bluuebunny/crossref_metadata_2025 huggingface dataset:
Epigenetics of thyroid cancer and novel therapeutic targets
Authors: Russo Diego , Damante Giuseppe , Puxeddu Efisio , Durante Cosimo , Filetti Sebastiano
Published: February 2011

An increasing body of evidence suggests that epigenetic changes (DNA methylation, remodeling and post-translational modification of chromatin) play important roles in thyroid tumorigenesis, as a result of their effects on tumor-cell differentiation and proliferation. Epigenetic silencing of various thyroid-specific genes has been detected in thyroid tumors. These changes can diminish the tumor's ability to concentrate radioiodine, which dramatically reduces treatment options. Epigenetic changes in tumor-promoting and tumor-suppressor genes also contribute to the dysregulation of thyrocyte growth and other aspects of tumorigenesis, such as apoptosis, motility and invasiveness. We provide a brief overview of the mechanisms underlying epigenetic regulation of gene expression and the current methods used to investigate it. This is followed by a review of the principal epigenetic alterations detected in thyroid cancer cells, epigenetic strategies for treating thyroid cancers and data from preclinical and clinical studies (some still underway) on the use in this setting of demethylating agents and histone deacetylase inhibitors.
Occupational Exposure of Dentists to Extremely‐low‐frequency Magnetic Field
Authors: Huang Shu‐Min , Lin Yu‐Wen , Sung Fung‐Chang , Li Chung‐Yi , Chang Ming‐Fong , Chen Pei‐Chun
Published: February 2011

Occupational Exposure of Dentists to Extremely‐low‐frequency Magnetic Field: Shu‐Min Huang, et al. Department of Public Health, College of Medicine, Fu‐Jen Catholic University, Taiwan—

Objective

To compare occupational exposure to extremely‐low‐frequency magnetic field (ELF‐MF) between dentists practicing in dental clinics and those employed in hospitals.

Methods

Thirty‐two dentists who worked at clinics (n=15) and 33 dentists employed at hospital dental departments (n=7) voluntarily provided their informed consent to participate in this measurement study. The study dentists were requested to wear an ELF‐MF dosimeter for some 3 h at work to determine their personal exposure. Spot measurements taken at a number of locations in each dental ofice were used to indicate the work environment exposure level. Additionally, ELF‐MF emitted from common dental equipment was also measured. All measurements were performed with EMDEX Lite meters.

Results

The average environmental exposure to ELF‐MF is higher in clinic dental ofices than in hospital dental departments (0.55 vs. 0.15 µT, p=0.008). Personal dosimetry showed that on average, clinic dentists spent 35.71 and 19.39% of their time at exposures above 0.3 and 0.4 µT at work, respectively. The corresponding igures for hospital dentists were 19.61 and 13.92%. Additionally, ELF‐MF was greater than 0.4 µT at 30 cm from all selected equipment, but the ELF‐MF generally diminished as the distance from dental equipment increased. Uultraviolet air sterilization system produced 3 times as much ELF‐MF as other dental equipment.

Conclusions

This study suggests the possibility of over‐exposure of dentists to power frequency ELF‐MF. Additionally, certain dental equipment may produce ELF‐MF levels greater than 0.4 µT in areas where dentists usually work when treating patients.
A Primer on Winter, Ice, and Fish: What Fisheries Biologists Should Know about Winter Ice Processes and Stream-Dwelling Fish
Authors: Brown Richard S , Hubert Wayne A , Daly Steven F
Published: February 2011

Stream-dwelling fish face highly-variable environmental conditions from fall to winter due to fluctuations in water temperatures, discharge, and ice conditions. We provide an in-depth description of the interactions between these complex environmental conditions and behaviors of stream-dwelling salmonids during winter. Fisheries managers should be aware of the conditions that fish confront during winter in order to make appropriate management decisions. Diverse habitats, including deep pools with low water velocities, coarse rock substrate, and abundant cover, as well as side channels and backwaters, aid in the survival of overwintering fish. The inflow of relatively warm groundwater into the water column can be an important factor affecting winter habitat. Considering the length of winter and the vulnerability of fish during winter, a broad understanding of winter ice process and their effects on stream dwelling fish can aid in the preservation and improvement of winter habitats.
Human Population Increase, Economic Growth, and Fish Conservation: Collision Course or Savvy Stewardship?
Authors: Limburg Karin E , Hughes Robert M , Jackson Donald C , Czech Brian
Published: February 2011

