bluuebunny/crossref_metadata_2025 huggingface dataset:
Tubing Stress Analysis to Design Completions for Mangala Oil Wells—Onshore India
Authors: Kumar Vipin , Singh Ratan , Mabunga Shodji J.
Published: January 2010

The Mangala oil field contains 27-30°API waxy, low GOR crude oil, with a wax appearance temperature within 5°C of reservoir temperature (60-63oC) and a pour point above 40°C. To meet the flow assurance challenges for such paraffinic crude, jet pumping with hot water at 85°C as power fluid is the first choice for an artificial lift system. Power fluid surface injection pressure is designed to be 3,000 psi. Wells are expected to produce up to10,000 barrels per day of oil or oil and water.

High temperature, high pressure power fluid in the annulus means that the completion string will be exposed to high external pressures and variations in the casing/tubing temperature profile during the life of the well. High compressive forces, the potential for collapse, wellhead growth and the extreme case of anticipated helical buckling make the well completion design quite challenging. It is important that the well completion design is capable of withstanding such conditions. The accurate representation and prediction of casing/tubing temperature, pressure profiles and loads in the casing/tubing during all well operations including jet pumping are crucial to assess the integrity of the completion string.

This paper describes the anticipated loads during the well life, and use of a wellbore thermal simulator, and tubular stress analysis software program to simulate the potential stress loads. This helped optimise the design of the casing and tubing strings to anticipate and foresee and avoid potential problems like connection leaks, permanent tubing buckling, packer load requirements, etc.
Steam-Solvent Coupling at the Chamber Edge in an In Situ Bitumen Recovery Process
Authors: Sharma Jyotsna , Gates Ian D.
Published: January 2010

Alberta, Canada contains about 170 Gbbl of recoverable heavy oil and bitumen; most of it with in situ viscosities in the hundreds of thousands to millions of cP. To mobilize and produce this oil, steam-based recovery methods such as Cyclic Steam Stimulation and Steam-Assisted Gravity Drainage are used. Given the large energy requirements and volumes of emitted greenhouse gas from these processes, there is strong motivation to develop enhanced recovery processes with lower energy and emission intensities. One incremental move to achieve this is by using steam-solvent hybrid processes such as ES-SAGD where solvent is co-injected with steam. Steam- solvent processes are the next generation of reduced emission to atmosphere recovery processes for heavy oil and bitumen reservoirs beyond current steam recovery methods. The controlling feature of these processes is the mobilization and drainage of oil at the depletion chamber edge. Furthermore, both oil phase viscosity – mobility and density – drainage – depend strongly on temperature and solvent concentration. Here, a simple model is derived to describe dynamics of thermo-solvent coupling effects in the mobile oil zone at the edge of a steam-solvent chamber. A double front system evolves: compositional and thermal fronts result with different length scales. They are coupled through velocity and viscosity fields. We investigate the extent to which these fronts affect oil mobility at the edge of the chamber. The solvent provides an additional means to raise oil phase mobility beyond that achieved with heat. The enhanced mobility is due to 1. lowered viscosity because of solvent dilution and 2. slightly raised oil saturation due to addition of solvent (raises the oil effective permeability). Due to synergistic interactions between heat transfer and solvent diffusion, the oil zone has higher mobility in the solvent-steam system over that of the steam-only one. Therefore, steam-solvent systems lead to lower energy and emission intensity thus "greening", to some extent, heavy oil and bitumen recovery technologies.
A Huge Oil Spill Naturally under Control in Abadan Refinery
Authors: Zoveidavianpoor Mansoor , Shadizadeh Seyed Reza
Published: January 2010

A rapidly expanding chemical and petroleum industry has been responsible for great improvements in the quality of urban areas in Iran over the last 100 years. The Abadan Refinery is located between the Arvandrud and Bahmanshir rivers in the highly populated Abadan city. These rivers supplies urban, industrial, and agricultural waters to Abadan city. During the war between Iran and Iraq, leakage of enormous volumes of oil and refined petroleum products from storage tanks and pipelines at the Abadan refinery to the surrounding environment occurred. Underground contamination resulted from that leakage is a serious and a growing enviromental concern in Abadan city. In this work, twenty boreholes were investigated by considering petroleum leakage to the surrounding area during and after the war. Geological conditions, stratigraphy and petroleum contamination underlying the Abadan refinery was determined from cores during the drilling of the boreholes.

Oil saturation of cores was defined for each borehole. Also, porosity, and density of the cores were measured in this project. The extent of the petroleum contaminated underground layers was determined in this study and the average depth of contaminated undrground layers is from the surface to the depth of 4.5 meter. Leakaged oil in place in underground layers of Abadan refinery was estimated to be 6,424,674 barrels. The results show that the majority of existing petroleum in underground layers at Abadan refinery was absorbed by clay.
Construction and Implementation of Integrated Production Network Model in A Complex Onshore Operation
Authors: Aditama P. , Sujai A. , Pamungkas H. W. , Firmansyah V. , Rohman A. F.
Published: January 2010

The development of oil and gas fields in recent years has become more technically and economically challenging. Interdisciplinary interaction is needed to have effective and efficient field planning. Indeed, it has been noted that field management by using integrated surface-subsurface modeling will have an extremely positive effect on production.

