bluuebunny/crossref_metadata_2025_split huggingface dataset:
Faulting, fault sealing and fluid flow in hydrocarbon reservoirs: an introduction
Authors: Knipe R. J. , Jones G. , Fisher Q. J. 
Published: April 2008

Abstract
A predictive knowledge of fault zone structure and transmissibility can have an enormous impact on the economic viability of exploration targets and generate considerable benefits during reservoir management. Understanding the effects of faults and fractures on fluid flow behaviour and distribution within hydrocarbon provinces has therefore become a priority. To model fluid flow in hydrocarbon reservoirs, it is essential to gain a detailed insight into the evolution, structure and properties of faults and fractures. Generation of realistic flow models also requires calibration with data on the fluid distributions and flow rates from hydrocarbon fields. Most hydrocarbon geologists at one time or another have asked the question ‘What is the behaviour of this fault?’. This question, as emphasized by the contributions to this volume, should more fundamentally be phrased; ‘What is the geometry of this fault zone, what are the nature and petrophysical properties of any fault rocks developed and how are they distributed in the subsurface?’. An additional important question is ‘What impact could the fault zone have on fluid flow through time?’. The properties and evolution of fault zones can be evaluated using the combined results of structural core and down-hole logging, microstructural and physical property characterization, together with analysis of faults from seismic and outcrop studies and well test data. Successful fault analysis depends upon the amalgamation of these data and incorporation into robust numerical flow models.
The appearance of potential sealing faults on borehole images
Authors: Adams J. T. , Dart C. 
Published: April 2008

Abstract

Electrical and acoustic borehole images provide data on the structure, width, spacing and orientation of potential sealing faults in the subsurface. These data bridge the ‘scale of observation gap’ between the resolution limits of more conventional data such as seismic data and core, and provide continuous records often up to several thousand feet long. Potential fault seals can be measured from vertical, deviated or horizontal wells and from either clastic or carbonate rocks. Five categories of potential fault seals can be described from images:
juxtaposition fault seals
place reservoir against seal lithologies and appear as sharp image contrasts;
clay lined fault seals
commonly appear as shale rich bands on electrical images, which may be either resistive or conductive depending on the resistivity of the host lithology, and low amplitude bands on acoustic images;
grain size reduction fault seals
appear as resistive or high amplitude features;
cemented fault seals
appear as highly resistive or very high amplitude features, and
open/vuggy faults
appear as conductive or very low amplitude features. An integrated approach to image interpretation incorporates not only borehole image data but also core, conventional wireline logs, pressure data and production information.
Structure and content of the Moab Fault Zone, Utah, USA, and its implications for fault seal prediction
Authors: Foxford K. A. , Walsh J. J. , Watterson J. , Garden I. R. , Guscott S. C. , Burley S. D. 
Published: April 2008

Abstract

The structure and content of the Moab Fault zone are described for 37 transects across the fault zone where throws range from less than 100 m to
c.
960 m. The 45 km long fault trace intersects a sedimentary sequence containing a high proportion of sandstones with good reservoir properties, interspersed with numerous mudstone layers. Typically, the fault zone is bounded by two external slip zones with the fault zone components separated by up to nine internal slip zones. Fault zone components are tabular lenses of variably deformed sandstones and sandstone cataclasites and breccia, with a wide size range, usually enclosed in a matrix of shaley fault gouge containing mm to m scale entrained sandstone fragments. Neither fault zone structure nor content can be predicted by extrapolation over distances as little as 10 m. Although variable in thickness, shaley gouge is always present except where the mudstone is <
c.
20% of the faulted sequence. The distribution of shaley gouge conforms with existing algorithms for predicting the presence or absence of shaley gouge in subsurface fault zones. The fault zone heterogeneity is attributed to tip-line and asperity bifurcation processes.
The gas permeability of clay-bearing fault gouge at 20°C
Authors: Faulkner D. R. , Rutter E. H. 
Published: April 2008

