Variety Of Reservoirs Research Articles

Is leishmaniasis the new emerging zoonosis in the world?

Leishmania is a genus of parasitic protozoa that causes a disease called leishmaniasis. Leishmaniasis is transmitted to humans through the bites of infected female sandflies. There are several different species of Leishmania that can cause various forms of the disease, and the symptoms can range from mild to severe, depending on species of Leishmania involved and the immune response of the host. Leishmania parasites have a variety of reservoirs, including humans, domestic animals, horses, rodents, wild animals, birds, and reptiles. Leishmaniasis is endemic of 90 countries, mainly in South American, East and West Africa, Mediterranean region, Indian subcontinent, and Central Asia. In recent years, cases have been detected in other countries, and it is already an infection present throughout the world. The increase in temperatures due to climate change makes it possible for sandflies to appear in countries with traditionally colder regions, and the easy movement of people and animals today, facilitate the appearance of Leishmania species in new countries. These data mean that leishmaniasis will probably become an emerging zoonosis and a public health problem in the coming years, which we must consider controlling it from a One Health point of view. This review summarizes the prevalence of Leishmania spp. around the world and the current knowledge regarding the animals that could be reservoirs of the parasite.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (ISC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of ISC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied ISC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several ISC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal, vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to air flow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil API gravity was higher. Based on the experimental results, a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

Epidemiological aspects of Leishmaniasis in the Pantanal region of Mato Grosso

Leishmaniasis is a disease caused by the protozoan Leishmania parasite that is disseminated by some species of sandflies and hosted by a variety of reservoirs. The objective of the present study was to evaluate the epidemiological situation of leishmaniasis in the municipalities of the Mato Grosso Pantanal. Human data were obtained from the Information System of Notifiable Diseases, and the canine and vector results from the State Department of Health of Mato Grosso. Between 2007 and 2016, 10 cases of visceral leishmaniasis and 499 cases of tegumentary leishmaniasis were identified in the Pantanal region. The surveillance studies regarding the canine reservoir demonstrated that the parasite was present in six of the seven municipalities. Vectors of visceral leishmaniasis were present in five municipalities and vectors of tegumentary leishmaniasis in six. Enhancement of services aimed at controlling this disease is fundamental to prevent an increase in the number of cases in the region.

Integrated Asset Model Enables Simulation of Complex, Multifield Asset

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 192603, “New-Generation Integrated Asset Modeling: High-Resolution Reservoir Multimodels Coupled With an External Steady-State Network Solver,” by Pietro Selvaggio, Fabrizio Freni, Roberto Rossi, Danielle Christian Di Giorgio, and Ivan Colombo, Eni, prepared for the 2018 Abu Dhabi International Petroleum Exhibition & Conference, Abu Dhabi, 12–15 November. The paper has not been peer reviewed. This paper presents an innovative application of the integrated-asset-model (IAM) approach to simulate a surface network collecting many complex fields and multiple constraints. The use of a last-generation high-resolution reservoir simulator (HRRS) made it possible to perform the reservoirs-network coupling directly by a field-manager (FM) process, which acts as an orchestrator for a variety of reservoirs and network-simulation instances. No third-party controller application was required because the FM of the HRRS directly managed the communication between the different reservoir models and the surface-network model. Introduction The ability to predict reservoir behavior has always played a fundamental role in the definition of a development project, and numerical simulation can be considered the first tool for a quantitative evaluation of reservoir performance. In the past decades, improvements in information technology have increased calculation capabilities, enabling development of dynamic simulators able to solve for more-complex reservoirs and dynamic processes. During the production-forecast phase, for example, technical constraints must be considered, primarily related to hydrocarbon rate (i.e., gas sale limitation, gas/water injection limits, flaring policies, limitations in export pipelines, and treatment capacity) and pressures (i.e., minimum required pressure to reach a treatment, separator working conditions, and export-pipeline design). The increasing development of fields located in remote or offshore areas and the growing interest in near-field exploration make it necessary to exploit common surface networks. In these situations, the previously mentioned technical constraints and limitations must be defined for the entire asset, thus accounting for the intrinsic connection between fields that become interdependent. With standard standalone reservoir simulation no longer able to identify and address these kinds of problems and constraints, integrating the reservoir and network is key to an optimized development strategy. The IAM brings together reservoir, well, and surface-facility models in a unique system for reservoir and well optimization. This methodology ensures that the interactions between all the components are accounted for correctly and, by coupling dynamic reservoir and facilities models into a single IAM, addresses backpressure, the mixing of different fluids, and flow assurance. Currently, two approaches are avail-able to perform the integration. The first is based on combining the reservoir models with a dedicated network simulator with optimization capabilities in a fully integrated model. The second approach is focused on using the capabilities offered by some commercial simulators in which the network solver, on the basis of precomputed hydraulic tables, is included in the simulator together with some features of reservoir coupling.

