Impervious Rock Research Articles

Parameters of hydraulic fracturing and disintegration of impervious rocks while preparing blocks for leaching

1. The maximum water injection pressure for hydrofracturing of Blyava ores was 12.1–12.9 MPa and for hydrodisintegration, 4.5–5.5 MPa. The calculated values of these pressures differ from the experimental ones by 20–25% and 25–36% respectively, which is satisfactory for natural-scale studies.

Permeability considerations about rock foundation on waste disposal

Abstract The use of the traditional permeability test (the water pressure test) to analyse the permeability of rock foundations for waste disposal, is not applicable in all materials because the high pressures used in the test may produce hydraulic fracturing. This paper describes a new permeability test, called the low pressure test or LPT, which is used to obtain the true permeability of a waste disposal foundation on weak and impervious rock. Finally, the results obtained with the use of the LPT to analyse the permeability of a waste disposal foundation are described.

Hydrocarbon Productivity Characteristics of Upper Jurassic Smackover Carbonates, Eastern Gulf Coastal Plain

ABSTRACT The Upper Jurassic Smackover Formation is a prolific oil and gas reservoir in the eastern Gulf Coastal Plain. To date, over 838 million barrels of oil and condensate and 2.4 trillion cubic feet of natural gas have been produced from 157 Smackover fields located in the area. The tectonic setting and depositional and postdepositional history of the Smackover carbonates and associated strata have been conducive to the formation of numerous petroleum traps, the accumulation and preservation of substantial organic matter, the thermogenic generation and preservation of large quantities of hydrocarbons, the formation of extensive porous and permeable reservoirs, the subsequent enhancement of reservoir quality, and the formation of a regional impervious seal rock. In addition, the timing of trap formation and hydrocarbon generation and migration have been important to oil and gas entrapment and preservation. An understanding of the factors that contribute to the hydrocarbon productivity of the Smackover will assist with improving the recovery of oil and gas from these limestones and dolostones.

Quartz‐kaolinite rocks from northeastern new south wales: distal products of a pluton‐driven hydrothermal system

In the Long Flat district of northeastern New South Wales, elongate lenses composed largely of quartz and kaolinite have been produced by the alteration of Palaeozoic volcaniclastic sedimentary rocks and silicic dykes. Alteration was brought about by heated acid waters, probably at temperatures of about 200°C, that circulated along fractures in otherwise impervious rocks, and the lenses are considered to delineate discharge channels of a hydrothermal circulation system associated with a cooling granite pluton. High water: rock ratios are indicated. SiO2 was added during alteration and CaO, Na2O, MgO and Sr, Cu, Zn and Pb were removed. Some of the metals mobilized may have formed mineralized veins of the type found in the surrounding region.

A Study of Flow Through a Fracture Network Described by Statistically Distributed Properties

An analysis of the confidence of flow solutions for stochastically generated hard rock formations study was carried out with the aid of a simplified synthetic model. The formation was conceptualized as a fracture network with a known geometric structure intersecting an impervious mass rock while fracture permeability was considered a stochastic process. Safety analysis of radioactive waste repositories includes prediction of travel times of possibly contaminated water particles from the repository to the biosphere. While such calculations require that rock properties, such as permeability, be known over the entire flow domain, only limited information is available in practice, and interpolation methods are called for. An a priori model was constructed as a first step, with fracture permeabilities generated according to a given probability distribution; this a priori model was considered the ''true'' formation. In a second step, a limited amount of information, similar to that obtained in reality from boreholes, was used to construct a conditioned-by-measurement model. Identical flow tests were performed on formations represented by the two models, and the flow rate ratios resulting from these tests served as the measure of confidence of the stochastically generated formation.

An overview of the state of geothermal energy

This paper provides an overview of the present status of geothermal energy world-wide. Although the origin of this form of energy dates back in history, its impetus (with the notable exceptions of Italy and Iceland) was the ‘energy crisis’ of the mid to late 1970s. A wide range of speculations were made during those years as to the potential contribution of geothermal energy to the world energy demand. The present lull in the energy scene allows a more realistic assessment of present and near future potential. Problem areas related to the development of the geothermal resource potential are also discussed. They address both natural, mainly liquid dominated, sources and the recovery of heat stored at depth in impervious rocks through man-made geothermal reservoirs known as the hot dry rock concept of heat mining.