Abstract

Permeability measurements of clay-bearing fault gouges have been made using the pulse-transient and pore pressure oscillation methods with argon as the pore fluid, and at effective pressures up to 160 MPa and at a constant pore pressure of 40 MPa. Samples were collected from the outcrop of a major transpressional fault in southeastern Spain, in three orthogonal directions relative to the planar fabrics developed within the fault zone. Measurements show the gouge to exhibit permeability anisotropies of up to 3 orders of magnitude. In addition, pressure cycling of the gouge reduced the permeability by 2 to 3 orders of magnitude after 5 pressure cycles, when minimum permeabilities slightly less than 10
−21
m
2
were measured.
Numerical simulation of departures from radial drawdown in a faulted sandstone reservoir with joints and deformation bands
Authors: Matthäi S. K. , Aydin A. , Pollard D. D. , Roberts S. G. 
Published: April 2008

Abstract
Field measurements constrain the fluid flow characteristics of an analogue hydrocarbon reservoir in the faulted Entrada sandstone, Arches National Park, Utah. These data comprise maps of the geometry, inhomogeneous permeability, and porosity of fault zones, joints, and deformation bands in a region where two discontinuous normal faults overlap. Two-dimensional computer simulations of drainage of this analogue reservoir identify normal faults with highly permeable slip planes as the most important reservoir inhomogeneities. These faults compartmentalize fluid pressure over timespans greater than years while fluid can be drained on the kilometre scale along their highly permeable slip planes. Joints induce the second most important distortions of radial drawdown, influencing the timespans over which fault signatures are observed in pressure decline curves. The joints often extend to the boundaries of the reservoir. This also reduces the time before the rate of pressure decline accelerates due to boundary interaction. Zones of deformation bands less than 25 cm wide with a spacing ≥30 m have little effect on radial drawdown in our single phase fluid flow simulations. When drawdown spreads with time over the deformation structures in the analogue reservoir, the different structures simultaneously influence the change of pressure at the wellbore (pressure derivative). This temporal overlap prohibits an analysis of the effects of individual structures. Drawdown does not ‘recover’ to radial flow after an inhomogeneity is encountered.
An integrated approach for characterizing fractured reservoirs
Authors: D’Onfro P. S. , Rizer W. D. , Queen J. H. , Majer E. L. , Peterson J. E. , Daley T. M. , Vasco D. W. , Datta-Gupta A. , Long J. C. S. 
Published: April 2008

Abstract
Experience has shown that fractures and faults within a given array are not all equally conductive or well-connected. To investigate new techniques for locating conductive fracture flow paths, a series of high resolution (1 to 10 kHz) crosswell and single well seismic surveys and interference tests were conducted in a shallow five spot well array penetrating a fractured limestone formation. Two inverse approaches for constructing fracture flow models were applied to the interference test data. Both approaches successfully reproduced the transient pressure behaviour at the pumping and observation wells and indicated a preferential fracture flow path between two wells aligned in an east-northeast direction, the dominant direction of fracturing mapped in the area. Crosswell and single well seismic experiments were performed before and after air injection designed to displace water from the fracture flow path and increase seismic visibility. The crosswell experiments showed that replacement of water with gas produces significant changes in the seismic signal. The single well reflection surveys were able to precisely locate the position of the fracture flow path. This location was confirmed by core from a slant well which intersected a single open fracture at the targeted depth.
An inverse problem to determine the piecewise homogeneous hydraulic conductivity within rocks
Authors: Lesnic D. , Elliott L. , Ingham D. B. , Knipe R. J. , Clennell B. 
Published: April 2008

