bluuebunny/crossref_metadata_2025 huggingface dataset:
CO2 EOR From Representative North Sea Oil Reservoirs
Authors: Akervoll I.. , Eirik Bergmo P..
Published: February 2011

Estimating the EOR potential in producing oil fields is an important input to decision making if large scale CO2-EOR is going to be employed in the North Sea. This paper describes the results from simulations of CO2 injection into conceptual reservoir models representative of water flooded oil fields in the North Sea.

Enhanced oil recovery (EOR) by CO2 injection is an attractive option because it has the potential to increase the oil, gas and condensate recovery of producing fields. In the North Sea a majority of the oil reservoirs have been subject to massive strategic and efficient water flooding resulting in high recoveries for most of the cases. However, more advanced tertiary recovery methods are sought to increase the recovery. Using CO2 as injection fluid has several advantages. Most oil compositions in the North Sea are miscible with CO2 at reservoir conditions something that will enable miscible displacement of the oil targeting residual (capillary trapped) oil after water flooding. The density of CO2 at reservoir conditions is in most cases lesser than the injected water and it may therefore reach other parts of the reservoir and consequently improve the sweep efficiency.

The North Sea shows a great variation in type of oil reservoirs and traps ranging in geological age from the Late Paleozoic to the Cenozoic. To cover the range of different geological classes, traps and recovery strategies a large number of scenarios has been simulated on conceptual sector models. Conceptual live reservoir oil is composed to represent fluid properties of a selection of 55 water flooded oil reservoirs in the North Sea that are considered potential candidates for CO2 injection. The selected reservoirs comprise 30 reservoirs in the UK sector, 20 in the Norwegian sector and 5 reservoirs in the Danish sector. The conceptual fluid model is composed and tuned to reflect the hydrocarbon pore volume (HCPV) weighted average properties of these 55 oil reservoirs.

Representative petrophysical properties and fluid compositions have been used in the models in order to schematically account for heterogeneities and phase behavior of the different reservoir types. Different injection schemes including CO2 injection with and without recirculation of CO2 breakthrough gas and CO2-WAG have been evaluated.
Sulfate Precipitation during CO2 Sequestration in Carbonate Rock
Authors: Mohamed I. M. , He J.. , Nasr-El-Din H. A.
Published: February 2011

Carbon capture and storage (CCS) has been proposed to mitigate the accumulation of CO2 in the atmosphere. Water alternating gas (WAG) technique is used in the industry to inject CO2 into underground formations either in sequestration or in EOR. CO2 dissolves in water, generating carbonic acid, which dissolves carbonate rock. The composition of the water is a critical factor that affects the rock permeability during sequestration. Sulfate content of the injected water can cause precipitation of calcium sulfate, which can negatively affect the rock permeability. This paper addresses potential formation damage due to sulfate precipitation during CO2 sequestration.

A core flood study was conducted using limestone cores. CO2 was injected at pressure greater than 1300 psi and temperatures (70 and 200°F). CO2 and brines were injected in WAG cycles under injection rates of 2 and 5 cm3/min. Seawater and formation brine were examined in this study. Core effluent samples were collected and concentrations of calcium and sulfate ions were measured to assess calcium sulfate precipitation. Core permeability was measured before and after the experiment.

The results show that temperature is the main parameter that affects sulfate precipitation during CO2 sequestration. Injection rate doesn’t have a significant effect on the core permeability. At high salinity calcium sulfate precipitation occurs even with low sulfate concentration present.
Solving Deep, Hard/Abrasive 16" Application Challenges with New PDC Technology Saves Operator 13 Days Rig Time, Kuwait
Authors: Al-Saeedi Mohamed , Al-Fayez Fayez , Sounderrajan Mahesh , Al-Mudhaf Mishary N. , Al-Kandary Abdul Q. , Mishra Manoj , Maliekkal Harish , Ghoneim Osama
Published: February 2011

Drilling the deep vertical 16" hole (starting at 9,300ft) in northern Kuwait is challenging due to the complex stratigraphic section that contains abrasive Zubair sand (with pyrite), reactive Ratawi shale, hard Ratawi, Minagish, Makhul limestones and Hith anhydrite (UCS 10-30kpsi). Completing the 16" section typically requires around 45 days of rig-time and four polycrystalline diamond compact (PDC) bits on a positive displace motor (PDM) driven bottom hole assembly (BHA). However, inconsistent PDC bit performance/durability and lack of downhole stability was causing premature bit/motor failure. The operator required new PDC technology that could efficiently drill the abrasive, Zubair and continue as far as possible into the Ratawi without premature cutter failure at acceptable rates of penetration (ROP). The PDC bit would also need to possess improved stability characteristics to reduce PDM failures/trip hours.