Globally, fishes and fisheries are in severe decline, driven in large part by economic and human population growth. Despite progress in environmental philosophies, legislation, and protection, conflicts between economic/human population growth and fish conservation remain and are intensifying at continental and global scales. The growth of the human enterprise ad infinitum is impossible because of dependence on finite resources; hence policies should leave a margin of error when dealing with the biophysical environment. We suggest a re-definition of Earth stewardship to serve as a conceptual bridge between ecology and economics, recognizing the hubris behind most economic models, which assume that the biosphere is a subset of the economy or else an externality, when in fact Homo sapiens is a species operating within the biosphere. Additional indicators that focus on a different suite of values (e.g., social justice, corporate responsibility, and ethics) would underscore the complexity of economic and human population growth effects on societies and ecosystems, and could help guide us away from unsustainable actions toward those that are “savvier” in terms of co-existence with the resources upon which we depend.
An Expert System Approach to Real-Time Diagnosis of Drill Bit Condition and Preventing its Damage
Authors: Salakhov Tagir R. , Yamaliev Vil U. , Dubinsky Vladimir
Published: February 2011

Introduction of modern computer technologies to drilling control systems opened new opportunities for real-time diagnosis of the drill bit conditions and preventing any further damage. While usage of MWD systems equipped with corresponding downhole sensors significantly increases the efficiency and accuracy of downhole drilling monitoring and diagnosis, there remains a niche in the market for much less expensive drilling monitoring systems based mainly on the surface measurements. These measurements usually include such parameters as static and dynamic hook load, stand pipe pressure measurements, surface torque, differential mud flow rate, and possibly some surface vibration data.

The expert system approach suggested in this paper offers an efficient way of combining some basic measurements provided by the surface sensors for early diagnosis and prevention of possible damage of the downhole drilling equipment, primarily the drill bit itself. This paper addresses both aspects of the proposed methodology – the system configuration and some details of the data analysis algorithms. The fundamental theory behind the proposed approach is based on certain elements of fractal analysis as well as artificial neural networks. A huge amount of data needs to be collected and organized in a database to cover different operational and varying drill bit conditions.

The data analysis is performed for multiple time frames in order to identify both a big picture and more specific details. Application of the fractal performances allows obtaining important practical information during standard field operations, without conducting a special controlled field experiment.

We present some real field data examples used for training our model and assessing the current drill bit conditions by using the proposed methodology. We believe that this methodology opens new opportunities for real-time drilling optimization that can be efficiently implemented within the scope of the existing drilling practice.
Classification of Oil and Gas Reservoirs Based on Recovery Factor: A Data-Mining Approach
Authors: Sharma A. , Srinivasan S. , Lake L. W.
Published: February 2011

Rigorous flow simulations to obtain estimates for recovery are infeasible given many combinations of reservoir and development scenarios. This motivates an alternative approach to calibrate likelihood of recovery using reservoir datasets. A proxy model relating reservoir, well, and operational factors to the ultimate recovery factor could guide subsequent field-scale flow simulations. There are two reservoir datasets that we have used for the classification and estimation of ultimate recovery: the Tertiary Oil Recovery Information System (TORIS) database for oil reservoirs and the Gas Information System (GASIS) database for gas reservoirs.

For oil reservoirs, 19 predictor variables were used to estimate the ultimate recovery factor. Cluster analysis was followed by linear regression analysis within the identified clusters that provided a reliable deterministic model for predicting the recovery factor. The linear regression model was compared with the empirical correlations given by Arps et al. (1967) and Guthrie et al. (1995). Analysis showed that geological and engineering parameters are correlated and both are important to the prediction of recovery factor. Later, we used a naive Bayesian approach on principal scores of the predictors for the calibration of recovery factor likelihood. The likelihood function of the recovery factor for oil reservoirs provided the uncertainty in recovery. It was computed to be multimodal and non-Gaussian.

In case of the gas reservoirs, good deterministic estimation was achieved by introducing cluster analysis to the data. The robustness of the linear regression model was tested on tight gas reservoirs. The likelihood of recovery factor was multimodal and non-Gaussian. It also indicates that gas reservoirs are less complex.
Vital Role of Nanopolymers in Drilling and Stimulations Fluid Applications
Authors: Singh Subodh , Ahmed Ramadan
Published: February 2011

Production of hydrocarbons from conventional, as well as unconventional resources, is becoming increasingly more difficult and expensive. Drilling fluid stability and performance in deeper, high-temperature high-pressure (HTHP) formations are still problematic, even for environmentally safer synthetic fluids.

Recent research has demonstrated that nano fluids have attractive properties for applications where heat transfer, drag reduction, formation consolidation, gel formation, wettability alteration, and corrosive control are of interest.

Nano fluids can be designed by adding nano-sized particles in low volumetric fractions to a fluid. The nano particles modify the fluid properties, and suspensions of nano-sized particles can provide numerous advantages. Nano-sized particles can impart sedimentary, thermal, optical, mechanical, electrical, rheological, and/or magnetic properties to a base material that can enhance its performance.