Confidence in Solutions of Flow Through Stochastically Generated Hard Rock Formations

AbstractConfidence in solutions of flow through stochastically generated hard rock formations was studied with the aid of a simplified synthetic model. The formation is conceptualized as a fracture network intersecting an impervious rock mass. The geometrical properties of the fracture network were assumed to be known while fracture transmissivities were considered a stochastic process.First, network fracture transmissivities were generated using a given probability distribution function. This a priori model was considered the “true formation”. In a second step, only a limited amount of information, similar to that obtained in reality from boreholes, was used to construct a conditioned-by-measurement model.Identical flow tests were performed on a formation constructed with limited data and on the “true formation”. The ratio of the rates of flow resulting from these tests was considered a measure of confidence in the stochastically generated formation. The results, with this model and a particular data set, show uncertainty values between 47% to 63%, corresponding to fracture sample sizes of 11% and 2% respectively, from the total number in the network.

Retorting of Single Oil-Shale Blocks With Nitrogen and Air

Abstract Experiments on retorting single oil-shale blocks were carried out to investigate the anomalous, last internal-beating phenomenon reported by the other investigators. Two 0.156-liter/kg (37.5-gal/ton) oil-shale polyhedral blocks (about 18 cm or 7.1 in. in diameter) with almost identical organic content and lithological Properties were heated at atmospheric pressure to 500 degrees C (932 degrees F) with a carrier-gas flow rate of 60 liters/hr (2.1 scf/hr). Carrier gas was air for one test and nitrogen for the other, while all the other experimental parameters were the same. The experimental results showed that the thermal behavior was the same for both runs and no anomalous, fast internal beating was observed. A third run with air at a higher flow rate (173 liters/hr or 6.1 scf/hr) also showed no sign of fast heating. Production of oil and gas was essentially completed in 5 hours under the beating mode of this study. Oil-recovery efficiency ranged from 80 to 91 percent Fischer assay. About 1 hour after the percent Fischer assay. About 1 hour after the beating started, almost no oxygen was detected in the effluent. The oxygen penetration into the shale was 1.5 cm (0.6 in.) or less. Introduction Oil shale is an impervious rock composed of very fine mineral particles intimately combined with solid organic matter. Prerequisites for in-situ retorting are the creation of sufficient surface area and fluid permeability within the rock to allow heat and mass transfer and to provide paths for fluid flow. In in-situ retorting, the oil-shale formation can be fractured by explosives (chemical or nuclear) or other means. The cost of fracturing such a formation varies inversely with the size of fragmented shale. On the other hand, more efficient heating of the fragmented shale and, hence, a higher kerogen conversion efficiency, can be achieved if the size of the fragmented shale is smaller. During retorting of 150-ton oil-shale experiments, Harak et al. observed that the thermocouple readings inside a 4-ton oil-shale block were higher than those on the block surface. Such an anomalous, fast internal-heating phenomenon (if it really happened) should be beneficial to an in-situ process because the requirement to reduce the process because the requirement to reduce the block size can be relaxed. However, it was found later that the fast internal heating was not real, but was the result of erroneous temperature readings resulting from chemical effects on the thermocouples. When the work of Harak et al. was first published, several investigations were initiated in published, several investigations were initiated in an attempt to substantiate their findings. Doggett heated single oil-shale blocks (77 to 142 kg) using air or N2 as a carrier gas. The presence of oxygen greatly increased the rate of heating deep in the rock. However, no quantitative comparison between the runs with air and N2 was feasible because of differences in the oil-shale grade, rock size, rock geometry, and thermocouple locations. Tyler cut single oil-shale blocks into hollow, thick-walled cylinders and heated the internal surface with air or N2. The temperatures inside the oil shale for the run with air were reported to be higher than those with N2. However, temperatures at the internal cylindrical surface were not given in the paper to compare with the reported internal temperatures. Mallon and Miller sealed pressure-sensing devices into oil-shale blocks (6.4 to 130 kg) that were heated. They observed periodic pulsing of the block internal pressure upon heating and concluded that the block internal temperature rose rapidly. Even though the work of the Laramie Energy Research Center did indicate that the phenomenon of fast temperature rise was not real, phenomenon of fast temperature rise was not real, the work of Mallon and Miller implied that the issue was not quite settled. Because of these conflicting reports, three carefully designed experiments were carried out in this report to investigate the so-called anomalous, fast internal-heating phenomenon. Refs. 3 through 5 report only on thermal aspects of oil-shale retorting. Very little experimental study has been published on the product formation from pyrolysis of single oil-shale blocks and the extent of oxygen penetration into the spent shale. The information is vital to the understanding of the fundamental mechanisms of oil-shale pyrolysis and is useful in verifying mathematical models. Johnson et al., in presenting a mathematical model to describe retorting of an oil-shale sphere, released a portion of their experimental data. SPEJ P. 331