An engineering team was assembled to analyze the latest drilling/PDC technologies, optimize BHA design, and determine the best practices to enable reaching section TD with two PDC bits/runs. A finite element analysis (FEA) based engineering system was utilized to predict the dynamic behavior of each BHA component. The resulting information led to greater bit stability when drilling in lithologies comparable to the specific field application. The development of a new abrasion resistant cutter was considered important to improving durability and maintaining cutting efficiency.

The in-depth study and PDC design changes/advanced cutter technology produced a new nine-bladed PDC bit. The new bit was run on a performance motor in Raudhatain field and set new PDC footage and ROP records for drilling through Zubair (1,200ft) in northern Kuwait (Figure 1). Historically, the Zubair alone required three/four TCIs or two/three PDCs to complete the formation interval. Next an eight-bladed PDC, fitted with the new cutter technology, drilled 2,508ft from Ratawi to section TD for the first time in Kuwait. The improved performance reduced rig hours by an average of 13 days for a total savings of approximately $390,000USD compared to the closest two PDC offset runs.
Application of Outcrop Analogs to Characterize Carbonate Reservoirs in the Pricaspian Basin
Authors: Kenter Jeroen A. , Playton Ted , Harries Paul (Mitch) , Katz David , Bellian Jerry
Published: February 2011

Slope systems flanking high-rising isolated carbonate platforms and dominated by "deep-reef" microbial boundstone are heterogeneous due to a spectrum of depositional processes that cause a high degree of vertical and lateral variability. In addition, they are conceptually complex as a result of their poorly understood depositional controls and insensitivity to sea level fluctuations.

The nature of the margins and slopes of the giant carbonate reservoirs of the Pricaspian Basin remains a controversial topic. Among the reasons is the poor quality of seismic data due to overlying salt as well as the lack of depositional models explaining their spatial distribution and seismic response. The use of analogs, in particular those from the Carboniferous of Spain, the Permian of New Mexico and Texas (USA), the Devonian of the Canning Basin (Australia), and the Triassic of the Dolomites (Italy), provide highly valuable depositional models.

Intact and seismic-scale outcrops in northern Spain, USA and Italy proved the existence of deep-reef microbial boundstone slopes that characteristically display high progradation rates, propensity for fracturing and collapse, and insensitivity to sea level. Cores from the Tengiz and Karachaganak fields, when tied with reflection terminations and log character, confirm the presence of such slopes, leading to a radical change in the depositional and reservoir models. Results from the Canning Basin and Permian Basin provided models for margin styles and the detrital portions of slope systems that were successfully applied to portions of the fields. Seismic geomorphology and stratigraphic interpretation, guided by understandings from outcrops, allowed for the subdivision into multiple styles of clinoforms, slope and basin sediment wedges, margin configurations, and secondary features (i.e. reentrants). These revised subdivisions better conform to and explain the observed trends in reservoir properties and connectivity of the fields.

Thus, integration of depositional models derived from outcrop analogs with seismic facies analysis, cores, log character and static and dynamic data is a critical step in reducing uncertainty and improving reservoir characterization, especially in cases where seismic response is obscured and well data is limited.
A New Method to Measure the Excess of H2S Scavenger in the Karachaganak Field
Authors: Ramirez Mario A , Casadiego Efrain , Spates Mary , Thekkabylov Almaz
Published: February 2011

The Karachaganak Field, which was discovered in 1979, is located in north-west Kazakhstan on the northern margin of the Pre-Caspian Basin. Production from this field contains 4 - 4..5% H2S. The Kashagan field, located offshore in the North West part of the Caspian Sea, averages 10-12% H2S concentration. An environmentally friendly H2S scavenger has been used in the Caspian area since 2006 in the invert emulsion drilling fluid systems. The operators had a standard practice of maintaining an excess of lime (2.5 kg/m3) as a supplementary sulphide removal additive and also raised concerns regarding the lack of a testing procedure to monitor concentration. This issue was regarded as being very important on the grounds of the significant risk that existed in the absence of more accurate method of monitoring scavenger concentration other than just mass balance calculations. The lack of ability to measure scavenger concentration more precisely in the invert emulsion fluid returned to the liquid mud plant (LMP), led to increased cost for the operator to maintain a safe concentration.

