bluuebunny/crossref_metadata_2025 huggingface dataset:
Offshore LNG Technology: A Comparative Study of Conventional and Futuristic Salt-Cavern-Based LNG Receiving Terminals
Authors: Rai Sanchit
Published: July 2008

Tight oil supplies, escalating oil prices, and towering energy demands have led to the revival of natural gas. It is now deemed to be the potential fuel of the near future. The trend now is toward supplying every cubic foot of inland and offshore natural gas to energy-hungry consumers. Liquefied natural gas (LNG) is recognized as the best form of gas transfer from remote inland and offshore fields to consumers around the world.

The natural gas is liquefied and shipped to distant receiving terminals. The main technical features of a conventional terminal facility include LNG carrier mooring systems, unloading facilities, cryogenic LNG storage tanks, LNG regasification systems, and gas send-out systems. The United States has five such conventional terminals and is the world's largest gas market, with gas demands expected to double by 2020. This demand is leading to the expansion and refurbishment of these conventional LNG receiving terminals, with the construction of several more in various phases of planning and development. In 2005, the US Department of Energy (DOE), along with 30 energy industry players, successfully completed a research study on the concept of an offshore facility to moor LNG carriers and unload and store LNG. This concept includes storing gas in salt caverns. This technology is claimed to be highly cost-effective and process-efficient, with better delivery capacity and security than other options. This idea is being implemented through the construction of such a modern LNG receiving terminal in offshore Louisiana.

Apart from the United States, LNG also offers great promise to such countries as Brazil, China, the United Kingdom, Mexico, Germany, and France. These countries are also contemplating LNG facilities development and upgrading.

This paper aims to present a qualitative comparison between conventional and futuristic salt-cavern-based LNG receiving terminals. The comparison is based on the use of technology for these terminals. This approach will be ultimately useful in understanding the technology implementation required for the development and modernization of LNG receiving facilities in such countries.
Economic Modeling of an Oil and Gas Project Involving Carbon Capture and Storage: Snøhvit LNG Field (Barents Sea, Norway)
Authors: Negrescu Matei
Published: July 2008

The Snøhvit Liquefied Natural Gas (LNG) project developed by StatoilHydro and partners in Norway is used as an example to describe how the carbon capture and storage (CCS) component of an oil and gas project can be isolated, modeled, and analyzed from an economic point of view. The Snøhvit development, which started production in late 2007, involved a CCS component from day one. Approximately 700,000 tons of CO2 captured from the liquefaction plant will be reinjected every year in an underground formation offshore. Furthermore, there are interesting alternatives for CO2 capture from the on-site power plant and for the use of CO2 for enhanced oil recovery (EOR) in a nearby oilfield, leading to several future development scenarios for CCS at Snøhvit.

Different development scenarios for CCS are analyzed to select the best development option. The economic modeling framework will also be used to assess the impact of the uncertainties on the project economics.

The analysis identifies that a key driver for the profitability of the project is the legislative setting for CCS. The involvement of the government is very important for the viability of the project, which needs a strong incentive, such as the current CO2 tax scheme or an emission trading scheme with strict allocation of emission targets. Under such conditions, a CCS project such as Snøhvit becomes a win-win situation: economically profitable for the operator and environmentally friendly.

From a broader perspective, addressing the economic and legislative uncertainty currently surrounding CCS projects for the oil and gas industry is crucial because this represents the main limiting factor for the further development of such projects. It is therefore essential that economic modeling tools such as the framework described in the present work become industry standards to ensure that projects which could be profitable for both the operator and the environment are not abandoned by pure lack of analysis ability.
Oil Fallout in the Vicinity of an Onshore Blowout: Observations on a Field Case
Authors: Oudeman P.
Published: July 2008

Oil deposition in the area surrounding a blowout is one of the most visible consequences of the loss of control over well flow. Less visible, but equally serious, are the short- to medium-term effects of oil coverage on the environment. Apart from the direct damage, studies indicate effects (e.g., reduced tree growth) that persist many years following the incident.

Hence, oil fallout, in the case of loss of well control, is a factor to be taken into account in decisions on well locations, emergency procedures, contingency planning, etc. This requires an estimate of the area around the well likely to be affected by oil fallout, given the geomorphology of the terrain, prevailing winds, and expected outflow conditions. Models to obtain such an estimate have been proposed, but application of these models (e.g., for environmental impact assessment) has been limited. In part, this limitation can be attributed to a lack of validation of the models because this requires a combination of well-effluent data, outflow conditions, meteorological data, a detailed terrain description, and fallout maps.

For the field case discussed in this paper, all the data necessary for validation were assembled from various sources ranging from the well operator and environmental agencies to meteorological and cartographic institutes. The relation between the observed pattern of oil deposition around the well and factors such as outflow conditions and wind speed and direction is analyzed with a simple model. This relationship demonstrates that the main factors determining the area affected by deposition of oil are the outflow conditions and the wind direction.

