Production performance of hydraulic fractures in tight gas sands, a numerical simulation approach. Journal of Petroleum Science and Engineering

Hydraulically fractured tight gas reservoirs are one of the most common unconventional gas sources being produced today, and will be a regular source of gas in the future. The extremely low permeability of tight gas sands leads to inaccuracy of conventional build-up and draw-down well test results. This is primarily due to the increased time required for transient flow in tight gas sands to reach pseudo-steady state condition. To increase accuracy, well tests for tight gas reservoirs must be run for longer periods of time which is in most cases not economically viable. The large amount of downtime required to conduct well tests in tight sands makes them far less economical than conventional reservoirs, which leads to the need for accurate simulation of tight gas reservoir well tests. This paper presents simulation results of a 3-D hydraulically fractured tight gas model created using Eclipse software. The key aims are to analyze the effect of differing fracture orientation, number and length. The focus of the simulation runs will be on the effect of hydraulic fracture orientation and length. The results will be compared to simulation runs without the abovementioned factors to determine their effects on production rates and well performance analysis. All results are plotted alongside an un-fractured tight gas scenario in order to put the hydraulic fracture performance in perspective. Key findings from this work include an approximately linear relationship between initial gas rate and the number of hydraulic fractures intersecting the wellbore. In addition, fracture length is found to have less of an impact on initial gas rate compared to number of fractures intersecting the wellbore, for comparable total fracture volumes

Characterizing natural fractures productivity in tight gas Reservoirs

Tight formations normally have production problems mainly due to very low matrix permeability and various forms of formation damage that occur during drilling completion and production operation. In naturally fractured tight gas reservoirs, gas is mainly stored in the rock matrix with very low permeability, and the natural fractures have the main contribution on total gas production. Therefore, identifying natural fractures characteristics in the tight formations is essential for well productivity evaluations. Well testing and logging are the common tools employed to evaluate well productivity. Use of image log can provide fracture static parameters, and welltest analysis can provide data related to reservoir dynamic parameters. However, due to the low matrix permeability and complexity of the formation in naturally fractured tight gas reservoirs, welltest data are affected by long wellbore storage effect that masks the reservoir response to pressure change, and it may fail to provide dual-porosity dual-permeability models dynamic characteristics such as fracture permeability, fracture storativity ratio and interporosity flow coefficient.Therefore, application of welltest and image log data in naturally fractured tight gas reservoirs for meaningful results may not be well understood and the data may be difficult to interpret. This paper presents the estimation of fracture permeability in naturally fractured tight gas formations, by integration of welltest analysis results and image log data based on Kazemi’s simplified model. Reservoir simulation of dual-porosity and dual-permeability systems and sensitivity analysis are performed for different matrix and fracture parameters to understand the relationship between natural fractures parameters with welltest permeability. The simulation results confirmed reliability of the proposed correlation for fracture permeability estimation. A field example is also shown to demonstrate application of welltest analysis and image log data processing results in estimating average permeability of natural fractures for the tight gas reservoir

Evaluating factors controlling damage and productivity in tight gas reservoirs

Production at economical rates from tight gas reservoirs in general is very challenging not only due to the very low intrinsic permeability but also as a consequence of several different forms of formation damage that can occur during drilling, completion, stimulation, and production operations. The common strategies used in tight gas reservoirs development are hydraulic fracturing and horizontal well drilling. However in many cases of tight gas reservoirs, the key factors that control well productivity and formation damage mechanisms are not well understood, since it is challenging to characterise them in tight formations.In this thesis I demonstrate how different well and reservoir parameters control well productivity and damage mechanisms in tight gas reservoirs. Reservoir simulation model for Whicher Range tight gas field is built and run. Analytical and numerical simulation approaches are integrated with core flooding experiments and tight gas field data analysis in order to characterize the key reservoir parameters and understand the effects of different parameters on well productivity.Using core flooding experiments data analysis, the relative permeability curves are generated for Whicher Range tight gas reservoir, and quantitatively is shown how the phase trapping damage can be reduced by use of oil based drilling fluid instead of water based fluid. A new technique of welltest analysis was introduced for tight gas reservoirs that can reduce uncertainties in estimation of average reservoir permeability, and also a new correlation that can determine permeability of the natural fractures in tight formations is proposed in this study. I study and analyse different well completion, production and reservoir data from Whicher Range tight gas field in order to identify why production rates are significantly lower than expectations, and investigate possible remedial strategies to achieve viable gas production rates.Based on this research, drilling long horizontal deviated wells using non-aqueous fluids in underbalanced conditions may be more efficient than hydraulic fracturing. As the optimum strategy to further improve the well productivity, drilling the well with a high deviation to intersect multiple sand lenses; orienting the wellbore direction perpendicular to the maximum horizontal stress to intersect higher permeability conduits and control wellbore instability issues; completing the well as open-hole to have the advantage of enlarged wellbore caused by large wellbore breakouts; running slotted liner to control wellbore collapse; open-hole perforation in the direction of maximum horizontal stress to reach a deeper formation penetration; and unloading the wellbore from drilling and fracturing fluids can help achieve commercial gas production rates from tight gas reservoirs