This paper discusses the design of a new method to be used in both OBM and WBM during field applications of the scavenger. The method is now used to monitor the excess scavenger in all the wells drilled in the Karachaganak field and to design subsequent treatments. The method has also contributed to improving the level of safety in the operation. The use of the proper scavenger concentration in combination with excess lime provides a primary and secondary barrier for protection against the influx of H2S
A Simple-to-Use Matlab-based Computer Program for Prediction of Formation Water Properties
Authors: Bahadori Alireza , Al-Haddabi Mansour , Vuthaluru Hari , Bahadori Meysam
Published: February 2011

Production of wet crude due to the raise in oil-water contact in many oil fields has been a growing field problem and consequently production of salty wet crude affects the quality of crudes. In this work, a simple computer program using Arrhenius-type function and Vandermonde matrix is presented for estimation of formation water properties for temperatures above 30°C and salt contents between 5 and 25 percent by mass. An Arrhenius type function has been selected because it is easier than existing approaches, less complicated with fewer computations and suitable for engineers. These expressions have been programmed using Matlab computational technical language and it can then be incorporated into further calculations that require predictions of formation water properties as functions of temperature and salt content. Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviation varying between 0.08 to 2.7 %. The method developed in this study is of immense practical value for petroleum engineers and practice engineers for a quick check on the formation water properties at various conditions without opting for any experimental measurements. In particular, chemical and petroleum engineers would find the proposed approach to be user-friendly with transparent calculations involving no complex expressions.
One Well Evaluation in Low Permeability Gas Sandstones from Nuclear Magnetic Resonance (NMR) Logs
Authors: Wen Tang
Published: February 2011

It is difficult for petrophysicists in evaluating reservoir porosity, permeability and irreducible water saturation in low permeability because of the complicated pore structure. NMR logs have the advantage in this aspect. In this paper, with the analysis of a well with low permeability sandstones, we proposed the models to calculate reservoir porosity based on three parameters models from conventional logs, the parameters of classic SDR and Timur-Coates models are calibrated from 36 core samples, from this, the permeability estimation models from NMR logs are obtained. At the same time, the relationship between pore structure index (K/ϕ) and irreducible water saturation are established for bound water saturation calculation. The application of this well shows that these methods and models are usable in low permeability sandstones.
Online Production Model
Authors: Narain M.. , AL-Nabhan T..
Published: February 2011

The objective of this paper is to discuss the development of a computer code based "Online Production Model" and to demonstrate its potential for optimizing Well Production or Equipment capacities of Oil & Gas handling facilities, in any oilfield.

The input data required for the model include the average dry and wet well production rates, GOR’s, capacity of each equipment within the oil & gas handling facilities, capacity limitations of the common facilities handling oil, gas & water of entire field and Laboratory data such as crude water cuts within the facilities.

Prior to development of this computer programme, calculations were limited to a fixed set of input data and a specific objective function.

With the availability of this model, the user has the freedom to modify (online) any input values (such as dry and wet well production rates, water cuts) to obtain the outputs for different sets of input data and objective functions on a single excel worksheet. On account of its modular structure, this model can be customized for input data from any oilfield.

The output of this model has been validated using KOC’s field data (averaged out over a period of several months) as input. However, for the purpose of confidentiality, the capabilities of the model shall be illustrated on fictitious field and laboratory data.

Technical Contribution

This model can be used for carrying out a "What if analysis" to predict future production trends (for e.g. at different production rates and varying GOR’s / water cuts) with the existing facilities.

It aids in determining bottlenecks of each facility as well as those of the common facilities to identify actions required to enhance production.

Performs an Online predictive analysis to calculate the equipment capacity upgrades (required under the best and worst case operating scenarios) at minimum additional costs to maximize yields.
Critical Evaluation of Shale Gas Reservoir Simulation Approaches: Single-Porosity and Dual-Porosity Modeling
Authors: Li James , Du C. Mike , Zhang Xu
Published: February 2011

Hydraulic fractures play a paramount role in the economical production of gas from shale gas formations. In the context of representing these formations as either single-porosity (SP) or dual-porosity (DP) media, different approaches have been used to represent the fractures in reservoir simulation models; for example, bi-wing planar planes, planar fracture networks, local grid refinements (LGR), discrete facture networks, hydraulic propped zones, and mircoseismic-based fracture networks. With their relatively short production histories, and because of the single-phase (gas) or two-phase (gas and water) nature of their production, most simulation models can reasonably history match the performance of any shale gas production well.

This paper reviews the evolution of different reservoir simulation models (SP-planar fracture, SP-planar fracture network, DP, DP-LGR, and DP-microseismic-based fracture network). Differences in SP and DP models are discussed, and examples demonstrate a match of the actual production from a shale gas well with the long-term prediction of each model.
Application of Production logging and Noise logging for Well Leak Detection, Case Study in Persian Wells
Authors: Salehi-Moorkani Reza , Mohamadipour Maryam
Published: February 2011

There are a variety of methods available to detect the source of downhole leak points include Production logs, down-hole cameras, thermal decay logs, and noise logs. However, many of these methods are not so much effective specially in case of very small leaks and can result in gathering data that requires a significant amount of logging assurance to interpret. Continuous logging has proven to be significantly more efficient in locating anomalies than static logging techniques commonly used in noise logging operations. Identification of the source of pressure communication between well tubing-casing and casing-casing annuli presents a huge challenge to petroleum engineers.