Non‐declining amphibians can be important reservoir hosts for amphibian chytrid fungus

AbstractAmphibian chytridiomycosis, caused by infection with Batrachochytrium dendrobatidis (Bd), is the most devastating vertebrate disease on record. Reservoir hosts are likely to be important in the Bd‐amphibian system because many amphibian species can carry infections without experiencing mortality. However, while a variety of reservoirs have been proposed, few have been empirically demonstrated to act as competent reservoir hosts. In this study, we investigate whether the common eastern froglet, Crinia signifera, a non‐declining species that is widespread in eastern Australia, is a reservoir host for Bd infection. We conducted a long‐term, large‐scale field survey to investigate disease dynamics in C. signifera at sites where four sympatric, threatened anuran species have severely declined. We also monitored Bd‐infected C. signifera in the laboratory to determine susceptibility and survivorship. Finally, we assessed population age structure to investigate disease impact in the wild. We found that C. signifera is a competent reservoir host, maintaining high prevalence and infection intensities in the wild and in the laboratory, with no signs of sub‐lethal effects or clinical disease. In the wild, the modal age is 4 years with individuals living up to 6 years, indicating that adults can survive across multiple years despite high infection prevalence and intensity. The occurrence of C. signifera at sites with remnant populations of threatened species likely contributes to ongoing disease impact in declining species decades after the arrival of Bd. The presence of C. signifera at sites where threatened species have become extinct inhibits effective reintroductions, and we recommend avoiding sites with high reservoir host abundance when planning reintroductions.

Investigation of the combustion characteristics of Bati Raman oil with sand

In situ combustion (ISC) is one of the thermal oil recovery processes that has been applied in a variety of reservoirs. The energy is generated within the reservoir by a series of multi-step reactions that provide energy to heat the reservoir and reduce oil viscosity. Also, the oil is upgraded in situ by burning heaviest fractions.In this study, combustion characteristics of Bati Raman crude are investigated. The Bati Raman oil field is the largest known oil field in Turkey. Ramped temperature oxidation (RTO) experiments with effluent gas analysis (EGA) are performed with oil-sand mixtures having different sand particle size. The results are analyzed using isoconversional kinetic approach, which is a model-free method, based on effluent gas analysis and temperature measurements. Effective activation energy values are estimated for the sample with two different sand particle size. Besides, for the same samples, laboratory combustion tube experiments are conducted to evaluate ignition and combustion front propagation characteristics. Asphaltene content and API gravity of the oil sample prior to experiments and produced oil are measured and compared. Results indicate that the oil is upgraded through a reduction in asphaltene content.A complete set of kinetics and combustion experiments are provided for Bati Raman oil. There are only limited number of studies in the literature to link kinetic experiments to proposed reaction models of ISC. This work presents a way to link a reaction model to isoconversional fingerprint obtained through kinetic experiments. In addition, it is shown that Bati Raman oil exhibits good combustion characteristics and it is associated with its isoconversional fingerprint.