To verify this result, a comparison with historical observations on oil fallout around gushers has been made. Although more sketchy, the same patterns emerge from this comparison, which strongly suggests that the methods developed to explain the fallout pattern of the field case discussed can be used over a wide range of conditions to predict the area affected by a blowout. This prediction can serve several purposes, such as site selection, definition of emergency procedures, environmental impact assessment, and contingency planning. Finally, it is noted that this method also applies in less dramatic situations (e.g., predicting droplet deposition around vent stacks).
Optimizer's Curse: Removing the Effect of This Bias in Portfolio Planning
Authors: Schuyler John , Nieman Timothy
Published: July 2008

Even with unbiased judgments and project calculations, an insidious bias will still be present in an approved projects portfolio. The screening and ranking process used to select projects causes an optimizer's curse (OC) effect (Smith and Winkler 2006). A portfolio's true outcome value will tend to fall below the forecast distribution mean. Stated another way, we should expect to be disappointed in the value of the eventual outcomes. This optimizer's curse effect can be huge: the true portfolio value might be half its forecast value when forecast in the usual way.

This paper describes a correction process based upon Bayesian inversion obtained with Monte Carlo simulation. Estimate/Actual distributions characterize component evaluation errors. The mean and standard deviation of the E/A distribution measures the quality of judgments and estimates. Examples demonstrate the value of better information in project or asset evaluation, portfolio optimization, and competitive bidding.

The premise of our approach to correct for optimizer's curse is straightforward enough, though implementing this method requires judging the population of evaluated projects—or at least assessing the shape of this population's distribution. We offer a process and guidelines for correcting for the optimizer's curse in both project and portfolio value calculations. Correcting estimates for systematic biases restores luster to the recommended expected value-maximizing decision policy. We also tie back to the winner's curse phenomenon (Capen et al. 1971) experienced in competitive bidding and how it affects bid optimization.
Rapid and Low-Cost Methodology to Obtain an Updated Compositional Model of Produced Fluids Using Separator-Discharge Data Analysis
Authors: Morales Fernando L. , Velázquez Juan Cruz , Hernandez Aaron Garrido
Published: July 2008

Fluid-characterization data used to build representative reservoir fluid models for reservoir and production engineering are generally scarce and very costly because of the expense of fluid sampling and analysis and operational related problems of well intervention. The problem turns more dramatic when the field to be studied has been producing for some time and its bottomhole pressure has reached the bubblepoint. In those cases, initial reservoir fluid data is more difficult to be used because some portion of the hydrocarbon's heaviest or lightest components, whether oil or gas is produced, may have been left in the reservoir and initial PVT data are no longer valid or very difficult to match to current fluid behavior.

One of the most common practices of obtaining fluid data is by taking well bottomhole samples, or by obtaining surface oil and gas mixture samples, and analyzing them in the lab using recombined methods. Because of the costs involved, including loss of time and production, operating companies do not obtain fluid data with the required frequency. Accordingly, engineers are left with the only option of using nonupdated or insufficient data that will affect the outcome of their simulation studies.

This work describes a rapid and low-cost methodology to obtain an updated compositional model for produced fluids using gas chromatography, oil characterization, and GOR from analysis of the separator fluid discharge. The required samples are easily collected with low cost to the operating company.

Then, a case history is shown wherein compositional fluid models obtained with the proposed method are used in well, surface-network, and process-facility simulation models, with excellent results. A comparison of field data against the simulation model results is also shown.
Offshore Natural Gas Liquefaction Process and Development Issues
Authors: Wood David , Mokhatab Saeid , Economides Michael J.
Published: July 2008

Liquefied natural gas (LNG) has yet to be deployed in the development of offshore fields in spite of several detailed studies completed and offshore technology development demonstrating its technical feasibility. The perceived risks associated with deploying unproven technology in a high construction cost and volatrile gas price environment have so far inhibited offshore liquefaction projects. The potential deployment of such technologies is of paramount importance considering the massive volumes of natural gas currently deemed as "stranded" and the exploitation of which is compelling not only because of the inherent economic benefit but also because of the otherwise adverse impact on oil production. It is conceivable that deep water offshore locations may contain quantities of natural gas rivalling those of onshore locations. Such a statement cannot even be confirmed because drilling for offshore natural gas reservoirs, expected to be found considerably deeper than oil reservoirs, has been unattractive exactly because of the absence of coherent exploitation strategies. If anything, the mere presence of large natural gas deposits even in the form of solution gas in oil is now often considered as largely undesirable because of the cost of just handling non-monetized natural gas. This paper discusses potential offshore LNG processes and reviews natural gas liquefaction cycles in the context of compactness, ease of operation, process safety, and efficiency.