This paper presents a brief description of two technologies for leak detection and the findings from the field trial. In this well two type of logging techniques are used: Production logging and Noise logging. These tools were run in an oil well with a history of leaking oil 600 meters away at surface. Analytical work prior to the trial had established that the wellhead seals and burning pit flow line were not the source of leak. The paper describes the interpretation of the results that indicated a possible casing leak. The results show that in Noise logging the source of leak is clearer than production logging. In some cases two logs have read the same values.
LCA Application for Casing Design Well Integrity: Case Study Aquifer External Corrosion Attack in Middle East
Authors: Nengkoda Ardian , Priyandoko Pajang , Soejoso Mia Wimala
Published: February 2011

For many years, casing has reported failed rapidly in some Middle East oil and gas wells due to external corrosion casing. Repairs of casing failures are not efficient and costly. Mitigation of external corrosion as a part of well integrity on well casing is important to prevent from such water attack, H2S bacterial activity, electrolytic effects, and cathodic reaction. The alternative solutions based on LCA (Life Cycle Analysis) have been studied with objective to understand the casing leak and failure based on statistical data and to see the economic solutions over the life of the well by option of the use of coatings, dual casing or increase the thickness of casing materials. Casing corrosion will result not only in the loss of the casing but also in the interruption of production, loss of the well, or even permanent damage to the reservoir. Some of the statistic from study showed that 60% of single casing wells failed within less than 8 years while the external corrosion confirmed as an evidence from corrosion log run in some wells, due to shallow aquifer corrosivity. The studied summarized that coated casing is attractive solution for life of the well and the field trial to see the abrasion and water corrosion resistance showed this conclusion. Future sidetracking and surveillance need to be considered for the coating protection.
Ongoing Development of Cementing Practices and Technologies for Kuwait Oil Company’s Deep HPHT Exploration and Gas Wells – Case History
Authors: Al-Saeedi M. J. , Al-Enezi D.. , Al-Mudhaf M. N. , Modak T.. , McKinnell D. C.
Published: February 2011

Exploration activities in the state of Kuwait have been focused on the search for high quality oil from the Jurassic formations and gas in the Triassic/Permian series. The wells drilled to these prospects are very challenging because of HPHT conditions, large casing sizes, oil base mud, presence of high levels H2S/CO2 and narrow pore/fracture pressure window. As such, the cementing of the deep strings in these wells has been extremely challenging. Over the last eight years a concentrated effort has been made to introduce new technologies and materials to improve the cementing practices both from operational and safety aspects.

In 2003 the success ratio for deep cementations was highly variable. KOC along with one of their cementing service providers worked on a series of changes to practices and materials with the aim of improving job quality with high repeatability. This was based primarily on the technologies being developed in HPHT wells around the globe and especially in the North Sea and it resulted in a notable improvement in cementing performance.

Technologies and practices that had been developed include spacer technology, application of synthetic retarders, fluid loss and anti-gas migration additive improvements, development of fine grained weighting additives, use of HPHT rheometers, systematic product control, minimizing handling and safer mixing practices at the well site.

This paper will discuss the application of these technologies, materials and practices over an eight year period as a case history to illustrate the improvements made in achieving consistent cement quality and final slurry placement for the deep casing and liner strings and will conclude with recommendations and lessons learnt during this process.
Stimulation Combined with Hydrajetting Technology Achieves Excellent Results in Gas Producers in Saudi Arabia: Field Cases
Authors: Alabbad E. A. , Solares J. R.
Published: February 2011

As a growing number of gas producers are drilled in deeper and tighter formations in Ghawar field in Saudi Arabia, and as wellbore accessibility becomes more challenging — in high-angle and horizontal wells in particular — effective stimulation is harder to achieve. Because the utilization of conventional perforating and stimulation methods has not achieved the targeted production rates, a different approach which combines hydrajetting techniques with other stimulation methods has been successfully field tested with excellent results. Hydrajetting technology is used to create sufficient slots along the wellbore wall to facilitate fluid entry, and provide an adequate communication channel from and into the reservoir. The use of the technology in different applications has overcome a number of the previously encountered challenges and allowed effective stimulation in a significant number of gas producers. This paper presents an overview of hydrajetting technology, provides details about the methodology being used, and shares results from three recent applications.
Development of Techniques to Integrate Hydraulic Fracturing Design and Reservoir Simulation Technologies — Application to Forecast Production of Stimulated Wells in Unconventional Gas Reservoirs
Authors: Fazelipour Waleed
Published: February 2011

Unconventional gas plays are becoming of increasing interest worldwide, as E&P companies search for alternative hydrocarbon resources. Successful E&P operators are increasingly using hydraulic fracturing to maximize production. Multistage hydraulic fracturing, the key technology to enhanced well performance, creates stimulated reservoir volumes (SRV) surrounding the stages. SRV are the main contributors to higher production profiles. Hence, it is very desirable for the E&P industry to evaluate and optimize the hydraulic-fracturing treatment to maximize profitability.

