bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impregnated Bits Design and Optimization: An Iterative Method for Improving Drilling Performances. Case Study: Hassi Messaoud Cambrian Reservoir in Algeria
Authors: Benalouane Y. , Mokrani S. , Ziani S. , Zerari D. , Dhina O. 
Published: December 2011

Abstract
Horizontal wells are drilled in Hassi Messaoud oilfield with 6" drains of +/−800m into the Cambrian reservoir using both PDM and Turbine. The multi layered reservoir is +/-3400m deep, mainly quartzite, sandstone and silt. Looking at the rock strength, the confined compressive strength can reach 60 kpsi. Therefore enhancing ROP and durability, when drilling the very hard and very abrasive Cambrian reservoir in Hassi Messaoud, remains one of the major drilling challenges.
This paper describes the iterative approach by which SONATRACH and NOV Downhole Tools Algeria are developing and improving impregnated bits for the very hard and very abrasive formations; for both applications: PDM and Turbine as well. The main objectives are to:
Enhance ROP. Increase durability. Maintain inclination and reasonable dogleg severity. Be able to drill out float equipments and shoe. Fit for both PDM and Turbine application Suit both OBD and UBD application
As all new bit types, a complete field study was carried out, including logs and rock strength analysis, offset wells comparison in order to bring into the light the first version of the design. Four versions of the impregnated bit were tested, so far.
The first version drilled 120m. A second version was tested, with an improvement related to the anti-coring cutters, replacing them by a new generation more wear resistant. The subsequent improvement consisted in increasing blade volume, enabling one of the best ROP achieved in Hassi Messaoud 5.27 m/h. To improve durability, blade volume was increased more. The bit achieved 365 m in one run, with an average ROP of 3.49 m/h.
In the last version developed and tested, an increase in the grit mix was made. The bit drilled an interval of 399 m with an average ROP of 3.89 m/h.
Furthermore, several design considerations have been taken into consideration in order to improve impregnated bits in relation to different types of lithology drilled. The newest design has the same blade volume and the same grit mix as the last bit design recently used in Hassi Messaoud field. However the blades are thicker and the hydraulics / water ways are optimized.
Blowout Control Operations in One of the Iranian Wells
Authors: Makvandi Mehran , Shahbazi Khalil , Bahmani Heaidar 
Published: December 2011

Abstract
Well control is one of the crucial tasks in drilling oil or gas reservoirs. It affects the overall cost of completing a well and in some cases leads to fatalities and numerous damages to environment.
During drilling 12 1/4" hole size at depth of 615m, one of the Iranian wells in the West part of the country was blown out in 2010. The entire drilling rig got fire and due to extreme temperature, substructure and wellhead were buried by mast, rig floor, top drive and drawworks. The temperature at the wellhead was estimated to be almost 950oC and pressure around 900 psi. These added to the difficulty of the kill operation. Moreover, the seepage of gas in the area around the well made the operation for the personnel very difficult.
Two parallel approaches were employed to control the well. They consisted of well capping (top kill) and relief wells (bottom kill). With a close observation of the process and a precise program, the top kill technique worked out and the well was controlled after an unbelievable time period of 38 days. One of the main issues in this operation was the removal of large debris around the wellhead.
In this paper, the details of the steps taken during the 38 days including the engineering design of the both approaches, the preparation of the area, removal of the debris, employing stinger and smoke stack, and the utilization of relief well as a development well are presented.
The Advantage of Incorporating Microseismic Data into Fracture Models
Authors: Shaffner J. , Cheng A. , Simms S. , Keyser E. , Yu M. 
Published: December 2011

Abstract
The Canadian sedimentary basin has long been exploited using vertical well-completion techniques, sometimes producing from multiple formation zones. With recent advancements in horizontal drilling and multistage-completion techniques, horizontal wells are quickly replacing vertical completions as the completion method of choice in many unconventional oil and gas reservoirs. A popular completion method uses openhole isolation packers and ball-activated sliding sleeves to target specific intervals along the wellbore during fracture treatments. This allows multiple stages to be completed in short periods of time because fracture operations often do not have to be shut down to precede to the next stage, compared to the more traditional plug-and-perf completion technique.
Microseismic mapping has proven effective in measuring fracture geometries, such as fracture half-length, height, azimuth, and stimulated reservoir volume. This paper outlines the workflow used in understanding and interpreting the created fracture geometry within individual openhole intervals of the openhole packer completion technique.
The microseismic data proves that created fracture geometry can vary dramatically along the openhole section of a horizontal wellbore. Microseismic mapping also indicates that fractures do not always initiate across from the sliding sleeve port, but can in fact initiate anywhere along the openhole section, exhibiting, in some cases, multiple fracture initiation points. The microseismic-mapping results of this project were used to identify reservoir coverage along the horizontal wellbore as well as identify areas in the reservoir that were not sufficiently stimulated.
By using information gained through microseismic monitoring, fracture models can be calibrated to match actual fracture geometry with modeled fracture geometry, resulting in a calibrated fracture model. Once defined, and using the well production history, the fracture model was used to forecast the future production of the well. Using the calibrated model can help operators optimize the number of stages, stage spacing, and fracture-treatment design to maximize reservoir contact and hydrocarbon recovery while minimizing completion costs.
Methodologies, Solutions, and Lessons Learned from Heavy Oil Well Testing with an ESP, Offshore UK in the Bentley Field, Block 9/3b
Authors: Brennan Barny , Lucas-Clements Charles , Kew Steve , Shumakov Yakov , Camilleri Lawrence , Akuanyionwu Obinna , Tunoglu Ahmet , Hayhurst Steve , Simpson John 
Published: December 2011