Particular attention is paid to the lower-efficiency turboexpander processes for plant capacities up to 3 million tonnes per annum (MTPA, approximately 0.43 Bcf/d). These cycles offer several advantages over the alternative optimized cascade and mixed refrigerant (MR) liquefiers for offshore applications.
Operating Multiphase Helicoaxial Pumps in Series To Develop a Satellite Oil Field in a Remote Desert Location
Authors: Saadawi Hisham
Published: July 2008

Abu Dhabi Company for Onshore Oil Operations (ADCO) has recently developed one of its satellite oil fields. The field is located in a remote desert location onshore the Emirate of Abu Dhabi, in the United Arab Emirates (UAE). The development concept is based on multiphase pumping and the entire field was developed using multiphase pumps.

Two helicoaxial pumps are used to pump 10,000 B/D of crude oil with associated gas and produced water to the host facilities in a nearby field some 30 km away. The pumps are installed in series. The pumps were commissioned successfully in 2006 and have been operating since then.

Huwaila field is the first and only oil field in the world where two multiphase helicoaxial pumps are operated in series. This paper describes the design, testing, and operational aspects of this unique experience.
Estimating the Cost of Errors in Estimates Used During Concept Selection
Authors: Jablonowski C. , Wiboonkij-Arphakul C. , Neuhold M.
Published: July 2008

This study examines the loss in project value incurred when concept selection decisions are based on erroneous estimates of input variables. Estimates of the magnitude of such losses are provided, along with an analysis of which input variable estimates matter most in determining value loss. A procedure for concept selection is defined to model the decision making process and is used in conjunction with a simplified asset development optimization model to estimate project values. The analysis compares project values resulting from concept selection decisions based on erroneous estimates to values based on an alternate hypothesis. Results suggest that the cost of using erroneous estimates for initial costs, expansion costs, and the timing of future expansion projects is comparable in magnitude to the cost of erroneous reserve estimates. Also, the cost of underestimating expected reserve volume tends to be larger than the cost of overestimating reserve volume, aggressive cost estimates are more destructive to value than conservative estimates, and conservative schedule estimates for the timing of expansion projects are generally more destructive to value than aggressive schedule estimates.
Automatic Ultrasonic Inspection of Steel Catenary Risers With a Corrosion-Resistant Alloy Layer
Authors: van der Ent Jan , van Nisselroij Jacq , Kopp Frans , Otter Andries , Weli Nwoji , Judd Steve
Published: July 2008

Corrosion-resistant alloy (CRA)-clad pipelines have austenitic girth welds. Such girth welds cannot be inspected by conventional ultrasonic methods and must to be examined by the nonconventional angle beam compression wave/creep-wave technique. Because of the dynamic nature of steel catenary risers (SCR) used in deep waters, very tight acceptance/rejection criteria apply.

This paper gives background information about the design and installation of SCRs, the material properties of such a design, and the inspection solution developed to examine such welds. In addition, the development and qualification as used in the Bonga project is demonstrated, and conclusions and recommendations are given.
The Effects of Partial Span Coverage for Deepwater Marine Risers and Tendons With Fairings
Authors: Allen Don W. , Henning Dean L. , Lee Li
Published: July 2008

Two sets of tests have been conducted on short fairings with a chord-to-pipe-diameter ratio of approximately 1.5 partially covering a long pipe that was towed under a rotating arm at Reynolds numbers equivalent to those experienced by many production risers. From the first set of tests, results for pipes with continuous fairings over various lengths of the outer end of the pipe are presented, as well as for two configurations with partial coverage. From the second set of tests, results for a series of partial fairing coverage tests are presented that consisted of a more systematic variation of fairing density on the outer two joints. The results produced several practical conclusions that can be used for more economical marine tubular designs.
Smoothbore Flexible Riser for Gas Export
Authors: Crome Tim , Binet Eric , Mjøen Stig
Published: July 2008

This paper describes the development of a novel design of smooth-bore riser for dry gas applications. It has been developed for use on the Statoil operated Åsgard field, located approximately 200 kilo-metres off mid-Norway.

Shortly after startup of gas export from what was then the world's largest semi-sub, Statoil's Åsgard B platform, a serious noise and vibration phenomenon was identified in the gas export system. This system consists of a manifold on the platform topsides connected to parallel flexible risers linked to a subsea Export Riser Base which feeds the gas into the 42-in. export pipeline to Norway. The noise, essentially a high-pitched whistling, and resulting vibration caused two fatigue failures of smallbore piping fittings on the topsides manifold, leading to gas leaks on the platform. There were also concerns related to the subsea piping. The source of the noise, in this dry-gas system, was related to vortex shedding of the gas flow past the internal carcass in the flexible risers.