One of the best technologies that can help understand the dynamics of unconventional reservoirs to optimize the wellbore placement and improve well productivity is reservoir modeling and simulation. Main challenges to dynamically model stimulated wells include: properly describing the hydraulic fractures, their geometry and position; and characterizing reservoir/ hydraulic-fracture properties. Innovative reservoir simulation techniques can optimize the number of hydraulic-fracturing stages required and realistically simulate their effect on production in heterogeneous reservoirs involving multiphase, multicomponent fluid-flow and adsorption/desorption mechanisms. However, the simulation approaches the E&P companies are utilizing, over simplify the complex growth and properties of hydraulic fractures, this might result in unreliable forecasts.

This paper presents modern techniques to accurately simulate hydraulically-fractured wells. The developed methodology seamlessly integrates hydraulic-fracturing design/growth software to reservoir simulators to import detailed descriptions of hydraulic-fracture attributes; offers flexible gridding schemes and populates the mentioned properties to enhance the modeling and evaluation process. Main conclusions of achievements include generating more reliable forecasts that are critical in understanding wells performance and optimizing the productivity.

This research has led to a game-changing methodology for the global E&P industry that enables operators develop an early understanding of stimulated wells performance where such detailed knowledge is vital to optimizing exploitation economics and estimation of unconventional reserves and resource potential.
Feasibility Study of Steam/Flue Gas Mixture Injection in Low Permeability Reservoir
Authors: Liu Renjing , Zhang Jianguo , Meng Liang , Liu Fei , Zuo Chao
Published: February 2011

Low permeability reservoir, with small pore radius, narrow throat and low permeability, accounts for a high proportion in the recent years. It is hard to develop by water flooding because of the high injection pressure. And thus gas injection is an attractive process owing to its high injection ability. However, gas channeling and poor flooding efficiency frequently occur during immiscible displacement, and thus the ultimate recovery is not as high as we expected.

To find a more effective method to resolve the problems above, we initially inject high temperature mixture gas of flue gas and steam to enhance oil recovery of low permeability reservoir, which combines the advantages of nitrogen gas injection, carbon dioxide injection and steam injection. In this paper, the experiments of different injection fluids, such as water, flue gas flooding, steam and high temperature mixture gas were conducted on low permeability natural cores under reservoir conditions. And the influence factors of mixture gas injection were investigated in detail by numerical simulation method.

The results show that, comparing with water flooding and flue gas flooding, the high temperature mixture gas flooding can enhance oil recovery dramatically. It can prevent gas breakthrough early and supplement formation energy quickly. It also can reduce heat loss and increase the heat areas. The steam distillation effect is enhanced during high temperature mixture gas injection, which can reduce residual oil saturation. The more proportion of carbon dioxide in mixture gas and the higher steam dryness are, the higher oil recovery enhanced is. There are different optimal injection rates and ratios of flue gas to steam under different reservoir conditions.

The result can be used to gas injection design and has great instruction meaning for the low permeability reservoir development.
Heavy Oil Characteristic Assessment for Field Facilities Selection Steam EOR: Case Study in Oman
Authors: Nengkoda Ardian , Hajri Moh'd , Armstrong Henry , Reerink Hendrikus , Chang Francis
Published: February 2011

Fluid characterization such assay composition, PVT and compatibility tendency are the most important issues in understanding the compositional behaviour identification and as an input for field facilities design and selection especially in steam EOR project for carbonate type of potential in Oman. The fluid characterization deals to addresses the following issues as such how many components should be used, how should the data be grouped and how should fluid description parameters be obtained and identified as early as possible to identify the major flow assurance issue across facilities. This paper discuss about integrated study and efective work flow to support the project Steam EOR facilities that cover 3 major facilities that are oil and gas processing, water treatment process and steam generation, each stages have been evaluated in correlation to identify a type of production chemical. As a result, the challenge of flow assurance issues are: heavy oil and water separation, H2S and CO2 generation from carbonate reservoir lead to corrosion and HSE, calcite scale, type of water treatment or desalination and steam quality management. The smart fluid characteristics assessment were mapped as a set of flowchart in identifying a critical physical or chemistry information, and determine the end fluid quality expectation, tolerance and economics. This paper demonstrate one example significance of fluid assessment for field development steam EOR project in Petroleum Development Oman, the concept are the real future vision for effective field facilities selection.
Trending of H2S from Reservoir After Acidizing from Well Contained SRB Bacteria: Souring Case Study in Southern Oman
Authors: Nengkoda Ardian , Mirza Muhammad , Ghozali Farid , Susandi Irman , Al Wardi Abdullah Ali
Published: February 2011