Diagnostic Accuracy of Computed Tomography Scan in Detection of Upper Gastrointestinal Tract Injuries Following Caustic Ingestion

Introduction: Endoscopy is an invasive procedure and finding noninvasive alternative tools in detection of probable upper gastrointestinal (GI) tract injuries following caustic ingestion is an area of interest. The present study aimed to evaluate the screening performance characteristics of thoraco-abdominal computed tomography (CT) scan in this regard.Methods: This prospective cross sectional study was conducted on patients presenting to emergency department following acute caustic ingestion. The findings of CT scan and endoscopy regarding the presence of upper GI tract damage were compared and screening performance characteristics of CT scan were calculated using MedCalc software.Results: 34 patients with the mean age of 35.38±13.72 years were studied (58.8% male). The agreement rate between CT scan and endoscopy regarding the grade of esophageal and gastric injuries was moderate (K= 0.38; p = 0.001) and fair (K= 0.17; p = 0.038), respectively. The sensitivity and specificity of CT scan in detection of esophageal damage were 96.29) 79.11- 99.80) and 57.14 (20.23 - 88.19), respectively. These measures were 89.65 (71.50 - 97.28) and 40.00 (7.25 - 82.95), respectively for gastric damage. The area under the ROC curve of CT scan in detection of esophageal and gastric damages was 0.76 (95% CI: 0.52 – 1.00) and 0.64 (95% CI: 0.35 – 0.94), respectively.Conclusion: Based on the findings of the present study, CT scan could be considered as a sensitive tool in ruling out upper gastrointestinal mucosal injuries following acute caustic ingestions. However, the correlation between endoscopy and CT scan findings regarding the grading of injury is not high enough to eliminate the need for endoscopy.

Immunological Compatibility Status of Placenta-Derived Stem Cells is Mediated by Scaffold 3D Structure

Placenta-derived amniotic epithelial cells (AECs), a great cell source for tissue engineering and stem cell therapy, are immunologically inert in their native state; however, immunological changes in these cells after culture and differentiation have challenged their applications. The aim of this study was to investigate the effect of 2D and 3D scaffolds on human lymphocyte antigens (HLA) expression by AECs. The effect of different preparation parameters including pre-freezing time and temperature was evaluated on 3D chitosan–gelatine scaffolds properties. Evaluation of MHC class I, HLA-DR and HLA-G expression in AECs after 7 d culture on 2D bed and 3D scaffold of chitosan–gelatine showed that culture of AECs on the 2D substrate up-regulated MHC class I and HLA-DR protein markers on AECs surface and down-regulated HLA-G protein. In contrast, 3D scaffold did not increase protein expression of MHC class I and HLA-DR. Moreover, HLA-G protein expression remained unchanged in 3D culture. These results confirm that 3D scaffold can remain AECs in their native immunological state and modification of physical properties of the scaffold is a key regulator of immunological markers at the gene and protein expression levels; a strategy which circumvents rejection challenge of amniotic stem cells to be translated into the clinic