This paper presents an extensive literature review to assess the application of nanotechnology in drilling and completion applications and evaluates the potential technical and economic benefits that this technology might provide to the industry.
Improving Efficiency of Coiled Tubing Operations on Vankor Field
Authors: Sitdikov Suleyman , Von Hertzberg Bert , Zagranichniy Stanislav
Published: February 2011

Coiled tubing is commonly used as an intervention tool for treatment delivery in long horizontal wells. As with any intervention tool, however, coiled tubing has operational limitations. Depending on the diameter of the horizontal sections and the well trajectory, accessing laterals greater than 1,000 m is often problematic or not possible due to helical friction lock-up. The well profiles in Vankor, a new frontier oil and gas field in East Siberia, are designed with a reverse bend in it allowing the horizontal section of more than 1,000 m the wellbore to be directly beneath the wellhead. There is an 800 m thick layer of perma-frost which is coupled with extremely low reservoir temperatures that complicates the intervention causing the wax precipitation in tubing.

Conventionally, it is possible to change the geometry of the intervention (CT OD), optimize the string design, utilize lubricants (metal to metal friction reducers), straighten the coiled tubing string, use downhole tractors and vibration tools. The use of different methods yields incremental reach of 5 – 20% in some cases. This paper highlights an approach that has been implemented in Vankor field to enable the coiled tubing intervention to access the horizontal lateral with the methods of string design optimization and utilization of downhole BHA vibration.

The coiled tubing string design requires the special attention for successful intervention in horizontal and extended reach wells. The optimized tapered string allows increasing the advance of coiled tubing to 5-15% compared to traditional design.

The vibrator tool can effectively increase CT access to the extended reach hole by reducing the implied friction coefficient of the wellbore up to additional 10 %. The tool is actually delaying the helical shape and reducing the number of coiled tubing contact points dragging on the well bore.

This paper reviews the engineering and operational challenges related to utilizing coiled tubing in Vankor field and the solutions required to overcome these issues.
Investigation of Oil-Trapping Mechanisms in Deepwater Gulf of Mexico
Authors: Li Xin , Lach Joseph , McMillen Kenneth
Published: February 2011

Oil recovery depends on geologic complexity – structure, stratigaphy and deposition – and rock and fluid properties. The work reported here illustrates the oil trapping mechanisms for 450 reservoirs in 83 mature deepwater fields in the Gulf of Mexico (DW GoM). The evaluation of trapped or forecast remaining was a precursor to determining improved oil recovery concepts as part of a project for the group RPSEA (Research Partnership to Secure Energy for America).

Neogene age reservoirs in the DW GoM are characterized as over-pressured with generally good rock and fluid properties. Drive energy is typically from a combination of rock compaction with some assistance from aquifer influx. Only a few engineered water injection projects have been implemented and no gas injection has been used to add drive energy. Oil recovery is reasonable with an average of 32% of original oil in-place (OOIP) with a 95% confidence and range between 21% and 42% of OOIP.

Several field examples of estimated trapped oil mechanisms are used to illustrate typical reservoir performance and the calculation methodology. Trapped oil is determined for the categories of capillary bound, non-connected to wells, high abandonment pressure or low abandonment water cut, limited drive energy, and poor sweep. The results indicate the improved recovery initiatives should focus on aqueous phase injection, pumping and artificial lift technology, and well and intervention technology.
Human Decision-Making in the Oil and Gas Industry
Authors: Mackie S. I. , Begg S. H. , Smith C. , Welsh M. B.
Published: February 2011

Business under-performance in the upstream oil and gas industry, and the failure of many decisions to return expected results, has led to a growing interest over the past few years in understanding the impacts of current decision-making tools and processes and their relationship with decision outcomes. A primary observation is that different decision types require different decision-making approaches to achieve optimal outcomes.

Optimal decision-making relies on understanding the types of decisions being made and matching the type of decision with the appropriate tools and processes. Yet the industry lacks both a definition of decision types and any guidelines as to what tools and processes should be used for what decisions types. It is argued that maximizing the chances of a good outcome in real world decisions requires the implementation of such matching. Comparing a "real world" decision-making model used by the upstream oil and gas industry with a theoretical model yields various prescriptions for optimal decision-making.