Ideally, a well stimulation activities is to increase production by improving such the flow of hydrocarbons from the drainage area into the well bore, however, however in one field in Southern of Oman, the acidizing created a trend of H2S increase. The common preliminary quick check usually will be based on the review of stimulation fluid characteristics whether carrying any sulphide or H2S and giving an impact to the wells. Some lesson learned in Oman is the water supply sources during the job always content H2S. The level of H2S after acidizing showed an alarming increase with time, casting doubts on future integrity assurance across the processing facility. As the materials used in the X and down stream receiving facilities are not to be NACE 175 souring compliant and consider H2S released are hazard for safety (HSE). The production chemistry and reservoir study have initiated an integrated H2S Monitoring and implemented a Mitigation Program by improving H2S onsite measurement and method revision and established proper well surveillance. As a result, the investigated the cause of souring show a positive SRB Bacteria and the acidizing cause a flash of H2S from Iron Sulfide scale as a product from bacteria populations. Overall its improved business performance, HSE awareness and saving the plant upgrade cost.
"SOYBEAN SLURRY" - A New Effective, Economical and Environmental Friendly Solution For Oil Congealing
Authors: Punase Abhishek D. , Bihani Abhishek D. , Patane Amol M. , John Ann , Arora Aman J. , Padalkar Chaitanya M.
Published: February 2011

The prospect of oil production from the Arctic region is attracting attention as the world is becoming more aware about the end of cheap and easy oil. The security and economic risks associated with the expensive and difficult oil remains very high. In deep-water projects, thousands of feet below the sea level, temperatures are near freezing. Combined with the high pressures present at these depths, oil congealment and ice-like hydrate formation is a commonly occurring phenomenon which results into flow restriction. This in turn leads to various production problems and hence substantial financial loss. To counter these problems, Soya slurry is proposed as an anti oil-congealer in this paper.

The soybean slurry consists of chemicals like Glycoprotein and unsaturated fats, which act as an anti freeze and suppresses ice nucleation effect. It is introduced in low concentration into the well bore which prevents the well bore fluid from congealing by increasing its thermal hysteresis and acting as an ice nucleation barrier. Even the viscosity of the wellbore fluid substantially reduces resulting in an easy and smooth flow through the pipeline with very less amount of friction experienced between the fluid and tubing.

Based on a detailed study, we have inferred that as soybeans are easy available, they have low cost and require simple application techniques, therefore they can provide an appropriate solution to the oil congealment problem.

This study will provide fresh physical insight into the phenomenon of anti oil congealer and help in countering the congealment problem in a more effective, economical and environment friendly way.
Tight Gas Reservoirs: Geological Evaluation of the Building Blocks
Authors: Shrivastava Chandramani , Lawatia Redha
Published: February 2011

Tight Gas Reservoirs (TGR) is attracting the attention of Oil & Gas industry from all quarters. Optimum exploitation depends upon the petrophysical evaluation and geological understanding. An insight into geological complexities of TGR is imperative to have a better evaluation of such reservoirs. This study details the tight gas sands (TGS) only as most of the TGR activities around the world are focused mainly on the clastics. It aims at explaining the different geological events that give rise to the tightness in the sandstone reservoirs and also presents a methodology to properly evaluate the geological complexities introduced. The TGS carry the imprint of both the primary depositional factors and secondary post-depositional ones. Grain size, sorting and distribution of detrital clay within a sequence stratigraphic framework govern the reservoir properties as depositional factors. Diagenesis is the key factor to control the tightness of the reservoirs after the deposition depending upon the compaction and cementation. Fractures are the post-depositional factors; the tectonic fractures along with the drilling induced ones provide an understanding of the stress regime and a clue towards planning the stimulation program. Conventional and sidewall cores with conventional open hole logs provide a larger understanding in terms of depositional environment and lithology variations. Detailed petrography with the help of XRD and SEM aids to understand the cementation pattern. Elemental capture spectroscopy and Spectral gamma logging can help correlating the cementation/ clay distribution within wells. Borehole images are quite helpful in capturing the textural variations which govern the differential diagenesis and also the drilling and natural fractures orientation and their association with rock facies. The study attempts to establish the need of proper geological evaluation which provides the building blocks for petrophysical and reservoir engineering evaluation to optimize the exploitation strategy.
Optimisation of Completions in Unconventional Reservoirs for Higher Ultimate Recovery
Authors: Snyder Daniel J. , Seale Rocky
Published: February 2011

Over the last decade, an industry wide shift to unconventional plays has occurred due to advances in technology allowing for the recovery of previously uneconomic reserves. The primary objective of completions in these unconventional reservoirs is to increase the effective surface area of the well to maximize reservoir contact. Horizontal drilling and multi-stage fracturing are two technologies which have accomplished this.

