bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of patterned nanoscale interfacial roughness on interfacial toughness: A finite element analysis
Authors: Reedy E.D.
Published: October 2008

A finite element analysis was used to determine how patterned, nanoscale interfacial roughness could potentially increase the apparent interfacial toughness of brittle, thin-film material systems. The pattern analyzed was composed of parallel channels with either a rectangular-toothed or a rippled cross-section. Results are presented for a thin, linear elastic, bimaterial strip loaded by displacing the top edge relative to the bottom edge. The finite element calculations indicate that the interface does not unzip in a steady, continuous manner. Instead, the crack tip stalls as it tries to kink in a direction that is offset from its original path. The apparent interfacial toughness is found to depend on the intrinsic interfacial toughness, the ratio of real-to-nominal interfacial area, the extent of ligament, tooth-tip damage that occurs before crack propagation, strain energy locked in by persistent contact, and the level of energy dissipation associated with dynamic fracture.
Hard transparent conducting hex-element complex oxide films by reactive sputtering
Authors: Chen Ta-Kun , Wong Ming-Show
Published: October 2008

Hard transparent conducting oxide films of hex-element AlxCoCrCuFeNi were deposited by reactive direct current (dc) magnetron sputtering using homogeneous alloy targets. The composition–property relation was investigated by changing the aluminum molar ratio, x value, from 0.5 to 2. The films comprise only a cubic spinel phase without other accompanying crystalline oxide phases and exhibit a high hardness up to 22.2 GPa. A small, negative deviation from Vegard’s law was observed for the spinel phase, which indicated changes in cation distribution. The optical transmittance in both the visible and infrared region is increased with aluminum content, however, together with a loss of film conductivity. The Hall measurements reveal a p-type conducting behavior for the Al0.5CoCrCuFeNi oxide film with a conductivity of 40.1 Ω−1cm−1, a carrier density of 5.81 × 1018 cm−3, and a mobility as high as 43.2 cm2V−1s−1. Moreover, Hall measurements show metallic conduction behavior for the Al0.5CoCrCuFeNi oxide film and thermal activated semiconducting properties for the Al1CoCrCuFeNi and Al2CoCrCuFeNi oxide films. Combine the crystal field theory and the x-ray photoelectron spectroscopy (XPS) measurements, the decrease of film conductivity is explained by the decreases of available carriers and mobility due to the fact that increasing aluminum content reduces the number of conducting cations at octahedral sites and increases the activation energy for electrical conduction. XPS analyses also show lots of excess oxygen originated from anion-rich growth condition in the films deposited at high oxygen partial pressure that produce p-type carriers lowering the electrical resistivity. The amount of excess oxygen decreases with increasing Al content and also contributes to the variation of conductivity with x value.
Pax8 protein stability is controlled by sumoylation
Authors: de Cristofaro Tiziana , Mascia Anna , Pappalardo Andrea , D'Andrea Barbara , Nitsch Lucio , Zannini Mariastella
Published: October 2008

The transcription factor Pax8 is involved in the morphogenesis of the thyroid gland and in the maintenance of the differentiated thyroid phenotype. Despite the critical role played by Pax8 during thyroid development and differentiation, very little is known of its post-translational modifications and how these modifications may regulate its activity. We focused our attention on the study of a specific post-translational modification, i.e., sumoylation. Sumoylation is a dynamic and reversible process regulating gene expression by altering transcription factor stability, protein–protein interaction and subcellular localization of target proteins. The analysis of Pax8 protein sequence revealed the presence of one sumoylation consensus motif (ψKxE), strongly conserved among mammals, amphibians, and fish. We demonstrated that Pax8 is sumoylated by the addition of a single small ubiquitin-like modifier (SUMO) molecule on its lysine residue 309 and that Pax8K309R, a substitution mutant in which the candidate lysine is replaced with an arginine, is no longer modified by SUMO. In addition, we analyzed whether protein inhibitor of activated signal transducers and activators of transcription (PIASy), a member of the PIAS STAT family of proteins, could function as a SUMO ligase and we demonstrated that indeed PIASy is able to increase the fraction of sumoylated Pax8. Interestingly, we show that Pax8 is targeted in the SUMO nuclear bodies, which are structures that regulate the nucleoplasmic concentration of transcription factors by SUMO trapping. Finally, we report here that the steady-state protein level of Pax8 is controlled by sumoylation.
Influence of visceral adiposity on ghrelin secretion and expression in rats during fasting
Authors: Li Rong-Ying , Li Xue-Song , Shao Li , Wu Zhi-yuan , Du Wen-Hua , Li Sheng-Xian , Zhao Shuang-xia , Chen Ke-min , Chen Ming-Dao , Song Huai-Dong
Published: October 2008