Abstract
The experimental measurement of the piecewise homogeneous hydraulic conductivity of a rock sample in which the location of the discontinuities is unknown appears difficult, even in a one-dimensional situation. However, the values of these quantities can be obtained numerically using additional boundary and/or interior measurements of the pressure from transient hydraulic experiments. In the direct problem, the hydraulic conductivity is known, and only a solution for the pressure field is sought. However, in the inverse formulation of the problem, both the hydraulic conductivity and the pressure are unknown and have to be determined using additional pressure measurements. The numerical method employed for solving the diffusion equation is based on the boundary element method as a direct solution procedure, combined with an ordinary least-squares technique. The sensitivity coefficients are calculated for the unspecified boundary conditions and for interior pressures, and clearly show the need for interior measurement information to be imposed on the solution of the inverse ill-posed problem. The uniqueness of the solution of the inverse problem is thoroughly numerically investigated using additional pressure measurements at several prescribed times from various numbers of wells and different well locations. For a material presenting a single discontinuity in the hydraulic conductivity, and subject to certain experimental conditions, it was found that when the number of time measurements is limited then two interior well pressure measurements are necessary and sufficient in order to render a good estimate of the exact solution. Otherwise, it is necessary to increase the number of time measurements at a single interior well location to accomplish the same result.
Fault controlled communication in the Sleipner Vest Field, Norwegian Continental Shelf; detailed, quantitative input for reservoir simulation and well planning
Authors: Ottesen Ellevset S. , Knipe R. J. , Svava Olsen T. , Fisher Q. J. , Jones G. 
Published: April 2008

Abstract
The Sleipner Vest field, located in blocks 15/6 and 15/9 on the Norwegian Continental Shelf, contains hydrocarbons (mainly gas condensates) within the marginal marine units of the Middle Jurassic Hugin Formation. The field is segmented into fault-bounded compartments, which exhibit differences in gas-water contacts of between 10 and 100m. Microstructural analysis of core samples has identified three principal fault types; cataclasites, developed from clean sandstones, framework phyllosilicate fault rocks created from impure sandstones and clay smears developed from phyllosilicate-rich units. The distribution of these has been linked to the phyllosilicate content of the undeformed Hugin reservoir at the time of deformation. Petrophysical property analysis has been used to quantify the representative permeabilities and threshold capillary pressures of the fault rocks and their undeformed equivalents. Juxtaposition/seal diagrams and detailed fault plane maps were also constructed and provide a basis for mapping sand-sand juxtapositions and the distributions of the different fault rock types with assigned permeabilities and capillary threshold pressures. The results provide an explanation of the mapped variations in gas-water contacts. An important correlation exists between the type of fault rock predicted to dominate the fault plane near the hydrocarbon-water interface and the difference in hydrocarbon depths across the faults. Compartments separated by faults with windows of juxtaposed clean sandstone cataclasites have small hydrocarbon-water level differences (7–11 m), suggesting that the low capillary threshold pressure (more permeable) cataclastic fault rocks control communication. Compartments separated by faults predicted to have extensive phyllosilicate-rich fault rocks (developed from impure sandstones and clay rich units) with high capillary threshold pressures correlate to larger hydrocarbon-water differences (>39 m), reflecting the reduced communication.
The structure and controls on fluid-rock interactions in ocean ridge hydrothermal systems: constraints from the Troodos ophiolite
Authors: Bickle M. J. , Teagle D. A. H. , Beynon J. , Chapman H. J. 
Published: April 2008

Abstract
Rb-Sr isotopic compositions of rocks and minerals from the Troodos ophiolite have been analysed to constrain the rate limiting mechanisms that control fluid-solid exchange, the extent to which recharge fluids were channelled and the thermal evolution of oceanic hydrothermal systems. Systematic regional sampling has confirmed the Sr-isotopic alteration profile suggested by Bickle & Teagle (1992). This has been previously interpreted as a consequence of recharge fluids percolating down through the extrusive series with kinetically limited fluid-rock interaction but altering the underlying ≈1 km section of sheeted dykes with near equilibrium fluid-rock Sr-isotopic exchange. Detailed Sr-isotopic profiles reported here across structural heterogeneities such as pillows, dyke margins and faults have failed to show isotopic gradients related to channelling of fluid. Rather the fluid flow in the recharge was pervasive and the degree of alteration is largely controlled by the extent of mineral recrystallization, primarily by albitization of plagioclase, and to a lesser extent by recrystallization of pyroxene. Hydrothermal recharge should cool the sheeted dykes much faster than the progression of the Sr-isotope alteration through the crust and rocks at greenschist facies (∼250°C) or higher temperatures are predicted only to be found within a few hundred metres of the basal boundary layer of the system. The alteration pattern on Troodos with a zone a kilometre or more in thickness altered at greenschist facies temperatures and with significant Sr-isotope exchange is thus not easily explained.
Significance of modern and ancient oceanic Mn-rich hydrothermal sediments, exemplified by Jurassic Mn-cherts from Southern Greece
Authors: Robertson A. , Degnan P. 
Published: April 2008