The two main methods of horizontal, multi-stage completions currently used in unconventional reservoirs are cemented liner "plug and perf" and open hole, multi-stage fracturing systems. This paper provides an introduction to unconventional reservoirs, describes the main methods of horizontal, multi-stage completions, and discusses how the choice of method can affect good fracturing practices as well as long-term production. Case study examples are presented from a variety of unconventional reservoirs including shale, tight sandstone and tight carbonate formations.

Operators working in a number of unconventional reservoirs, such as shales and other tight rock formations are experiencing faster than expected production decline rates, resulting in reduced long-term, ultimate recovery. This may be in part due to the abandonment of good fracturing practices with the advent of horizontal, multi-stage fracturing. Issues such as near wellbore conductivity, flowback, and fracture tortuosity, which can have a significant effect on the long-term production of wells, need to be considered when choosing a completion method, particularly for unconventional reservoirs.

Unconventional plays are becoming a significant part of the oil industry today and will become a bigger part in the future. It is important that the reservoirs are completed optimally to achieve maximum recovery. The information provided in this paper is applicable to unconventional resource plays worldwide.
A Study of Several Environmentally Friendly Clay Stabilizers
Authors: El-Monier I. A. , Nasr-El-Din H. A.
Published: February 2011

Quaternary amine-based chemicals have been used for many years as clay stabilizers. An Al/Zr-based clay stabilizer, A, was developed. It showed great effectiveness in mitigating fines migration and overcame the leaching effect of HCl. In this study, Stabilizer A was examined and its performance was compared with two commercial clay ones: tetramethyl ammonium chloride and choline chloride.

The type of cores (6 in. length and 1.5 in. diameter) that were used is Berea sandstone of 60-85 md; mainly contained 5 wt% kaolinite. Various coreflood experiments were performed to assess the effectiveness of each of the three stabilizers at 200 and 300°F. Inductively Coupled Plasma was used to analyze the core effluent to measure the concentrations of key cations.

During tetramethyl ammonium chloride and choline chloride corefloods, significant amount of fines were noted in the core effluent samples, which means that these stabilizers were not effective. A bad odor of ammonia was noted during mixing of choline chloride with HCl acid. Choline chloride was effective at high concentrations. Stabilizer A showed good behavior during coreflood experiments, and proved to be better than the two commercial stabilizers at low concentrations. Stabilizer A worked very well, and no bad smell or fines were produced. In addition, Stabilizer A is an inorganic-based fluid, environmentally friendly, and does not have any smell; in contrast to quaternary amine chemicals. Unlike previous Al-based stabilizers (hydroxy aluminum solutions), the new stabilizer was not removed by HCl and no decline in permeability was noted following HCl injection.
Life Extension and Assessment of Existing Offshore Structures
Authors: Solland Gunnar , Sigurdsson Gudfinnur , Ghosal Anupam
Published: February 2011

An increasing number of platforms are reaching their design life. For various reasons these platforms will require an assessment of their structural integrity. As examples one may experience operational changes of the platform that may lead to increased loads or there may be damages that reduce the structural capacity. Consequently, the design premises may have changed significantly and may result in increased uncertainty about the safety of the structure. In such cases the assessment process is focused towards reassuring that the structure has adequate safety.

When performing these assessments the engineer is faced with tasks where little guidance is found in design standards and the analyses that are required are often based on advanced techniques and methodology that seldom is used in design of new structures. The cost of doing advanced analysis is relatively low compared to replacement of an existing structure, but relatively high compared to moderate additions of e.g. steel in the design of a new structure. Design standards are based on theories, methods and experience for structures in a given design life (e.g. fatigue design and corrosion protection design). When this design life is extended, sound methods for ensuring that the structures are still sufficient safe is needed. Such methods will normally be "condition based design", where inspection, maintenance and repairs are included in the assessment in integrated way.

This paper discuss the overall assessment process for life extension and outline procedures connected to how to deal with the specific aspects that engineers meet when performing assessment for structural life extension.
On the basis property of the root functions of differential operators with matrix coefficients
Authors: Veliev Oktay
Published: February 2011

We obtain asymptotic formulas for eigenvalues and eigenfunctions of the operator generated by a system of ordinary differential equations with summable coefficients and periodic or antiperiodic boundary conditions. Then using these asymptotic formulas, we find necessary and sufficient conditions on the coefficients for which the system of eigenfunctions and associated functions of the operator under consideration forms a Riesz basis.
Does the Genitive Operate in the Hungarian Case System?: I. The é-Genitive
Authors: Bielecki Robert
Published: February 2011