Abstract
Due to increased hydrocarbon demand and technological advances, production from heavy oil fields in the United Kingdom Continental Shelf (UKCS) has become possible over the past 10 years. Despite substantial reserves in the UKCS with crudes less than 20° API, most of the activity has been confined to exploration and appraisal drilling. The main reason for the restricted activity has been the high uncertainty of the reservoir and fluid properties. Operational complexities inherent to heavy oil also limit the use of conventional appraisal-well testing technology.
A method was developed to determine the most suitable technology for testing wells with heavy oil using an electrical submersible pump (ESP). The solution was applied in the Bentley field located in the UK sector of the North Sea in block 9/3b, on which final appraisal well 9/3b-6Z was flow tested in December 2010.
The technical challenges included a short weather window, maintaining fluid mobility through the surface-testing equipment, oil and gas separation for metering, obtaining accurate flow measurements, and designing the most appropriate ESP system. A combination of technologies—dual-energy gamma ray venturi multiphase flowmeter, real-time monitoring, and a novel ESP completion—provided a solution that enabled successful well test execution. A multirate test reaching a final stabilized rate of 2900 bpd, with a subsequent period of pressure buildup was accomplished in less than 2.5 days with 10 to 12° API crude. A key lesson was how to obtain the quality of data that would enable reservoir engineers to extract with confidence a productivity index and perform pressure transient analysis for reservoir characterization. This success paves the way for development drilling to commence on the Bentley field at the end of 2011, but also demonstrates potential that can enable new heavy oil field developments.
Fracture Stimulation Diagnostics in Horizontal Wells Using DTS
Authors: Tabatabaei M. , Zhu D. 
Published: December 2011

Abstract
Horizontal wells with hydraulic fracture treatments have been proven to be an effective method for developing unconventional oil and gas reservoirs. During the last several years, fracturing methods have evolved and improved rapidly, however, there still exists many uncertainties in fracture design. Several fracture diagnostic techniques have been developed to improve the understanding of the fracturing process. In this study, after reviewing the application and limitations of the current fracture diagnostic techniques, we describe the application of distributed temperature sensing technology (DTS) as a complementary tool for real-time fracture diagnostics. DTS has enabled us to observe the dynamic temperature profile along the wellbore during the treatment. However, quantitative interpretation of dynamic temperature data is very challenging and requires in-depth mathematical modeling of heat and mass transfer during the treatment.
We have developed a thermal model to simulate the temperature behavior along the wellbore during the treatment as well as during the shut-in period. This model takes into account the effect of all significant thermal processes involved, including conduction and convection.
Examples are presented to illustrate how this model can be applied for fracture stimulation diagnostics. Estimation of the fracture initiation points, number of created fractures, distribution of stimulation fluid along each isolated zone, effectiveness of isolation are the problems that DTS can help us to obtain the answers. This information can be used for more accurate fracture modeling and better estimation of fracture conductivity and fracture geometry, and therefore to optimize the future treatments and also evaluate the well performance.
Effect of Methane Co-injection in SAGD – Analytical and Simulation Study
Authors: Sharma Jyotsna , Moore R. G. , Mehta Raj 
Published: December 2011