Further implications are examined in relation to a variety of oil and gas decisions by documenting both a definition of decision types as well as guidelines to what decision-making processes should be used with what decision types. The paper looks at a comparison between what tools and processes companies are now using for some of the decision types and compare these with what they should be using in order to lead to optimal decision-making.
Acid-resistant Foamer Used to Control Gas Breakthrough for CO2 Drive Reservoir
Authors: Liu XiangBin , Wang FengShan , Zhang ZongYu , Xin Wang , Zhou WanFu , ZhongLian Han , HaiJing Wang , DeFu Zou , Guo Li , HaiRong Fu
Published: February 2011

Due to the prone gas breakthrough in CO2 immiscible flooding, the development effect was poor. In order to block off gas breakthrough channels, improve gas injection/production profile, and increase sweep volume & efficiency, two different acid-resistant and oil-resistant foam systems were developed according to reservoir characteristics and fluid features in Daqing peripheral oilfield. The foam system swelled 4times, the half-life was 83h, and core resistance coefficient was 120 under the condition of PH=3 and 60% oil saturation. Filed test results showed that the systems can effectively block off gas channels, decrease inefficient circulation, increase CO2 sweep volume & efficiency as well as displacement efficiency. The tested well gas injection pressure rose by 3.5MPa after resuming injection. Dominant injection direction changed obviously and gas sweep area increased enormously. Connected wells’ gas oil ratio decreased with an average valid period of 11 months and cumulative oil increment of 467t. This gas breakthrough blocking off technology is suitable for gas flooding development of Daqing peripheral oilfields which have ultra-low permeability, and has the advantages of high efficiency and low costs. It provides a sound technique support for gas flooding development.
BHA and Drill String Fundamentals: Technology Training for Beginners
Authors: Wakefield Sarah , Pigusch Katrina
Published: February 2011

In the industry, there is an abundance of highly technical engineer-based training available on drill string design, but a different approach is required for employees that simply need a basic understanding of drill string principles. Some trainees and shop-hands have a need for a basic understanding of bottom hole assembly (BHA) fundamentals and drill string design in order to build a foundation for future training courses as well as eventually make informed choices on the job.

To meet this need during our training course, we chose five basic topics that covered BHA fundamentals and drill string design, and we covered each of the five topics using current adult learning fundamentals. The content we chose was: BHA components and assemblies, drill pipe anatomy and identification, connection science, failure mechanisms and basic drill string design. Exercises designed specifically for the content required students to label the critical pin and box area of a connection, create posters on failure mechanisms and calculate the maximum overpull for drill pipe, among other things. Our objective was to provide training that not only addressed the necessary technical information, but also presented the content in a way that was geared towards learning and retention.

Pre and post test results, along with course evaluations, offered evidence this introductory level course provided the students with an effective foundation of knowledge. Most students left the course with a better understanding of BHA fundamentals and were able to describe specific ways that the course would help them do their jobs better. Information provided in the paper can benefit trainees or shop-hands seeking a basic understanding of drill-string principles. The information is also applicable to training departments industry-wide looking to develop introductory technical training.
Finding the Best Alternative for Plugging Problem in MEG Regeneration Unit Using AHP Method
Authors: Khorrami Z. , Karimkhani B. , Farhadi F.A.
Published: February 2011

MEG regeneration and injection unit regenerates aqueous MEG. The main goal of this unit is approaching desired MEG concentration whereas MEG loss via removed water is a big issue. Circulating glycol is polluted with Ca++ and Mg++ which forms carbonate scale and causes plugging of pipe lines, filters, lean/rich exchanger, still column packings and reboiler tube bundle and decreases their efficiency, consequently increases MEG loss via top product. Different alternatives exist according to similar experiences around the world. Using specific criteria and AHP (Analytical Hierarchy Process) method priority of these alternatives has been found. Results are as following:Increasing number of filtersUsing parallel filtration systemReplacing charcoal filters in short periodsIncreasing flow rate in case of no operational problem

Considering all constrains, final recommendation includes improvement of operational conditions, regular cleaning of equipments and enhancing filtration system.
Effective Well and Reservoir Management Reverses Production Decline in a Brownfield Cluster in South Oman – A Case Study
Authors: Mirza M. , Al Saadi Hassan , Effendi Andryas , Hafidz Fidi Abdul , Anwar Zul
Published: February 2011

A complex brown-field cluster in South Oman showed decline in production despite aggressive level of development and infill drilling over the last few years. This cluster has more than 18 fields, with 10 of them are producing. Different major reservoirs distributed across several stratigraphic horizons and contains moderate to highly viscous oil (10 to 400 cP). The reservoirs comprise unconsolidated fluvial, fluvial deltaic and glacial sandstones of Palaezoic age. The geologically complex field due to large number of faults and fractures has been on production of more than 15 years and has been developed using vertical and horizontal wells during different phases of development. One water injection well is in operation in one major field for more than 5 years.

Reservoir surveillance and management in this cluster poses a formidable challenge due to:

- Significant well-stock (more than 150 wells) of different types (vertical, deviated, horizontal, multi-lateral) - Problem associated with data acquisition as all the wells are completed with pumps (beam pump, progressive cavity pump and electrical submersible pump) and most of them are completed with some sand-control devices - Un-efficient water injection management - Logistically problems associated with large distance between the Well and Reservoir Surveillance and Production team at company office and the operational team at field location.