Initially, two roughbore risers were installed; this was sub-sequently increased to a total of four, including one spare. The increase to three operating export risers had been planned from the start of the project to reflect increased export volumes from Åsgard. However, while it was now possible to manage the gas flow such that the noise and vibration was controlled, this could not be achieved without unacceptable pressure losses along the length of the flexible risers. This problem was related to longer term operation of the Åsgard Transport System as the export volume through it, and hence the required operating pressure, increased with the inclusion of export from new fields, such as Kristin.

After comprehensive work with export system monitoring, dynamic simulations, and assessment of alternative export arrangements, Statoil invited Technip to validate the concept of a flexible smoothbore structure for the Åsgard B gas export riser system. This paper describes the background for, and special measures implemented in, the design of the world's first smoothbore flexible riser for gas export. This design is such that noise from the risers is eliminated while, at the same time, a smooth internal bore significantly reduces the pressure losses along the riser, allowing the full potential of the Åsgard Transport System to be achieved. The first smoothbore gas export riser was installed in late Autumn 2006 as a replacement for one of the existing standard roughbore risers.

Hence, the new application of smoothbore riser technology to the novel gas export riser design for Åsgard gives several benefits:

Noise and vibration issues are eliminated. Pressure losses are reduced. Environmental benefits are achieved from the subsequent re-duction in need for compression.
High-Integrity Protection Systems (HIPS): Methods and Tools for Efficient Safety Integrity Levels Analysis and Calculations
Authors: Signoret Jean-Pierre
Published: July 2008

High Integrity Protection Systems (HIPS) are more and more extensively used in the oil industry to replace conventional safety systems, and this paper aims to show how to efficiently evaluate their Safety Integrity Levels (SIL) as required by the IEC 61508 (1998) and 61511 (2003) standards. These standards provide rigorous formal processes to build the safety of Safety Instrumented Systems (SIS) and are very efficient from an organizational point of view. However, difficulties still arise with definitions and probabilistic calculations, and for this reason our company has developed a set of probabilistic methods and tools to overcome such difficulties. They are based on traditional holistic approaches and the powerful algorithms developed in the reliability field over the past 30 or 40 years: Fault Trees, Markov processes, and Monte Carlo simulation performed on behavioral models (e.g., Petri nets or formal languages). They are briefly analyzed in this paper using simple examples to highlight the principles. This paper is mainly focused on HIPS working in low-demand-mode (i.e., with less than one demand per year according to the standards) and HIPS such as High Integrity Pressure Protection Systems (HIPPS), but indications are given for HIPS functioning in continuous modes of operation. The main conclusions are that, when properly handled, Fault trees are very efficient for low-demand topside HIPS; that the Markovian approach is interesting but practicable only for very small systems; and that Monte Carlo simulation on behavioral models is efficient in all cases. From our point of view, these approaches are simpler to handle than the informative formulae proposed in the present issue of the standards. Therefore, we have begun to disseminate these approaches and we strongly recommend our contractors to use them.
Flow Assurance and Artificial Lift Innovations for Jubarte Heavy Oil in Brazil
Authors: Colodette Giovani , Pereira Carlos A. G. , Siqueira Cézar A. M. , Ribeiro Geraldo A. S. M. , Rodrigues Roberto , de Matos João S. , Ribeiro Marcos P.
Published: July 2008

The Jubarte field, in the Campos Basin, Brazil, was discovered in January 2001. It is located approximately 80 km offshore from the State of Espírito Santo, under water depths between 1,000 and 1,500 m, containing oil of 17°API and viscosity of 14 cp at reservoir conditions.

This work presents a review of the artificial lift and flow assurance aspects faced by PETROBRAS in the exploitation of Jubarte heavy oil, starting from the features of the pilot phase. It details all the challenges posed and innovations proposed and implemented for Phase 1 field development, as well as expectations for the subsequent Phase 2.
Novel Coalescer Technology in First-Stage Separator Enables Single-Stage Separation and Heavy-Oil Separation
Authors: Fjeldly T. A. , Hansen E. B. , Nilsen P. J.
Published: July 2008

Aibel (former ABB Offshore Systems) has for a long while carried out fundamental research on compact separation. A significant part of the development has been to incorporate robust electrostatic coalescers into three phase separators. The current technology enables single-stage separation and accelerates separation of oil and water. The most recent product developed to enable single-stage separation is the Low Water Content Coalescer (LOWACC). The LOWACC is an electrostatic coalescer element, enhancing and accelerating the separation in an oil/water/gas separator. It is designed to operate as a polishing element for removal of the remaining droplets of water and is designed to be located downstream the Vessel Internal Electrostatic Coalescer (VIEC), which is a bulk separation device. A prototype polishing element, together with the bulk separation device, has been tested on several different real crude oils ranging from API 17 to API 29. For the API 29 crude, the water in oil (WiO) content was successfully reduced below 0.5% without the use of chemicals. For the challenging API 17 oil, the oil in water (OiW) was reduced to below 2–5%. All the test results verified good separation even with tough separation conditions that created stable emulsions and small droplets. The produced water leaving the separator contained 2 to 200 ppm oil in water.
AKPO: A Giant Deep Offshore Development
Authors: Rafin F. , Laîné A. , Ludot B.
Published: July 2008

All deep water offshore projects are challenging. They are large developments, difficult to implement and often beyond the limits of proven technologies at their inception.

