of the study of seven cores in western Collier County begun in 1996 and reported in Weedman and others (1997) and Edwards and others (1998). This joint U.S. Geological Survey and Florida Geological Survey project is designed to acquire subsurface geologic and hydrologic data in southwest Florida to extend current ground-water models, thereby expanding the utility of these models for land and water management. In this report we describe the lithostratigraphy, geophysical logging, sedimentological analysis, dinocyst biostratigraphy, and strontium-isotope stratigraphy of these ten cores. The three geophysical logs (natural gamma-ray, induction conductivity, and neutron porosity) assumed to be related to formation lithology and water quality show that a number of clay-rich zones are present in all of the boreholes, and that pore-water conductivity increases with depth. The clay-rich zones are confirmed by visual examination of core material and sedimentological analysis. The relative transmissivity calculated at 10-foot-thick intervals shows that in six of the boreholes, high values are associated with the shallow aquifer in the 0-40 ft interval. Two of the boreholes (the most northerly and the most easterly) showed relatively higher values of transmissivity in permeable zones at or somewhat below 100 ft in depth. Core geology and logs indicate that the deeper aquifers are not more permeable than similar deeper zones in the other boreholes, but rather that the shallow aquifer appears to be less permeable in these two coreholes. The Arcadia (?) Formation was only penetrated in the deepest core where it is late Miocene in age. The Peace River Formation was penetrated in all but the two westernmost cores. It yields a late Miocene age, based on both dinocysts and strontium-isotope stratigraphy. The top is an irregular surface. Age and stratigraphic relations suggest that the upper part of the Peace River and lower part of the unnamed formation are at least partially equivalent laterally. The unnamed formation was recovered in every core. It is thinnest in the northernmost core and thickest to the west. Ages calculated from strontium isotopes range from 6.9 to 4.6 million years ago (late Miocene to early Pliocene). The top of the unnamed formation is deepest to the north and it becomes shallower to the southwest. The Tamiami Formation also was recovered in every core and consistently yields early Pliocene ages; it yields late Pliocene ages near the top in two cores. The age and lateral relations strongly suggest that the lower part of the Tamiami Formation and the upper part of the unnamed formation are lateral facies of each other. The Fort Thompson (?) Formation, Miami Limestone, and undifferentiated siliciclastic sediments and limestone at the very top of the cores were not dated.

Florida↗
USGS1999

Geohydrology of monitoring wells drilled in Oasis Valley near Beatty, Nye County, Nevada, 1997

Twelve monitoring wells were installed in 1997 at seven sites in and near Oasis Valley, Nevada. The wells, ranging in depth from 65 to 642 feet, were installed to measure water levels and to collect water-quality samples. Well-construction data and geologic and geophysical logs are presented in this report. Seven geologic units were identified and described from samples collected during the drilling: (1) Ammonia Tanks Tuff; (2) Tuff of Cutoff Road; (3) tuffs, not formally named but informally referred to in this report as the 'tuff of Oasis Valley'; (4) lavas informally named the 'rhyolitic lavas of Colson Pond'; (5) Tertiary colluvial and alluvial gravelly deposits; (6) Tertiary and Quaternary colluvium; and (7) Quaternary alluvium. Water levels in the wells were measured in October 1997 and February 1998 and ranged from about 18 to 350 feet below land surface. Transmissive zones in one of the boreholes penetrating volcanic rock were identified using flowmeter data. Zones with the highest transmissivity are at depths of about 205 feet in the 'rhyolitic lavas of Colson Pond' and 340 feet within the 'tuff of Oasis Valley.'