Human Mycobiota-Selected Ontocenoses of Students of Natural Science and Medicine

Objectives: The aim of this study was to compare the prevalence of yeast-like fungi and yeasts on the mucous membranes of a group of students of Natural Sciences and Medicine. Materials and methods: The study involved 156 students of the Faculty of Biology and Biotechnology (FB&B) and 37 students of the Faculty of Medical Sciences (FMS). Material samples were collected with sterile cotton swab from the nose, mouth and throat. The identification of fungi was carried out by the evaluation of macrocultures and microcultures on Nickerson agar and biochemical features. Results: Yeast-like fungi and yeast were isolated from 41.97% of the subjects (81 people). The fungal colonization of the mucous membrane was observed in 59 students of the Faculty of Biology and Biotechnology (37.82%) and 22 students (56.46%) of the Faculty of Medical Sciences. The obtained fungi were classified into 31 taxonomic units. The predominant species were Candida dubliniensis and Lachancea thermotolerans (syn. Kluyveromyces thermotolerans). 14 species with defined status of BSL were recorded. Conclusions: Yeast and yeast-like fungi were more frequent among students of Biology and Biotechnology, than students of Medical Sciences. In students of FB&B greater taxonomic diversity of fungi was found than in students of FMS. The species diversity and prevalence of fungi observed in students of the Life Sciences are determined not only by lifestyle, but mainly by the possibility and frequency of contact with a variety of reservoirs and sources of potentially pathogenic fungi. The occurrence in human ontocenoses of 14 species classified to 1st and 2nd class of Biosafety Level is also very important.

Techbits: China Workshop Examines Fractured Carbonate Reservoirs

Techbits An SPE Applied Technology Workshop (ATW) on “The Characterization of Effective and Efficient Development of Fractured Carbonate Reservoirs” was held 15-18 June 2014 in Nanjing, China. Participants reviewed recent advances in exploration and production and the technical challenges presented by these reservoirs. A variety of carbonate reservoirs exist worldwide, mainly paleokarst reservoirs. Because of various scales, poor continuity, strong heterogeneity, accumulation in vugs and fractures, and complex flow behaviors, the efficient development of fractured carbonate reservoirs is quite challenging. Li Yang, cochairperson of the workshop, opened the session and ATW Chairman Wang Zhigang delivered one of two keynote speeches. He focused on the challenges and current activities of a key carbonate reservoir, Tahe, that he said represented the theme of the ATW. Usman Ahmed, also a workshop cochairperson, introduced the second keynote speaker, Christine Ehlig-Economides. She recalled an ATW a decade ago that also had focused on the Tahe reservoir. She set the stage for a discussion on how much the industry has advanced and the challenges that lie ahead. In his keynote speech, Wang of Sinopec described the technical challenges and techniques used at Sinopec’s Tahe oil field in western China. The Tarim basin is the company’s largest carbonate play, with proven reserves of 1.3 billion tons and depths of 5300 m to 6300 m. The oil and gas accumulated in pores, vugs, and fractures of severe heterogeneity and depth make it difficult to predict and describe reservoir characteristics, he said. Carbonate reservoir characterization and evaluation techniques have been developed that have improved the predictability of the carbonate reservoir and its distribution and have increased drilling success, he said. In the Ordovician carbonate reservoir of Tahe, a series of techniques such as paleokarst landform categorization, paleokarst cycle division, hydrocarbon accumulation period analysis, logging for reservoir identification, and evaluation have been implemented. In addition, massive acid fracturing (high pumping pressure, high injection rate, large scale) has become a major technique for development at the field. In sum, the technical challenges are: Ultradeep, highly heterogeneous reservoirs with low-resolution seismic data make it difficult for reservoir prediction. The form of fractures and vugs and oil and gas accumulation in such reservoirs make reservoir modeling difficult. A variety of reservoir fluid systems exist, which lead to a complex oil-water distribution. Current simulation techniques need to be further improved. Severe channeling and breakthrough were detected after waterflooding was applied. Further research is needed to improve waterflooding, residual oil characterization, and water-control techniques. Drilling activities are extremely challenging and costly. Drilling technology needs to be further developed or modified.