This paper presents the interdisciplinary teamwork between subsurface and surface engineering in their efforts to construct an integrated production model for Kaji Semoga field, a large and complex onshore production field located in South Sumatra, Indonesia. The model covers about 180 wells, which are spread over 45 clusters, and surface facilities in three field processing stations. It covers all facilities from well up to the nearest field station for separating gas from oil and for compressing it prior to distributing to clusters and finally injecting the well. The model also incorporates 84 new ESP, which will be installed by the end of year 2009 to replace the existing gas lift system.

The model predicts an additional oil gain of 2,500 bopd (14.7%) as a result of installing ESP. About 170,000 blpd of liquid will be produced after the ESP installation project is completed. Consequently, liquid handling in each station has become a critical issue to be resolved before all the ESPs are installed. Several operational manoeuvers have been carried out to handle the forthcoming produced liquid by utilizing the model. About 300 bopd (1.8%) of oil gain from the cluster flow diversion scenario has already been realized.

Apart from the liquid handling issue, the model also highlights the future gas-lift gas requirement for the remaining gas lift wells. Several active compressors can be shut down as a result of the outcome of the model, so the operating cost can be reduced significantly. The model also identifies potential bottlenecks along the production trunkline, which can result in a potential reduction of 140 bopd. In addition, the model also identifies a potential oil gain of about 220 bopd (1.3%) if back pressure on several production trunklines can be minimized.

Field engineers have benefitted from the use of this model: it can help them assess any changes or manoeuvres in the field. This is expected to add about 200 bopd (1.2%). Some of these changes and manoeuvres are being executed this year.
Reservoir Management of Brown Field: Kalol, A Case Study
Authors: Vij R. K. , Das Minoti , Kumar Sudhansu
Published: January 2010

Kalol is a multi-layered field comprising of nine pay zones. Pay zones II, III and IV are both oil and gas bearing while pay zones V, VI + VII, IX + X, XI and XII are oil reservoirs. The field has in-place (PD) reserves of 131.84 MMt of oil with an ultimate (PDD) component of 18.23 MMt as on 1.4.2009 respectively. The cumulative production as on 1.4.2008 is 12.77 MMt of oil leading to a recovery of 9.7%.As on 1.4.2008 a total of 610 wells are drilled of which 385 wells are completed as oil wells with 329 flowing & 56 non-flowing wells, 23 as flowing gas wells and 80 as water injection wells. Out of total flowing oil wells 91 % are operating on artificial lift with 140 wells on SRP and 159 wells on gas lift. The average rate of production during the year was 1140 tpd of oil and 259000m3/d of gas. The oil production was maintained mainly by development drilling, zone transfers, lift management and faster revival of ceased wells. Water injection is being carried out in pay zones K-III, V, VI+VII, IX+X and XII through 68 wells @2600 m3/d. Due emphasis was given for pressure maintenance schemes to meet instantaneous void age compensation through proper redistribution and focused water injection.

Induction of various technologies are been attempted to maintain the oil production rate from this Brown field, major among them are drilling of Horizontal, Multi-lateral and high angle wells, MEOR technologies, application of PDB technology, Hydro-fracturing, Stimulations of tight sand stone-layer, enhancing the quantity and quality of water injection for effective pressure maintenance and improving the recovery factor.

Various surface and sub-surface interventions through multi-disciplinary team approach have paid rich dividend and production of the field have enhanced through these initiatives. Paper will discuss the innovative approaches conceptualize and implemented in the field for maintaining and enhancing the production level and improving the reservoir health.
Investigation of Gas Well Liquid Loading With a Transient Multiphase Flow Model
Authors: Yusuf Rahel , Veeken Kees , Hu Bin
Published: January 2010

Liquid loading in gas wells occurs when the gas flow rate falls below a critical value due to reservoir depletion where the accompanying liquids can not be lifted up to surface. Since liquid loading has a detrimental impact on production, deliquification methods need to be employed in order to recover the production. To choose the right deliquification measures and achieve a timely deployment, it is therefore important to predict the onset of liquid loading in advance. Traditionally, the Turner correlation has been used for this purpose. However, latest published data from deviated large diameter offshore wells show that the Turner correlation can underpredict the critical gas rate by 20-200%. The operators can be misled by this prediction and are often not well prepared for tackling the liquid loading as they may think the problem is still some years away.

Liquid loading is a transient phenomenon in nature and thus needs to be described by a dynamic multiphase flow model. In the present study, instead of modifying or improving the Turner correlation, a comprehensive dynamic multiphase flow model is used to predict the onset of liquid loading. Totally fourteen offshore gas wells were simulated using the dynamic model. The predicted critical gas flow rates are validated against field data and the predictions lie within the ±20 % error margin. The effect of condensate gas ratio (CGR) on liquid loading is also investigated. The simulations show that it is possible for low CGR wells that the critical gas flow rate can decrease with the increasing CGR. This is also in line with the field observations.