The case study presented in this paper describes how a sustained well and reservoir surveillance and management strategy implemented across the entire value chain starting from the planning to operation stage in this cluster could not only arrest but literally reverse the well and field production decline trend using the existing well stock. The paper clearly illustrates that success of reservoir surveillance and management rests not only on the application of right technology but more on close integration among various disciplines in a cohesive work environment.
A Reservoir Simulation Model for Ground Freezing Process
Authors: Shen Chonghui , Mckinzie Bill , Arbabi Sepehr
Published: February 2011

Ground freezing technology has been applied in Colorado oil shale formation to control ground-water flow for Shell's In-situ Conversion Process (ICP). The circulation of coolant through subsurface pipes causes the formation water to freeze and plug off permeable channels, and results in an impermeable flow barrier (also known as a freeze wall). The freeze wall will be used to isolate the developing area from the undeveloped area for ground-water protection and product containment. Because the ground freezing in our application is intended to be operated in conjunction with ICP, there is a need to develop an integrated reservoir simulation model with the capabilities for both freezing and in-situ conversion processes. This paper describes the development of a reservoir simulation model for ground freezing process. It also discusses some of the simulation challenges of ground freezing process in a reservoir simulator. The developed model has been calibrated with data from a 2003 field test and used to assess the sensitivity of freeze wall closure time with respect to freeze-hole spacing, initial formation temperature, ground water flow strength (hydraulic conductivity and gradient), and water salinity etc. The simulation results revealed that the freeze-wall closure time depends strongly on freeze-hole spacing, water seepage rate and formation temperature.
A Practical Approach for Calculating EOS Coefficients
Authors: Ahmed Tarek , Meehan D. Nathan
Published: February 2011

Cubic equations-of-state (EOS) mathematically relate pressure, volume, and temperature. These equations describe the volumetric and phase behavior of single components and mixtures requiring only the critical properties and acentric factor of each component including the plus-fraction. For pure compounds, the required properties are well defined; however, nearly all naturally occurring gas and crude oil fluids contain heavy fractions that are not well defined. These heavy plus-fractions are mixtures of hundreds of paraffinic, naphthenic, aromatic, and other organic compounds that cannot be discretely identified and described. These heavy fractions are often lumped together and called the "plus-fraction" (e.g. C7+ fractions). Adequately characterizing these undefined plus fractions in terms of their critical properties and acentric factors has been long recognized as a challenge in compositional analysis using EOS models. Changing the characterization of the plus fraction can have a significant impact on the volumetric and phase behavior of a hydrocarbon mixture predicted by EOS models. In applying EOS in compositional modeling and PVT analysis, empirical correlations are used to estimate critical properties and acentric factors of the plus-fractions. Coefficients for these empirical expressions were generated by matching critical properties of pure components; however, the applications of these empirical relationships are extended to estimate the critical properties the plus-fractions.

This paper presents a practical approach for calculating EOS parameters "a, b, and α" of the plus-fraction from its readily available measured physical properties, i.e., molecular weight "M" and specific gravity "γ". Our objective is to improve the predictive capability of EOS models. A new model was developed based on the Peng-Robinson Equation of State "PR EOS" and with the modification as outlined in this paper. The predictive capability of the modified PR EOS is displayed by matching a set of laboratory data on several crude oil and gas-condensate systems. Performance of the proposed method was also compared with predictive PVT results generated by two commercial compositional simulation models. Additional validations were made by comparing results from applying the proposed approach with those of Coats and Smart4 regression methodology with PR EOS.
An Investigation of Heavy-Foam Properties for Offshore Drilling
Authors: Liu Chunlei , Zhang Nan , Guo Boyun , Ghalambor Ali
Published: February 2011

A unique problem in drilling oil and gas wells offshore is the narrow window between the formation pore pressure and fracture pressure. The current drilling practice with constant-density drilling fluids requires excessive casing programs and larger, more expensive rigs to drill offshore wells. Although different techniques, such as dual-gradient drilling, have been used to ease the problem, they are limited to certain geological conditions. This study investigated the properties of heavy foams that may be used in offshore drilling to solve the problem.

In this study we performed a systematic investigation of heavy foams which are defined as the foams generated using weighted water and brine. Our study focused on rheological modeling, polymer selection, and foam properties. This paper presents our experimental results from 5 heavy foam systems namely water-barite-nitrogen system, water-hematite-nitrogen system, water- KCl-nitrogen system, water-CaBr2-nitrogen system, and water-CaBr2-barite-nitrogen system. We conclude that all of the investigated heavy foams behave as Bingham-Plastic fluids with an exception that the heavy foams from the water-barite-nitrogen system show Power-Law behavior. The best heavy foams from the water-CaBr2-nitrogen system were generated using Guar Gum as viscosifier. Foams from the water-CaBr2-nitrogen system have better stability and quality than those from the water-KCl- nitrogen system. Data from this study may serve as a base for selecting heavy foams in drilling offshore oil and gas wells.
New Method to Deconvolve Well-Test Data Under Changing Well Conditions
Authors: Houzé Olivier , Tauzin Eric , Allain Olivier
Published: February 2011

Recent work on deconvolution allows well test interpretation engineers to combine several shut-in periods into a single, much longer deconvolved response, allowing identification of boundaries overlooked in the analysis of these individual shut-ins.