AKPO field is located in block Offshore Mining License (OML) 130,200 km offshore Nigeria in 1400 m of water. At plateau production, AKPO will produce and export 175,000 B/D of condensate and will export, at startup, 320 MMscf/D of gas to Bonny NLNG plant, onshore Nigeria.

AKPO reservoirs characteristics have greatly influenced the development scheme while still making it technically and economically viable. AKPO reservoirs consist in a 620-million-recoverable-barrels accumulation of a critical fluid made of very light oils up to 53°API and classified as condensate, with well head shut-in pressures up to 400 bars, fluid temperature up to 116°C at wellhead, and very high gas liquid ratio (GLR). AKPO is not only a giant condensate field, but also a gas field with 1 Tcf planned gas export.

With such particular reservoir conditions, the AKPO development scheme is very challenging and maximizes the use of proven and generic technologies whenever possible.

The development is taking place at a time when the supplier market is very buoyant. This, in turn, has created additional challenges with respect to the availability of skilled resources and obtaining quality products on time.

The paper addresses the challenges of AKPO development and in particular some of the key technical issues.

A unique hybrid condensate production/gas export development scheme which maximizes hydrocarbon recovery Reservoir management requiring massive pressure maintenance facilities, extensive use of intelligent and selective completions, and subsea multiphase flow measurements A development drilling strategy and well architecture. A subsea layout compromise, aiming at maximum reliability and availability. Extensive qualification and testing program of equipment to meet with the reservoir conditions. An FPSO concept pushed to the limit to handle high volume of high-pressure (HP) fluids together with a very large gas inventory. The securing of resources in terms of dry dock slot, marine spread and deep offshore drilling units in a buoyant market.

TOTAL, with 24% interest, is the operator on OML 130 on behalf of Petrobras of Brazil, Sapetro of Nigeria, China National Offshore Oil Corporation of China (CNOOC), and Nigerian National Petroleum Corporation (NNPC) of Nigeria.

AKPO achieved Project sanction on 25 April, 2005, when OML 130 was awarded by the Nigerian authorities. AKPO is currently under development with drilling and construction underway, with first production planned before the end of 2008.
Improved Mechanical IGF Technology for Floating Production Storage and Offloading Application-First Installation Theory and Practice
Authors: Rivet Crystal , Movafaghian Shaya , Chen James
Published: July 2008

This paper is intended to be part of the continuous development and adaptation of mechanical-cylindrical induced-gas-flotation (IGF) technology that meets the demands of today's offshore production practices as the best-available technology (BAT). The focus of this paper relates theory to practice for this new, yet proven, technology, and presents the real-life example of one of its applications. This paper presents the problem-solving and selection process adopted by Chevron Corp.'s North America Operations Team at the Typhoon production facility, located in the deepwater Gulf of Mexico. The paper compares alternative solutions, and the economic advantages and disadvantages of each. It also provides an in-depth analysis of the performance achieved after installation of the dual cell on the basis of the theoretical model developed for this equipment.
Experimental Research on Treatment of Produced Water From a Polymer-Flooding Process Using a Double-Cone Air-Sparged Hydrocyclone
Authors: Liu Shumeng , Zhao Xuefeng , Dong Xigui , Miao Baolin , Du Wei
Published: July 2008

Produced water from polymer flooding (polymer-produced water) is difficult to treat by the conventional gravity settling process. A new type of double-cone air-sparged hydrocyclone (DcASH) has been designed, and its fundamental structure and operating principles are introduced in this paper. Experimental research on treating produced water from polymer flooding has been carried out, showing that the DcASH has a high treatment capacity. The oil concentration of treated water was less than 100 mg/L, which satisfied the requirements of the next deep-bed filtration process stage. Compared to gravity settling, conventional hydrocyclones, and flotation, the DcASH has a higher separation efficiency, which indicates that DcASH will have good application prospects in oilfield produced-water treatment.
Unified Modeling of Gas/Oil/Water-Pipe Flow-Basic Approaches and Preliminary Validation
Authors: Zhang Hong-Quan , Sarica Cem
Published: July 2008

A unified model is proposed for the prediction of flow behavior during production and transportation of gas, oil, and water through wellbores and pipelines. In gas/oil/water three-phase-pipe flow, the phase distributions and hydrodynamics are described on the basis of two criteria: gas/liquid flow pattern and oil/water mixing status. The three-phase flow is treated as gas/liquid two-phase flow, if the two liquids are fully mixed, or as a three-layer stratified flow at low flow rates in horizontal or slightly inclined pipes. Most three-phase flows fall between the two extremes, partially mixed with slippage between the two liquid phases. Closure relationships describing the distribution between the liquid phases, namely mixing and inversion, are proposed. The model predictions are compared with experimental data of gas/oil/water pipe flows. Significant improvements are observed over the predictions by the two-phase unified model of Zhang et al. (2003a), which assumes a fully mixed liquid phase.
Creating a Culture To Deliver Sustainable HSE Performance
Authors: Buell R. S.
Published: July 2008