Although circulating ghrelin levels correlate inversely with adiposity at baseline, little is known about the effect of percent visceral adipose tissue value (PVATV) on ghrelin expression and secretion in response to fasting. Our study demonstrated that ghrelin increased with 24-h fasting in rats with the lowest PVATV (less than 6%), after 3 days in rats with intermediate PVATV (6–9%) and 5 days in rats with the highest PVATV (greater than 9%). Ghrelin mRNA in the stomach was increased after 3 days in low-PVATV (5.8±0.9%) rats but not in high-PVATV (14±1.6%) rats. Therefore, both ghrelin secretion and mRNA were delayed in response to fasting in rats with increased visceral fat. In rats matched for PVATV, but with different body weights, the fasting induced similar levels of increased ghrelin while in rats with different PVATV ghrelin secretion was different in response to fasting, even when body weights were matched in two groups. These data suggested that the initial PVATV, not lean mass, was related to the pattern of plasma ghrelin in response to fasting in rats.
Developing Russia's Young Petroleum Professionals in a Global Context
Authors: McMorran Paul , Pongratz Reinhard
Published: October 2008

Low oil prices in the mid-1980’s, and widespread industry restructuring since the 1990’s, have drastically impacted our industry workforce. In the West, fewer students in technical disciplines generally, and on petroleum-related courses particularly, are a cause for concern. Loss of oil and gas talent and experience to other, more "stable" industries, drive global fears of a deepening demographic crisis.

Russia is different. Its specialized oil & gas universities have not suffered the downsizing seen by some Western counterparts, and continue to provide a potent source of engineers and geoscientists. These institutions have adapted in the past decade as technologies, new to Russia, revolutionize drilling performance and boost production. Oil and gas drive the country’s economy, and its industry is an established "employer of choice". Campuses across Russia have also become a significant source of graduates for global operators and service companies.

In-company development programs, blending Russian experience with best practice from abroad, turn qualified graduates into competent young professionals. Building on strong but often specialized academic foundations, these develop skills to tackle the multidisciplinary tasks on which success in today’s industry increasingly depends.

Combining the perspectives of an Operator and a Service Company, this paper describes how such programs were developed to meet specific local needs in a global context. It will show how the creation of a Service Company training center in Siberia, for students from other countries as well as Russia, has brought technical and cultural diversity to the learning process. Sharing knowledge and technical excellence has become part of daily business among young professionals, and rapidly-growing SPE membership across Russia facilitates this exchange.
PinPoint Multistage Fracturing Stimulation – Global Applications and Case Histories from Russia
Authors: Pongratz R. , Stanojcic M. , Martysevich V.
Published: October 2008

Creating multiple zone stimulations in complex reservoirs presents unique challenges for the completion engineer. Effectively stimulating each individual pay interval using separate fracturing treatments can be costly and time consuming. Historically, efforts to stimulate multiple zones usually consisted of casing fracs with limited entry perforating and using sand plugs to separate zones, or tubing fracs with retrievable bridge plugs and packers. The challenge was to rethink the approach to this technology and develop more cost effective and efficient solutions. Those efforts have resulted in a new approach called pinpoint stimulation.

New pinpoint stimulation methods have resulted in reduced cycle time for operators. This means doing multiple service operations in a single trip to the well. If performed individually, perforating, fracturing, setting isolation plugs, and cleaning out the wellbore for each interval can add days or weeks to a completion, delaying production-to-sales and increasing overall costs. Now, we perforate, fracture stimulate, and clean out with a single trip to the wellsite. Each treatment stage is customized for the intervals treated and many more intervals can be stimulated economically. Pinpoint multistage fracturing is available in 16 different processes for many types of well completions.

In this paper, we present different techniques for a wide variety of applications and provide actual treatment data and results including recent case histories from Russia.
Candidate Selection Process for Fracturing Combined with RPM Treatments for Western Siberia Oilfields Based on Case Studies
Authors: Prudnikova Antonina , Anashkin Alexey , Dalrymple Dwyann
Published: October 2008

Major oil producers in western Siberia widely use hydraulic fracturing to increase recovery from maturing reservoirs. Minimizing the quantity of produced water that typically accompanies increased hydrocarbon production is considered to be of the utmost importance. The traditional approach has been to limit well selection for fracturing treatments to candidates where stimulation can be efficiently performed without a subsequent increase of post-frac water cut. This significantly reduces the desired development of targeted fields.

In general, there are two main reasons for water production increase: (1) fracture propagation to water-saturated formations caused by the absence of reliable barriers and (2) phenomenon of water coning caused by pressure drawdown through a highly conductive fracture channel during the exploitation period. To mitigate the problem of post-stimulation water production increase, a relative permeability modifier (RPM) can be applied. The RPM itself is a polymer that can be pumped as a preflush to fracturing treatments or throughout the whole job. Under formation conditions, RPMs decrease the relative permeability of rock (reservoir) to water with almost no effect on the permeability of hydrocarbons. This is crucial to increase the oil-mobility ratio because it allows production of higher oil volumes without unacceptable quantities of associated water production.