Recent dedolomitization and the origin of the rusty crusts of Northumberland; a reply

ABSTRACT Two forms of dedolomitization. surface and near-surface, are found in the dolomitic Carboniferous rocks of the Middle Limestone Group of the northeast coast of Northumberland, England. This work is primarily concerned with the surface form of dedolomitization which is taking place in the Recent and sub-Recent, rusty-looking weathering crusts of the ferroan (iron-rich) dolostones. The rusty colour is caused by the presence of iron hydroxides in the weathering crusts. These iron hydroxides and the associated dedolomites are genetically related. The susceptibility of ferroan dolomites to dedolomitization is apparently caused by their metastability in the surface environment. Circulating sea or fresh water along permeable zones in the carbonates exposed at or near the present erosional surface is responsible for the oxidation and hydration of the ferrous iron content of the metastable ferroan dolomites as well as the dedolomitization of these dolomites. The dedolomitization mechanism has Been found to be a process of great potential in converting highly impermeable and impervious dolomitic rocks into a porous and permeable state. The detection of such a phenomenon in carbonate rocks at depth may, therefore, not only indicate an unconformity, but may help in the prediction of potential oil or gas reservoirs.

Preliminary study on the Ruiz geothermal project (Colombia)

The Ruiz region, located in the median part of the Colombian Central Cordillera, is featured by several Tertiary and Quaternary volcanic edifices and by a number of hot manifestations. This situation suggested that a feasibility study could be made for a research project of endogenous fluids. The project region stretches over an area of about 15,000 km 2. Research carried out was intended to reconstruct: lithological-stratigraphical features of the region, in terms of reservoir and cap-rock; volcanologic and structural events; hydro-geological situation; type and nature of manifestations. It was thus possible to single out the existence of two major circulation systems, separated from each other by a thick complex of impervious rocks. The former system chiefly develops at rather shallow depths within volcanic rocks; the latter develops at considerable depths within fractured quartzitic and carbonate terrains of the metamorphic regional basement. The deep circulation system is supplied by a wide absorption area located at altitudes exceeding 3500 m, close to the main volcanic edifices. All waters of the analyzed manifestations surely have a meteoric origin and appear to be merely involved in the shallow circulation.

A Computer Method to Calculate Two-Phase Flow in Any Irregularly Bounded Porous Medium

Abstract A fast method is needed for calculating thoroughly the performance of two-phase flow in reservoir rock with complex geometry. The authors present such a method and show its accuracy by comparison with laboratory performance of a five-spot pattern. In making the performance calculations, the quadrant of the five-spot pattern was divided into four channels. The computer time required for the calculation was one minute. This is roughly about 1/4 minute per channel. Introduction By using an electronic computer it is now possible to make reservoir performance calculations in which fewer assumptions and more significant variables are included than was possible with a desk calculator. These performance calculations include such variables as the properties of the reservoir rock and its contained fluids, properties of the rock-fluid system and even different well-spacing patterns. Usually, the more variables that are included the higher the computer cost-and time on the computer is expensive. As a result, a short procedure is needed so the many variables will be included and accurate performance calculations will result. If a reservoir is composed of alternate layers of permeable and impervious rock, and if each conducting layer has a different relative permeability, the combined computer cost for calculating each layer by the present long computer programs (which includes different well-spacing patterns and other variables) would be expensive. The performances of complex spacing patterns in a field often are studied by a potentiometric model, but in these model studies the analogy is to the flow of only a single phase. This paper presents a procedure to calculate the performance of a five-spot pattern with two phases flowing using a potentiometric model as a guide for the dimensions of channels and other related data. The time required to calculate the complete performance is about one minute on the IBM 7090 or four minutes on the IBM 704. The procedure can be extended to calculate the performance of more complex well spacings or an entire field with little modification. The procedure has been tested on the performance of the laboratory water floods of a five-spot pattern reported by Douglas, et al. The range of viscosity ratios in the laboratory experiments is from 0.083 to 754, which is extensive. The accuracy of the performance calculations is excellent as shown by the plotted points in Fig. 1.The recovery as influenced by the geometry of the five-spot, taking into account the deviation from true radial character, has been predicted by Aronofsky and Ramey. The authors used a potentiometric model to determine the sweep efficiency to breakthrough of the flooding agent. Dyes, Caudle and Erickson, by means of a laboratory model, show the influence of mobility ratio on recovery after breakthrough of the injected material. Dyes, et al, used the X-ray shadowgraph technique and miscible phases in their studies. Craig, Geffen and Morse from the analysis of the performance of their laboratory model correlate many variables, including average saturation of a flooding agent determined by permeability relationship. Craig, et al, used X-ray shadowgraphs to determine the sweep efficiencies in sandstone models. JPT P. 679^