Nevada↗
USGS1999

Characterizing fractured-zone flow using numerical flow-log models

Water-quality monitoring and hydraulic testing in fractured bedrock aquifers involves two important tasks: 1) identifying the hydraulically active fractures intersecting the borehole, and 2) inferring how the specific entry or exit ports in the borehole wall are connected to large-scale flow paths in the region surrounding the borehole. Effective characterization of fractured bedrock flow results when hydraulically active fractures and fracture zones are first identified using flow logs, and then the hydraulic properties of these active zones are given by subsequent hydraulic tests. A more difficult technical problem is relating the hydraulic properties of the few specific fractures that serve as borehole entry ports to the large-scale hydraulic properties of the surrounding rock mass. This problem is addressed through a generalized borehole flow model inversion formulated so that the boundary conditions at the outer edge of the boundary layer can be inferred from the properties of measured borehole flow.

Book chapter↗
USGS1998

Flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations

A numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high-resolution flowmeters. The model is designed to (1) precisely compute flow in a borehole, (2) approximate the effects of flow in surrounding aquifers on the measured borehole flow, (3) allow for an arbitrary number ( N ) of entry/exit points connected to M < N far-field aquifers, and (4) be consistent with the practical limitations of flowmeter measurements such as limits of resolution, typical measurement error, and finite measurement periods. The model is used in three modes: (1) a quasi-steady pumping mode where there is no ambient flow, (2) a steady flow mode where ambient differences in far-field water levels drive flow between fracture zones in the borehole, and (3) a cross-borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole. The model gives estimates of transmissivity for any number of fractures in steady or quasi-steady flow experiments that agree with straddle-packer test data. Field examples show how these cross-borehole-type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass.

Water Resources Research↗
USGS1998

Design, operation, and data analysis for a wireline packer system in open boreholes, with field-test results from Belvidere, Illinois

A wireline-operated packer was designed for use with a standard geophysical logging system. The packer probe consists of a downhole packer inflated with water removed from the borehole by an in-line submersible pump, and a differential pressure transducer calibrated to measure the hydraulic-head difference between the zones above and below the packer. Analysis of the packer data is based on a numerical model that predicts the water levels above and below the packer for a given set of aquifer zones of specified hydraulic head and transmissivity. Various computations are used to indicate the sensitivity of the packer measurements to the hydraulic head and transmissivity contrasts between aquifer zones. The wireline-packer probe was field tested in a series of open-bedrock boreholes in Belvidere, Illinois, at a site where vertical hydraulic-head differences are produced in a horizontally stratified aquifer by water production from an underlying aquifer. Analysis of the wireline-packer data produced estimates of hydraulic-head gradient and aquifer-zone transmissivity consistent with results from straddle-packer hydraulic tests. However, the wireline-packer data also indicated that there are significant variations of vertical hydraulic gradient with depth, and that the gradient is sharply reversed near the bottom of the boreholes. This result is consistent with upward ambient flow measured on previous occasions near the bottom of these boreholes, and has important consequences for the monitoring of ground-water flow at the study site.

Illinois↗
USGS1997

Borehole sampling of fracture populations - compensating for borehole sampling bias in crystalline bedrock aquifers, Mirror Lake, Grafton County, New Hampshire

The clustering of orientations of hydraulically conductive fractures in bedrock at the Mirror Lake, New Hampshire fractured rock study site was investigated by comparing the orientations of fracture populations in two subvertical borehole arrays with those mapped on four adjacent subvertical roadcuts. In the boreholes and the roadcuts, the orientation of fracture populations appears very similar after borehole data are compensated for undersampling of steeply dipping fractures. Compensated borehole and pavement fracture data indicate a northeast-striking population of fractures with varying dips concentrated near that of the local foliation in the adjacent rock. The data show no correlation between fracture density (fractures/linear meter) and distance from lithologic contacts in both the boreholes and the roadcuts. The population of water-producing borehole fractures is too small (28 out of 610 fractures) to yield meaningful orientation comparisons. However, the orientation of large aperture fractures (which contains all the producing fractures) contains two or three subsidiary clusters in orientation frequency that are not evident in stereographic projections of the entire population containing all aperture sizes. Further, these subsidiary orientation clusters do not coincide with the dominant (subhorizontal and subvertical) regional fracture orientations.