Several fracturing job RPM treatments have been performed on different oilfields in western Siberia, and not all of them can be considered successful. Both satisfactory and unsatisfactory results were analyzed to classify the major groups of parameters that had the most impact on the final well performance. Based on this data, the candidate selection process for fracturing combined with RPM treatments for western Siberia oilfields should be improved to achieve more desirable treatment results. This paper contains guidelines to select the proper well for this type of treatment and, based on the case study, brings attention to different groups of parameters, related not only to formation properties but also to well preparation process and design criteria, that can significantly affect the final result.
Shallow Penetration Particle-Gel System for Water and Gas Shutoff Applications
Authors: Dalrymple Dwyann , Eoff Larry , Vasquez Julio , van Eijden Jip
Published: October 2008

This paper presents the development of a particle-gel (PG) system for water shutoff operations. This system combines an organically crosslinked polymer (OCP) system with non-cement particulates to provide shallow matrix shutoff in openhole or perforated completions. The PG system can be considered as an alternative to standard cement squeeze operations, repairing casing leaks, sealing off thief zones, and addressing lost-circulation zones.

The OCP system, which comprises the fluid portion of the PG system, easily penetrates into the formation matrix. It has proven successful in the oil industry with more than 350 jobs performed around the world. The addition of particulates to the OCP system resulted in synergistic results. The PG system provides (1) leakoff control for shallow penetration into the rock matrix and (2) squeeze-pressure properties. The slurry filtrate (OCP) is thermally activated. After exposure to the targeted bottomhole temperature of the well, it forms a three-dimensional gel structure. The transition time from slurry to gel is controlled by the crosslinker concentration of the OCP system and is not altered by the addition of the particles, wellbore fluids, or variations in lithology (sandstone, dolomite, limestone, shale, etc).

Bullheading the PG system into the well allows easy placement and calculation of treatment volume. The limited and controlled leakoff into the matrix during the PG system squeeze results in a controlled depth of invasion. Selective perforation of the oil zones re-establishes the desired hydrocarbon production from the targeted interval. The PG system can be easily washed out of the wellbore, as compared to cement, which must be drilled out. The temperature range of the PG system is 80 to 350°F. To date, more than 54 jobs have been performed with this system. This paper presents case histories, methodology of job designs, and results obtained from laboratory evaluations.
Scalability and Usability Aspects of Reservoir Simulation
Authors: Frost R. J. , Parker M. J. , Ponting D. K.
Published: October 2008

A parallel reservoir simulation system is described. The basic algorithm allows masses or saturations to be used to define the state of the reservoir. The parallel structure and the way in which data is moved for computation and input/output is described. For good parallel performance the workload needs to be balanced between the processors when the simulation is running. However, in most practical cases the majority of cells are inactive, inactive cells being identified during the preliminary grid calculations. These also need to be distributed, to avoid a memory peak which would limit the maximum problem size. A method for re-factoring the simulation between the processors to avoid this is detailed.

The need to use modern object-orientated coding methods and obtain good numerical performance in parallel processors leads to the use of C++ and MPI for the core solver. A simple class structure which has proved effective for simulation code development is described.

For the supporting system there are requirements of portability and efficiency. Portability because simulation data is normally prepared and viewed on a different machine from that on which the simulation is run. Efficiency is important in the transfer of data between machines and when displaying large models in three dimensions. A Java based code has proved highly effective in meeting these requirements.

Traditionally, simulator input has taken the form of a keyword orientated text file. Modern users expect a more visual interface to their data. A system is described which combines the virtues of both approaches, being based on a set of tables and grid arrays. Data may entered and viewed flexibly, but the advantages of a formatted file are retained. Problems of the migration of legacy data to such new systems are considered, with possible solutions.
First Results of Cyclic Steam Stimulations of Vertical Wells with Radial Horizontal Bores in Heavy Oil Carbonates
Authors: Ursegov Stanislav , Bazylev Alexander , Taraskin Evgeny
Published: October 2008

This work shows the first experience of cyclic steam stimulations of vertical wells with radial horizontal bores in the deep heavy oil carbonates of the Usinsk Permian – Carboniferous reservoir.

In the end of 2006, more than 30 radial horizontal bores of approximately 100 m length each were drilled in 8 vertical wells, 5 of which were then stimulated by steam injection.

Radial drilling in low productivity carbonates without the following cyclic steam stimulations were ineffective because it did not resulted in significant increase in the well productivity.

