Packer Tests Research Articles

Analytic Assessment of the Water Table Drawdown, Seepage, and Back Pressure at Rudbar PSPP

The impoundment of the Rudbar dam raised underground water level. On the right bank, the elevation of the water table is monitored in exploratory boreholes. The water table has remained below the level of the reservoir. The lower level of the water table is due to underground tunnels and galleries that behave as drains. Special analytic developments have been carried out to analyze the behavior of the water table during impoundment. The peculiarity of the model is that it considers a draining tunnel in an open aquifer with a free water table. Two new equations are obtained: one for inflow of water and the other for the water table drawdown. These equations are used to assess the water table elevation in the exploratory boreholes, calculate the hydraulic conductivity of the rock mass from the measured seepage in the conveyance tunnel, and determine the efficiency of the sealing from the measured back pressure on the extrados of the drainage gallery. The comparison of the calculated hydraulic conductivity with the available information from measurements with packer tests and DFN predictions will reveal the importance of scale effects and uncertainties.

Substantiation of the rock massif permeability based on packer tests

There are uncertainties, concerning the hydraulic properties used in groundwater flow models while constructing them. This article shows the ranges of changes in hydraulic properties and their optimization for a groundwater flow model in a heterogeneous geological environment of the Nizhnekansky massif.

Formation pressure and fluid flow measurements in marine gas hydrate reservoirs, NGHP-02 expedition, offshore India

Abstract Open Hole Modular Dynamic Testing (MDT) measurements were conducted in a gas hydrate-bearing sand-rich reservoir offshore India during the National Gas Hydrate Program 02 (NGHP-02) Expedition. The primary goal of this test was to obtain effective reservoir petrophysical properties in the presence of gas hydrates. The test plan included a series of pre-hydrate dissociation flow and build-up (shut-in) tests, and an attempt to dissociate gas hydrate in a sand-rich reservoir by depressurization to collect formation fluid samples and to further characterize in situ gas hydrate stability conditions. Schlumberger's wireline MDT tool was used in a dual-packer configuration to isolate the formation being tested. This paper presents the results of the open hole MDT measurements that were conducted in Hole NGHP-02-23-C in Krishna-Godavari Basin at a water depth of 2553.5 m. The MDT dual packer test was conducted in 27 cm (10.63 in) diameter open hole section of the borehole within a 1-m interval isolated between two inflatable packers with the midpoint of the test interval at 2853.0 m below rig floor (mbrf) (271.0 m below sea floor (mbsf)). This was the first gas hydrate MDT test ever conducted in ultradeep water to characterize a gas hydrate reservoir system. Pre-hydrate dissociation testing was performed with a drawdown period (depressurization) of 20 min followed by a build-up (shut-in) of 20 min. The measured formation pressure was 4090.7 psia and the formation fluid (i.e., water) mobility was calculated at 1.98 mD/cP. During the second dissociation phase of the same test a maximum pressure drawdown of 840 psia was achieved; however, falling short of the 1120 psia drawdown required for dissociation. During the dissociation test the flow line pressure stabilized at a flowing pressure of 3250 psia which can be attributed to the relatively high mobility of the free water phase in the hydrate-bearing reservoir. Good quality formation pressure and near well bore mobility data was acquired that yielded a “high confidence” reservoir effective radial permeability-thickness product of 0.2 mD.m (or a horizontal effective permeability of 0.1 mD assuming a reservoir thicknees of 1.8 m) using pressure transient analysis (radial flow regime was achieved) despite unstable borehole conditions and complex operations in these shallow unconsolidated sedimentary sections.

Stress Measurements for an In Situ Stimulation Experiment in Crystalline Rock: Integration of Induced Seismicity, Stress Relief and Hydraulic Methods