Time-domain large-signal modeling of traveling-wave modulators on SOI

Silicon photonic modulators have strong nonlinear behavior in phase modulation and frequency response, which needs to be carefully addressed when they are used in highcapacity transmission systems. We demonstrate a comprehensive model for depletion-mode Mach–Zehnder modulators (MZMs) on silicon-on-insulator, which provides a bridge between device design and system performance optimization. Our methodology involves physical models of p–n–junction phase-shifters and traveling-wave electrodes, as well as circuit models for the dynamic microwave-light interactions and time-domain analysis. Critical aspects in the transmission line design for high-frequency operation are numerically studied for a case of p–n–junction loaded coplanar-strip electrode. The dynamic interaction between light and microwave is simulated using a distributed circuit model solved by the finite-difference time-domain method, allowing for accurate prediction of both small-signal and large-signal responses. The validity of the model is confirmed by the comparison with experimental results for a series push–pull MZM with a 6 mm phase shifter. The simulation shows excellent agreement with experiment for high-speed operation up to 46 Gb/s. We show that this time-domain model can well predict the impact of the nonlinear behavior on the large-signal response, in contrast to the poor prediction from linear models in the frequency domain

Climate Change and Respiratory Diseases:Relationship between SARS and Climatic Parameters and Impact of Climate Change on the Geographical Distribution of SARS in Iran

Climate change affects human health, and severe acute respiratory syndrome (SARS) incidence is one of the health impacts of climate change. This study is a retrospective cohort study. Data have been collected from the Iranian Ministry of Health and Medical Education between 17 February 2016 and17 February 2018. The Neural Network Model has been used to predict SARS infection. Based on the results of the multivariate Poisson regression and the analysis of the coexistence of the variables, the minimum daily temperature was positively associated with the risk of SARS in men and women. The risk of SARS has increased in women and men with increasing daily rainfall. According to the result, by changes in bioclimatic parameters, the number of SARS patients will be increased in cities of Iran. Our study has shown a significant relationship between SARS and the climatic variables by the type of climate and gender. The estimates suggest that hospital admissions for climate-related respiratory diseases in Iran will increase by 36% from 2020 to 2050. This study demonstrates one of the health impacts of climate change. Policymakers can control the risks of climate change by mitigation and adaptation strategists

Investigation of Post Harvesting Time and Size Effects on Tomato Mechanical Strength under Quais-Static Loading

ABSTRACT Reduce waste maintain quality of agricultural products and the optimal design of machines and processing equipment, knowing the mechanical properties are essential. In this study, using a Texture analyzer on the fruit of tomato, Early kind of CH, mechanical stress testing within a factorial experiment in completely randomized design factors independent of fruit size (S), at three levels, time after harvest (T), as well as three levels, on the mechanical properties, force and required energy to Relaxation percent of fruit, were studied. Analysis of variance showed that with increasing size of tomatoes, compressive power and energy increases with increasing time after harvest, but energy and relaxation force at the time (t 2 ) increased, but at the time (t 3 ) decreased. The interaction results show that the more fruit size is great, the compressive force and power of fruit were also increased and this effect for investigate relaxation feature (R %) till 24 hours after harvest for the average size would be increased but with time after harvest was reduced to 72 hours

Economic Efficiency of Intensive Care Units Department of Hospitals Affiliated With Yazd University of Medical Sciences: A DEA Approach

Introduction:Hospitals as the most expensive health care system is an operational unit, considering the cost efficiency of this unit is very important. The aim of this study was to evaluate the performance of the intensive care units of hospitals affiliated with Yazd University of Medical Sciences. Methods:This is a descriptive - analytic study performed in 2014. Intensive care units of 8 hospitals affiliated with Yazd University of Medical Sciences were included in this study. Data envelopment analysis (DEA) was used to evaluate the economic efficiency of intensive care units. Input variables included the number of physicians, nurses, and active beds, as well as the number of equipment (ventilator), and output variables included bed occupancy rate and the number of patients discharged healthy. Input prices contained the doctors and nurses income, bed price, and depreciation cost of equipment (ventilator). Results:The findings show that among 8 studied hospitals, the efficiency of 5 hospitals were 1 and the efficiencies of the other hospitals were 0.174, 0.645, and 0.855. The mean economic efficiency of intensive care units of all hospitals was 834.0 in 2014. Conclusion:By ameliorating the allocation of resources allocated for hospitals including human resources and equipment, the efficiency level of hospitals can be improved. Key¬words:Economic Efficiency, Educational Hospital, Data Envelope Analysis (DEA). Citation: Abedi M, Bahrami MA, Yusefzadeh H, Kiani MM, Moeeni M.Economic Efficiency of Intensive Care Units Department of Hospitals Affiliated With Yazd University of Medical Sciences: A DEA Approach.Journal of Health Based Research 2016; 2(1): 29-38