Demands on the petroleum industry are driving continual improvement of health, safety, and environment (HSE) performance. It has become widely recognized that the deliberate and structured creation of HSE culture directly affects HSE performance. Developing HSE culture is a complex recipe that combines values, leadership, management systems and processes, behavioral and cognitive psychology, technology, equipment, and HSE expertise. This combination creates a culture or "way of working in the organization."

There are many theoretical and practical papers on the creation and assessment of HSE culture. For a leader in E&P operations, the distillation of this large body of knowledge into an appropriate course of action can be a daunting task. A generic HSE cultural-maturity model is provided in this work. HSE culture is further defined in terms of cultural dimensions. To improve HSE performance, development of culture cannot be confined within an E&P operator's organization. Contractors, partners, service providers, and suppliers must also be included in the development of HSE culture. Guidance is provided to help the E&P practitioner work collaboratively with contractors to develop, sustain, and improve HSE culture and performance. Pragmatic examples are provided for diagnosing HSE culture.
Comprehensive Risk-Evaluation Approaches for International E&P Operations
Authors: Clare Jay B. , Armstrong Louis
Published: July 2008

Managers of E&P projects and operations are often required to make decisions on the basis of a variety of factors including, but not limited to, safety, finance, security, and company reputation. Often these factors are hard to quantify or may be in direct conflict with each other. Therefore, it is critical that decision makers use an approach to assess risks associated with each factor in a consistent and defensible manner. The selected approach needs to be robust enough to quantify the risk sufficiently, but simple enough to allow for ease of use and interpretation of results. In this paper, we present several approaches by which risk criteria can be defined, and then present resulting risk profiles for E&P operations in developing nations, thereby increasing the number of tools available to those faced with making such business decisions.
Subsea Development of Okwori and Nda Oil Fields, Niger Delta
Authors: Stenger B. A. , Guinot F. , Clauss C. , Otevwemerhuere J. , Ezeukwu T. E. , Aubert O.
Published: July 2008

Addax Petroleum's operated Okwori oil field, offshore Nigeria, illustrated the benefits of reviving shelved projects, because of an insufficient return on investment using more traditional approaches, by applying more recent technical and contractual solutions.

The Okwori project demonstrated the feasibility of developing small and geologically complex offshore oil fields in medium water depth of 440 ft with subsea technologies traditionally used for large fields.

In the subsurface, the Okwori wells combined multiple selective completions hydraulically controlled from the surface with expandable sand screens as the downhole sand exclusion solution. This combination of equipment in subsea wells used to fully develop a small offshore oil field marked another technological first in Nigeria.

Far away from pre-existing facilities and with less than 50 million bbl of median technical reserves at the time of project sanction, the Okwori oilfield development went a step further than the more usual subsea tieback to a pre-existing offshore production facility. The Okwori development plan was based on horizontal subsea trees flowing to a leased spread-moored floating production storage and offloading (FPSO) vessel by means of (6-in.) flexible subsea flowlines and risers.

The Okwori leased production facilities had a built-in capability for additional tiebacks such as the Nda oil field, whose development was completed in October 2006, or for later redeployment in other parts of the acreage depending on further exploration and appraisal drilling.

A review of the field operations to date highlighted a steep learning curve in the formulation of completion design, completion fluids, stimulation, downhole sand exclusion systems, and bean-up/bean-down procedures.
Integration of Hard and Soft Data to Characterize Field‐Scale Hydraulic Properties for Flow and Transport Studies
Authors: Segal Eran , Bradford Scott A. , Shouse Pete , Lazarovitch Naftali , Corwin Dennis
Published: July 2008