This study brings forth the importance of transient multiphase flow modeling and opens new frontiers for dynamic simulation of gas well deliquification, which shall set up guidelines from dynamic point of view for implementing the right deliquification measures so that more production can be recovered when loading has happened.
Hydraulic Fracture Propagation in a Naturally Fractured Reservoir
Authors: Chuprakov D. A. , Akulich A. V. , Siebrits E. , Thiercelin M.
Published: January 2010

We present the results of numerical modeling that quantify the physical mechanisms of mechanical activation of a natural fault due to contact with a hydraulic fracture. The analysis of the total stress state along the fault during the hydraulic fracture coalescence stage makes it possible to define a criterion for reinitiation of a secondary tensile crack at the fault. Numerical simulations of the fracture interaction for a wide range of key parameters have been performed to detect the possible fracturing scenarios.
A Derivation of Drilling Fluid Modeling for Pr # 2 Well (Kg Basin - India) in Terms of Geo-pressure Gradient and Geo-mechanical Stress for Extra Wellbore Stability of Its over Pressured Highly Reactive - Water Sensitive Shale Column of 1225 Mtrs in 8-½ Inch Borehole from 2883 Mtrs to 4108 Mtrs Tvd: A Critical Analysis of Shear Failure Pressure and Chemical Osmosis during Fluid - Shale Interactions
Authors: Giri Jagdish P.
Published: January 2010

Success of achieving extra well-bore stability in highly reactive shale column of 1225 mtrs, in PR#2, is attributed to adequate pre-well planning, execution of drilling plan and guidelines, and the K+Cl -Polymer Drilling fluid chemistry. Well-bore cleaning and hydraulic modeling in an integrated geo-pressure gradient and critical analysis of shear failure pressure due to chemical osmosis and fluid - shale interaction was the significant attribute on well-bore stability. Pre well modeling of well-bore stability in problematic shale - zones and hole cleaning in its deeper final phase, contributed to stable hole behavior during unexpectedly longer durations on non - drilling downtime for frequent surface equipment failures, etc. Paper critically analyzes shear failure pressure and chemical osmosis during fluid - shale interaction to improve better well construction - design and drilling fluid modeling for productive oil - field economics in entire KG Basin - India. Key conclusions drawn from such a critical analysis of water based K+Cl - K+ Lignite/PHPA Polymer mud system include: Hole cleaning and hydraulic model derived in this analysis, proved to be quite useful in the pre well planning process as well as in post - well analysis on high bore-hole stability.Chemical osmosis and shale - fluid interaction further demonstrated the pore pressure transmission, and geo-pressure variance, and its integration with geo-mechanical stress and shear failure pressure derived the well-bore stability modeling.

The case study presented compares original mechanical stability and hydraulic- fracturing estimates with the critical mud weight identified for successfully completing this difficult operation. Descriptions of well-bore stability and fluid losses are presented along with drilling fluid parameters used to combat them. Method used for estimating formation pore pressure, in-situ stresses and formation rock properties are also described. Additionally, possible explanations for differences between planned and actual stability estimates are explored with future recommendations for similar operations.
Experimental Investigation of Biopolymer and Surfactant Based Fluid Blends as Reservoir Drill-in Fluids
Authors: Ogugbue Chinenye C. , Rathan Mayur , Shah Subhash N.
Published: January 2010

Biopolymers present non-toxic and degradable fluids that have been used extensively in reservoir drill-in fluids (RDF) to drill through reservoir rocks in oil and gas wells. Their numerous advantages, such as viscosity enhancement, filtration control, flocculation prevention, friction pressure reduction during turbulent flow conditions and shale stabilization amongst others have made them indispensable in oilfield applications. At the same time, the inherent formation damage as a result of the polymer molecules settling or being adsorbed on or into the reservoir rock pore spaces has been an area of concern to the industry. On the other hand, surfactant based fluid (SBF) systems typically leave little residue or formation damage compared to biopolymer systems, thereby gaining acceptance as RDF’s. Low interfacial tension existing between SBF’s and the produced or injected fluids is one of the major criteria for this reduction in formation damage. However, SBF has much higher fluid leak-off at reservoir conditions than wall-building biopolymer fluids, which has significantly limited their use in the industry.