Integrating radial drilling and cyclic steam stimulations proved highly effective by reducing oil viscosity. The average growth of oil rate was about 15.0 tones per day.
Dynamic Induced Fractures in Waterfloods and EOR
Authors: van den Hoek P. J. , Hustedt B. , Sobera M. , Mahani H. , Masfry R. A. , Snippe J. , Zwarts D.
Published: October 2008

It is well established within the Industry that water injection mostly takes place under induced fracturing conditions. Particularly in low-mobility reservoirs or when injecting contaminated water (e.g. PWRI), large fractures may be induced during the field life.

This paper presents a new modeling strategy that combines fluid-flow and fracture-growth (fully coupled) within the framework of an existing ‘standard’ reservoir simulator.

We demonstrate the coupled simulator by applications to a model five-spot pattern flood model, and to a number of actual field cases (waterfloods, produced water disposal) worldwide. In these field cases, validity checks were carried out comparing our results with available surveillance data. These applications address various aspects that often play an important role in waterfloods, such as shortcut of injector and producer, vertical fracture containment, and reservoir sweep. We also demonstrate that induced fracture dimensions can be very sensitive to typical reservoir engineering parameters, such as fluid mobility, mobility ratio, 3D saturation distribution (in particular, shockfront position), positions of wells (producers, injectors), and geological details (e.g. flow baffles, faults).

The results presented in this paper are expected to also apply to (part of) EOR operations (e.g. polymer flooding).
ESP Monitoring and Diagnosis Enables Operational Efficiency
Authors: Molotkov R. V. , Stephenson G. B. , Seale S. R.
Published: October 2008

A major exploration and production company operated Block 15 and unified fields Eden-Yuturi and Limoncocha from 1986 to May 2006, when the contract passed back to the Ecuadorian Government.

In 2004 a decision was made to implement an ESP Real Time Monitoring and Diagnosis system in order to optimize production and improve ESP operations. The system includes automation hardware equipment and a server-client software package.

The purpose of this paper is to give details about the benefits of remote monitoring and control of Electrical Submersible Pumps, and the real results achieved from using the ESP monitoring and diagnosis system to monitor, analyze, and remotely control ESP performance at Block 15. In this paper, we will highlight ways in which the ESP diagnosis system has enabled material improvements in operational efficiency at Block 15.
Carbonate Reservoir Simulation Improvement on Base of Well-Test Data to Increase Forecast Reliability
Authors: Gulyaev D. , Chernoglazova N. , Fedoseev M.
Published: October 2008

Field development plans has been made on base of numerical reservoir models for many years in Russia. Nevertheless poor quality of lots of models makes them unable to provide reliable production forecast and optimize reservoir management. This is one of the reasons of relatively low recovery on fields in Russia. Numerical reservoir models quality can be significantly increased by wider usage of well-test and production-logging results for reservoir modeling.

JSC «Gazprom Neft» field example of carbonate reservoir shows that well-test and production-logging results can significantly decrease uncertainty in reservoir modeling and increase forecast reliability.
Breaking the Completions Paradigm: Delivering World Class Wells in Deepwater Angola
Authors: White Daniel , Whaley Kevin , Price-Smith Colin , Keatinge Patrick
Published: October 2008

The Greater Plutonio development, deepwater offshore Angola, is BP's largest subsea development. The "soft" rock reservoirs require sand-control completions that are some of the most complex and challenging in the world. A commonly accepted view is that effective sand-control can result in sacrificing well productivity; however, the 23 wells completed to date have broken that paradigm with world class results and the largest well potentials in the history of BP.

All twelve deepwater production wells employed Open Hole Gravel Pack completions, achieving outstanding results and technical limit productivity along with exceptional mechanical reliability and integrity. From the first well, they have all shown zero formation damage, resulting in individual well potentials up to 80 MBD. To support this prolific production capability, effective voidage replacement has been essential. Therefore, the injection well completions were designed to deliver equivalent well performance, while still providing robust sand-control. Based on this, Cased Hole Frac-Pack completions were selected for the initial gas and dual service injection wells with Stand-Alone Screen completions for the water injectors. The injector completions were as successfully deployed as their producer counterparts with technical limit injectivity on all the wells, setting a new standard for flow efficiency in high transmissibility reservoirs and delivering some of the largest water injector completions in BP's portfolio.

The Greater Plutonio completions excellence story is one of a truly performance driven and innovative team. Productivity indices are up to four times greater than prognosed and mechanical skins in production wells are all zero (compared with +5 to +20 in analogous fields). This is underpinned by comparable injection performance and furthermore, the over 99% mechanical reliability and full data acquisition uptimes have substantially reduced the probability of costly well interventions in the future.