International Journal of Rock Mechanics and Mining↗
USGS1997

Integrity of production wells and confining unit at the Naval Weapons Industrial Reserve Plant, Dallas, Texas, 1995

Ground water in the shallow alluvial aquifer is contaminated at the Naval Weapons Industrial Reserve Plant, Dallas, Texas. Five production wells at the site are cased through the alluvial aquifer and underlying units and are screened in either the Paluxy or Twin Mountains aquifers. Three abandoned wells, originally completed in the Twin Mountains aquifer but filled with drilling mud in 1958, also penetrate the alluvial aquifer. The Paluxy and Twin Mountains aquifers are used for drinking-water supplies in and around the Dallas-Fort Worth metroplex. Trichloroethylene and its degradation products, dichloroethylene and vinyl chloride, and the metal chromium previously have been detected in the shallow alluvial aquifer. Current (1995) analyses of water-quality samples taken from the static water column of the five production wells and one of the abandoned wells indicate no trichloroethylene, dichloroethylene, or vinyl chloride in the water column of these wells. Chromium was detected in all samples, but concentrations were less than the practical quantitation limit, which is the regulatory action level for this site. The results of borehole geophysical log analysis indicate that two of the production wells could have vertically connected intervals where cement bonding in the well annulus is poor. The other production wells have overall good bonding. Temperature logs do not indicate flow behind casing except in the screened interval of one well. Geophysical logs show the Eagle Ford Shale ranges from 147 to 185 feet thick at the site. The Eagle Ford Shale has low permeability and a high plasticity index. These physical characteristics make the Eagle Ford Shale an excellent confining unit.

Texas↗
USGS1996

Hydrogeology of the Hawaii Scientific Drilling Project borehole KP-1 1. Hydraulic conditions adjacent to the well bore

Temperature and formation resistivity logs obtained in borehole KP-1 of the Hawaii Scientific Drilling Project indicate that the adjacent formation is characterized by several zones of distinctly different average temperature and water salinity. A series of hydraulic analyses and water sampling programs were conducted to rule out the possibility of local hydraulic effects associated with the presence of the borehole in the generation of these apparent groundwater zones. Hydraulic tests and sampling with the borehole cased to a depth of 710 m and open below that depth indicate that the deep aquifer contains seawater at a temperature nearly identical to that of the open ocean at the same depth. Various analyses give estimates of aquifer transmissivity of about 10-3 m2/s in the vicinity of the borehole. Isolation of this deeper aquifer from the overlying groundwater zones was investigated by perforating the casing at six locations and then measuring the changes in water level in the borehole, in the salinity of the fluid column, in the temperature profile of the fluid column, and in the rate of flow in the fluid column induced by the perforations. These results positively confirm that the zones of distinctly different formation properties indicated on the temperature and resistivity logs are not caused by flow in or around casing. Flow and fluid column salinity induced by the perforations also confirm significant differences between the hydraulic heads and geochemistry of the different groundwater zones inferred from the well logs.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

Hydrogeology of the Hawaii Scientific Drilling Project borehole KP-1 2. Groundwater geochemistry and regional flow patterns