An extensive campaign to characterize rock stresses on the decameter scale was carried out in three 18–24 m long boreholes drilled from a tunnel in foliated granite at the Grimsel Test Site, Switzerland. The survey combined stress relief methods with hydrofracturing (HF) tests and concomitant monitoring of induced seismicity. Hydrofracture traces at the borehole wall were visualized with impression packer tests. The microseismic clouds indicate sub-vertical south-dipping HFs. Initial inversion of the overcoring strains with an isotropic rock model yielded stress tensors that disagreed with the HF and microseismic results. The discrepancy was eliminated using a transversely isotropic rock model, parametrized by a novel method that used numerical modelling of the in situ biaxial cell data to determine the requisite five independent elastic parameters. The results show that stress is reasonably uniform in the rock volume that lies to the south of a shear zone that cuts the NNW of the study volume. Stress in this volume is considered to be unperturbed by structures, and has principal stress magnitudes of 13.1–14.4 MPa for σ1, 9.2–10.2 MPa for σ2, and 8.6–9.7 MPa for σ3 with σ1 plunging to the east at 30–40°. To the NNW of the uniform stress regime, the minimum principal stress declines and the principal axes rotate as the shear zone is approached. The stress perturbation is clearly associated with the shear zone, and may reflect the presence of more fragmented rock acting as a compliant inclusion, or remnant stresses arising from slip on the shear zone in the past.

An alternative approach to understanding groundwater flow in sparse channel networks supported by evidence from \u2018background\u2019 fractured crystalline rocks

Size and shape of individual flow-features, and not their ‘organization’ in sets of predominant orientation, are the major influences on the ability of groundwater to percolate through sparse channel networks. Measurements in background fractured crystalline rocks proposed for nuclear waste repositories provide useful insight. Flow-features are observed as locations of increased transmissivity during packer or flow testing in boreholes. They are conceived here as channels on fracture surfaces. Findings are based on numerical modelling and a general formula by Barker (2018) for the percolation of two-dimensional (2D) objects in 3D space. Equidimensional shapes are found to be the least efficient at forming percolating networks. As discs are evolved into highly eccentric ellipses, percolation thresholds for number, area and intersection density decrease. At the same time, the percentage of features forming the active flow path declines from about 10% for discs to a few per cent for 50:1 ellipses. Compiling recent field measurements of area density of flow-features reveals low values within a limited range (0.01–0.8 m−1). When this range is combined with practical values of likely channel width, long narrow flow-features are the only reasonable components of a sparse percolating network. Conventional equidimensional discrete fracture networks are considered unlikely. Innovative field investigation and modelling methods based only on hydrogeological measurements are suggested. It is concluded that this consideration of shape supports the approach, broadly termed the ‘long channel’ concept. Barker J.A. (2018) Intersection statistics and percolation criteria for fractures of mixed shapes and sizes. Comput Geosci 112:47–53.

Characterization and Remediation of Karst Collapse Columns for Mining Safety and Environmental Protection: A Case Study in Renlou Coal Mine, China

Karst collapse columns are unique collapse structures in karst terranes. Coal mining in China has exposed numerous such features of tens of meters in diameter and hundreds of meters in height. Hydraulically conductive collapses functioned as groundwater pathways between underground workings and aquifers, resulting in water inrushes during coal mining. Over the last 60 years, water inrushes through these collapses have caused fatalities, economic losses, and degradation in the environment. Determination of locations and hydrogeological characteristics of the karst collapse columns are essential in preventing water inrush incidents through them. Advanced geophysical prospecting, directional drilling, aquifer testing and accompanied dye tracing are effective approaches to detecting and characterizing these structures. Five geophysical techniques consisting of both surface and underground geophysical surveys and directional drilling of three exploratory boreholes up to 986 m deep identified a concealed collapse feature of more than 135 m high in Renlou Coal Mine, China. The roof of the collapse feature was at approximately 785 m deep, and there was an open void of 1.5 - 2 m high at the top. Geotechnical properties, results from packer testing and tracer testing, monitoring of potentiometric pressures, and geochemical fingerprinting suggested that this collapse column was hydraulically conductive and still actively developing. Water in the confined thin-bedded limestone and Ordovician limestone aquifer that either overlies or underlie coal seams could flow into the underground working areas if this feature were not identified in advance but encountered during mining. A grouting program was designed and implemented to construct a water plug in the collapse that effectively cut off the hydraulic connections from the aquifers to the underground workings. Successful construction of the water plug in the collapse was confirmed by performance monitoring of the aquifers.