This paper discusses the keys to the successful delivery of this world class completions performance and covers best practices and resultant well performance data of the first 23 wells from the planned initial 43 subsea well development.
Title Measurement of Component-Wise Gas Liquid Mixtures Flaw Rate
Authors: Akhmetzianov A. V. , Kasimov A. M. , Lunkin B. V. , Ermolaev A. I.
Published: October 2008

Here are examined measurement methods and instrumentation of two-phase multicomponent oiler production by using compensation method of volumetric flow measuring and resonance (radio wave) technique of composition measuring for technological control of the picked product directly in in the pipeline's flow area without separation of the phases.
Log Interpretation Methodology in Polygenetic Deposits of the Vikulovskaya Suite at the Kamennoye Field (Thin-Layer Storm Deposits and Incised Valley Fill Complex)
Authors: Lopatin A. Yu , Medvedev A. L. , Masalkin Yu. V , Valencia R.
Published: October 2008

The Vikulovskaya deposits of the Kamennoye field are marked by fine interbedding of sandstones and silts. The thickness of sandstone interbeds varies from a few millimeters to 50–60 centimeters. Well logging data interpretation in such a section often presents great difficulties. In the first place this is associated with the determination of the resistivity of oil-saturated sandstones which have a low resistivity without any correction for laminated shaliness and very often can be interpreted as water-saturated. The corruption of well logging porosity values as well as difficulties in net thicknesses delineation, add the complexity (qualitative indicators do not work, quantitative ones are corrupted). Certainly, up-to-date high-resolution geophysical logging tools help in some instances (3DEX - Baker Atlas, Multiarray Triaxial Induction Tool, FMI - Schlumberger). But they are expensive, and above issues need to be solved in a large amount of existing wells using conventional or even "clipped" well logging suite. Using various mathematical algorithms to obtain volumetric parameters is often ineffective due to the well logging data. The present paper shows how the profound understanding of Reservoir Geology helped to pass from lithotypes interpretation to geological facies interpretation and thus to solve some problems of well logging data interpretation.
The Development of an Intelligent Sensor for the Monitoring of Pipeline System Integrity
Authors: Umeadi Bonny B. N. , Jones K. G.
Published: October 2008

This paper presents experimental studies that integrate and develop a prototype sensor to monitor, analyse and communicate any changes in oil/gas/water pipeline performance in such a way that reduces pipeline failures and the associated disruption to supply, damage to the environment and cost to the company. In the oil steel pipeline systems industry alone, the financial implications of pipeline failures have been estimated at £2.5 billion year.

Further, current methods of detection rely on periodic inspection which misses more occurrences of failure than it identifies. What is needed is a semi-continuous monitoring system that not only recognises imminent pipeline failure characteristics but also automatically transmits a warning to a central control centre.

This paper reports the findings of a laboratory based test programme to evaluate the potential for vibration sound emission detection to form the basis of such an early warning system. Attenuation and waveform analysis were used to identify theoretical changes in the flow characteristics of a liquid medium as it passed along a damaged section of pipe.

The effectiveness of piezoelectric sensors to detect the changed flow characteristics were evaluated for a range of artificially induced defects. The flow characteristics were analysed (using spectrum analysis of the signal across a number of frequency bands) and compared to the theoretical predictions. The results show that a piezoelectric vibration sound emission sensor can detect changes in the flow characteristics of water and diesel oil to a level of accuracy that could form the basis of an integrated wireless sensor device. Further qualitative diagnosis theory can form the basis of an algorithm which could be used to associate the changed flow characteristics with underlying pipeline defects without third party intervention.
Particularities of Hydraulic Fracturing in Dome Type Reservoirs of Samara Area in the Volga-Urals Basin
Authors: Parfenov A. N. , Sitdikov S. S. , Evseev O. V. , Shashel V. A. , Butula K. K.
Published: October 2008

The majority of hydraulic fracturing work in Russia is being done in the Western Siberian basin where operators and service companies have gathered significant amount of experience and knowledge. The sweeping success of hydraulic fracturing in Western Siberia organically expanded to projects in Tymen-Pechora and Volga-Urals basin. Both basins are geologically, lithologically and stratigraphically vastly different from West Siberia. Adding the difference in the maturity of the fields, with significantly depleted reservoirs, high asphaltene and paraffin oil content varying the hydrocarbon properties, it is understandable that the extensive knowledge gained in Western Siberia can not be translated to the less frequent but well engineered and planned stimulation campaigns in the Volga-Urals basin.

This paper presents a summary of the knowledge gained in Samara fields of the Volga-Urals basin, with emphasis on the results obtained and highlighting the differences with the Western Siberian approach to hydraulic fracturing.

Samara area is characterized with relatively low temperature, high permeability, low pressure, laterally and vertically restrained dome type sandstone and carbonate reservoirs that are located in tectonically active, high stress environment. Although correct candidate selection and fracture design, the degree of the pre-stimulation formation damage has proven to be significantly different from the comparative formations in Western Siberia hydraulic fracturing has proven again to be a successful stimulation method.