Fractures in Sedimentary Rocks: ABSTRACT

The most abundant kind of deformation of rocks is by fracturing. There are three principal classes of fractures--(1) joints, (2) faults, and (3) small, irregular breaks (including shatter and breccia zones). In general, joints may be defined as more or less regular groups of relatively long fractures that are paralleled by little or no displacement or orientation of rock components. Joints occur in sets that may be parallel, radiate, or concentric. Sets occur singly or severally and with no universality of systems. The angular relations of intersecting sets range from sharply acute End_Page 1099------------------------------ to normal. In a given area two or three sets may be about equally developed in length and frequency, or one set may predominate. Joint sets may be confined to single beds or transect several formations and extend for more than a hundred miles. Strong and possibly thick beds tend to be less jointed, but existing joints are relatively long. Thin, relatively brittle beds are almost always jointed normal to their bedding. Relatively weak rocks are generally disrupted by small, irregular breaks. Shale, mudstone, claystone, and siltstone probably are much more fractured than any other sedimentary type, but the breaks are generally tight, inconsistently oriented, short, irregular, and commonly oblique to the bedding. Although individual joints are comparatively short in shale or claystone they are probably concentrated into zones which may have marked vertical or horizontal extent. The most persistent and apparent jointing in regions of flat beds is nearly vertical. Very many if not most joints appear to have formed soon after deposition during compaction, irregular settling, and broad, although irregular downwarping of the area of accumulation. Such early formed joints may be local and irregular, or they may be widely developed and display certain marked trends because of secular deep-seated wrenching, to broad coupling stresses acting mildly upon the entire area of deposition, or because of persistent depositional lineations. Composition, degree of consolidation, and bed-to-bed variation in brittleness or ductility strongly affect the amount of early fracturing. Early formed joints as well as some late ones have been thought to be caused by earthquakes and earth tides, but wind and glacial movement may more easily joint some types of near-surfa e rocks. Despite the evidence of early jointing during little or no deformation, undoubtedly new jointing develops during moderate and strong crustal deformation. During this operation early formed joints may be extended and the angular relations between sets may be changed. Under dynamic compression the stress pattern becomes more intricate, refracted, and variable. The local stress patterns change repeatedly with the progression of the deformation and the development of principal flexes and shear zones. Fracture thresholds are reached at various times and places for the various rock components, and withal the fracture pattern in its culmination is likely to be a complex mixture of reoriented non-diastrophic and multiple-stage tectonic joints, some of small and some of great dimensions. In general, however, the fracturing is accentuated in the parts that are otherwise most deformed and in the beds least supported by adjoining incompetent members. Fracture systems of uplifts and fold belts commonly have such a complex derivation that they bear little obvi us or regular relation to them. Fracture reservoirs for petroleum result where relatively brittle rocks are broken in an irregular manner and on a scale and frequency that may develop in a network in otherwise effectively impervious rocks. Sandstone, for example, may have many large fractures, but interconnection and imperviousness are not generally great. Shale or claystones may contain many fractures, but they are usually tight, short, and not so effectively connected. Fracture reservoirs may occur in any common lithologic type with the possible exception of salt. The requisites for effective development of fractured reservoirs in claystone or impervious siltstone appear to be (1) increased brittleness with respect to adjacent similar beds and (2) proximity of source petroleum. Shatter and breccia zones of several origins may also serve as tabular reservoirs or channels between reservoirs. These form principally in association with faulting or with folding where brittle beds are in maximum stress imbalance or reach a threshold of fracturing. End_of_Article - Last_Page 1100------------