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

AbstractAssessing the hydraulic connectivity of fractures by single‐borehole investigations is crucial to radioactive waste disposal but is still a challenge as such connectivity is difficult to measure directly. This study presents geological, hydrological, hydrochemical, and rock‐mechanical data for three faulted/fractured mudstones (the Koetoi, Wakkanai, and Palfris Formations) and proposes a new methodology for assessing the hydraulic connectivity of fractures. The methodology consists of three steps: (a) dividing the formation into two domains with a ductility index (DI) of >2 and <2 (DI is defined as the effective mean stress normalized to the tensile strength of intact rock), (b) estimating the hydraulic connectivity of fractures by analyzing pressure change obtained by packer tests and geological interpretation, and (c) verifying the estimation using pore pressure and water chemistry/geochemistry. The first step is necessary because the failure mode of damage‐zone fractures in fault zones can differ between the DI > 2 and DI < 2 domains, which may lead to significant differences in the hydraulic connectivity of fractures. During the second step, potential domains in which the hydraulic connectivity of fractures is limited are identified where upward trends, characterized by slopes of ∼0.5–1.0, are observed during the middle to late period of elapsed time on log‐log plots of pressure derivatives. Although the third step can be performed in various ways, this study employs the observation of pressure anomalies and the detection of young external water. Analyses of the three formations demonstrate the applicability and reliability of the proposed methodology.

Interpretation of high pressure pack tests for design of impervious barriers under high-head conditions

High pressure packer test (HPPT) is an enhanced constant head packer test widely applied for characterizing the permeability or coupled hydromechanical properties of fractured rocks under high water pressure condition, but it remains an issue about how to choose a representative quantity from the test data for the design of impervious barriers in high-head geotechnical projects. In this study, the typical type curves of HPPTs are summarized and related to the intactness of rocks, flow condition in fractures and the possible hydraulic fracturing phenomenon in the tested rocks. Based on an interpretative model recently developed for HPPTs, a criterion is proposed to determine a proper permeability rate from the HPPT data for design of grout curtains by taking into account the type curves and the transition of flow conditions, and is applied to illustrate the implication of the proposed criterion for the design of impervious barrier in a high arch dam foundation. The proposed criterion could be of significance in the design of impervious barriers for reducing the risk of leakage in rocks under high water pressure condition.

Remedial investigations of karst aquifers: a case study at former Marietta Air Force Station, Lancaster County, Pennsylvania

A phased multi-disciplinary approach was used to investigate potential environmental impact on the overburden aquifer and karst (bedrock) aquifer from the historic use of a suspected fire training pit at the former Marietta Air Force Station in Lancaster County, Pennsylvania. Investigation techniques have included direct push technology, real-time sample analysis via use of a mobile laboratory, earth resistivity imaging/induced polarization, geophysical borehole logging, packer testing, installation of one multi-port well with five sampling ports set in the karst aquifer, installation of multiple conventional monitoring wells, and completion of multiple rounds of groundwater sampling and data analysis. Both the vertical and lateral extents of groundwater contamination by chlorinated volatile organic compounds were delineated in the overburden and karst aquifer. The pathway-focused human health risk assessment has indicated that groundwater remediation is required to meet the federal and state health standards for volatile organic compounds. Based on the hydrogeological conditions and the nature and extent of the delineated contamination, plumes in both the overburden and karst aquifers, chemical oxidation (in the karst aquifer), and enhanced bioremediation (in the overburden aquifer) have been selected as the preferred alternatives for groundwater remediation, with monitored natural attenuation included as a common component of both alternatives.

Hydraulic Conductivity Modeling of Fractured Rock at Grasberg Surface Mine, Papua-Indonesia

Packer tests and slug tests were conducted at 49 points at the Grasberg surface mine, Indonesia to obtain hydraulic conductivity data. The HC-system approach, which relies on rock quality designation, lithology permeability index, depth index, and gouge content designation, was applied. Geotechnical drill holes in 441 locations, consisting of 4,850 points of information, were used to determine the K values using the equation K = 2x10 -6 x HC 0.5571 . The K values, which were within the range of 10 -8 and 10 -5 m/s, were distributed into five alternative 3D distributions using Ordinary Kriging (OK) and Artificial Neural Network (ANN). The result of the ANN modeling showed that some of the K values, with log K varying from -10.51 m/s to -3.09 m/s, were outside the range of the observed K values. The OK modeling results of K values, with log K varying from -8.12 m/s to -5.75 m/s, were within the range of the observed K values. The ANN modeled K values were slightly more varied than the OK modeled values. The result of an alternative OK modeling was chosen to represent the existing data population of flow media because it fits well to the geological conditions.