In this paper, several blends of a SBF or visco-elastic surfactant (VES) and a water soluble biopolymer, welan gum have been used to develop a SBF-biopolymer fluid system based upon compatibility, rheological and visco-elastic behavior. The study was performed by characterizing biopolymer-VES fluid systems for their ability to retain their rheological and visco-elastic properties at elevated temperatures. Data analysis showed that the blend captures the merits of the individual fluid systems, as well as reduction in overall cost as compared to using a SBF mud by itself. Blends consisting of higher concentrations of welan gum showed good thermal stability and retention of viscosity at elevated temperature. Hence, cost reduction is achieved in the amount of SBF utilized. Also, the results of surface tension measurements showed that the binary system exhibited values much lower than welan gum fluid, and about the same as the SBF. Filter press tests results showed the blends to have a lesser fluid loss. Other potential applications of this binary system are also discussed.
Case Study of the Impact of Cold and Hot Waterflooding Performance by Simulation and Experiment of High Pour Point Oil Reservoir, Liaohe Oilfield, North-east China
Authors: Zhou Wei , Tang Zhong-hua , Orodu Oyinkepreye D.
Published: January 2010

Block Shen-95 has been under cold waterflooding for 17 years. Of particular interest is the low recovery of 11.27% for the North Block due to crude oil cloud point being very close to the reservoir temperature. Formation damage near the wellbore region is controlled at production wells by hot-oiling and low injection rates of non-isothermal waterflooding.

Optimizing production necessitated looking at core-scale experiment and reservoir-scale simulation waterflooding performance at different temperatures. The intent also, is basically to condition core-scale flooding observations to properly initialize the numerical model. Based on experiment carried out on core samples, sharp decline in oil displacement efficiency occurred, increase in residual oil saturation and increase in the intensity of formation damage below the cloud point. Reservoir simulation depicted decline in production with decreasing flooding temperature captured specifically by change in viscosity around the wellbore region. Change in flow dynamics due to change in relative permeability was not efficiently captured and formation damage impact on porosity and permeability.

Reservoir-scale performance for high pour point oil reservoir can better be understood by considering the effects of formation damage on storativity and transmissibility, and fluid rheology. The irreversible process of wax precipitation may cause permanent damage if further from the wellbore region.
Single String Packerless ESP Gas Lift Hybrid; Optimizing Production and Minimizing Loss
Authors: Prakoso N. F.
Published: January 2010

Kaji Semoga (KS) field has produced primarily from limestone and has until recently contained sufficient gas for gas lift usage. However, KS gas production is declining rapidly: it is estimated that by 2013 it will produce insufficient gas. As a result, some new forms of artificial lift are being considered to replace gas lift, and since the end of 2008 new ESP and HPU projects have been carried out with the aim of such a new form of lift. As a result of implementing these projects, ESP wells will be the dominant artificial lift for production wells in KS, contributing to approximately 70% of total oil production

On the other hand, there are risks of downtime associated with the use of ESP. The main risks concern downhole problems, which need rig deployment, and electrical problems, which cause the ESPs to shut down. Fixng these problems may require a considerable amount of time - several days or even weeks - due to reasons such as unavailability of a rig and/or spare parts. This will inevitably result in loss of oil .production.

To avoid such production loss, an ESP / gas lift hybrid system has been implemented, whereby gas lift is prepared as a backup. This hybrid system consists of an ESP unit installed along with a gas lift system in single tubing, with no packer and 1 (one) (screen orifice) gas lift valve, 1 (one) sliding sleeve door, and 1(one) complete ESP unit.

All ESP wells in KS (currently 70 wells and counting) now use this configuration. The gas lift hybrid system has been used as backup during ESP downtime. This configuration can produce 35% of liquid compared to normal ESP liquid production, and as a result an oil loss of 4400 bbls was prevented during 2009.
Flood Front Estimation With Streamline Modeling: A Case Study of a Mature Field in Assam, India
Authors: Singh A. K. , Jain V. K. , Marathe R. V.
Published: January 2010

Waterflooding as a means of secondary recovery is one of the oldest techniques used in the petroleum industry. The design and development of the waterflood usually attracts the most attention and surveillance is a relatively less rigorously followed practice, although its importance in the waterflood's success cannot be understated. There are many techniques for monitoring a water injection/waterflood project. Estimation of flood front with Streamline modeling is a simple and powerful method to understand the injected water movement as it offers a direct visualization technique to map the flood front. This understanding is also at par/ supplementary to finite difference Simulation in mostof the cases.

This paper describes a field example of estimation of flood front movement in a mature oil field using in-house developed Streamline modeling based on which infill drilling was optimized and fresh areas were identified for new inputs which added economic value to the Asset.

The case study brings out the technique's effectiveness as a simple, low cost, quick look tool of Reservoir Surveillance in waterflooding and how it can be used in such cases.

Based on the results presented herein, it is concluded that such innovative methods for quick decision making including economic aspects can make the difference while selecting surveillance methodology.
An Integrated Approach for Development of KG Offshore Marginal Fields
Authors: Gomathi M. , Kumar Anil
Published: January 2010

A number of discoveries in Tertiary Sequence have been made in shallow water Krishna Godavari offshore along with several new pools. These discoveries are spread over an area of 130 sq.km, lie in water depths ranging from 8 m to 20 metres and are located at a maximum distance of approx.15 km from shore. Some of the discoveries having substantial volumes in this area have already been commercialised and put on production since 2001.