Initial algorithms by von Schroeter et al (2004)1 require the individual shut-in responses to be consistent in terms of wellbore storage and skin. An alternate method by Levitan (2005)2 allows inconsistent early time responses to be combined, but requires multiple deconvolutions and an iterative search of the reservoir initial pressure.

The new suggested algorithms waive the von Schroeter et al limitation without the drawbacks of the Levitan method. These algorithms are illustrated with real data coming from permanent gauges. This paper also points out the remaining limitations of the deconvolution process.

This paper was written as a technical communication. It was made a short as possible in order to complement past publications1-2 on the subject. Readers are invited to use these publications for the details of the equations and a more exhaustive list of references.
High Resolution Reservoir Monitoring using Crosswell Seismic
Authors: Nalonnil Ajay , Marion Bruce
Published: February 2011

Crosswell seismic is an emerging technology which provides highly detailed images of the subsurface at the reservoir scale. The technology has the potential not only to delineate complex structure but also to monitor the effectiveness of hydrocarbon recovery and CO2 sequestration strategies.The technique employs tomographic surveying, whereby a transmitter and receiver are deployed in separate wells. With this setup, interwell velocity profiling and structure can be obtained from direct wave and reflection processing respectively.

With hydrocarbon recovery and CO2 sequestration becoming more prominent in the oil and gas industry, the ability to monitor the efficiency of these strategies is paramount. In this paper, two case studies of crosswell seismic surveying are discussed with the focus on high resolution imaging and monitoring during CO2 injection for improved oil recovery and sequestration respectively. A brief description of the measurement theory and its capabilities is provided, followed by a description of the processing workflow and finally a discussion of the acquired results.

These two cases discussed demonstrate that crosswell seismic was able to successfully monitor the injection through velocity profiling in time lapse and provide answers as to why and how the flow has occurred through interpretation of the crosswell reflection seismic section. The results clearly show that crosswell seismic could significantly reduce the uncertainty and risk associated with injection processes for both improved recovery and sequestration.
A Decision Support System for Cost-effective Assessment of Sand Production Risk and Selection of Completion
Authors: Rahman Khalil , Khaksar Abbas , Kayes Toby
Published: February 2011

An early study of sand production prediction and management is increasingly becoming an important part of an overall field development study. This is because the petroleum industry is expanding its production operations in more challenging unconsolidated rocks and depleted reservoirs. Complex well completion architectures that are sand prone are also increasingly used. This requires a reliable sand production prediction method that can model the sand production risk over life of the field. Reliable sand production assessment methods are essentially based on geomechanical approaches that integrate in-situ stresses, reservoir pressure and its depletion trend, rock strength, well trajectory, completion type and planned drawdown. Use of grossly empirical, often unreliable, methods to infer sand production risk could result in either unnecessary an upfront sand control cost or sand management cost during production due to unpredicted sanding.

This paper demonstrates by application to a field case in South East Asia how to develop and use a decision support system for credible sand production assessment and completion selection. Once a geomechanical model is built and sand production assessments have been carried out for a few wells by a robust sand production prediction model, the knowledge and information can be converted into a decision support system for new wells in the field. Provided the field Earth stresses and the reservoir pressure are applicable, the system then needs only a log-derived rock strength profile for sanding evaluation and decision making for new well trajectory and completion configuration. Using the existing geomechanical model, calibrated og-derived rock strength profiling and field supported sanding prediction, a simple flow chart is developed to assist well engineers to decide the completion type by taking into account the risk of sand production and hole collapse during production. The availability of such a decision support system assists the well and production engineers to follow a quick, cost-effective, simplified but sound approach for sand production assessment and completion selection as opposed to being grossly empirical, or too rigorous.
Integrated PoF and CBM Strategies for Improving Electronics Reliability Performance of Downhole MWD and LWD Tools
Authors: Zhan Sheng , Ahmad Izhar , Heuermann-Kuehn Ludger , Baumann Joerg
Published: February 2011

Electronics that operate under downhole drilling conditions, such as printed circuit board assemblies (PCBAs) in measurement-while-drilling (MWD)/logging-while-drilling (LWD) tools, can experience a significant amount of extremely high temperatures and vibration stresses over their lifetimes, which may induce failures during deployment. This study demonstrates the methodologies on integrated physics of failure (PoF) for improving the reliability performance of MWD/LWD tools.