Comment on “Depth-discrete specific storage in fractured sedimentary rock using steady-state and transient single-hole hydraulic tests” by Patryk M. Quinn, John A. Cherry, Beth L. Parker, J. Hydrol. 542 (2016) 756–771

Quinn et al. (2016) presented a method to estimate storativity (S) of fractured sedimentary rock from straddle packer tests after transmissivity (T) of aquifer was determined from low-flow constant-head (CH) step tests. Constant-rate pumping tests were carried out to determine S by using the Cooper and Jacob (1946) approximation. Estimating the aquifer parameters depends on a matching of observation data to theoretical response which is mathematically obtained from a physical model. The results of both constant rate injection and withdrawal tests in the borehole C6zone17 cannot show this simulation. This comment proposes a reasonable procedure to estimate storativity.

Hydraulic In situ Testing for Mining and Engineering Design: Packer Test Procedure, Preparation, Analysis and Interpretation

Hydraulic in situ measurement of rock mass permeability by packer (Lugeon) testing is an inherent and integral element of many engineering, hydrogeological and mining investigation. This paper describes and discusses geotechnical testing in the design process from a consulting practitioner’s perspective. This study focuses on the Packer testing planning, procedure, results & interpretation. Packer test system is an optimum method for obtaining values of hydraulic conductivity in wells that are difficult to analyse using conventional slug test systems. Packer tests are carried out to assess the variability of a borehole as it intersects various hydrogeological units. It gives vertical distribution of hydraulic properties and water quality in the aquifer and usually cheaper than a nest of wells and gives more continuous record and this knowledge can often be essential for a proper design. The role, objectives, types and interpretation of testing, limitations and recommended good practices as part of the geotechnical design process are outlined through the examination of test data from a case record.

Depth-discrete specific storage in fractured sedimentary rock using steady-state and transient single-hole hydraulic tests

A method is presented for obtaining depth-discrete values of specific storage (Ss) from single-hole hydraulic tests in fractured rock boreholes using straddle packers (1.5–17m test intervals). Low flow constant head (CH) step tests analyzed using the Thiem method provide transmissivity (T) values free from non-Darcian error. Short-term, constant-rate pumping tests (0.5–2h) analyzed using the Cooper-Jacob approximation of the Theis method provide S from the hydraulic diffusivity using the Darcian T value from the CH step test. This synergistic use of two types of hydraulic tests avoids the common source of error when pumping tests (injection or withdrawal) are conducted at higher flow rates and thereby induce non-Darcian flow resulting in the underestimation of T. Other errors, such as well bore storage and leakage, can also substantially influence S by causing a shift in the time axis of the Cooper-Jacob semi-log plot. In this approach, the Darcian T values from the CH step tests are used in the analysis of the transient pumping test data for calculating S throughout the pumping test using the Cooper-Jacob approximation to minimize all of the aforementioned errors, resulting in more representative S values. The effect of these non-idealities on the measured drawdown is illustrated using the Theis equation with the Darcian T and S values to calculate drawdown for comparison to measured data. The Ss values for tests in sandstone obtained from this approach are more consistent with confined aquifer conditions than values derived from the traditional Cooper-Jacob method, and are within the range of field and lab values presented from a compilation of literature values for fractured sandstone. (10−7–10−5m−1) This method for obtaining Ss values from short-interval, straddle packer tests improves the estimation of both K and Ss and provides opportunity to study their spatial distribution in fractured rock.