Carbonate reservoirs that constitute some 50% of the oil bearing rock in the area have seen the first acid fracturing treatments performed, including the introduction of various diverter methods in the area. The success of the pilot project is addressed as it sets a milestone in carbonate stimulation in the Volga-Urals basin.
Foam Fracturing: New Stimulation Edge in Western Siberia
Authors: Oussoltsev D. , Fomin I. , Butula K. K. , Mullen K. , Gaifullin A. , Ivshin A. , Senchenko D. , Faizullin I.
Published: October 2008

The majority of oil exploited from Russian oilfields today comes from the Volga-Urals and Western Siberian basin, where large-scale fracturing and coiled tubing operations have been on-going for the past six years. In the mainly brown fields, tertiary recovery methods such as water-flooding are implemented to maintain financial viability of the well stock. In many areas, however, production wells do not benefit enough from the water flood, or the injection scheme is not optimized.

A consequence of reservoir pressure depletion is the increase in filtrate leak-off of drilling, completion as well as stimulation fluids. The sensitivity of the formation to wellbore fluids, the impact of the wettability changes and near wellbore damage is not fully evaluated on all formations and fields. It is though evident that the volumes of wellbore fluids lost to the reservoir impact final productivity. It equally affects the possibility to flow the well back after stimulation treatment. Hydraulic fracturing treatments have become the most popular completion method in Russia, and foam-based fracturing fluids seems to be a possible solution to the above problems. Foam, though, has evaded application in the region until recently.

Absence of foam to this point is mostly due to equipment requirements and logistic complexity. A hydraulic fracturing treatment based on foam as the main proppant carrier fluid effectively reduces the amount of liquid pumped overall, provides better fluid-loss control and aids in post-treatment flowback. Foam fracturing causes less damage to the formation and proppant pack, therefore improving the productivity of the well.

A variety of reservoirs and the impact of foam fracturing is described and analyzed in this paper, from typical shallow gas to challenging deep oil reservoirs, using numerous fluid systems such as foamed visco-elastic surfactants to stable- and superfoams.
Productivity Prediction for Fractured Wells in Tight Sand Gas Reservoirs Accounting for Non-Darcy Effects
Authors: Motiur Rahman M.
Published: October 2008

Reliable prediction of production profile for fractured wells is important for hydraulic fracturing optimization. Contribution of Russian researchers (Hristianovich, Zheltov, Goldstein, Entov) in hydraulic fracturing is worldwide recognized. The production profile includes early transient period that is followed by pseudo-steady-state production. Usually, the transition period for conventional reservoirs lasts for months while for tight sands with permeabilities far below millidarcy, it can exceed years. Therefore, two regimes are important for production profile prediction in tight sand reservoirs.

Drawdown values in tight sands significantly exceed those for conventional reservoirs, so gas velocity in well fractures is also exceedingly higher. At high Reynolds numbers, inertia effects have the same order of magnitude that the viscous (Darcy's) pressure losses. It results in well productivity decrease. Therefore, it is important to account for non-Darcy effects in fractured well modelling.

In the current paper, the inertia non-Darcy pressure losses are incorporated in the mathematical model for gas production via fractured well in tight sand reservoirs by including the quadratic term into momentum balance equation for gas flow in fracture. The model is based on matching of semi-analytical solutions for transient and pseudo-steady-state flows towards well and extends the previous research by considering non-Darcy effects. The iterative procedure allows predicting production profile up to 15 years in fields with permeability 0.005-0.2 md. The model developed aims optimization of hydraulic fracturing in tight sand gas fields.
Application of Outcrop Analogues to Optimize LWD Acquisition for More Confident Formation Evaluation in High Angle and Horizontal Wells
Authors: Tyurin E. , Benefield M.
Published: October 2008

Outcrop analogues are very helpful in generation of the reservoir depositional model but are restricted in their application to formation evaluation. They represent a missed opportunity, in particular in the interpretation of high angle and horizontal (HA/HZ) well log response. In our vision they give us access to the depositional controls on vertical and lateral petrophysical rock properties variations as well as actual geometry of the geological bodies; both matters are critical for confident formation evaluation in HA/HZ well setting.

The primary objective of this study is the integration of geological answers and petrophysical information to construct forward models of our high technology LWD datasets. We assign a major significance to the visual comparison of the rock picture and a simulated tool response, supported by a detailed petrophysical analysis.

We initially used the Ainsa 1 Pyrenean deepwater turbidite outcrop with the petrophysical properties of analogous offshore West Africa reservoirs. Across-channel geological complexity (thin layering and low NTG in marginal part; pinch-outs, amalgamations and rock property variation in the axial part) is valuable to demonstrate improved strategies of interpretation solutions in channel to lobe turbidite settings. Steps to forward model the LWD data include many of today's reservoir characterization procedures: sedimentological description, lithofacies to petrofacies associations, core and field scale 3D petrophysical properties simulation, upscaling, true resistivity matrix generation and resistivity anisotropy evaluation. Forward modeling of tool response accounts for different measurement natures, geometries and DOI's (from meters in resistivity to cm in radioactivity, images and magnetic resonance).