Sediment distribution pattern in some Iranian dams based on a new empirical reservoir shape function

Sedimentation greatly affects the future performance of reservoirs and thus is a main concern of designers. Reservoir sedimentation is influenced by many parameters, with reservoir shape among the most important. Different empirical and semiempirical methods based on reservoir shape parameters have been previously researched to predict sediment distribution patterns. Our extended investigation over hydrographic maps of 10 large dams in Iran found a strong relationship between reservoir shape and sediment distribution pattern. As a result, we introduced a new method for the prediction of sediment accumulation in reservoirs using a parameter that determines the reservoir shape. This parameter is used to show how accurately reservoir shape can be approximated by its equivalent pyramid. Equivalent pyramid was defined at each reservoir cross section, with the cross sectional area as its base and the distance from the reservoir end as its height. We recommend this new technique to predict long term cumulative distribution of sediment in preliminary design stages for a wide variety of reservoirs with mainly fine-grained sediment particles.

Technology Focus: Reservoir Simulation and Visualization (July 2009)

Technology Focus For many years, the title of this feature has been "Reservoir Simulation and Visualization," but year by year fewer papers are submitted on visualization. This clearly reflects that 3D visualization is no longer a novelty—it is a standard part of our workflow. This trend ties with another I noted last year—greater inclusion of geological modeling in history-matching workflows. Visualization is an essential part of the geological-modeling workflow, one of the geologist's key quality-checking steps, and only with good 3D-graphics workstations did geological modeling become mainstream. However, it does not seem likely that history matching will die out as a topic for papers any time soon! A great variety of techniques are being deployed to automate the process of history matching (improving the engineer's productivity) and to improve the quality of the result. Several experimental-design techniques are reported, as researchers continue attempts to extract the maximum benefit out of the fewest runs. It will be interesting to see if developments in hardware, leading to ever-reducing computing costs, result in a change of emphasis. Although history matching remains a key focus, the broader application of mathematical-optimization techniques to prediction is emerging as a key topic of interest. This application goes to the heart of our role as reservoir engineers, and it is good to see history matching treated as merely a means to an end, rather than an end in itself. The variety of reservoirs being developed and studied with simulation continues to grow, and the boundaries of technology continue to stretch. Naturally fractured carbonates, heavy oil under thermal recovery, tight gas, shale gas, coalbed methane, and other projects all feature more-complex and sophisticated wells. The 2009 SPE Reservoir Simulation Symposium produced many excellent papers on the underlying technology and algorithms of simulation and its application: It is good to see that innovation continues. Sadly, many of these papers do not lend themselves well to the synopsis format of this feature, so I strongly urge you to track down the Proceedings from a colleague if you were unable to attend. Reservoir Simulation and Visualization additional reading available at OnePetro: www.onepetro.org SPE 118178 • "An Integrated Case Study From Seismic to Simulation Through Geostatistical Inversion" by S. Soni, SPE, Fugro-Jason, et al. SPE 119139 • "Comparison of Stochastic Sampling Algorithms for Uncertainty Quantification" by L. Mohamed, SPE, Heriot-Watt University, et al. SPE 122934 • "A Workflow for Integrated Barnett Shale Gas Reservoir Modeling and Simulation" by C. Du, SPE, Schlumberger, et al.

Focused seismic monitoring

StatoilHydro has deployed a large range of geophysical reservoir monitoring technologies to a variety of reservoirs over the last 10–15 years. Seismic reservoir monitoring is today an integral part of our field management, with proven business value.