As these discoveries are dispersed in scattered pockets, it is imperative that the development plan considers an economically viable integrated approach. Innovative technical and commercial advances have enabled operators worldwide to develop fields once considered uneconomical or marginal. This paper discusses economisation strategies such as The feasibility and methodology of developing these fields using a cluster based phased approach for early production and better field management.Tie-in strategy to existing and planned offshore and onshore infrastructure in the vicinity.Early production from existing nonexpendable wells either through commingled or sequential production depending upon reservoir characteristics and operational feasibility have been taken into consideration.Drilling of appraisal /development well has been considered only where economic conditions are favourable.The feasibility of developing these fields using minimum facility platforms including leased or new built re-locatable self-installing platforms has been worked out. The design premise of considering this type of platforms is to minimize fixed platform structures, re-use of these platforms for future marginal field discoveries and a more efficient capital expenditure profile.
Digital Oilfied Workflows for Increased automation
Authors: Pande Anil
Published: January 2010

With the ever increasing difficulties related to finding reservoirs, as well as the harsher and more remote environments that they exist in, there is a need to make the best use of workflows and automated processes that leverage digital technologies based on oilfield automation for end to end flows, so as to meet the desired business objectives. This paper discusses the basic requirements to achieve these objectives, by covering what are the essential elements for end to end workflows, based on automation in different stages of the oilfield, that is the basis for technology driven workflow processeses.
Refinement of Chemical Selection for the Planned ASP Pilot in Mangala Field - Additional Phase Behaviour and Coreflood Studies
Authors: Pandey Amitabh
Published: January 2010

Mangala is the largest discovered oil field in the Barmer Basin, India. Initial oil production began in September 2009, and an alkaline-surfactant-polymer (ASP) pilot will start-up early in 2010. Details on the design of the ASP pilot including the laboratory evaluations and simulation studies have been presented earlier. Laboratory evaluations involved screening and optimisation of the ASP slug formulation based on IFT measurements, adsorption measurements, polymer rheological and thermal stability studies, and a series of linear and radial corefloods. Additional experiments were conducted for refinement and optimization of the chemical selection, specifically targeting even lower residual oil saturations than what was attained previously.

These experiments focused on new surfactant types that are more suitable for solubilising the viscous and waxy Mangala oil. The focus was on detailed phase behaviour evaluation rather than physical measurement of IFT, which allowed relatively quick analysis of a number of surfactants in a short time period. Both salinity scans and oil scans were performed because of significant acidic components in the Mangala crude which react very favourably with injected alkali to produce in situ soap. The resulting phase diagram confirmed the presence of a favourable salinity gradient for the ASP flooding. The best chemical formulation was used in long (1ft) Berea and composite Mangala corefloods and showed very high displacement efficiency for relatively low surfactant concentration, which confirmed the robustness of the phase behavior approach for chemical selection. Mechanistic simulations using the UTCHEM simulator assisted in further optimization of the ASP slug formulation. These experiments helped refine the chemical selection for the planned EOR pilot and reduced the technical risks by improving the robustness of the slug design.
Case History: First Isochronal Reservoir Test Successfully Performed Worldwide at a Bottomhole Temperature Greater Than 430° F
Authors: Khati Milind , Pedrosa Luis , Farooqui M. Y. , Khan Z. A.
Published: January 2010

Gujarat State Petroleum Corporation, Ltd (GSPC) wished to evaluate a reservoir in an offshore well on the Indian East Coast where bottomhole temperature was more than 433°F. The Initial DST had shown significant potential for the zone of interest; and therefore, GSPC decided to perform isochronal testing to obtain more detailed reservoir pressure information. In this environment, the DST tools would be required to function continuously in the high-temperature conditions for more than 16 days in order to retrieve the required data without interruption. These conditions would definitely challenge the capabilities of the currently available drill-stem testing (DST) equipment.

This paper describes how DST tools rated to 450°F-bottomhole temperature and 15,000-psi differential-pressure were configured to maintain integrity and successfully evaluate the well. The tools were annulus pressure responsive (APR) that would be operated with pressure applied to the annulus from the surface. The string included a multi-cycle downhole tester valve, a multi-cycle circulating valve, a blowout preventer (BOP) safety valve, a tubing tester valve, a secondary circulating valve, and safety circulating valves. The multi-cycle circulating valve added the flexibility to displace the string with nitrogen for well stimulation, if the well did not flow.

The data describes the careful preparation of the toolstring, the extreme conditions in which the DST tools had to operate to evaluate the well successfully, and how the meticulously prepared toolstring was capable of meeting GSPC’s requirements. The DST tools performed satisfactorily for more than 16 days during the test.

This job set a world record for the service company for a reservoir test performed in these high-temperature conditions and may have set a world record for all testing operations performed by other service companies as well.

