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Open Fractures (open + fractures)
Selected AbstractsReal-time mud gas logging and sampling during drillingGEOFLUIDS (ELECTRONIC), Issue 3 2006J. ERZINGER Abstract Continuous mud gas loggings during drilling as well as offline mud gas sampling are standard procedures in oil and gas operations, where they are used to test reservoir rocks for hydrocarbons while drilling. Our research group has developed real-time mud gas monitoring techniques for scientific drilling in non-hydrocarbon formations mainly to sample and study the composition of crustal gases. We describe in detail this technique and provide examples for the evaluation of the continuous gas logs, which are not always easy to interpret. Hydrocarbons, helium, radon and with limitations carbon dioxide and hydrogen are the most suitable gases for the detection of fluid-bearing horizons, shear zones, open fractures, sections of enhanced permeability and permafrost methane hydrate occurrences. Off-site isotope studies on mud gas samples helped reveal the origin and evolution of deep-seated crustal fluids. [source] Reconstruction of palaeo-burial history and pore fluid pressure in foothill areas: a sensitivity test in the Hammam Zriba (Tunisia) and Koh-i-Maran (Pakistan) ore depositsGEOFLUIDS (ELECTRONIC), Issue 2 2003L. Benchilla Abstract The burial and pore fluid pressure history of fluorite ore deposits is reconstructed: (i) at Hammam Zriba,Djebel Guebli along the eastern margin of the Tunisian Atlas; and (ii) at Koh-i-Maran within the northern part of the Kirthar Range in Pakistan. Both the deposits are hosted by Late Jurassic carbonate reservoirs, unconformably overlain by Late Cretaceous seals. Microthermometric analyses on aqueous and petroleum fluid inclusions with pressure,volume,temperature,composition (PVTX) modeling of hydrocarbon fluid isochores are integrated with kinematics and thermal 2D basin modeling in order to determine the age of mineralization. The results suggest a Cenozoic age for the fluorite mineralization and a dual fluid migration model for both ore deposits. The PVTX modeling indicates that the initial stage of fluorite cementation at Hammam Zriba occurred under fluid pressures of 115 ± 5 bars and at a temperature close to 130°C. At Koh-i-Maran, the F3 geodic fluorite mineralization developed under hydrostatic pressures of 200 ± 10 bars, and at temperatures of 125,130°C. The late increase in temperature recorded in the F3 fluorites can be accounted for by rapid rise of hotter fluids (up to 190°C) along open fractures, resulting from hydraulic fracturing of overpressured sedimentary layers. [source] Hydraulic pathways in the crystalline rock of the KTBGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Günter Zimmermann Fracture systems and fluid pathways must be analysed in order to understand the dynamical processes in the upper crust. Various deterministic as well as stochastic fracture networks in the depth section of the Franconian Lineament (6900 to 7140 m), which appears as a brittle ductile shear zone and prominent seismic reflector, were modelled to simulate the hydraulic situation at the two boreholes of the Continental Deep Drilling Program (KTB). They led to estimations of the hydraulic permeability in crystalline rock. The geometrical parameters of the fractures, such as fracture locations and orientations, were determined from structural borehole measurements, which create an image of the borehole wall. The selection of potentially open fractures was decided according to the stress field. Only fractures with the dip direction (azimuth) of the fracture plane perpendicular to the maximum horizontal stress field were assumed to be open. The motivation for this assumption is the fact that the maximum horizontal stress is higher than the vertical stress from the formation, indicating that the state of stress is a strike-slip faulting. Therefore, the probability of open fractures due to this particular stress field at the KTB sites is enhanced. Length scales for fracture apertures and extensions were stochastically varied and calibrated by hydraulic experiments. The mean fracture aperture was estimated to be 25 ,m, assuming an exponential distribution, with corresponding permeability in the range of 10,16 m2. Similar results were also obtained for log-normal and normal distributions, with a variation of permeability of the order of a factor of 2. The influence of the fracture length on permeability of the stochastic networks was also studied. Decreasing the fracture length beyond a specific threshold of 10 m led to networks with vanishing connectivity and hence vanishing permeability. Therefore, we assume a mean fracture length exceeding the threshold of 10 m as a necessary assumption for a macroscopic hydraulically active fracture system at the KTB site. The calculated porosity due to the fracture network is of the order of 10,3 per