The range of the results acquired shows that basic LWD suites often do not provide an accurate result in a heterogeneous environment. For example, in our case water saturation is overestimated by around 30% total through improper use of the classical data. Our study highlights that reservoir parameterization in the presence of all scales of heterogeneities, sand mixtures and thin laminations is enhanced through proper application of gamma ray, resistivity, density, neutron and NMR for the pore volumetrics and imaging for the geobody shaping.

Using the approach to a contrasted West Siberian field case with inherent low resistivity contrast and invasion of WBM demonstrates further interpretational challenges. The work ultimately permits a more confident selection of logging suites and subsequent improvement in application of the acquired data to formation evaluation in high angle and horizontal well situations.
Development and Field Application of a Low pH, Efficient Fracturing Fluid for Western Siberian Oil and Gas Wells
Authors: Gupta D. V. S. , Le H. V. , Batrashkin A. , Nevsky P.
Published: October 2008

Hydraulic fracturing has proven to be one of the best technologies to improve productivity from oil and gas wells. Careful consideration must be given to fracturing fluid selection, particularly when the fluids have to be prepared with local waters. Siberian waters are particularly troublesome because of the presence of iron and bicarbonate and hardness, depending on the water source. Some hydrocarbon reservoirs are under-pressured and require the use of energized fluids, while others are sensitive to water-based fluids due to clay swelling and migration.

Proppant pack damage due to gel residue is one the primary causes of low production rates after hydraulic fracturing treatments. To minimize the damage and therefore maximize production, a new premium highly efficient fracturing fluid was developed. This premium system incorporates low polymer loading carboxymethyl guar polymer and a zirconium-based crosslinker. An adjustable crosslink delay makes the fluid ideal for deep well fracturing and coiled tubing treatment as frictional pressure losses can be minimized. The system can be energized or foamed with CO2 and N2 or may also be used in binary foam systems.

This paper will compare the new fracturing fluid system with alternative guar borate system used in Russia, in terms of proppant pack cleanup, rheological properties, proppant transport and fluid loss as well as other parameters. Various rheological evaluations using high-pressure, high-temperature rheometers as well as a foam loop; fluid leak-off testing; and proppant pack conductivity and regain permeability evaluations are presented.
Optimization of Coiled Tubing Interventions on Extended-Reach Openhole Completions in a Field in Saudi Arabia
Authors: Beheiri Faisal I. , Al-Mubairik Abdulrahman J. , Al-Mulhim Abdulrahman K. , Al-Meshal Fahad M. , Noguera Jose , Sierra Leopoldo
Published: October 2008

Drilling new generation wells with longer horizontal sections, to maximize the reservoir contact, has brought many challenges to well interventions using Coiled Tubing (CT). In most cases, the complexity has pushed CT interventions to the limits, driving the development of new solutions to extend the reach to total well depth.

The number of these extended-reach wells has grown significantly in recent years in Saudi Arabia, especially in this new development field where more than 120 extended reach water injection wells were placed in the reservoir flanks. The water injection wells in this study area are complex due to the combination of large bore tubular, lower reservoir pressure and horizontal openhole (OH) completion, with lengths from 3,000 ft to almost 5,000 ft.

During the initial CT i nterventions in this field, several challenges were encountered, e.g., stuck CT differentials, slack-off weight through severe doglegs, tight spots, and other obstructions. Extensive knowledge was gained by performing an extensive simulation, studying the horizontal section geometry and analyzing the operational data. Based on the findings, combinations of techniques were introduced to the procedure to extend the reach and minimize the operational problems and costs.

The key components of our new implemented strategy were buoyancy reduction by using nitrified fluids and new viscoelastic surfactant (VES) friction reducer or drag reduction agents. In addition, combinations of other techniques were employed, e.g., optimizing the pull tests frequency in the OH and improving CT movement practices.

This paper discusses the difficulties and challenges of the initial stage of the stimulation campaign, performed in horizontal OH water injector wells using CT. Also, it presents the results and analysis of the effect of buoyancy, CT pipe size and new friction reducer for the referenced wells. The study leads to a new cost effective and reliable technique, which once implemented, conduces to maximize the CT reach without using mechanical devices, e.g., agitators or tractors.
Productization of Data
Authors: Heggelund Dag G. , Andresen Vidar
Published: October 2008

An error in software, science, or data has an equal opportunity to yield incorrect results. Imagine using a computer or a software program that randomly gave the incorrect answer 30% of the time. Productization of hardware and software has given us products of much higher quality. This paper presents a methodology, DQM, for productizing the data.