Locating Casing Shoe Leaks With Radioactive Argon

Published in Petroleum Transactions, AIME, Volume 204, 1955, pages 213–216. Abstract Radioactive materials were used underground before the advent of the nuclear reactor. Radium containing ores have been mixed with cements and other materials for later location in oil wells by gamma ray logging since 1940. Perforating bullets have been marked with radium salts, and radioactive materials have been added to drilling muds to find the cause of "lost circulation." More recently colloidal suspensions of radioactive cobalt-60 and silver-110 and solutions of I-131 have been used in waterflooding operations to determine injection profiles, flow paths and water velocities. In this paper a recent and interesting underground tracer application is discussed. Development work and field engineering were carried out under the direction of Tracerlab, Inc., with assistance from personnel of the client. A gaseous tracer, argon-41, was used in an attempt to determine the cause of leakage from an underground gas storage reservoir. Statement of Problem This gaseous tracer application was carried out for the Natural Gas Storage Co. of Illinois. This company has developed an underground gas storage field 1,750 ft below the surface of the earth near the village of Herscher, Ill., about 60 miles south of Chicago. The total volume of gas stored in the field was estimated to be about 13 billion cu ft in the spring of 1954. The field has a maximum estimated storage capacity of 90 billion cu ft. The gas is contained in the Galesville sandstone, previously a water bearing formation of about 25 per cent porosity. The water as it is pushed out by the gas forms a barrier for the gas around the edge of the reservoir. Over the top and beneath the bottom of the reservoir are located several layers of impervious rock, which barring cracks or unplugged and unknown wells should act as seals.

Role of Cap Rock in Oil Accumulation

In the first series of experiments described, efforts were made in the laboratory to obtain an accumulation of oil in a sand saturated with salt water under an impervious cap rock. Various agents that have been recognized as of probable assistance in the migration of oil were enlisted to secure the anticipated accumulation of oil in two types of simulated geologic structures. These efforts to secure an accumulation beneath an impervious cap rock resulted in failure. A porous cap rock was used in the second group of experiments to secure the accumulation of oil. These experiments were successful. It was found that the cap rock was eventually sealed or made impervious by a process of differential viscosity. This process may have resulted from a chemical reaction between the oil and the sulphate radical, a common constituent of both connate and meteoric water, which increased the viscosity of the oil. The increased viscosity of the oil eventually sealed the cap rock.

Studies in Paleogeology

Paleogeology is defined as the science of the geology of ancient time. Paleogeologic maps are presented which show the areal geology and the regional structure of the region of the United States at the beginning of Mississippian time; in early Pennsylvanian time; and at the beginning of Cretaceous (Comanche) time. Similar maps may be prepared of other surfaces exposed during geologic time and they may be compiled for other countries. These maps have a wide application and give a different picture of geologic history. Oil and gas are found as high in their containing reservoir as it is possible for them to move. If true of the present, it must have been true in the past and a study of the changing areal and structural geology during geologic time becomes of prime importance. The earliest, therefore the most important, trap to form in many American petroleum provinces was a reservoir rock which was wedged out and overlapped by an impervious cap rock. Paleogeologic maps offer a means of locating these wedge edges and their application to petroleum geology opens a different approach to the problem of finding petroleum reserves.