Abstract
This paper considers the occurrence of Mn-oxide-rich hydrothermal deposits in the modern oceans and presents a case history of Jurassic Mn-cherts from a Tethyan area in Southern Greece. Manganese-oxide hydrothermal sediments are known from a wide variety of oceanic settings, including both on and off the axis of spreading ridges, in back-arc basins, arc-related areas, rifts and in small ocean basins. These Mn-rich sediments differ markedly from the chemical composition of better known metalliferous deposits associated with high-temperature black smokers (i.e. Fe-rich ochres and Fe-Mn-rich umbers). The ancient example discussed in detail here is that of Late Jurassic Mn-rich cherts spatially associated with basic-intermediate composition volcanics within sutured oceanic units in the Peloponnese, S Greece. The Mn enrichment there is interpreted as related to hydrothermal activity associated with Late Jurassic off-axis volcanism, rather than to a spreading ridge source. The Mn is strongly fractionated from Fe and is concentrated in thin beds and laminations, interpreted as of primary depositional origin. The silica is assumed to be mainly biogenic, as reflected in an association with red radiolarian cherts. The source hydrothermal activity is likely to have been of low-temperature type. Similar Mn-oxide deposits occur elsewhere in the Mesozoic Tethyan area, including N Greece, SW Turkey, Cyprus and Oman, and in other orogenic belts (e.g. in California). There are also metamorphosed counterparts of Mn-rich hydrothermal deposits that include metalliferous pelites and cherts; e.g. Cyclades, S Greece and Franciscan Complex, California. The record of deep-sea hydrothermal deposits exposed on land following tectonic emplacement is biased towards off-axis Mn-deposits within abyssal sediments, since axial spreading ridges (including massive sulphides, umbers and ochres) are rarely preserved, owing to subduction.
Ancient vent chimney structures in the Silurian massive sulphides of the Urals
Authors: Herrington R. J. , Maslennikov V. V. , Spiro B. , Zaykov V. V. , Little C. T. S. 
Published: April 2008

Abstract
Exceptionally well preserved volcanogenic massive sulphide ores at Yaman Kasy in the Silurian of the southern Urals have yielded not only well-preserved sulphidized vent macrofauna but also fragments of vent chimneys. All fragments show a broad 3-fold mineralogical zonation. An outer zone which forms the chimney/conduit wall comprises largely pyrite and marcasite which is laminated or collomorphic and is commonly porous. In one fragment this zone is characterized by a honeycomb-like structure in the pyrite, infilled by barite, sphalerite and chalcopyrite. Dendrite growth textures branch outwards towards the chimney wall. The middle of the three zones comprises largely pyrite with chalcopyrite and sphalerite as thin veinlets and infillings. The innermost zone is dominated by chalcopyrite. Minor gold and bismuth tellurides occur at the boundary between the middle and the inner zones. The inner zone is interpreted as the hydrothermal conduit lining and in all cases is defined by bladed chalcopyrite, which shows a texture consistent with growth toward an inner open space. The central part of the conduit is now infilled with sphalerite or in one case pyrite, chalcopyrite, silica and minor barite. Fluid inclusion studies indicate the presence of high-temperature (> 350°C) fluids of around 3.5 0.000000e+00quivalent NaCl in the basal parts of the massive sulphide mound with cooler temperatures (< 100°C) recorded in barite from the upper part of the mound. Barite is associated with chimney fragments, as worm tube infillings and as later cross-cutting veins. Preliminary S and Sr isotope data from sulphides and sulphates supports both igneous and seawater sources for sulphur in the hydrothermal system with evidence for seawater circulation and sulphate precipitation beneath the sulphide mound. The results are consistent with a similar model of chimney growth to that proposed for modern vent sites. It is proposed that a high temperature fluid flux through open conduits fed black smoker activity accompanied by lateral fluid diffusion through the chimney wall which mixed with seawater. The result of this is a combination of conductive cooling and fluid mixing leading to precipitation of distinctively zoned mineral assemblages across the vent conduit wall. The occurrence of tellurium, bismuth and precious metal-bearing phases indicates some similarities with the geochemistry of sulphides from other Palaeozoic massive sulphide deposits associated with felsic volcanic centres.
Relics and antiquity revisited in the modern vent fauna
Authors: McArthur A. G. , Tunnicliffe V. 
Published: April 2008