PoF discussed in this study is for identifying and understanding failure modes, failure mechanisms, and failure sites of drilling electronics for their particular life-cycle loading conditions. This PoF study is a systematic methodology, integrated with data acquisition technologies, conditional-based maintenance (CBM) and failure analysis techniques to actualize the real-time life management on improving maintenance decisions, and providing guidance to incorporate reliability into the well-planning and operation processes, thus enabling monetary savings for the oil company and the MWD/LWD service provider.

Through data acquisition technologies, the drilling environmental profile is captured by the sensor and recorded in the memories of the MWD/LWD tool. Based on the drilling environmental profiles, the drilling stress and loading conditions are retrieved and calculated for estimating the remaining life of the drilling electronics. With CBM strategy, electronic units assessed with high risk results are excluded from being deployed to the field to avoid potential failure in the field. PoF is followed up to investigate the failure mechanism of units returned from field. Real-case studies on MWD/LWD tools operated onshore the U.S. and in the Asia Pacific region are presented.

The objective of this study is to enable real-time electronics reliability assessment on MWD/LWD tools under their actual application conditions. When combined with PoF models, CBM strategy is capable of making continuously updated predictions on the remaining life of electronics based on the in-situ drilling environmental and operational conditions.
Elliptical Geometry Model for Sand Production during Depletion
Authors: Aadnoy B.S. , Kaarstad E.
Published: February 2011

Sand production is a key issue when selecting completion solutions. Not only the immediate choice of technical solution is affected, but also the long term plans for workover operations and the choice of Intelligent Well Systems (IWS) for mitigating the sand production problems.

In this paper we investigate the effects of in-situ stresses and rock properties combined with the optimal well geometry. The well is initially circular, but the collapsed state should be modelled with elliptical geometry. The volume of sand produced in a depletion phase is then computed from the equilibrium state of the borehole. The models are explicit analytical and simple to use.
Laboratory Development and Field Application of Novel Cement System for Cementing High-temperature Oil Wells
Authors: Wan X. , Zhang H. , Li Y. , Yang Y. , Shan H. , Xiao Z.
Published: February 2011

Cementing high temperature exploration wells present a number of challenges to well construction engineers. High bottom hole static temperature (above 100°C), very low pump rates and excessively long job times due to the constraints imposed by tight annular clearances and the use of heavy, viscous drilling muds and cement slurries, and formation complexities (salt layer, high leakoff, unstable formations) all contribute to the operational risks not only during placement of the cement slurry in the wellbore, but also later to the set cement sheath during the life of the well. Various cement systems have been applied with unsuccessful results.

A new cement formulation developed has helped to resolve the problems encountered in cementing these exploration wells and eight jobs have been completed in the field with great success. Synergistic effect between the new retarder and fluid loss control additive improve the system performance significantly such as low fluid loss rate, minimal free water, proper rheology, predictable thickening time, high resistance to salt contaminations, and no adverse effect on set cement strength. An effective laminar flow spacer was also developed and used to displace drilling muds effectively to enhance its placement and improve the cementing bond.

This paper will describe details of thorough and systematic laboratory development of the new cement system and present case histories to document its effectiveness for cementing high temperature exploration wells.
A Practical Approach to Evaluating Drilling Projects
Authors: Nkwocha Chimerebere
Published: February 2011

In the past estimating drilling performance or project performance for well engineering projects has been carried out in a combination of ways such as accounting for time based events that eventually result in costs or financial relationships. It is rather unfortunate, but the requirement within the industry still remains the quantification of projects and project costs as a function of cost or financial exposure. In most cases the situation is one of which inherent peculiarities within the project, though not man-made, are somewhat relegated to the background during project evaluation. Frequently this is due to the inability of project teams to quantify the parameters required to adequately establish key contributory factors responsible for overall project performance. In this paper I have tried to postulate a rather straight-forward method of establishing performance metrics without so much as deriving complex equations an engineer may find highly impossible or cumbersome to fully regularize to provide any meaningful relationship from one well to the other. The relationship model developed tries to relate both operational and financial efficiencies as a project/well specific performance factor referred to as TPI, i.e. the "Technical Performance Index". The TPI is specific to each well and a regional average provides an indication for overall performance. This paper does not consider completion operations or any operation related to well testing or workover operations at this moment but focuses primarilly on dry-hole operations up until the well is programmed for completions.
Improved Polymer-Flood Management Using Streamlines
Authors: Clemens Torsten , Abdev Joseph , Thiele Marco
Published: February 2011

Recently, modern streamline simulation has been extended to polymer flooding. In this work, we extended the applicability of streamline simulation further to efficiently manage polymer injection projects. We first present our methodology and then demonstrate the applicability of our approach using a Romanian field as an example. Owing to the price of polymers, an optimised injection strategy is crucial to minimise costs, maximize sweep, and thereby ensure profitability of a polymer flood.