Field‐scale flow and transport studies are frequently conducted to assess and quantify various environmental and agricultural scenarios. The utility of field‐scale flow and transport studies, however, is frequently limited by our inability to characterize the heterogeneous distribution of hydraulic properties at these sites. In this study, we present an integrated approach, using both “hard” and “soft” data sets of field and laboratory scales in conjunction with pedotransfer functions, interpolation algorithm, and numerical modeling to characterize the hydraulic properties of the vadose zone. The approach is demonstrated at two 5‐ by 5‐m field plots selected for research on the transport and fate of nutrients and pathogens. We used hard data to quantify the magnitude of the hydraulic properties at selected locations in these plots and included laboratory and field measurements of the hydraulic properties from undisturbed cores and the instantaneous profile method, respectively. More abundant soft data included inductive electromagnetic readings and approximate particle‐size distribution information. The nearest neighbor interpolation algorithm was used to generate a heterogeneous realization of the saturated hydraulic conductivity on these plots. Numerical modeling of steady‐state water infiltration and redistribution experiments was used to compare laboratory‐ and field‐scale hydraulic properties and to refine our conceptual model of the vertical and lateral flow at this site. Good agreement between simulated and measured water contents and water pressure heads was obtained, indicating that field‐scale hydraulic properties were accurately quantified for these conditions. This article provides a real‐world example of how to combine information and approaches to tackle the difficult challenge of characterizing the hydraulic properties at a field site.
Field‐Scale Analysis of Flow Mechanisms in Highly Heterogeneous Mining Media
Authors: Webb G. , Tyler S.W. , Collord J. , Van Zyl D. , Halihan T. , Turrentine J. , Fenstemaker T.
Published: July 2008

A large‐scale injection and tracer test was conducted in highly heterogeneous Au ore under typical mining practices of heap leaching. A total of 24 zero‐tension lysimeters were installed beneath an active Au heap leaching operation and irrigated for 90 d with a cyanide solution. While rapid breakthrough of the wetting front suggesting preferential flow was observed in some lysimeters, the majority of the fluid flow did not follow preferential pathways. Rather, those lysimeters showing the most rapid breakthrough also showed the lowest steady‐state drainage flux, suggesting that while rapid flow through the 6‐ to 8‐m profile could occur, only a small percentage of the applied fluid volume was transmitted through these rapid pathways. Electrical resistivity imaging from the surface showed qualitatively good correlation between observed resistivity and the onset of drainage in adjacent lysimeters and also appeared to track the reaction of the infiltrating fluids with the carbonate ore and a lime amendment. The observation of limited preferential flow supports the empirical observations that heap leaching of Au ore with run‐of‐mine, end‐dumped placed rock is a surprisingly efficient reactor in spite of the large heterogeneity inherent in these materials that would be expected to produce preferential flow.
Effect of the Lower Boundary Condition and Flotation on Colloid Mobilization in Unsaturated Sandy Sediments
Authors: Sharma Prabhakar , Abdou Hesham M. , Flury Markus
Published: July 2008

In unsaturated soil columns, the boundary condition imposed at the column outlet may cause experimental artifacts. Our objective was to study in situ colloid mobilization during transient, unsaturated flow as affected by the boundary condition at the column outflow. We conducted colloid mobilization experiments by infiltrating unsaturated sandy sediment columns under different bottom boundary conditions: a seepage and a suction control. The mechanisms of colloid mobilization were investigated using force calculations (adhesive and interfacial forces), complemented with flotation experiments, where colloids in the bulk fluid and at the liquid–gas interface were measured separately. More colloids were mobilized under seepage than under suction‐controlled boundary conditions. The shape of the colloid breakthrough curves also differed: for the seepage boundary, the maximum of the colloid concentration occurred at the beginning of the column outflow, but for the suction‐controlled boundary, colloid concentrations in the outflow increased gradually before reaching a maximum. Colloid mobilization increased with flow rate and decreased with ionic strength for both boundary conditions; however, colloids were mobilized even at ionic strength exceeding the critical coagulation concentration (CCC). Flotation experiments showed that colloids were located both in the bulk fluid and at the liquid–gas interface at electrolyte concentrations less than the CCC, but only at the liquid–gas interface when the CCC was exceeded. Theoretical considerations confirm that interfacial forces at the liquid–gas interface exceeded adhesive forces at all ionic strengths. Both experiments and theory show that the liquid–gas interface had a dominant effect on colloid mobilization.
The Effects of Anisotropy on In Situ Air Permeability Measurements
Authors: Chief Karletta , Ferré Ty P. A. , Hinnell Andrew C.
Published: July 2008

Previous research has established a correlation between air permeability (ka) and saturated hydraulic conductivity for agricultural soils based on ex situ air permeability (kex situ). In situ air permeability (kin situ) measurements in nonagricultural soils, however, have shown a decrease in correlation that may be attributed to soil anisotropy. Our objectives were: (i) to examine the effects of anisotropy on kin situ using a three‐dimensional air flow model; (ii) to develop a method to identify anisotropy using kin situ and kex situ measurements; and (iii) to determine the sample volume of an air permeameter as a function of the permeameter design and the anisotropy ratio. Numerical results showed that the ka measured in situ in anisotropic media results in some average of the horizontal and vertical permeabilities. The averaging depends on the degree of anisotropy and the ratio of the diameter to the insertion depth of the permeameter. Therefore, a shape factor developed for an isotropic soil can give unreliable results. We determined that paired in situ and ex situ permeability measurements can be used to infer the anisotropy ratio. This approach is more accurate if the vertical permeability, kaz, is higher than the horizontal, kax The sample volume does not extend outside of the air permeameter for high kax/kaz It is stretched vertically for low kax/kaz A field experiment showed qualitative agreement with model predictions, but anisotropy alone was not able to fully explain the difference between kin situ and kex situ
Comparison of Three Methods for Discretizing the Storage Term of the Richards Equation
Authors: Kosugi Ken'ichirou
Published: July 2008