Mobility of arsenic in a Bangladesh aquifer: Inferences from geochemical profiles, leaching data, and mineralogical characterization

Aquifer geochemistry was characterized at a field site in the Munshiganj district of Bangladesh where the groundwater is severely contaminated by As. Vertical profiles of aqueous and solid phase parameters were measured in a sandy deep aquifer (depth >150 m) below a thick confining clay (119 to 150 m), a sandy upper aquifer (3.5 to 119 m) above this confining layer, and a surficial clay layer (<3.5 m). In the deep aquifer and near the top of the upper aquifer, aqueous As levels are low (<10 μg/L), but aqueous As approaches a maximum of 640 μg/L at a depth of 30 to 40 m and falls to 58 μg/L near the base (107 m) of the upper aquifer. In contrast, solid phase As concentrations are uniformly low, rarely exceeding 2 μg/g in the two sandy aquifers and never exceeding 10 μg/g in the clay layers. Solid phase As is also similarly distributed among a variety of reservoirs in the deep and upper aquifer, including adsorbed As, As coprecipitated in solids leachable by mild acids and reductants, and As incorporated in silicates and other more recalcitrant phases. One notable difference among depths is that sorbed As loads, considered with respect to solid phase Fe extractable with 1 N HCl, 0.2 M oxalic acid, and a 0.5 M Ti(III)-citrate-EDTA solution, appear to be at capacity at depths where aqueous As is highest; this suggests that sorption limitations may, in part, explain the aqueous As depth profile at this site. Competition for sorption sites by silicate, phosphate, and carbonate oxyanions appear to sustain elevated aqueous As levels in the upper aquifer. Furthermore, geochemical profiles are consistent with the hypothesis that past or ongoing reductive dissolution of Fe(III) oxyhydroxides acts synergistically with competitive sorption to maintain elevated dissolved As levels in the upper aquifer. Microprobe data indicate substantial spatial comapping between As and Fe in both the upper and deep aquifer sediments, and microscopic observations reveal ubiquitous Fe coatings on most solid phases, including quartz, feldspars, and aluminosilicates. Extraction results and XRD analysis of density/magnetic separates suggest that these coatings may comprise predominantly Fe(II) and mixed valence Fe solids, although the presence of Fe(III) oxyhydroxides can not be ruled out. These data suggest As release may continue to be linked to dissolution processes targeting Fe, or Fe-rich, phases in these aquifers.

Pressure‐dependent seismic response of fractured rock

Effects of external stress and pore pressure variations on the seismic signature of fractured rocks remain of interest to geoscientists and practicing geophysicists. Commonly, the effects are modeled theoretically, assuming fracture faces to be rough surfaces contacting each other via the surface asperities. The model proposed here differs from other models of this kind in that (1) fracture roughness is described by a single parameter and (2) a controlled degree of hydraulic connectivity between fractures and equant pores is introduced. This adds to the model's convenience and makes it applicable to a wide variety of reservoirs. The model predictions of seismic velocities in fractured rock at variable stress are consistent with experimental data. For fixed effective stress, the model predictions coincide with those obtained using the model with ellipsoidal fractures of certain average aspect ratio and the same fracture porosity.Apart from known effects, the model introduced predicts an amplification of the stress variation influence on fracturing‐induced anisotropy with an increase of connected equant porosity, a decrease of VP/VSwith effective stress, and implicit frequency dependence of the VP/VSrelation. It is also shown that amplitude versus offset (AVO) anomalies caused by fluid replacement can be seriously distorted if the fluid replacement is accompanied by significant variations of pore pressure, as, for example, at intense gas production. Neglecting these effects can lead to erroneous conclusions on shear modulus dependence on the pore fluid type. Qualitatively, in rocks with azimuthally aligned fracturing, the increase of effective stress affects AVO gradient in about the same way as the increase of water saturation parameter Vw. In contrast, the AVO intercept is not affected by variations of effective stress, while fluid replacement effect on the intercept is significant. Potentially, this can help distinguish the effects of pore pressure variations and fluid replacement on the AVO attributes.