Detailed hydrogeological analysis of a deep-seated rockslide at the Gepatsch reservoir (Klasgarten, Austria)

The hydrogeology of the deep-seated, slowly creeping Klasgarten rockslide in Austria is investigated in this study based on detailed surface and subsurface field data, laboratory analyses, and analytical and numerical simulations. Field data are derived from several deep exploration and monitoring boreholes, an exploration drift located within the rockslide, and geological and geomorphological mapping. Particular attention is given to the pore pressure measurements and their temporal and spatial variability. These pore pressure variations are controlled by a thin layer of clayey fault gouge (representing the basal shear zone of the rockslide), a high-permeability rockslide mass, and moderately fractured paragneissic bedrock. Variably saturated equivalent-continuum hydraulic conductivities and storage properties are derived from packer tests, laboratory tests and optical televiewer images. These data sets are used for two-dimensional numerical groundwater models to study the flow-field and pore-pressure variations caused by the reservoir water-level fluctuations, the transient groundwater infiltration from snowmelt and precipitation along the slope, and the exploration drift. The strongest pressure transients in the rockslide are caused by reservoir level fluctuations and not the natural groundwater recharge, even at substantial distances from the reservoir. The response times are very short and only a minor distance-dependent attenuation is observed. The results of this study are essential to analyse the hydromechanical control of the deformation behaviour of rockslides adjacent to hydropower reservoirs. Further, it helps to understand how the formation of a rockslide can change the original bedrock aquifer.

Blended head analyses to reduce uncertainty in packer testing in fractured-rock boreholes

Open boreholes in fractured rock often cross-connect fractures with differing hydraulic head and the head differences between these fractures cause vertical flow in the water column. This cross-connection has potential to bias transmissivity (T) values obtained from straddle packer tests. This study demonstrates how measurements of the blended head in the open-hole segments above and below the straddle-packer test interval can be used to correct packer tests for cross-connection effects. A pressure response observed in the open-hole segment above and/or below the packers isolating a test interval during a hydraulic test indicates short-circuiting of water from the injection interval through the vertically connected fracture network to the open-hole segments, resulting in the overestimation of T. A method is presented using blended head concepts to minimize this error using a trial-and-error procedure to determine the short-circuiting flow rate to account for the head conditions in the open-hole segments during each hydraulic test. Observed differences between the measured head and the calculated blended head in the open-hole segments above and below the test interval are attributed to cross-connection effects around the 1-m-long packers. The head and corrected T values determined from packer tests are used to estimate the flow in and out of the open hole at each of the intervals tested for assessing the cross-connection effects under open borehole conditions. Understanding open-hole flow dynamics gives insight about the potential for vertical cross connection of chemical constituents caused by the open hole.

Non-Darcy's law-based analytical models for data interpretation of high-pressure packer tests in fractured rocks

High-pressure packer test (HPPT) is an enhanced constant head packer test for characterizing the permeability or coupled hydromechanical properties of fractured rocks under high-pressure groundwater flow conditions. The interpretation of the HPPT data, however, requires further investigations due to the non-Darcy flow prone to occur in the tested rocks at high flow velocities. In this study, two analytical models were presented based on the Forchheimer's law and Izbash's law, respectively, for interpretation of the HPPT data, which can be readily reduced to Hvorslev equation in laminar flow condition. The proposed models were applied to data interpretation and hydraulic parameter estimation for the HPPTs performed in fractured sedimentary rocks located at about 450m depth in central Hainan Island, and validated by numerical simulations on the tests. The results indicate that both of the proposed models well reproduce the non-Darcy flow behavior observed in the HPPTs before the initiation of hydraulic fracturing. Overall, the Forchheimer's law-based model is advantageous for its clear physical meanings, but the Izbash's law-based model could be more convenient when the obtained P–Q curves are divided into different phases according to the flow conditions in the fracture system. Also pointed out were the theoretical flaws in an existing Izbash's law-based analytical model, which lead to a misestimate of hydraulic conductivity and an inconsistency between the analytical solutions and numerical results.

Engineering-geological properties of carbonates and shale: their implications for dam construction in Mekelle, Northern Ethiopia