A series of downhole and surface water samples were taken from the 1‐km‐deep KP‐1 borehole located on the eastern flank of the island of Hawaii. Early samples from depths of more than 700 m showed salinities nearly equivalent to seawater but having anomalous cation concentrations that are attributed to ion exchange between formation fluids and residual drilling mud clays. Later deep samples found only minor variations from seawater cation chemistry that are consistent with low‐temperature weathering of basalts; δ 18 O values are equivalent to seawater values and are consistent with this interpretation. Carbon 14 activities of dissolved inorganic carbonate indicate a water age ranging from 5890 to 7170 years B.P. and fluid transport rates of 1.8 to 2.2 m/yr. Fluid samples from perforations at 310 m in the borehole demonstrate that a freshwater aquifer is present at the Mauna Kea/Mauna Loa interface; borehole resistivity logs indicate that it is ∼200 m thick. Although it has not yet been possible to obtain samples of the freshwater zone without contamination from the deep saline fluids, the chloride concentrations of the low‐salinity zone are estimated using a mixing enthalpy calculation to be less than 100 mg/L. Light stable isotope data indicate that the fresh water at 320 m is derived from recharge entering the island at an average elevation of 2000 m. Inferred 14 C activities of the dissolved bicarbonate in the freshwater zone indicate an average calibrated age of 2200 years B.P. and an average fluid velocity of at least 14 m/yr. A regional water flow model is proposed that suggests that the fresh water found at the 320‐m depth is derived from rainfall recharge from the middle elevations of Mauna Kea volcano. This rainfall is channeled beneath the Mauna Loa lavas by the thick soil layer separating the two volcanoes. A second shallow fresh‐to‐brackish water zone, derived from Mauna Loa recharge, is also inferred to exist below the carbonate formation that underlies the shallow basal lens. The results of our preliminary study of the groundwater system below the KP‐1 drill site demonstrate that intervolcano and interflow aquicludes can have a substantial impact on water circulation and discharge from young island volcanoes.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

Analysis of fractures intersecting Kahi Puka Well 1 and its relation to the growth of the island of Hawaii

As part of the Hawaii Scientific Drilling Project, Kahi Puka Well 1 penetrated about 275 m of Mauna Loa basalts overlying a sequence of Mauna Kea flow units as it was drilled and cored to a total depth of 1053 m below land surface. A borehole televiewer (BHTV) was run in most of the well in successive stages prior to casing in order to obtain magnetically oriented acoustic images of the borehole wall. A total of 283 individual fractures were identified from this log and characterized in terms of strike and dip. These data are divided into three vertical sections based upon age and volcanic source, and lower hemisphere stereographic plots identify two predominant, subparallel fracture subsets common to each section. Assuming that most of the steeply dipping fractures observed in the BHTV log are tensile features generated within basalt flows during deposition and cooling, this fracture information can be combined with models of the evolution of the island of Hawaii to investigate the depositional history of these Mauna Loa and Mauna Kea basalts over the past 400 kyr. The directions of high-angle fractures appear to be generally parallel to topography or to the coastline at the time of deposition, as is supported by surface mapping of modern flows. Consequently, an overall counterclockwise rotation of about 75?? in the strike of these fractures from the bottom to the top of the well represents a systematic change in depositional slope direction over time. We attribute the observed rotation in the orientations of the two predominant fracture subsets over the past 400 kyr to changes in the configurations of volcanic sources during shield building and to the structural interference of adjacent volcanoes that produces shifts in topographic patterns.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

Integrated borehole logging methods for wellhead protection applications

Modeling of ground water infiltration and movement in the wellhead area is a critical part of an effective wellhead protection program. Such models depend on an accurate description of the aquifer in the wellhead area so that reliable estimates of contaminant travel times can be used in defining a protection area. Geophysical and hydraulic measurements in boreholes provide one of the most important methods for obtaining the data needed to specify wellhead protection measures. Most effective characterization of aquifers in the wellhead vicinity results when a variety of geophysical and hydraulic measurements are made where geophysical measurements can be calibrated in terms of hydraulic variables, and where measurements are made at somewhat different scales of investigation. The application of multiple geophysical measurements to ground water flow in the wellhead area is illustrated by examples in alluvial, fractured sedimentary, and fractured crystalline rock aquifers. Data obtained from a single test well are useful, but cannot indicate how conductive elements in the aquifer are connected to form large-scale flow paths. Geophysical and hydraulic measurements made in arrays of observation boreholes can provide information about such large-scale flow paths, and are especially useful in specifying aquifer properties in wellhead protection studies.

Engineering Geology↗