Advantages included elimination of coiled tubing, increased safety for this type of operation, and a reduction of rig time compared to other testing jobs.
Reservoir Model History Matching With Particle Swarms
Authors: Mohamed Linah , Christie Mike , Demyanov Vasily
Published: January 2010

History matching optimisation in Bayesian framework is a fairly recent approach to quantify uncertainty in oil industry. Currently some innovative global optimisation approaches such as evolutionary algorithms and swarm intelligence methods have gained popularity for tackling history matching problems.

Particle swarm optimisation (PSO) is a swarm intelligence approach for solving optimisation problems. In this approach particles are moving points in parameter space. The position of a particle is a candidate solution to the optimisation problem. Each particle searches for better positions in parameter space by updating its velocity according to rules originally inspired by behavioural models of the movement of flocks of birds.

Recently the PSO algorithm has shown to be a promising tool for finding acceptable multiple history matched models quickly (Mohamed et al., 2009). However, the algorithm control parameters which balance between exploitation–exploration trade–off are to be studied for history matching problems. In this paper we investigate some basic PSO variants for updating the control parameters using a real–life case study.

It is shown that PSO could be improved by optimising the PSO control parameters. Some variants converge faster to good fitting regions in parameter space leading to a fewer number of reservoir simulation runs though others maintain diversity of the reservoir models better for this reservoir example. This study helps better employing the PSO algorithm for reservoir model history matching and uncertainty quantification.
Geomechanics, ECD Management and RSS to Manage Drilling Challenges in a Mature Field
Authors: Caicedo H. , Pribadi M. A. , Bahuguna S. , Wijnands F. , Setiawan N. B.
Published: January 2010

The Serang Field, offshore East Kalimantan, Indonesia was discovered in 1973. Production started in 1993. Although it is a mature field with 120 wells, drilling still faces challenges in the form of severe lost circulation and stuck pipe events. Side tracks often need to be drilled and drilling budget overruns can be significant. The 2006 drilling campaign of 5 wells saw the loss of several BHAs and needed 4 sidetracks, due to stuck pipe events.

In order to improve the drilling operation and to uncover root causes of the losses and pack-offs, a detailed geomechanical evaluation was conducted. The study began with a comprehensive data audit and drilling event review. All the captured information and log data was then used to create a Mechanical Earth Model (MEM) for wellbore stability planning of future wells.

Key findings of the study were that lost circulation occurred in high permeability zones in shallow carbonates (8-1/2" intermediate hole section) and were not caused by drilling induced fractures. A contingency plan was developed to drill to section TD with sea water, should losses occur. Breakouts, aggravated by low mud weights, lost circulation events, high deviation and slim hole contributed to poor hole cleaning, which caused the packoff incidents in the 6 1/8" sections.

Safe and stable mud weight windows were established to mitigate hole collapse and stuck pipe. Since losses can occur even at low mud weights but do not usually have severe consequences, the team decided it was more important to focus on avoiding breakouts and improve hole cleaning with higher mud weights, improved drilling fluids with stress cage system to drill through depleted reservoirs, controlled drilling, ECD management to prevent formation breakdown and the use of Rotary Steerables to improve hole cleaning. The recommendations of the study were incorporated during a 3 well drilling campaign in 2009. All 3 wells were drilled and completed within budget and without stuck pipe incidents.
Ambiguity and the Equity of Rating Systems: United States Brokerage Firms, 1995–2000
Authors: Fleischer Anne
Published: January 2010

This paper challenges the suggestion in prior research on rating systems, and categories more generally, that such systems help facilitate exchange by providing information and distinguishing between different products, proposing that in some instances they create ambiguity instead. I hypothesize that ambiguity in a rating organization's classification system increases with the number of conflict-of-interest relationships it has with producers of the products it rates. Using the rating systems of over 100 U.S. brokerage firms between 1995 and 2000 as a setting, I find that as levels of underwriting increase, so too does the ambiguity of the brokerage firm's rating system. The result is a market for classification based on choices of the market intermediaries rather than the attributes of rated objects themselves.
Constraints on the Control Benefits of Brokerage: A Study of Placement Agents in U.S. Venture Capital Fundraising
Authors: Rider Christopher I.
Published: January 2010

This paper theorizes about constraints on brokers' control benefits. I propose that brokers prefer to represent high-quality actors and that the value an actor places on representation is inversely related to the actor's perceived quality. But matching of more reputable brokers with higher-quality actors should mitigate these quality constraints. Empirical analyses of 1,028 venture capital funds raised by 745 firms from 2001 to 2006 support the theory. The likelihood that a firm's venture fund is represented by a placement agent first increases and then decreases with firm quality, measured as size, experience, and status. Neither those that value representation most (i.e., funds of low perceived quality) nor those that placement agents would most like to represent (i.e., funds of high perceived quality) are most likely to be represented by a placement agent. Results also show that more reputable placement agents represent funds raised by higher-quality firms, which indicates that a broker's reputation mitigates constraints on the control benefits of brokerage.
From Pabst to Pepsi: The Deinstitutionalization of Social Practices and the Creation of Entrepreneurial Opportunities
Authors: Hiatt Shon R. , Sine Wesley D. , Tolbert Pamela S.
Published: January 2010