cent, which at first sight contradicts the estimated matrix porosity of 1 to 2 per cent from borehole measurements and core measurements. It can be concluded from these results, however, that if the fluid transport is due to a macroscopic fracture system, only very low porosity is needed for hydraulic flow with permeabilities up to several 10,16 m2, and hence the contribution of matrix porosity to the hydraulic transport is of a subordinate nature. [source] A comparison of cross-hole electrical and seismic data in fractured rockGEOPHYSICAL PROSPECTING, Issue 2 2004J.V. Herwanger ABSTRACT Cross-hole anisotropic electrical and seismic tomograms of fractured metamorphic rock have been obtained at a test site where extensive hydrological data were available. A strong correlation between electrical resistivity anisotropy and seismic compressional-wave velocity anisotropy has been observed. Analysis of core samples from the site reveal that the shale-rich rocks have fabric-related average velocity anisotropy of between 10% and 30%. The cross-hole seismic data are consistent with these values, indicating that observed anisotropy might be principally due to the inherent rock fabric rather than to the aligned sets of open fractures. One region with velocity anisotropy greater than 30% has been modelled as aligned open fractures within an anisotropic rock matrix and this model is consistent with available fracture density and hydraulic transmissivity data from the boreholes and the cross-hole resistivity tomography data. However, in general the study highlights the uncertainties that can arise, due to the relative influence of rock fabric and fluid-filled fractures, when using geophysical techniques for hydrological investigations. [source] Orthopaedic patients' experience of motor vehicle accident in SingaporeINTERNATIONAL NURSING REVIEW, Issue 1 2008K.L. Tan mn (ortho nrsg) Aim:, The purpose of this paper is to present a study that explored the experiences of orthopaedic patients injured in motor vehicle accidents (MVAs), from the time of the accident until 6 months after being discharged from hospital. Background:, Trauma injuries from MVAs are increasing, with the number of deaths from such injuries continuing to rise. Victims often sustain open fractures to more than one part of their body and need rehabilitation and support to adjust to long-term chronic or permanent disability. In the last decade, research pertaining to trauma nursing has concentrated on neurologically injured patients. Although there is a paucity of research on the nursing perspective of psychological care for non-neurologically injured patients, the majority of studies located were mainly quantitative in nature and did not analyse the personal experiences of orthopaedic patients. Method:, A qualitative naturalistic inquiry approach was used, which provided a first-hand account of the traumatic MVA event experienced by six orthopaedic participants in Singapore. Data were collected from face-to-face in-depth interviews. Participants were voluntarily recruited through purposeful sampling and ,snowballing'. Interviews were audiotaped and transcribed verbatim in preparation for analysis. Findings:, The analysis of information explicated four main themes: the experience of the event, the effect of hospitalization, surviving the event and self-transformation. Conclusion:, The study provided an understanding of orthopaedic patients' experience of MVA in Singapore. The findings of the study have the potential to contribute to the limited qualitative research available concerning victims' experiences of MVAs and nurses caring for MVA victims. [source] OBTAINING FRACTURE INFORMATION FOR LOW-PERMEABILITY (TIGHT) GAS SANDSTONES FROM SIDEWALL CORESJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2006S. E. Laubach We illustrate a fracture characterization technique applicable to all tight gas sandstones. The technique uses microfractures and cements in the rock mass identified using SEM-based cathodoluminescence imaging to provide information on unsampled large fractures, including strike and cross-cutting relationships, intensity, and likelihood of preserved open fractures. We applied the technique in two tight gas sandstone wells in the Pennsylvanian Pottsville Formation, Black Warrior Basin, Alabama, USA. In one well, data was obtained entirely from drilled 1,inch diameter sidewall cores that were oriented using image logs and features visible in cores. We predicted fracture porosity preservation in large fractures using late cements in the rock mass as a proxy for fracture observation. Results from the technique are consistent with what is known of large fractures in this area. Where we predicted open, high intensity fractures, substantial gas flares were observed during drilling. By combining microstructural and diagenetic observations, it is possible to overcome the inadequate fracture sampling that plagues