Growing water demand poses severe problems to the population in the Mekelle Outlier, Northern Ethiopia. Hence, storing of rain water for water supply becomes one of the top agenda in the area. Several earth-fill dams are constructed for irrigation and drinking water supply purposes over the last 15-20 years. However, as collected data indicated more than 60% of these earth-fill dams have excessive leakage due to the problematic engineering geological nature of the carbonates and shale rocks of the study area. Giba dam is one of the currently proposed largest dams to alleviate the water supply problem of the Mekelle city. In the current study, engineering-geological mapping, core drilling, geophysical surveys and laboratory works have been conducted for the dam project to evaluate the engineering-geological nature of rocks of the area. Qualitative and quantitative rock masses properties such as permeability, strength and deformation are analyzed using Packer test, Rock Quality Designation (RQD), and Rock Mass Rating (RMR) systems. Analyzed results displayed that: (i) the RQD values are highly variable for all the rock masses. For example, 60% of limestone (Lst), 50% marly limestone (MLst) and 72% shale (Sh) are categorized as poor /very poor RQD values. RMR values also imply that Lst, MLst and gypsum are classified class-III while Sh is classified in class-IV (ii) considering the rock mass shear strength parameters (C, ϕ), the Lst, MLst, and gypsum have a moderate strength while Sh as low strength. More than 92% the Lst and 84% of the MLst falls in the 5-50 and >50 Lugeon Value classes. Thus, area covered by both the Lst and MLst needs treatment (e.g. grouting). Similarly, 50% and 20% of the packer test values of shale falls in the <1 and 1-5 Lugeon value classes respectively. The studied rock properties implies that the limestone layer is not suitable for the construction of the earth-fill dams in terms of water tightness while that of the calcareous shale and/or mud rock is good site for reservoir area as it is water tight. Keywords : Carbonate rocks, Shale, Rock mass, Packer test, Giba dam, Mekelle, Ethiopia.

Estimating hydraulic conductivity of fractured rocks from high‐pressure packer tests with an Izbash's law‐based empirical model

AbstractHigh‐pressure packer test (HPPT) is an enhanced constant head packer test for characterizing the permeability of fractured rocks under high‐pressure groundwater flow conditions. The interpretation of the HPPT data, however, remains difficult due to the transition of flow conditions in the conducting structures and the hydraulic fracturing‐induced permeability enhancement in the tested rocks. In this study, a number of HPPTs were performed in the sedimentary and intrusive rocks located at 450 m depth in central Hainan Island. The obtained Q‐P curves were divided into a laminar flow phase (I), a non‐Darcy flow phase (II), and a hydraulic fracturing phase (III). The critical Reynolds number for the deviation of flow from linearity into phase II was 25−66. The flow of phase III occurred in sparsely to moderately fractured rocks, and was absent at the test intervals of perfect or poor intactness. The threshold fluid pressure between phases II and III was correlated with RQD and the confining stress. An Izbash's law‐based analytical model was employed to calculate the hydraulic conductivity of the tested rocks in different flow conditions. It was demonstrated that the estimated hydraulic conductivity values in phases I and II are basically the same, and are weakly dependent on the injection fluid pressure, but it becomes strongly pressure dependent as a result of hydraulic fracturing in phase III. The hydraulic conductivity at different test intervals of a borehole is remarkably enhanced at highly fractured zone or contact zone, but within a rock unit of weak heterogeneity, it decreases with the increase of depth.

Grouting Improvement in a Mined-Out Area under Tangshan-Tianjin Expressway, China

Expressway construction in mined-out area is faced with some challenges, such as differential settlement and excessive deformation. This paper presents a case study of grouting improvement in a mined-out area under Tangshan-Tianjin expressway, China. The geological conditions in the mined-out area and the mechanisms of surface subsidence are described. A detailed grouting treatment scheme is planned and carried out to reinforce the rock masses. Technical requirements for grouting are described to ensure the reinforcement effect. Verification of the reinforcement effect is carried out using several techniques such as packer test and core drilling method. The results show that the proposed grouting scheme achieves desired effects.

Combined use of straddle packer testing and FLUTe profiling for hydraulic testing in fractured rock boreholes

A combination of high resolution hydraulic tests using straddle packers and transmissivity (T) profiling using the FLUTe flexible liner method (liner profiling) in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of T along the entire hole. The liner T profiling method takes a few hours or less to scan the entire borehole length resulting in a T profile. Under favorable conditions this method has good reliability for identifying the highest T zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner. In contrast, for one short test interval (e.g., 1–2 m) the multiple-test, straddle-packer method takes a few hours to measure T with good precision and accuracy using a combination of steady-state and transient tests (e.g., constant head step tests, slug tests, and constant rate pumping tests). Because of the time consuming aspect of this multiple-test method, it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing. The T profile from the liner method is instrumental in selecting high permeable zones for application of the multiple-test method using straddle packers, which in turn, refines the T estimation from the liner profile. Results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures.