bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzyme Breakers for Chemically Modified Starches
Authors: Battistel E. , Bianchi D. , Fornaroli M. , Guglielmetti G. , Europa P. , Cobianco S. 
Published: December 2007

Abstract
The filter cake removal is still an important concern both for producers and injectors. Mainly in long horizontal completion sections, the cleanup of the filter cake does not always occur spontaneously because sometimes the drawdown in the production direction is not enough. For injection wells a chemical treatment is usually required for an efficient cleanup. Acids and oxidizers may not be applied in high sensitive and/or in low temperature formations but the use of a proper enzyme breaker may lead to an efficient degradation of the polymeric materials preventing great permeability impairment.
The use of linkage specific enzymes instead of mixture of generic hydrolytic enzymes has given in the last years a significant improvement to the breaker performance. Linkage specific enzymes give the possibility to select the specific chemical linkage to be broken within a well defined polymeric substrate. This means that the enzyme activity can be tailored according to the well conditions as well as to the drilling fluids properties and composition. Breaker efficiency is also related to the size distribution of generated polymeric fragments. However, previous studies suggested that although the filter cake degradation seems effective from a fluid loss point of view, the polymeric fragments produced by the filter cake degradation may contribute to formation damage. It is therefore important to gain information on the degradation reaction mechanism by studying not only the enzyme specificity on a particular polymeric substrate but also the chemical nature of the end point products.
The laboratory data presented in this study show that starch specific enzymes such as amylases, cellulases and glucosidases are highly efficient to degrade native and chemically modified (cross linked) starches. The specificity of the enzyme activity on the different polymeric substrates as well as the molecular weight distribution of the degradation fragments were studied and characterized. It was found that each enzyme is not only linkage specific but also regio-specific, that is, it is able to degrade chemically different regions of the starch polymeric chain. The effects of the activity of different enzyme breakers were investigated by filter cake treatment tests.
The Missing Link—Identification of Reservoir Compartmentalization Through Downhole Fluid Analysis
Authors: Elshahawi H. , Hashem M. , Mullins O. C. , Fujisawa G. 
Published: December 2007

Abstract
Reservoir compartmentalization is a major cause of production underperformance in the oilfield. A well drilled into a compartmentalized reservoir will see only part of the hydrocarbon in place over the production time scale. The obstruction to free flow can be sealing faults, fault baffles, pinching out layers, sand lenses or low permeability areas. Although it is recognized that a comprehensive approach to compartmentalization must make combined use of all available rock and fluid data, the case studies in this paper show Downhole Fluid Analysis (DFA) to be one of the most effective techniques in recognizing compartmentalization via fluid signature comparisons and fluid density inversions. Corroboration with geological, petrophysical, reservoir engineering and production data confirms the strength of the DFA technique
Fluid compositional variations must be considered in order to acquire fluid samples representative of the reservoir at large and to devise optimal production strategies. In addition, fluid compositional variations can be utilized as a tool to identify compartmentalization because different compartments are likely to be filled with different fluids. The limitation on use of such techniques in the past has been the need to rationalize the use of wireline sampling to collect and analyze only the necessary samples. In this paper, DFA is shown to be the "missing link." It provides the information necessary to optimize the sampling process and to decide in real time on where sampling is needed without necessarily having to bring all samples to surface.
Application of CHI Modelingsm Using Pulsed Neutron to Create Pseudo-Open Hole Logs
Authors: Reed S. , Quirein J. , Torne J. P. , Morales M. , Bernal J. , Perez M. , Casares M. 
Published: December 2007

Abstract
The Burgos Basin, located in Northeastern Mexico, has sometimes been very difficult to evaluate with openhole wireline tools because over-pressured formations present a problem when trying to reach a balanced borehole condition. This paper will discuss three problem wells, presenting both CHI Modeling results used to solve the problems as well as an alternative method of obtaining resistivity behind casing.
Case History #1 looks at the Fundador Field which has been a particular problem in this area, presenting both drilling and logging difficulties. Because of borehole problems associated with over-pressured formations encountered in this well, it was not possible to acquire openhole wireline logs across the intermediate drilling zone. After the well was completely drilled and cased, a pulsed neutron tool was run across the entire well to assist in the evaluation. By using the resistivity data acquired in the previous section of openhole along with the pulsed neutron data logged in cased hole across the same interval, the missing resistivity data was predicted over the entire intermediate zone. The pseudo resistivity log was created using only the pulsed neutron data obtained across the intermediate zone, processed with the CHI (Cased Hole Interpretation) Modeling program. The final resistivity is also compared to a second method of obtaining resistivity behind casing used by another service company.
Case History #2 uses CHI Modeling to create pseudo openhole logs that were subsequently used as inputs to a volumetric evaluation. The CHI Modeling results are compared to an alternate method of obtaining resistivity behind casing. Testing results are documented to confirm the validity of both the CHI Modeling and the volumetric evaluation.
Case History #3 documents where the CHI Modeling technique was successfully applied through two strings of casing where density data was not available. A comparison to the original openhole logs is presented confirming that this technique is a valid option when additional openhole information is required in a partially logged well.
This paper will discuss the procedures used to evaluate three case histories using CHI Modeling, and present two comparisons with a second cased hole resistivity measurement. Production data is also presented to validate this technique.
The use of pulsed neutron logs to acquire pseudo openhole data is shown to be a valid alternative when drilling conditions do not permit normal data acquisition in openhole; or when additional openhole information is required after the well has been cased.
3D Analysis for Wellbore Stability: Reducing Drilling Risks in Oriente Basin, Ecuador
Authors: Torres Villalobos M. E. , Frydman M. , Casalis D. , Ramirez A. , León M. F. , Villalba E. 
Published: December 2007

AbstractThis work describes a 3D approach that was used to reduce drilling risks and unscheduled events in Palo Azul field. The field is in the Oriente foreland basin (Figure 1), contiguous to the Ecuadorian Andean foothills. A portion of the field presented an unexpected igneous intrusion (laccolite) just above the reservoir formation. The 3D analysis combined 3D seismic information with the 3D structural and geological model to generate a 3D geomechanical model. The mechanical earth model (MEM), relied on onsite real-time monitoring, was used to support drilling decisions, providing predictions of well trajectory, casing points, and mud window.The 3D velocity/amplitude cube, derived from one portion of the 3D seismic program, was used as the base to construct the MEM. To capture the uncommon structural characteristics associated with the complex geological structure, an innovative methodology was developed. Steps included special reprocessing of sequences of the seismic data; structural model reinterpretation; 3D seismic velocity analysis; population of the rock properties in the 3D domain (Geostatistical approach); integration with wireline logs; core measurements analysis; and drilling history review of the offset wells. The real-time geomechanics support allowed making important decisions in time when unplanned events occurred while drilling.This new methodology created a systematic approach to well planning that reduces drilling risks in the development of a complex area. The value added by the integrated team's efforts was demonstrated by drilling the next two wells with significant reductions in costs and nonproductive time. A sensitivity analysis of different well trajectories across fractured zones was performed. Wellbore stability forecasts were compared with reference to the 3D model developed. The results obtained contribute to a better understanding of the mechanics of stress development around a magmatic intrusion and a faulted/folded zone.The methodology developed allows better insight into the parameters that must be included in the 3D MEM creation and wellbore stability forecast for similar environments. This method also serves as a good basis for further development, such as sanding studies, completion design optimization, reservoir studies, and uncertainty analysis.
Rock-Drilling Fluid Interaction Studies on the Diffusion Cell
Authors: Muniz E. S. , da Fontoura S. A. B. , Lomba R. F. T. 
Published: December 2007

Abstract
This paper presents a new set of rock-drilling fluid interaction tests carried out in the diffusion cell using saline solutions and mineral oil on a Brazilian offshore shale. The diffusion cell was designed to apply hydraulic and chemical gradients through shale samples in order to evaluate shale-fluid interaction. The proposed test allows the determination of rock permeability, the coefficient of reflectivity (membrane efficiency) and the ionic diffusion coefficient. These parameters are essential to carry out proper wellbore stability analysis when taking shale-drilling fluid interaction into account. Shale characterization, testing methodology and test results are described. The results showed an average permeability of 46 nD and membrane efficiency less than 2 % for the tested shale.
Role of Asphaltene in Foamy Oil Flow
Authors: Adil I. , Maini B. B. 
Published: December 2007

Abstract
The role of foamy oil flow in cold production of heavy oil has attracted considerable attention in the literature. It has been suggested in several studies that there may be a link between the presence of high Asphaltenes content and the foamability of oil. However, a systematic examination of the impact of Asphaltenes on the performance of solution gas drive, in connection with foamy oil flow, has not been reported. This paper presents an experimental study that addresses this issue.
The objective of this study was to examine whether or not the presence of Asphaltenes has a strong influence on the performance of foamy solution gas drive. To this end, parallel solution gas drive experiments were conducted with a heavy crude oil from Lloydminster area and a de-asphalted version of the same oil. To eliminate the influence of oil viscosity, the original crude oil was diluted with a 50-50 mixture of heptanes and toluene to reduce viscosity to the same level as that of the de-asphalted oil. The experiments were carried out in a visual sand pack that permited observation of bubble formation in the sand.
The results show that the effect of asphaltene content varies with the depletion rate. At higher depletion rates, the oil recovery and production profile of crude oil with asphaltene is different from those without asphaltenes. The presence of asphaltenes, appears to facilitate bubble nucleation, decreases the critical super-saturation and helps in maintaining the dispersed gas flow by suppressing bubble coalescence. However, as the depletion rate declines, the incremental recovery due to asphaltenes diminishes. The two crude oil samples provided similar recovery and production profile when the depletion rate was the slowest one used in this work.
A Review of Matrix Acidizing Sandstones in Western Siberia, Russia
Authors: O'Driscoll K. , Stolyarov S. , Kalfayan L. 
Published: December 2007

AbstractMatrix acidizing of sandstone formations in Western Siberia, Russia has been a technology application that has been largely ignored by operators in this area. Poor acidizing practices and difficult mineralogies have lead to poor results from matrix acidizing treatments applied in the past. With the relative success of skin bypass fracturing treatments and the development of a fracturing stimulation environment within Russia, matrix acidizing has been rendered essentially irrelevant. This paper reviews past and present practices and explores the reasons why matrix stimulation has been largely unsuccessful in Western Siberia. The paper also explores the developing need for matrix treatments, particularly in horizontal wells, and the application of modern acidizing systems and techniques in Western Siberia and the challenges associated with applying these "new" technologies
Gas Segregation in Turning Flows: Analogy with a Gas-Handler
Authors: de Matos A. , Franca F. A. 
Published: December 2007

Abstract
This paper presents experimental data and numerical results on the phase distribution of gas-liquid bubbly flows taking place inside a U-bend pipe curve of square cross-section. The main purpose was to contribute the understanding of analogous processes taking place in gas-handlers. The experimentation was performed with air-water superficial velocities in the range of 0.03 m/s to 0.14 m/s and 0.88 m/s to 2.12 m/s, respectively. The centrifugal force based Froude number (buoyancy/centrifugal force) varied from 0.15 to ~1. To measure the phase distribution, a conductive probe technique was used. The Two Fluid Model was applied to simulate the flow. The numerical algorithm was set-up to account for two turbulence models and other closure relations representing interfacial pressure term and the generalized interfacial force. Results and comparisons are commented.
Effective Reservoir Management of Thin Oil Rims
Authors: Samsundar K. , Moosai R. , Chung R. 
Published: December 2007

Proposal
The Mahogany field in Trinidad and Tobago was developed as a dedicated gas field with reserves of 2.6 TCF to supply gas to the Atlantic LNG Plant in 1999. A major contributor to the gas in place is the 21 sand, which has reserves of 350 bcf. In addition however a thin oil rim (of 60ft) was discovered in this 21 sand. Initial recovery estimates for this thin oil rim was put at 18% with an estimated recoverable reserves of 18mmstb. At that time it was considered to be a marginal development. Approximately 30mmstb later, the development and management of the 21 sand thin oil rim have been a remarkable success story.
The 21 sand is now set to deliver a recovery factor 34%, a best in class in the industry. Since first coming online in early 1999 the production and reservoir management philosophies have changed to respond to the depletion of this thin oil rim. Each phase of the field life, from first oil to mature asset, has provided its unique set of challenges. The Mahogany team has always risen to these challenges through the practical application of new technology and innovative thinking.
This paper will discuss how the production and reservoir management strategy for the 21 sand has evolved along this journey, highlighting the difficulties encountered, actions taken and the success of these interventions. This continuous reservoir management has clearly shown the economical viability of producing a thin oil rim with a large gas cap.
Production Control Through Main-Wells Telemetry
Authors: Distefano G. , Pioli A. 
Published: December 2007

Abstract
This work describe PETROBRAS ENERGIA experience settling a Control Production model based in telemetry on main wells, that impact in meaningful form in the production. Also, this work describe applications, advantages and disadvantages that they can be observed in the experiences accomplished in Puesto Hernandez Oilfield in Neuquen Province in the Argentinean Patagonia
Nowadays, the control of the production using instrumentation and control technology is very common over the oilfields around the world, but in mature fields where a low lifting cost is required, implementation of this technology can not be accomplished without take care in which wells are applied and which not.
In the Puesto Hernandez oilfield, the monitoring of the production is accomplished through the wells telemetry in those wells that are important in the production.
Due to Puesto Hernandez is a mature field with secondary recovery and great quantity of water, the telemetry and control is made on injector wells, wells with electro-submersible pumps (ESP) and in those wells of great quantity of associated net oil like well with Progresive Cavitation Pumps (PCP).
This model in addition to having a very good relationship cost - benefit, focusing the control in those principal vectors of production being an interesting alternative for mature fields, where an integrated control of all the wells can require a high important investment that it is not sustained by this type of fields
Streamline-Based Global History Matching for Geological Modeling Calibration. Application to a Giant Fluvio-lacustrine Sandstones Reservoir Field
Authors: Galacho M. , Vázquez P. , Paci V. , Fernández G. , Canosa C. 
Published: December 2007

Proposal Abstract
The Dynamic Numerical Simulation in Flowlines (DNSFL) is an alternative tool adapted for handling Fine Scale Dynamic Models. DNSLF uncouples reservoir geometry and heterogeneity from transport equations, solving problems dominated by convective flows in a faster and computationally more efficient way. This allows to build Models of greater spatial discretization and, consequently, to better represent reservoir heterogeneity. This feature has been particularly relevant for studying the current case, that consists of great extension reservoirs with considerable facial and stratigraphical variations.
In this paper a workflow is presented, using the above DNSLF properties, in a Global History Matching to develop the "Fine" Scale Geologic Model Calibration and the Definition of a Preliminary Static-Dynamic Model of a giant field of Neuquén Basin, Argentina.
The analyzed field is constituted by fluvio-lacustrine deposits, nine sand-clay cycles (only six of them were modeled), partially connected reservoirs; with 380 actives wells in commingled production and water injection; and with a long and detailed history of simultaneous primary and secondary events.
CPU runtimes around 70 minutes were achieved using a 808860 grid cells Model, with 111 quarterly based timesteps in a Pentium 4 PC, 2.2GHz CPU and 2GB RAM. This showed that it was possible to work with a big Model in short processing time.
With this preliminary model, based on a well-groups-level global history matching, a clear conceptualization of the current primary and secondary production mechanisms, and its productive behavior, was obtained. This reservoir conceptualization was a strong guide for the Global History Matching process.
Geostatistical and Upscaling procedures applied for the definition of the Simulation Model could be evaluated by means of sensitivities analysis on some model parameters.
This preliminary model allowed sensitivities to make recommendations on future work stages, including Geological Model refinements and detailed History Matching.
PDC Bits Run on Turbodrills: The History, Facts and Current Developments
Authors: Seale R. , Conroy D. 
Published: December 2007

Abstract
Over time there has developed a perception that PDC bits are not typically run at high speeds. This perception has propagated from the perception belief that PDC cutters at high speeds will generate enough heat to thermally degrade the cutter or the impact damage at high speeds will destroy the cutter. However, twenty years ago when PDC bits were in their infancy, they were in fact run very successfully at high speeds. Many ROP records in these older fields were drilled with PDC bits on high speed drives. Over time however, PDC bit designs have transgressed to enable better performance when coupled with slower drive mechanisms, such as rotary and positive displacement motors (PDM).
PDC technology has evolved dramatically over the last decade and it has become evident that further substantial developments based on the type of drive mechanism being used will lead to specific designs. This is vital, as different drive mechanisms behave differently, not only with regard to RPM, but also concerning tool plus bit generated vibration, depth of cut (DOC), blade count, cutter density, profile, etc. Analyzing the history of PDC bits run at high speeds and more recently the current designs which are primarily run at lower speeds proves this hypothesis.
The developmental process for further enhancements to PDC bit performance will be two fold. One, to make the PDC bit durable enough to last over long drilling intervals without sacrificing ROP, and two, to base the design on the specific run parameters a particular drive mechanism delivers. Discussions in this paper will detail the history of PDC bits run at high speeds, while addressing the particular design and characteristics required for successfully running PDC bits at high speeds, and finally addressing the research and development currently underway to optimize high speed PDC bit performance.
Effect of Compositional Grading on Reservoir Fluid Characterization: Case Study
Authors: Salehirad Y. 
Published: December 2007

Abstract
The variation of fluid composition with depth in a reservoir is called compositional grading. As depth increases, the mole fraction of light components decreases, density increases and GOR decreases1. In the case of these reservoirs prediction of phase behavior and accurate characterization of reservoir fluids becomes more critical. The reservoir under study is a saturated oil reservoir with a large initial gas cap and a tall column of oil. This fractured carbonate reservoir contains intermediate oil and is produced under natural depletion mechanism at the all of its life time2.
In this work several complete PVT reports from different depths of Asmari reservoir that show definite variations in composition and physical properties (especially saturation pressure), and some other reservoir/field data were used. Two fluid samples were chosen as the most representative samples, one for light samples and another for heavy samples. Also an optimum regression method was applied using a PVT package to characterize the reservoir fluid system. Finally results were prepared to use in Asmari reservoir simulation.