Abstract
Steam-Assisted Gravity Drainage (SAGD) is a commercially viable recovery method for oil sands of Athabasca, where other methods have been unsuccessful. In one variation of SAGD, a small amount of a non-condensable gas is added to the injected steam to maintain pressure in the chamber while utilizing the energy in place, reducing steam consumption and providing thermal insulation from overburden heat losses. The role of gas during steam-gas co-injection processes, in terms of its effects on chamber development, bitumen flow rates and heat losses is not fully understood and therefore is the main focus of this work.
A new analytical model for gas injection in SAGD is derived, taking into account the three-phase flow of gas, oil and water in the reservoir. The analytical theory is used to predict the fluid flow rates as well as phase mobility, relative permeability and saturation profiles in the mobile oil region. The theoretical results are replicated by fine grid numerical simulations. Methane was used as the non-condensable gas for the purpose of this study as it is the main solution gas in most reservoirs. It is, however, believed that the findings of this study are equally applicable to other non-condensable gases such as nitrogen, air, helium and others. Fine grid numerical simulations were performed to gain a visual understanding of gas distribution in a SAGD chamber and its effect on in-situ steam quality, overburden heat losses, phase saturations and fluid flow rates. The simulation results support the predictions of the mathematical theory.
The results of the analytical and numerical study reveal that methane co-injection with steam is in general unfavorable in a SAGD operation. The injected methane tends to accumulate at the steam condensation front which lowers the heat transfer rate of steam to the adjacent oil resulting in lower oil production rates and slower growth of the chamber.
Relative Permeability of Coal to Gas (Helium, Methane, and Carbon Dioxide) and Water – Results and Experimental Limitations
Authors: Ham Y. S. , Kantzas A. 
Published: December 2011

Abstract
Relative permeability of coal to gas and water is an important variable in coalbed methane (CBM) reservoir development as it is required for reserve estimation and field production planning. In this study, two coal samples (GP and GS) were used to determine the relative permeabilities using three gases (He, CH4 and CO2) at three different operating pressures (100, 300, 400 psi) and a constant overburden pressure of 800 psi. Both drainage and imbibition curves were obtained. Unsteady state displacements were used.
The petrophysical properties of these coal samples were also measured. The very low absolute permeability of the cores (0.07 mD) required special procedures to minimize errors. The experimental results presented here showed that the relative permeabilities were typically very low for all gases and high for water. The irreducible water saturation showed correlation with the type of gas (non-adsorbable He to strongly adsorbable CO2) and pressure.
It is concluded that coal relative permeability to gas and water depended on the nature of gas and the operational pressure. Relative permeability of coal changed also because of fluid-mineral interactions. It is concluded that the GP and GS samples tended to be more water-wet at higher pressures in the case of the adsorbable gases, viz. methane and carbon dioxide. However, in the case of non-adsorbing helium, higher pressure prevented the influx of water into the larger pores leading to smaller irreducible water saturation.
Accuracy of non-invasive intracranial pressure measurement
Authors: Seddighi Amir , Zadeh Alireza , Seddighi Afsoun , Zali Alireza 
Published: December 2011

AbstractNon-invasive measurement of intracranial pressure (ICP) reduces the complications and cost for both patient and health care systems. Improvement of non-invasive methods has led to development of systems for reproducing continuous, real-time non-invasive ICP signals. So far, non-invasive methods have been tailored for the patients with head trauma. We have used Schmidt’s auto-adaptive method to assess the accuracy of this method for patients after surgery for supratentorial brain tumors. Data from forty patients with the diagnosis of brain tumor operated from 2008 to 2010 were used to estimate the accuracy of Schmidt’s method in our patients. We obtained the model parameters from 30 recordings. We determined the ICP wave form for the remaining patients by both invasive and non-invasive techniques. In the test group, by invasive method, the mean ICP±2SD was 17.1 ± 6.6 mmHg and using non-invasive method, the mean ICP ± 2SD was 16.5 ± 5.4 mmHg. The calculated error was 4.6 mmHg using root mean square errors. The average Pearson correlation between the estimated and real waveforms was 0.92. We believe that application of this method is acceptable for post-operative assessment of ICP in brain tumor patients.
Clinical, radiological, and pathological features of 24 atypical intracranial epidermoid cysts
Authors: Ren Xiaohui , Lin Song , Wang Zhongcheng , Luo Lin , Jiang Zhongli , Sui Dali , Bi Zhiyong , Cui Yong , Jia Wenqing , Zhang Yan , Yu Lanbing , Chen Siyuan 
Published: December 2011

Object
Most intracranial epidermoid cysts typically present with long T1 and T2 signals on MR images. Other epidermoid cysts with atypical MR images are often misdiagnosed as other diseases. In this study the authors aimed to analyze the incidence and the clinical, radiological, and pathological features of atypical epidermoid cysts.

Methods
Among 428 cases of intracranial epidermoid cysts that were surgically treated between 2002 and 2008 at Beijing Tiantan Hospital, cases with an atypical MR imaging appearance were chosen for analysis. Clinical and pathological parameters were recorded and compared in patients with lesions demonstrating typical and atypical MR appearance.