In this paper, we examine the dual role that social movement organizations can play in altering organizational landscapes by undermining existing organizations and creating opportunities for the growth of new types of organizations. Empirically, we investigate the impact of a variety of tactics employed by the Woman's Christian Temperance Union (WCTU), the leading organizational representative of the American temperance movement, on two sets of organizations: breweries and soft drink producers. By delegitimating alcohol consumption, altering attitudes and beliefs about drinking, and promoting temperance legislation, the WCTU contributed to brewery failures. These social changes, in turn, created opportunities for entrepreneurs to found organizations producing new kinds of beverages by creating demand for alternative beverages, providing rationales for entrepreneurial action, and increasing the availability of necessary resources.
An Experimental Study of the Coking Process
Authors: Ebrahimi Somayeh , Moghaddas Jafarsadegh
Published: January 2010

The coking process includes two dynamic and isothermal steps. In this process, some factors control the coke formation kinetics. In this research, effects of some important and effective parameters of feed on the quality of petroleum coke were studied. Two hydrocarbon residue feeds; Cracked Fuel Oil (CFO) and Styrene Monomer Tar (SMTAR) were used at 500°C with atmospheric pressure of nitrogen used as an inert gas. Rate of weight loss and gas evolution from these feeds were considered by data of thermal analysis TG (thermogravimetry) and DTG (derivative thermogravimetry). Based on the results, CFO was assigned as the better feed. After selecting better feed, simultaneous thermogravimetry-differential analysis (TG-DTA) was used to study the pyrolysis kinetics of CFO. Samples were heated in a TG-DTA apparatus in nitrogen atmosphere at a temperature range of 37-600°C. The activation energy (Ea) and pre-exponential factor (A) were calculated from the experimental results by using a three stage Arrhenius-type kinetic model and showed that CFO pyrolysis kinetics at temperature ranges 37-285, 320-450 and 467-600°C follows first, second and first order kinetics, respectively. Attentive to temperature increase and reaction progress, activation energy and pre-exponential factor indicated different values at each stage. Also, kinetics of the isothermal step of coke formation was studied during heating of CFO. Samples were reacted in a tube furnace at 450°C and with nitrogen atmosphere. The kinetics of coke formation for petroleum residue was followed by solvent extraction (insolubility in hexane (HI), toluene (TI)) and a development of TI approximate to apparent first order kinetics. The rate constant at this temperature was calculated and it was also observed that the coke formation had been started at a temperature below 450°C.
Stratigraphy of the Krs Gradac section (SW Serbia)
Authors: Radoicic Rajka , Jovanovic Divna , Sudar Milan
Published: January 2010

In the Krs Gradac section (near to Sjenica, SW Serbia), a transition of a carbonate platform to basin facies are outcropped: Norian-lower Liassic shallow-water carbonates, middle Liassic-lower Dogger Ammonitico Rosso facies, and upper Bathonian into lowermost Cretaceous deep-water radiolarites in which the carbonate graded bed and mass flow layer are intercalated. The presence of a lower Dogger condensed sequence with the Bajocian protoglobigerinid event was hitherto not evidenced. It is documented that components of a graded bed are of extrabasinal (upper Triassic-lower Tithonian carbonate platform sediments) and intrabasinal (radiolarite, meta-andesite) origin, indicating a tectonic event not older than the early Tithonian. This tectonic event caused the fracturing of the carbonate platform, also partly basinal area. Consequently, the age of the graded bed is not older than the lower Tithonian. In the uppermost radiolaritic sediments in the Krs Gradac section (?middle-upper Tithonian-lowermost Cretaceous), a mass flow layer appears, which contains clasts of intrabasinal origin - different radiolarites, siliceous radiolarian argillites (some of which are unconsolidated with washed radiolarians and sponge spicules in a ferruginous sediment), sandstone grains, etc. The mass flow event is estimated as Berriasian. In the Krs Gradac radiolarite succession, the authors recognized two deep-water formations, an older one, upper Bathonian-lower Tithonian, between hardground (Dogger) and a graded bed, and a younger formation, which started with a graded bed. This formation, according to its stratigraphic position, corresponds to ?middle-upper Tithonian-lowermost Cretaceous.
Linoporella buseri Radoicic, 1975, revisited: A Liassic dasycladalean alga from the Dinarides and continental Italy
Authors: Radoicic Rajka , Conrad André , Carras Nicolaos
Published: January 2010

The Liassic Linoporella buseri is re-examined, on the basis of an abundant material of reefal origin, originating from the newly described type-locality in Slovenia. It is compared with the Berriasian-Valanginian type-species L. capriotica, studied by BARATTOLO & ROMANO (2005). Both species have three orders of laterals. In L. buseri, however, apart of other, clear cut differences, the tertiary laterals are usually hair-like, occasionally phloiophorous at tip, forming a distal cortex such as in L. capriotica. Consequently, the genus Linoporella is slightly emended, to fit observations made on the two species.
Thermal stability of segmented polyurethane elastomers reinforced by clay particles
Authors: Pavlicevic Jelena , Budinski-Simendic Jaroslava , Szécsényi Mészáros , Lazic Nada , Spirkova Milena , Strachota Adam
Published: January 2010

