Geomechanical Response Of Overburden Caused By CO2 Injection Into A Depleted Oil Reservoir

This study investigates the hydro-mechanical aspects of carbon dioxide (CO2) injection into a depleted oil reservoir through the use of coupled multiphase fluid flow and geomechanical modeling. Both single-phase and multiphase fluid flow analyses coupled with geomechanics were carried out at the West Pearl Queen depleted oil reservoir site, and modeling results were compared with available measured data. The site geology and the material properties determined on the basis of available geophysical data were used in the analyses. Modeling results from the coupled multiphase fluid flow and geomechanical analyses show that computed fluid pressures match well with available measured data. The hydro-mechanical properties of the reservoir have a significant influence on computed fluid pressures and surface deformations. Hence, an accurate geologic characterization of the sequestration site and determination of engineering properties are important issues for the reliability of model predictions. The computed fluid pressure response is also significantly influenced by the relative permeability curves used in multiphase fluid flow models. While the multiphase fluid flow models provide more accurate fluid pressure response, single-phase fluid flow models can be used to obtain approximate solutions. The ground surface deformations obtained from single-phase fluid flow models coupled with geomechanics are slightly lower than those predicted by multiphase fluid flow models coupled with geomechanics. However, the advantage of a single-phase model is the simplicity. Limited field monitoring of subsurface fluid pressure and ground surface deformations during fluid injection can be used in calibrating coupled fluid flow and geomechanical models. The calibrated models can be used for investigating the performance of large-scale CO2 storage in depleted oil reservoirs

Maintenance strategy for bridges using reliability concept and analytical hierarchy process

Civil infrastructure in most of countries is getting old and therefore, there is a tremendous need to assess their safety levels. Among civil infrastructure, bridges are one of the main components and there is a need to study more on their safety and durability to minimize the maintenance cost and to avoid sudden failures. This paper presents bridge maintenance strategy which consists of two parts: (1) reliability based condition assessment procedure and; (2) analytical hierarchy process (AHP) based resources prioritization. In reliability based assessment, safety margins are initially proposed depending on the types of bridges. It is assumed that load and strength are random variables. Elementary reliability indices and thereby elementary failure probabilities are estimated for each safety margins. Then, system failure probability of the bridge is calculated for the time of consideration. Finally, this system failure probability is used to get system reliability index of the bridge and it is used as an index to express the condition of the bridge for the considered time. Secondly, AHP is implemented to identify the order of resources prioritization among set of bridges. The selected criteria are safety, cost of maintenance actions and relative importance of the bridge. Relative importance varies depending on historical importance, age and route of bridge location. The proposed methodology is applied to a collection of five bridges in Sri Lanka to estimate their safety levels and resources prioritization in bridge maintenance

Histoplasmosis in Sri Lanka - a masquerader in a strange land: A Case Report

We present a patient with an oral mucosal ulcer who was diagnosed with disseminated histoplasmosis. This fungal infection is endemic in the United States, and thus may be not considered in the differential diagnosis of oral ulcers in Sri Lanka. Furthermore, it may mimic many common diseases found in Sri Lanka. It is therefore important to be aware of this entity, since it is potentially curable if diagnosed and treated early.</p

Oxidation and sulfidation resistant alloys with silicon additions

The Albany Research Center (ARC) has considerable experience in developing lean chromium, austenitic stainless steels with improved high temperature oxidation resistance. Using basic alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo alloys with Si and Al addition at a maximum of 5 weight percent was selected for potential application at temperatures above 700ºC for supercritical and ultra-supercritical power plant application. The alloys were fully austenitic. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700ºC to 800ºC. Oxidation resistances of alloys with Si only additions were outstanding, particularly at 800ºC (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800ºC, showed a zero weight gain in subsequent testing for 1000 hours at 700ºC. Similar improvements were observed for Si only alloy after H2S exposure at 700ºC compared with type 304 stainless steel. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms at ARC. Depth profile analysis and element concentration profiles (argon ion etching/x-ray photoelectron spectroscopy) were conducted on oxidized specimens and base material at the National Energy Technology Laboratory

Hydrogen Separation Membranes Annual Report for FY 2006.