Results
An atypical epidermoid cyst accounts for 5.6% of the whole series. Radiologically, 58.3% of atypical epidermoids were misdiagnosed as other diseases. Compared with a typical epidermoid cyst, atypical epidermoid lesions were significantly larger (p = 0.016, chi-square test). Pathologically, hemorrhage was found in 21 patients with atypical epidermoid cyst and is significantly correlated with granulation (p = 0.010, Fisher exact test). Old hemorrhage was found in 13 cases and was significantly correlated with cholesterol crystals. Twenty-one patients were followed up for 1.3–8.6 years after surgery. The 5- and 8-year survival rates were both 100%. Three patients experienced cyst recurrence. The 5- and 8-year recurrence-free rates were 95% and 81.4%, respectively.

Conclusions
Radiologically, an atypical epidermoid cyst should be differentiated from dermoid cyst, teratoma, schwannoma, glioma, craniopharyngioma, and cavernous angioma. A tendency toward spontaneous hemorrhage is confirmed in atypical epidermoid cysts, and a hypothesis was proposed for spontaneously intracystic hemorrhage in atypical epidermoid cysts. Follow-up confirmed long-term survival of patients with atypical epidermoid cysts.
Reliability, Limit States and Action Factors for ISO 19906
Authors: Thomas Graham A.N. , Bercha Frank G. , Jordaan Ian 
Published: December 2011

Abstract
The new international code ISO 19906 "Petroleum and natural gas industries - Arctic offshore structures" [1] was published in December 2010 after more than nine years of development. ISO 19906 uses the limit states design approach. Compliance is based on ensuring that the action effects arising from each factored action combination do not exceed factored resistances. The partial action factors have been calibrated to reliability targets. This paper describes the philosophy behind the quantification and use of the reliability targets, the definition of the limit states and action combinations, the philosophy of principal and companion environmental actions, and how the calibrated values of the action factors were incorporated in the action combinations.

Introduction
The new ISO 19906 has been developed in Working Group 8 (WG8) of ISO Technical committee TC67/SC7 "Offshore structures". Experts from all arctic nations and from most other nations involved in the design of offshore structures in arctic and cold regions participated in WG8. Consequently, all the arctic nations and all European nations have undertaken to adopt ISO 19906 into their sets of national standards, and ISO 19906 is expected to be adopted worldwide for design of arctic offshore structures. This paper explains the design approach and underlying structural reliability levels in order to assist with application of the code in different ice covered environments and regulatory jurisdictions.
Reliability targets for arctic offshore structures have been used to calibrate the values of partial action factors for use in limit states action combinations, with particular focus on environmental actions arising from sea-borne ice, see Maes and Thomas [2] and OGP report 422 [3]. If these partial action factors are applied to Ultimate Limit State (ULS) and Abnormal (Accidental) Limit State (ALS) action combinations and the resulting action effects do not exceed factored resistances, the reliability targets are deemed to be achieved

Reliability Targets
"Reliability Target" as used in ISO 19906 is expressed as an annual probability of failure which is associated with global structural failure or with component failure leading to global structural failure. In common with the other ISO codes for offshore structures, namely ISO 19900 [4] and its associated standards, commonly known as the ISO 19900-series, ISO 19906 considers both life-safety and environmental protection through specifying three exposure levels, L1, L2 and L3, as defined in ISO 19902. [5].
Experience from Vessels Operating in Ice in the Double Acting Principle
Authors: Vocke Maximilian , Ranki Erkki , Uuskallio Arto , Niini Mikko , Wilkman Goran 
Published: December 2011

Abstract
Most of the traditional icebreakers have had good capability to run astern in ice even if the vessels are not designed for that. The development during the last 16 years has made it possible that running astern could be considered as the main way of operation in heavy ice conditions. The key to this development has been the use of azimuthing podded propulsion, which gives the vessel the benefits of both electric propulsion and excellent maneuverability. During these years there has been a number of vessels designed and built according to this operation principle. A lot of operation experience has been gained during dedicated full-scale ice trials and during practical operation of the ships. The possible propulsion devices today include the direct electric podded drives and mechanical azimuth drives.
This paper concentrates on the evolution of the concept, description of realized projects and operational experience of the double acting principle gained so far including information of the capability of the vessels in different ice conditions.

Background
First the development of the Azipod electric azimuth propulsion took all the attention in the beginning of the 1990ies [1]. However already the possibility of running astern in difficult ice conditions could be seen. Several projects were drafted and vessel concepts developed [2]but finally the Neste Oil's 106000 DWT tanker project built by Sumitomo in Japan in 2003 based on the concept developed by Aker Arctic's predecessor Kvaerner Masa-Yards Arctic Technology, [3, 4]. This project showed without any doubt that a vessel can be good both in open water and ice [5].

Double acting principle
In general it must be said that level ice breaking is only a small fraction of the total sailing time. The reason, why level ice is so often spoken about is that level ice thickness measurement is easy to perform and ship performance in level ice is easy to measure.