Preservation of Oil During Erosion of Reservoir Rocks

Some of the most prolific oil fields in the United States are productive from porous rocks below unconformities of major importance. The oil is found trapped at the unconformity in porous rocks of pre-unconformity age sealed by non-porous rocks of post-unconformity age. If it is assumed that the oil formed and accumulated in the primary uplifts, it becomes necessary to explain how this oil was preserved during the long erosional interval when even the reservoir rocks were exposed and eroded. This problem is avoided if it be assumed that the oil was either not formed until after the deposition of the post-unconformity impervious rocks, or was introduced into the pre-unconformity reservoir rocks in post-unconformity time along the unconformity or in some other manner. It is believed that an impartial survey of the geological data affords no evidence either that the oil was formed in post-unconformity time or was introduced at a later date. Comparisons of the rock sections containing the unconformities with sections of identical age and lithology without great unconformities show the oil occurrences in both to be much alike. It seems just as reasonable, therefore, to assume the formation of oil to have occurred by the time the folding began which enabled accumulation to start. If this belief is accepted the problem of preserving the oil during exposure and erosion of its reservoir rocks must be squarely faced. The writer points out a protective mechanism. The action of gravity alone will protect the oil because (1) by definition an uplift lies above its surroundings, is an area of run-off of surface waters, and the exposed porous rocks constitute areas of intake, and (2) the underground fluid level of a major uplift never lies at the surface of erosion, but at appreciable depths below the surface. This protective process is latent in all uplifts undergoing erosion. Other factors necessary before this potentially protective mechanism becomes effective are (1) depth to underground fluid level when submergence occurs, (2) rate of deposition of impervious post- nconformity beds compared to rise of oil level toward eroded ends of reservoir rocks, (3) efficacy of post-unconformity sediments as impervious seals.

Oil Prospects of the Northwest Basin of Western Australia

Northwest Basin is one of seven sedimentary basins situated in whole or in part within the great state of Western Australia which covers an area about one-third the size of the United States. The basin, which has great artesian water flows, is 400 miles long and 175 miles wide, with a population of possibly 2,000 persons, the business of whom is mainly sheep farming. The formations range in age from Carboniferous to Recent, of which by far the most important are Permo-Carboniferous, Mesozoic, and Oligocene strata. Except in the Oligocene the greater part of the stratigraphic section is sandstone. No important impervious cover rocks are known and no positive seepages or other evidences of oil or gas could be found. Dips are high in the Permo-Carboniferous of the eastern ma ginal area; they decline to low monoclinal dips in the central areas and are again fairly high in certain coastal ranges of Oligocene age. Aside from the structure, however, no favorable fundamental conditions could be found. The basin is believed unfavorable for the existence of oil or gas in commercial quantity.

Classification of Springs

CONTENTS INTRODUCTION ACKNOWLEDGMENTS DEFINITION OF THE TERM CHARACTERISTICS OF SPRINGS SPRING WATER CLASSIFICATION Springs Due to Deep-seated Water Springs Due to Shallow Water Springs in Porous Rock (Depression Springs) Springs in Porous Rock Overlying Impervious Rock (Contact Springs) Springs at the Outcrop of a Horizontal Surface Springs at the Outcrop of an Inclined Surface Springs at the Outcrop of an Irregular Surface Springs in Porous Rock between Impervious Rock (Artesian Springs) Springs in Impervious Rock Tubular Springs Fracture Springs KEY TO THE CLASSIFICATION OF SPRINGS

IX.—Glacier Motion and Erosion

Although the ice of many glaciers, more especially thosewhich move over massive impervious rocks, is clean andalmost free from rock fragments, in many cases towards the bottomof the glacier, boulders, pebbles, and even masses of clay, mud, or sand abound. The rock-masses have evidently been derived from The floor over which the glaciers move, for the fragments become more numerous as we descend in the ice, the upper portion of the glacier being often quite free from foreign matter.

THE SANITARY AND UNSANITARY RELATIONS OF UNDERGROUND WATERS.Read in the Section of State Medicine, at the Forty-second Annual Meeting of the American Medical Association, held at Washington, D. C., May, 1891.

Gentlemen :—It is not my intention to deal at any length with this subject, but rather to present some of the principles to be observed in the selection of drinking waters. Much has been said with regard to the dangers of drinking water from wells; but it has not been until recently that the differentiation has been made as regards wells that are dangerous and those that are healthy. As a general principle, it may be said that practically all really underground waters are sanitarily good; but it must be clearly understood what is meant by an underground water. For instance: 1. A water lying in a shallow dug out in prairie or bog land, down only to the impervious clay or rock below, cannot fairly be called underground water. 2. Neither can a well down even into a true water-bearing stratum of sand or gravel, be called an underground water,