Problems Associated with the AMS Dating of Small Bone Samples: The Question of the Arrival of Polynesian Rats to New Zealand

We have AMS dated samples of Pacific rat (Rattus exulans) bone “collagen” and filtered gelatin samples from the prehistoric site of Shag River Mouth, New Zealand. The age of occupation of this site has previously been determined based on 50 radiocarbon measurements. The site dates to the late Archaic phase of southern New Zealand prehistory (about 650–500 BP; 14th–15th century AD). The results of rat bones which we have dated produce a range in ages, from about 980–480 BP, a difference we attribute to a combination of effects. Pretreatment appears to be an important variable, with results showing differences in 14C age between the progressive “collagen” and filtered gelatin chemical treatment stages. Amino acid profiles suggest there is a proteinaceous but non-collagenous contaminant which is removed by the more rigorous pretreatment. Stable isotopes vary between pretreatments, supporting the removal of a contaminant, or contaminants. Variation in δ15N values imply a range in uptake of dietary protein, and might suggest a potential influence from the local aquatic environment or the consumption of marine-derived protein. Rats are opportunistic, omnivorous mammals, and, therefore, obtain carbon from a variety of reservoirs and so we ought to expect that in environments where there is a variety of reservoirs, these will be exploited. Taken together, the results show that rat bone AMS 14C determinations vary in comparison with the established age of the site, but are in notably better agreement with non-collagenous data than in previously published determinations (Anderson 1996).

Antibiotic Resistance: What Is the Impact of Agricultural Uses of Antibiotics on Children’s Health?

Antimicrobial resistance has reached crisis stage in human medicine. The rapid acceleration of multidrug-resistant bacteria in the past 2 decades has overtaken new drug development, and patients and clinicians are faced with the prospect of untreatable infections. Although much of the problem stems from overuse and misuse of antimicrobial agents in human medicine, large-scale use of antimicrobials in agriculture also contributes to the crisis. Agricultural uses of antibiotics produce environmental exposures in a variety of reservoirs, which select for resistant microbes and microbial genes. This article presents the major lines of evidence documenting the risks to human health of some of the agricultural uses of antimicrobials. A brief review of the microbiologic antecedents of resistance is followed by a discussion of agricultural uses of antimicrobials and a targeted review of the literature, which provides the background knowledge and evidence necessary for pediatricians and other clinicians to be informed and to advocate for judicious use of antimicrobials in all sectors.

Sulfide Removal and Prevention in Gas Wells

Summary Major problems in oil and gas operations result from the biogenic formation of H2S in the reservoir. The presence of H2S results in increased corrosion, iron sulfide formation, higher operating costs, reduced revenue, and constitutes a serious environmental and health hazard. A new technology that removes and prevents the formation of biogenic H2S has been developed. The technology is based on the addition of low concentrations of a water-soluble nutrient solution, which selectively stimulates the growth of an indigenous microbial population, thereby inhibiting the detrimental sulfate-reducing bacteria (SRB) population, which causes the generation of H2S. This deliberate and controlled modification of the microflora and reservoir ecology has been termed biocompetitive exclusion. This directed alteration of the microbial ecology is achieved by the introduction of a nutrient formulation that favorably influences the dynamics of the reservoir microflora. The treatment system does not require the addition of microbial cultures. Periodic well treatments have been shown to dramatically reduce or completely eliminate sulfide levels and establish control of the system in diverse field demonstrations supported by the U.S. Dept. of Energy. Field data in a variety of reservoirs will be presented that demonstrate the effectiveness of this new approach to treating and remediating wells with high levels of H2S. The versatility and low cost of this novel technology offers the petroleum industry a practical and cost effective methodology for the control of H2S in oil and gas wells.

Collisions with ice/volatile objects: geological implications--a qualitative treatment.

An aperiodic collision of the Earth with extra-terrestria] ice/volatile bodies is proposed as a mechanism to produce rapid changes in the geologic record. Due to the volatile nature of these bodies, evidence for their impacts, particularly in the ocean might be subtle and best seen as 'spikes' in the geochemical or fossil record against normal background. Differing effects would result depending on the site of the major break-up of the object: in the atmosphere, on land, or in the ocean. This paper focuses on the effects of adding material to the seas, oceans, and atmosphere. The treatment is largely qualitative, however mass balance calculations were used to estimate the relative mass needed to affect changes in a variety of reservoirs. Although actual impactors probably have a variable composition, the effects of water-, C-, N-, and S-containing objects are discussed. In the atmosphere, effects could include increased rain acidity, increased levels of nutrients, and enhanced greenhouse warming/cooling. Oceanic effects might include increased oceanic productivity (nitrogen-containing objects). As a result of increased chemical weathering and/or greenhouse effects, increased temperatures coupled with enhanced productivity could result in wider-spread oceanic anoxia or altered calcite/aragonite stability. Possible examples of such impacts from the geologic record and potential biotic effects are given.