The objective of this work is to develop dense ceramic membranes for separating hydrogen from other gaseous components in a nongalvanic mode, i.e., without using an external power supply or electrical circuitry. This goal of this project is to develop two types of dense ceramic membrane for producing hydrogen nongalvanically, i.e., without electrodes or external power supply, at commercially significant fluxes under industrially relevant operating conditions. The first type of membrane, hydrogen transport membranes (HTMs), will be used to separate hydrogen from gas mixtures such as the product streams from coal gasification, methane partial oxidation, and water-gas shift reactions. Potential ancillary uses of HTMs include dehydrogenation and olefin production, as well as hydrogen recovery in petroleum refineries and ammonia synthesis plants, the largest current users of deliberately produced hydrogen. The second type of membrane, oxygen transport membranes (OTMs), will produce hydrogen by nongalvanically removing oxygen that is generated when water dissociates at elevated temperatures. This report describes progress that was made during FY 2006 on the development of OTM and HTM materials

Durable Zinc Oxide-Based Regenerable Sorbents for Desulfurization of Syngas in a Fixed-Bed Reactor

A fixed-bed regenerable desulfurization sorbent, identified as RVS-land developed by researchers at the U.S. Department of Energy's National Energy Technology Laboratory, was awarded the R&amp;D 100 award in 2000 and is currently offered as a commercial product by Sued-Chemie Inc. An extensive testing program for this sorbent was undertaken which included tests at a wide range of temperatures, pressures and gas compositions both simulated and generated in an actual gasifier for sulfidation and regeneration. This testing has demonstrated that during these desulfurization tests, the RVS-1 sorbent maintained an effluent H2S concentration of &lt;5 ppmv at temperatures from 260 to 600 C (500-1100 F) and pressures of 203-2026 kPa(2 to 20 atm) with a feed containing 1.2 vol% H{sub 2}S. The types of syngas tested ranged from an oxygen-blown Texaco gasifier to biomass-generated syngas. The RVS-1 sorbent has high crush strength and attrition resistance, which, unlike past sorbent formulations, does not decrease with extended testing at actual at operating conditions. The sulfur capacity of the sorbent is roughly 17 to 20 wt.% and also remains constant during extended testing (&gt;25 cycles). In addition to H{sub 2}S, the RVS-1 sorbent has also demonstrated the ability to remove dimethyl sulfide and carbonyl sulfide from syngas. During regeneration, the RVS-1 sorbent has been regenerated with dilute oxygen streams (1 to 7 vol% O{sub 2}) at temperatures as low as 370 C (700 F) and pressures of 304-709 kPa(3 to 7 atm). Although regeneration can be initiated at 370 C (700 F), regeneration temperatures in excess of 538 C (1000 F) were found to be optimal. The presence of steam, carbon dioxide or sulfur dioxide (up to 6 vol%) did not have any visible effect on regeneration or sorbent performance during either sulfidation or regeneration. A number of commercial tests involving RVS-1 have been either conducted or are planned in the near future. The RVS-1 sorbent has been tested by Epyx, Aspen Systems and McDermott Technology (MTI), Inc for desulfurization of syngas produced by reforming of hydrocarbon liquid feedstocks for fuel cell applications. The RVS-1 sorbent was selected by MTI over other candidate sorbents for demonstration testing in their 500-kW ship service fuel cell program. It was also possible to obtain sulfur levels in the ppbv range with the modified RVS-1 sorbent

The Pitfalls of Central Clearing in the Presence of Systematic Risk

Through the lens of market participants' objective to minimize counterparty risk, we provide an explanation for the reluctance to clear derivative trades in the absence of a central clearing obligation. We develop a comprehensive understanding of the benefits and potential pitfalls with respect to a single market participant's counterparty risk exposure when moving from a bilateral to a clearing architecture for derivative markets. Previous studies suggest that central clearing is beneficial for single market participants in the presence of a sufficiently large number of clearing members. We show that three elements can render central clearing harmful for a market participant's counterparty risk exposure regardless of the number of its counterparties: 1) correlation across and within derivative classes (i.e., systematic risk), 2) collateralization of derivative claims, and 3) loss sharing among clearing members. Our results have substantial implications for the design of derivatives markets, and highlight that recent central clearing reforms might not incentivize market participants to clear derivatives