AbstractA total of 464 species is currently known from hydrothermal vents, with 820eing endemic. More strikingly, endemicity at hydrothermal vents reaches high taxonomic levels with 18 families, 4 superfamilies, 2 suborders, and 1 order endemic. It has been proposed that this magnitude of endemicity is reflective of an ancient, refugial fauna. A review of the many endemic groups reveals that hydrothermal vent communities have mosaic origins. Many endemic groups have recent origins while some appear to reflect ancient faunal elements that have survived in hydrothermal vent refugia. Some may be members of groups surviving refugially throughout the deep-sea while others may have survived refugially in a variety of sulphide-rich habitats, such as hydrothermal vents, hydrocarbon seeps and sunken whale bones. Evolution of sulphide tolerance and especially symbioses with chemoautotrophic bacteria may be threshold adaptations for invasion of multiple sulphide-rich environments. These environments may provide protection from certain causes of extinction. In addition to reviewing current views on endemic taxa, a molecular systematic investigation of the evolutionary origins of vent endemic neomphalinid gastropods is presented.
Decoupling post-glacial tectonism and eustasy at Huon Peninsula, Papua New Guinea
Authors: Chappell John , Ota Yoko , Campbell Colin 
Published: April 2008

Abstract

Late Quaternary uplift of coral terraces varies along the coast at northeast Huon Peninsula, Papua New Guinea, but the uplift rate has been assumed to be constant at any given locality in previous studies. Measurements indicate that rates for the last 7000 and 120 000 years were similar but this may be coincidence, because uplift at Huon Peninsula is dominated by isolated, metre-scale events with recurrence intervals around 1000 years. Using age-height data from 54 corals from the post-glacial reef, we examine the uplift rate over the last 13 000 years near Kwambu, where facies changes in a drill core indicate several uplift events before 7 ka
bp
. To separate uplift from sea level, a eustatic curve for Kwambu was generated by the global sea-level model described by Lambeck, recalibrated to new, Late Pleistocene sea-level data. With Barbados as a test case, predictions compare well with observations reported earlier, but predicted sea levels for Kwambu cannot be reconciled with the coral data unless the water depth of coral growth at the site was greater than estimated previously.
Neotectonic implications of a lineament-coplanarity analysis in southern Calabria, Italy
Authors: Cornet Yves , Demoulin Alain 
Published: April 2008

Abstract
A synthesis of the geodynamical interpretations proposed in the literature shows that the respective role of different possible driving mechanisms in the Neogene and Quaternary tectonic evolution of southern Calabria is still under discussion. Owing to different methodological approaches and scales of observation, the same holds true for marine terrace levels recognized in the area of Reggio Calabria. Their number, elevation, spatial correlation and age, as well as their tectonic significance, are still debated, resulting in some uncertainty about the timing and rate of the regional uplift and its local variations. To complete the mapping of fault zones potentially dislocating the marine terraces, a three-dimensional (3D) morphometrical analysis of lineaments has been carried out. From a data-set composed of linear structures recognized on an illuminated digital elevation model (17 km × 18 km in size) centred on Reggio Calabria, the method aims at identifying lineaments pertaining to a single plane. Assuming that faults may be assimilated to planes at the local scale, the coplanar lineaments allow the 3D attitude and location of fault or fracture planes to be determined. The planes retained as tectonically significant (on the dip value and number of coplanar lineaments) have been successfully compared with the existing faults as well as with geomorphological data (long river profiles) of southern Calabria. Beyond mapping the main faults of the study area, the coplanarity analysis highlights the existence of conjugate faults within the NW-SE fault zone of Terreti-Monte Embrisi. It also locates some E-W striking faults which were previously known only at the outcrop scale.