The aim of this work was to determine the influence of clay nanoparticles on thermal properties of segmented polyurethanes based on hexamethylene- diisocyanate, aliphatic polycarbonate diol and 1,4-butanediol as chain extender. The organically modified particles of montmorillonite and bentonite were used as reinforcing fillers. The structure of elastomeric materials was varied either by diol type or chain extender content. The ratio of OH groups from diol and chain extender (R) was either 1 or 10. Thermal properties of prepared materials were determined using modulated differential scanning calorimetry (MDSC). Thermal stability of obtained elastomers has been studied by simultaneously thermogravimetry coupled with DSC. The glass transition temperature, Tg, of soft segments for all investigated samples was about -33?C. On the basis of DTG results, it was concluded that obtained materials were very stable up to 300?C.
Curing kinetics of alkyd/melamine resin mixtures
Authors: Jovicic Mirjana , Radicevic Radmila
Published: January 2010

Alkyd resins are the most popular and useful synthetic resins applied as the binder in protective coatings. Frequently they are not used alone but are modified with other synthetic resins in the manufacture of the coatings. An alkyd/melamine resin mixture is the usual composition for the preparation of coating called 'baking enamel' and it is cured through functional groups of resins at high temperatures. In this paper, curing kinetics of alkyd resins based on castor oil and dehydrated castor oil with melamine resin, has been studied by DSC method with programmed heating and in isothermal mode. The results determined from dynamic DSC curves were mathematically transformed using the Ozawa isoconversional method for obtaining the isothermal data. These results, degree of curing versus time, are in good agreement with those determined by the isothermal DSC experiments. By applying the Ozawa method it is possible to calculate the isothermal kinetic parameters for the alkyd/melamine resin mixtures curing using only calorimetric data obtained by dynamic DSC runs. Depending on the alkyd resin type and ratio in mixtures the values of activation energies of curing process of resin mixtures are from 51.3 to 114 kJ mol-1. The rate constant of curing increases with increasing the content of melamine resin in the mixture and with curing temperature. The reaction order varies from 1.12 to 1.37 for alkyd based on dehydrated castor oil/melamine resin mixtures and from 1.74 to 2.03 for mixtures with alkyd based on castor oil. Based on the results obtained, we propose that dehydrated castor oil alkyd/melamine resin mixtures can be used in practice (curing temperatures from 120 to 160?C).
FTIR analysis and the effects of alkyd/melamine resin ratio on the properties of the coatings
Authors: Cakic Suzana , Boskovic Ljiljana
Published: January 2010

Alkyd/melamine resin mixtures are mainly used in industrial baking enamels. The effects of the alkyd/butylated melamine resin ratio (from 90/10 to 50/50) and curing temperature (from 110 to 180?C) on the crosslinking and properties of the coating are presented in this paper. The curing reactions through functional groups of resins were monitored by FT-IR spectroscopy. The hardness, elasticity, degree of adherence and gloss were also determined. Optimal coating properties could be achieved with an alkyd/melamine resin ratio of 80/20, a curing temperature of 150?C and a curing time of 20 min.
The influence of size and structure of metal orthodontic bracket base on bond strength on tooth enamel
Authors: Mitic Vladimir , Janosevic Mirjana , Tanic Tatjana , Sasic Mirjana
Published: January 2010

Introduction. The factors which may influence the bond strength of the applied orthodontic brackets on the tooth surface are the size and structure of the bracket base. Objective. The aim of the paper was to investigate the influence of size and shape of different types of brackets on bond strength on the enamel and analyze the remaining quality of adhesive material on the tooth surface after debonding of orthodontic brackets (adhesive remnant index - ARI). Methods. In this study, three types of metal brackets of different sizes and shapes of Dentaurum manufacturer were used (Utratrimm, Equilibrium 2, Discovery, Dentaurum, Inspringen, Germany). The brackets were applied onto the middle part of the anatomic crowns of buccal surfaces of 30 premolars extracted for orthodontic reasons. In addition, the pre-treatment of teeth by 37% orthophosphoric acid and adhesive material System1+ (Dentaurum, Germany) were used. Results. The mean value of the bonded brackets bond strength of Discovery type after debonding was 8.67?0.32 MPa, while the value of the bonded brackets bond strength of Equilibrium 2 type amounted to 8.62?0.22 MPa. The value of the bonded brackets bond strength of Ultratrimm type after debonding was 8.22?0.49 MPa. There were no statistical differences in the values of bond strength regarding all three groups of the investigated orthodontic brackets (F=4.56; p<0.05). Conclusion. The base size and design of metal orthodontic brackets did not play a significant role in bond strength, while the values of ARI index were identical in all three investigated groups.