Treating data as a product is a fundamental requirement in any data quality process. In this paper we apply productization to upstream E&P data and refer to it as making data suitable for a specific process. Treating data as a product forces the definition of data requirements, in a similar manner as we are accustomed to define requirements for other products. The degree that the data product meets these requirements defines the quality of the data product. Productization of data thereby yields a measurable definition of data quality.

This paper shows how productization of data yields a productivity centric definition of data quality. It further shows that Data Quality can be decomposed into five dimensions:

Completeness Consistency Content Uniqueness Validity

By applying an extended Design for Six Sigma (DFSS) approach, we show that data quality can be measured using the traditional sigma score. Our studies show that for organizations that do not utilize a data quality process the overall quality is less then three sigma, resulting in a resource waste of more than 30%. We further present findings regarding how organizations are adopting the new data product paradigm along with the overall impacts and lessons learned.
Analysis of Production Data with Elliptical Flow Regime in Tight Gas Reservoirs
Authors: Badazhkov D. , Ovsyannikov D. , Kovalenko A.
Published: October 2008

Analysis of production data for tight gas reservoirs is based on pressure transient (PT) analysis, which is now a conventional procedure for fractured tight gas reservoirs. Key parameters can be estimated during the analysis: fracture conductivity, fracture half-length and reservoir properties. Most PT analysis methods deal with bilinear, formation linear, and pseudo-radial flow regimes. It is well known that an elliptical flow regime can appear between formation linear and pseudo-linear flow regimes. Sometimes the period is very short and cannot be identified. But there are many cases when only formation linear and elliptical flow regimes are present in production data records and the time needed to reach the pseudo-radial period is more than decades. Most PT analysis methods substitute elliptical flow regime for pseudo-radial, which may lead to the incorrect calculation of key parameters of reservoirs and fractured wells.

In this study, we present the development of an approach for elliptical regime analysis in the production data record for calculation of key parameters of finite-conductivity fractured wells and reservoirs: fracture conductivity, fracture half-length, reservoir permeability, and effective drainage area. This method uses an analytical equation for elliptical flow period and estimation of parameters from the equation. The development is based on more stable deconvolution analysis of production data with variable rate/pressure and more reliable analysis of response function after deconvolution. We present here some synthetic and field cases to demonstrate the results of calculations.
Determination of Fracture Azimuth in Palnikovskoye Field Western Siberia Using Tiltmeter Technology
Authors: Mironov V. S. , Diyashev I. R. , Brovchuk A. V. , Stanley G. R. , Davidson B. M.
Published: October 2008

Knowing the direction or azimuth of the fracture orientation is important in development of a low permeability reservoir with horizontal wellbores. The orientation of the horizontal wellbore will determine if the hydraulic fractures are longitudinal or transverse to the wellbore. The angle of the wellbore to the hydraulic fracture not only affects the recovery factor from the reservoir, but also influences the completion strategy.

The objective of this project was to measure the azimuth of the far field fracture during hydraulic fracture treatments to determine the preferential fracture direction. Prior to the mapping project it was assumed that preferential fracture orientation in Palnikovskoye filed is North-South. Initially the orientation of the horizontal section of the well 436 was designed transverse to the plane of fracture propagation.

Using an array of 42 Surface Tiltmeters the fracture azimuth was measured during the hydraulic fracture treatments performed in the Palnikovskoye Field, Western Siberia. The fracture azimuth measured with the tiltmeters was different than estimated in the field development plan. Therefore, the direction of the horizontal wellbore was altered so the fracture would propagate transverse to the wellbore.

Application of this technology is important in any field where fracture stimulation is important to field development. This was the first deployment of tiltmeter mapping in Russian Federation, several modifications were made for the standard procedures that have been developed from mapping thousand of fracture treatments in other parts of the world. Future fracture treatments in Western Siberia can now be mapped in a more efficient manner.

First phase of the project included hydraulic fracture mapping on three vertical wells to estimate fracture orientation, and use this data to optimize drilling direction of the lateral in horizontal well. The second phase included hydraulic fracture mapping of five stages in the horizontal wellbore.
Gas Drainage Reserves Evaluation Based on Specific Reserves Per Well
Authors: Kolbikov Sergei
Published: October 2008

Gas reserves estimation based on the actual well production data has a particular interest due to big spacing for gas fields. Proposed method is based on the differential equation of specific reserves depletion and uses mostly primary well production data. The method was proved on the results from numerical modeling for different reservoir quality and time dependent well completions.

An example of the method application to an actual field development is described with analysis of drainage volume variations in time. The method allows to calculate the values of drainage volumes as a function of time for individual wells, group of wells, pools. Calculation of drainage reserves of the pool in time allow to verify geologic reserves, estimate an effectiveness of its development.

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