We compared three methods for discretizing the storage term of the Richards equation: the traditional chain rule expansion approach (Method A), a mass conservative approach based on a mixed form of the Richards equation (Method B), and another mass conservative approach using a chord‐slope approximation for the specific moisture capacity (Method C). The results of three test problems indicated that Method A could not achieve a perfect global mass balance even if the iteration number in the Picard iteration scheme was large enough to bring a perfect solution convergence. Both Methods B and C successfully produced perfect mass balances. Method C produced step‐by‐step decreases in the global mass balance error as the Picard iteration level increased, which corresponded well with step‐by‐step decreases in the solution convergence error. Method B produced more accurate mass balances than Methods A and C for every Picard iteration level; when this method was used, the global mass balance error became negligible before the solution converged. Analytical evaluation of Method B revealed the mechanisms for removing the mass balance error. As the difference between the matric pressure head, ψ, lessens between the previous and current Picard iteration levels, the water retention curve becomes more linear in the region bounded by the two ψ values. As a result, the difference in the water content between two consecutive Picard iteration levels is accurately approximated by using the difference in the two ψ values, which results in a remarkable reduction in the mass balance error, allowing Method B to produce better results than Method C.
Studying Master Paintings to Promote Painting Skills: The Role of Visualization, Copying from Memory, and Spatial Ability
Authors: Moreno Roxana , Morales Marilen
Published: July 2008

Middle-school students with low prior-knowledge in art studied a set of masterpiece paintings by visualizing a reproduction of the artwork (visual group), by being given a description of the artwork (verbal group), or both (dual group). Within each group, some students recreated the artwork from memory whereas others created a painting of their choice. The dual group outperformed the visual group on a retention test and recreated more elaborated visual elements from the masterpieces than the verbal and visual groups. Spatial ability predicted students' ability to recreate the masterpieces. The results support a two-stage information processing model of visual perception and cognition and suggest that verbal information can act as a substitute for prior knowledge in guiding students' processing of complex visual information.
The Perception and Evaluation of Visual Art
Authors: Hagtvedt Henrik , Patrick Vanessa M. , Hagtvedt Reidar
Published: July 2008

Visual art is a complex stimulus. Drawing on extant theory that the interplay of affect and cognition evoked by a stimulus drives evaluations, we develop a generalizable model for the perception and evaluation of visual art. In three stages, we develop scaled measurements for the affective and cognitive components involved in the perception of visual art and present a structural equation model that integrates these components in art evaluation.
Even Higher Global Inequality than Previously Thought: A Note on Global Inequality Calculations using the 2005 International Comparison Program Results
Authors: Milanovic Branko
Published: July 2008

Using the new results of the International Comparison Program 2005, the author reestimates inequalities between mean country incomes and global inequality among world citizens. All types of international inequality are found to be greater than previously thought (that is, as calculated using earlier data on countries' price levels). The main reason for the higher inequalities is that domestic price levels in most populous Asian countries (China, India, Philippines, Bangladesh) are some 40 percent higher than previously estimated. This implies not only higher global inequality but significantly greater global poverty head counts.
Updated U.S. Congressional Budget Office Data Reveal Unprecedented Increase in Inequality
Authors: Bernstein Jared
Published: July 2008

The U.S. Congressional Budget Office recently updated its authoritative data series on household incomes, 1979–2005. The new data reveal a sharp increase in income inequality over the past few years. The increase in income inequality (both pre- and post-tax), as measured by the change in the shares of income going to different income classes, was greater from 2003 to 2005 than over any other two-year period covered by the CBO data.
Public Policy Implications of Tobacco Industry Smuggling through Native American Reservations into Canada
Authors: Kelton Max H. , Givel Michael S.
Published: July 2008

From 1980 to 1994, the Canadian government enacted major tax increases on tobacco products. These actions initiated significant tobacco smuggling from the United States into Canada through a few U.S. Native American reservations to undercut the price of Canadian tobacco products. The tobacco industry blamed rampant smuggling on excessive taxation; however, research shows that the tobacco industry had actually promoted smuggling schemes to both increase profits and provide an argument for tobacco taxation reduction. Although the smuggling has resulted in numerous U.S. and Canadian criminal convictions of tobacco industry officials and partners, significant smuggling continues throughout the world. For the few Native Americans involved, the smuggling was lucrative and they were able to avoid criminal prosecution through tribal sovereignty. Industry-supported tobacco smuggling has had a profoundly negative effect on Canadian public health that must be brought to light to prevent future similar occurrences.