Does the Genitive Operate in the Hungarian Case System?: I. The é-Genitive

After three centuries of discussion concerning the genitive case in Hungarian, the authors of the latest academic grammars - in contrast to many of their predecessors - no longer distinguish this casal category. Different cases in Hungarian should, according to them, be distinguished only on the basis of their forms (endings). Such an extreme unilateral approach to this category seems to have simplified at first sight the description of the Hungarian language, erasing from it any case syncretism. From the point of the view defended in the present paper, however, talking about linguistic entities without taking into account their meaning is illusory; even in the case of meaningless speech segments such as phonemes it is the meaning of the segments in which they occur that constitutes the ultimate instance allowing them to be distinguished at all. The same applies to case. The moderate approach to the category of case adopted here, taking simultaneously into account its (i) morphological, (ii) semantic and (iii) syntactic properties, leads irrevocably to the restoration of the genitive in the description of the Hungarian language. As a specific feature of this language one should consider the sharp distinction between two subclasses of the genitive case: (i) the non-attributive (é-genitive) and (ii) the attributive genitive (Ø-/nak-/nek-genitive). Only the first of these (the é-genitive) will be discussed in detail. The second (the Ø-/nak-/nek-genitive) will be the subject of a continuation of the present paper. Recognition of the é-genitive seems to have been blocked by those of its properties which seem to be quite incongruous with those of other Hungarian cases. It is claimed, for example, that the marker -é - unlike the markers of other cases - seems not to express any syntagmatic function. This function is expressed by the case marker attached after the morpheme -é (A diákét (láttam) '(I saw) The student's one'). In the view of the author, however, the lack of syntagmatic function in the case of the morpheme -é is not so obvious. On the other hand, such "discrediting" properties for a case marker candidate, as the property of not occupying the final morphotactical position (diákét), can be viewed as entirely irrelevant for the category of case. The adopted approach seems to make possible a description of this fragment of the Hungarian case system from a more homogenous perspective, showing the interplay of different casal meanings within the boundaries of one word.
Influence of Wheat and Maize Starch on Fermentation in the Rumen, Duodenal Nutrient Flow and Nutrient Digestibility
Authors: Šimko Milan , Čerešňáková Zuzana , Bíro Daniel , Juráček Miroslav , Gálik Branislav , Straková Eva , France James , Alzahal Ousama , McBride Brian
Published: February 2011

We investigated the effects of feeding diets with different starch sources on fermentation in the rumen, duodenal nutrient flow and nutrient digestibility. The basis of the diets was maize silage and alfalfa hay supplemented with wheat meal in diet W, or maize meal in diet M. The experiment was performed on four Black-Spotted bulls with mean live weight of 525 kg, which were fed twice daily at 06.30 and 18.30 h. Experimental animals were fitted with ruminal fistulae and duodenal T-shaped cannulae. Cr2O3was used as a marker of nutrient flow to the duodenum. Rations were formulated so that the ratio of starch to crude fibre (CF) was 2.1:1 and the percentage of CF was maintained at 17% (DM). Duodenal chymus was collected at 2-h time intervals. Starch origin significantly affected ruminal fermentation. Concentration of propionic, butyric and lactic acid was higher with wheat than with maize meal. When the maize meal was the source of starch there was a significantly higher flow of fat, CF, nitrogen-free extract, and starch into duodenum. Differences in duodenal flow of crude protein were not significant across the starch sources. Intake of wheat meal or maize meal increased duodenal flow relative to intake by 33% or 42 % respectively. The apparent digestibility of dry matter (76 ± 2%), crude protein (67 ± 0.9%), CF (64 ± 1.9%), nitrogen-free extract (82 ± 1.5%) and organic matter (76 ± 1.3%) was significantly higher by offering wheat meal.
The Slime Production by Yeasts Isolated from Subclinical Mastitic Cows
Authors: Türkyılmaz Süheyla , Kaynarca Seyhan
Published: February 2011

The aim of this study was to isolate yeasts from subclinical mastitic cows and to investigate the slime production by the isolated yeasts. The material used in this study included 339 milk samples from 152 dairy cattle with subclinical mastitis.Milk wasplated onto blood agar, MacConkey agar and Sabouraud dextrose agar. Forty-onesamples (12.1% of total milk samples) were found positive for the yeast by API 20 C AUX identification system. The isolated yeasts were classified into four genera ofCandida, Trichosporon, CryptococcusandSaccharomyces.TheCandidaspecies were following:C. krusei,C. kefyr,C. guilliermondii,C. famata,C. rugosaandC. utulis. Other yeasts were identified asTrichosporon mucoides,T. asahii,Cryptococcus laurentii,C.  neoformansandSaccharomyces cerevisiae. Slime production was tested on Congo red brain heart infusion agar and evaluated according to Congo red phenomenon. Fifteen (36.6%) strains were slime factor positive: seven wereC. krusei, fourC. kefyr, oneC. guilliermondii, oneC. famata, oneT. asahii, and oneC. laurentii. The results of the present study indicate that yeast mastitis is significant for causing economic losses and slime production is mostly found in non-albicans Candidaspecies. Therefore, non-albicans Candidaspecies should be examined for slime production.