石灰岩油層の岩質キャラクタリゼーション

This paper proposes a novel method for the grouping of rock types for the successful estimation of the in-situ absolute permeability accurately and for the smooth interpolation of relative permeability endpoints which are inevitably required for reservoir simulation models. The method consists of the grouping reservoir rocks based on the concept of electrical facies in accordance with their response to the wireline log attributes. The results showed excellent matching of the estimated absolute permeability and relative permeability endpoints to the core data prior to the application of the hydraulic unit method and multi-variate regression on each data group.The individual electrical facies showed the unique petrophysical characteristics each other, and their distribution frequency in each sedimentary zonation exhibited distinguishing feature possibly reflecting the sedimentary environment.The proposed approach lead to the great success on the description of the carbonate reservoir, of which petrophysical characteristic is so complicated that accurate enough estimation of the pointwise petrophysical properties could not be obtained by simple application of the ordinary hydraulic unit method nor multi-variate regression. The methodology is totally general and is considered to be applicable for a variety of reservoirs.

A Review of Horizontal Drilling in (PDO) Exploration (1990-1993)

In Petroleum Development Oman (PDO), horizontal drilling started in 1986 with a three-well trial in north Oman, targeted at chalky oil reservoirs prone to gas/water coning and low production rates. The results were not sufficiently encouraging to lead to further activity in the short term. Horizontal well technology evolved rapidly, however, and in 190 PDO embarked on a more ambitious trial by the petroleum engineering and exploration functions of eight wells in a variety of reservoirs in north and south Oman. The results were extremely positive to the extent that this trial has led to continuous horizontal drilling activity. By the end of the 1992, PDO will have drilled nearly 90 horizontal wells and seem likely to drill at least 50 such wells each year for the foreseeable future, 10 of which will be for exploration/exploratory appraisal purposes. The exploration horizontal wells have been drilled in unconnected accumulations and new discoveries with a two-fold objective: first of all to test the scope of productivity improvement for (1) thin oil columns in reservoirs with strong bottom-water drive, (2) good porosity and low-permeability oil-bearing reservoirs with depletion as a drive mechanism, (3) heavy/highly viscous oil-bearing fractured carbonate reservoirs, and (4) poorly connected/developedmore » channels, and second to outline the lateral extent of reservoir development.« less

Epidemiology of Clostridium difficile-induced intestinal disease.

The epidemiology of Clostridium difficile-induced intestinal disease is an intriguing subject about which there are few answers but many remaining questions. Although it is accepted that altered intestinal microecology (usually the result of antimicrobial therapy) is a major predisposition to disease, the details of microbial interactions are not yet known and clearly involve more than simple overgrowth of a resistant member of the resident flora. A variety of reservoirs of C. difficile are recognized. These include endogenous carriage, environmental contamination, and zoonoses, but the relative epidemiologic importance of these varied sources is yet to be determined. Because minor variations in methods for cultivation of C. difficile can markedly affect the ability to detect the organism, even the prevalence of endogenous carriage by various populations is not fully defined. There is good evidence for nosocomial acquisition of disease, but the frequency of this event and the usefulness of preventive measures need to be determined. The development of a typing system would provide a valuable tool for investigating many of the remaining questions. Finally, in addition to the recognized risk factors, which include the apparently predisposing alteration in intestinal microecology and exposure to C. difficile, there appear to be other, as yet undefined, variables that help to determine whether disease will occur. Perhaps the elucidation of the details of the pertinent microbial interactions as well as an understanding of the relevant host-pathogen relationships will provide important insights into the epidemiology of C. difficile-induced disease.