evaluation of natural fractures and that relies solely on observations of macroscopically visible fractures. [source] EVALUATION OF THE CONTROLS ON FRACTURING IN RESERVOIR ROCKSJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2005D.C.P. Peacock The style, geometry and distribution of fractures within reservoir rocks can be controlled by numerous factors, including: rock characteristics and diagenesis (lithology, sedimentary structures, bed thickness, mechanical stratigraphy, the mechanics of bedding planes); structural geology (tectonic setting, palaeostresses, subsidence and uplift history, proximity to faults, position in a fold, timing of structural events, mineralisation, the angle between bedding and fractures); and present-day factors, such as orientations of in situ stresses, fluid pressure, perturbation of in situ stresses and depth. The relative timing of events plays a crucial role in determining the geometry and distribution of fractures. For example, open fractures are commonly clustered around faults if the open fractures and faults formed at the same time, but clustering does not tend to occur if the open fractures pre-date or post-date the faults. Understanding these factors requires traditional geological skills, including the analysis of one-dimensional (line-sampling) data from core, borehole images and exposed analogues. This paper reviews the factors that control fractures within reservoir rocks and discusses methods to assess those controls. Examples are presented from Mesozoic limestones in southern England. It is shown that traditional geological skills are of vital importance in determining the rock characteristics, structural and present-day factors that control fractures. [source] Risk factors for nosocomial intensive care infection: a long-term prospective analysisACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2001P. Appelgren Background: To identify risk factors for nosocomial infection in intensive care and to provide a basis for allocation of resources. Methods: Long-term prospective incidence study of risk factors for nosocomial infection in the surgical-medical intensive care unit of a university hospital. Results: A total of 2671 patients were admitted during four years, and 562 of 574 patients staying >48 h were observed during 4921 patient days (median length of stay 5 days, range 2,114). Of these, 196 (34%) patients had 364 nosocomial infections after median 8,10 days, an infection rate of 14/100 admissions. Infection prolonged length of stay 8,9 days and doubled the risk of death. The infections were 17% blood stream, 26% pneumonias, 34% wound, 10% urinary tract and 13% other infections. The incidence of bloodstream infection declined significantly during the study years, from 12% to 5%. In multiple regression analysis, the important variables for infection were central venous catheter, mechanical ventilation, pleural drainage and trauma with open fractures. High age, immunosuppression and infection on admission did not influence the risk of acquiring infection. Trauma patients constituted 24% of the study population. Trauma with open fractures increased the risk of infection more than twice (P=0.003), mainly due to wound infections. Conclusion: Trauma cases, with open fractures, were the patients most at risk of infection, despite low disease severity scores. Resources to prevent nosocomial infection should be allocated to these patients. [source] Fijian seasonal scourge of mango tree fallsANZ JOURNAL OF SURGERY, Issue 12 2009Anuj Gupta Abstract Background:, Mango tree falls are a frequent presentation at any health facility in the South Pacific. This study aims to identify (i) the number of admissions because of falls from mango trees; (ii) epidemiology; (iii) seasonal trend; (iv) injury profile; and (v) hospital care provided. Methods:, Retrospective case review on all mango tree falls related injuries resulting in admissions at the Lautoka Hospital, Fiji during a 1-year period (2007). Patient records were analysed to identify specific injury patterns such as upper/lower limb fractures, spinal cord injury and head injury, caused by mango tree falls. Results:, Thirty-nine cases were identified. Eighty-two percent (n= 32) of the falls occurred in the mango season (June,November). Seventy-two percent (n= 28) of the patients were males and 28% (n= 11) were females. Seventy-six percent were aged 5,13 and only 21% were adults. Also, 77% (n= 30) of the patients were ethnic Fijians and 23% (n= 9) were Fijian-Indians. Sixty-four percent (n= 25) had closed fractures and 17% (n= 7) had open fractures. Fifty-six percent (n= 22) of the fractures were of the fore arm. There were two cases of spinal cord injury, four cases of head injury, one ICU admission and one death. Average hospital stay was 7.56 days. Conclusion:, All these injuries were recreational and the majority in the urban setting. They were all avoidable. [source] | |||||||||||||