The biggest advantage of streamline simulation compared to traditional finite-difference modelling is that polymer floods can be optimised on a well pattern basis. By being able to plot cumulative oil produced as a function of polymer injected for an individual well pattern, underperforming patterns—injectors and associated offset producers—can easily be indentified and rates, concentration, and slug size modified to improve the local efficiency of the flood. In this paper we introduced a new metric: the polymer injection efficiency as a function of time for each pattern and show how it is central to contain costs while improving oil recovery.

We demonstrate our management methodology on a Romanian oil field that has been operating since 1961 with 21 injectors and 136 producers. We show that the utility factor (mass of polymers injected per volume of incremental oil produced) can be reduced while sustaining oil recovery. We conclude with a discussion on streamline simulation as an enabling technology for reservoir management decisions for polymer floods and floods in general.
The First 16-in. PDC Bit and RSS Application in Vietnam
Authors: Van Hung Le , Van Minh Vu , Heisig Gerald , Heuser William
Published: February 2011

For the development drilling phase of Ca Ngu Vang (Golden Tuna, Block 9-2, offshore Viet Nam), the 17 ½-in. section was deepened, compared with previous wells, to better suit the well design. The technological challenge centered on drilling the interbedded sand and shale Con Son sequence through the Bach Ho Shale, to total depth (TD) the section in the early Miocene with one drill bit and bottomhole assembly (BHA) at an economically viable rate of penetration (ROP).

Operator Hoan Vu JOC previously tested several different drilling methods with limited success, including employing a roller cone drill bit on rotary and later a PDC bit in tandem with a mud motor. This paper discusses the post-offset well analysis and the cooperative effort between the operator and service company that resulted in the introduction and successful implementation of a new 16-in. PDC bit and rotary steerable system (RSS) with real-time vibration monitoring. The new BHA combination drilled the section in one run, surpassing all ROP expectations, while meeting all directional drilling objectives. Following the successful run, which was the first application of a 16-in. PDC bit and RSS tandem in Vietnam, the bit exhibited minimal wear.

The authors examine the application and share the technical and operational lessons learned with recommendations for optimizing performance in future similar applications.
Blocked Isocyanate Fluid System for Water Shut Off Application
Authors: Mohd Shafian Siti Rohaida , Hassan Abdul Azim , Ismail Suzylawati , Teng Ling Kong , Irawan Sonny
Published: February 2011

Application of gelled polymer solution containing one or more reactive component of a polymer and a crosslinker has been widely used as water shut off fluid. They were used with the ability to reduce water production by two main performance criteria. First by reducing water relative permeability more than oil permeability using disproportionate relative permeability reduction (DPR) or relative permeability modifier (RPM), and secondly by totally block the fluid flow/total shut off using strong gels.

The current invention is related to polymerization process for total water shut off. In this study blocked isocyanate was identified and chooses as an active component in the fluid system. The polymerization process was initiated when the temperature of the injected zone reached the deblocked temperature (~90°C and above). The blocking agent (contain in the fluid) starts to unblocked and allow the isocyanate to react with other component in the system to form hard solid polyurethane. This polyurethane will form a barrier to totally block the flow of formation fluid during production.

This paper presents the performance of a blocked isocyanate water shut-off fluid designed for PETRONAS field. The newly designed fluid is one component system which works in the temperature range between 80 – 120°C. The effects of temperature at 80, 95 and 120°C and aging of core flooding experiments in water saturated condition, the treated sandstone Berea cores showed high extrusion pressure of 100psi/inch. This system is applicable for total water shut off where at residual oil saturation and irreducible water, high extrusion pressure was achieved.
Assessing Stability of Reservoir Bounding Faults While Drilling
Authors: Fernández-lbáñez Fermín , Castillo David , Firth Andrew , Courteney Steven
Published: February 2011

Drilling experience and well data acquired during field exploration and development can be used to characterize the geomechanical properties of faults and its implications on risk assessment. We have built a geomechanical model based on the available logging and drilling data, along with failure observations from different offset wells. Modeling results have revealed a present-day stress field characterized by a transitional normal faulting to strike-slip stress regime. The large, seismically resolvable faults have been brought into a three-dimensional numerical geomechanical model to determine the stress conditions near these faults. The stress tensor is here combined with a failure criterion to assess the potential for fault instability.

Drilling through some of these faults is required to reach the main field targets. We have investigated the effective stresses acting on each fault surface in order to determine whether these faults are active under the current stress field. To understand the risk of losses while drilling, we have estimated the required downhole mud weight pressure to induce shear failure along the main fault surfaces. None of the faults considered in this study are active; however, drilling through these structures may reactivate some fault segments. MWD data has been successfully used to validate the model and highlight the importance of fault stability assessment to help control bottom hole pressures and mitigate the risk of losses while drilling.