bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlating optical coherence tomography images with dose distribution in late oral radiation toxicity patients
Authors: Davoudi Bahar , Bizheva Kostadinka , Wong Alexander , Dinniwell Robert , Levin Wilfred , Vitkin Alex
Published: August 2014

Background and objective:

Late oral radiation toxicity occurs in about half of the patients who undergo head-and-neck radiotherapy, reducing the quality of life drastically. The total delivered radiation dose has been shown to be one of the predictors of these late complications. To demonstrate this, the studies carried out so far have used either visual observation together with symptom-based scoring systems or histology to evaluate the tissue response. However, the former lacks imaging information on tissue subsurface and the latter is invasive and exposes the patients to additional risks. Therefore, there is a need for a non-hazardous, non-invasive subsurface monitoring tool that can provide more objective information on dose-dependent response of normal oral tissue to radiation.

Materials and methods:

To address this unmet clinical need, optical coherence tomography (OCT) was used. A clinical study was conducted on 14 late oral radiation toxicity patients and 5 age-matched healthy volunteers. OCT structural images were acquired from different oral regions in both cohorts and were then de-speckled in order to provide a better visualization of the subsurface layers and features. The alterations in patients’ de-speckled OCT images compared to the healthy cohort are reviewed, and potential correlations between the total dose to specific regions and the abnormal features observed in the OCT images of the same sites are discussed.

Results:

OCT images were acquired from 32 sites in 14 patients, 15 of these sites belonged to the regions which received >50 Gy radiation dose and the rest to the region which was irradiated to <50 Gy. The de-speckled OCT images from the former group showed major differences, such as total layer disruption, compared to the images of healthy oral tissue. The de-speckled OCT images from all but one of the regions which received <50 Gy showed normal features and layer definition compared to healthy oral OCT images. Same results were observed in an intra-patient comparison of the ipsilateral (dose >70 Gy) and contralateral (dose <25 Gy) soft palate of one of the patients, suggesting the results are independent of anatomical differences between individuals.

Conclusion:

This preliminary clinical study showed the ability of OCT to differentiate subsurface features in the oral regions that received high radiation dose (>50 Gy) compared to healthy oral tissue. These results can be used to design a prospective study to monitor oral subsurface changes periodically (e.g., every 6 months) following radiotherapy, to further understand the mechanism of late radiation toxicity and its relation to dose.
Oxidative stress and genetic markers of suboptimal antioxidant defense in the aging brain: a theoretical review
Authors: Salminen Lauren E. , Paul Robert H.
Published: August 2014

Normal aging involves a gradual breakdown of physiological processes that leads to a decline in cognitive functions and brain integrity, yet the onset and progression of decline are variable among older individuals. While many biological changes may contribute to this degree of variability, oxidative stress is a key mechanism of the aging process that can cause direct damage to cellular architecture within the brain. Oligodendrocytes are at a high risk for oxidative damage due to their role in myelin maintenance and production and limited repair mechanisms, suggesting that white matter may be particularly vulnerable to oxidative activity. Antioxidant defense enzymes within the brain, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST), are crucial for breaking down the harmful end products of oxidative phosphorylation. Previous studies have revealed that allele variations of polymorphisms that encode these antioxidants are associated with abnormalities in SOD, CAT, GPx, and GST activity in the central nervous system. This review will focus on the role of oxidative stress in the aging brain and the impact of decreased antioxidant defense on brain integrity and cognitive function. Directions for future research investigations of antioxidant defense genes will also be discussed.
The effects of monetary policy regime shifts on the term structure of interest rates
Authors: Abdymomunov Azamat , Kang Kyu Ho
Published: August 2014

We investigate how the entire term structure of interest rates is influenced by changes in monetary policy regimes. To do so, we develop and estimate an arbitrage-free dynamic term-structure model which accounts for regime shifts in monetary policy and price of risk. Our results for US data from 1985 through 2008 indicate that (
The Sound of Emotion
Authors: Van Zijl Anemone G. W. , Toiviainen Petri , Lartillot Olivier , Luck Geoff
Published: August 2014

What is the effect of performers’ experienced emotions on the auditory characteristics of their performances? By asking performers to play a music phrase in response to three different instructions we attempted to answer this question. Performers were instructed to do the following: 1) play while focusing on the technical aspects of their playing; 2) give an expressive performance; and 3) focus on their experienced emotions, prior to which they were subjected to a sadness-inducing mood induction task. Performers were interviewed after each playing condition. We analyzed the tempo, articulation, dynamics, timbre, and vibrato of the performances obtained as well as the interview data. A focus on technique resulted in technically appropriate performances, a focus on expressivity in more extraverted and externally projected performances, and a focus on experienced emotions in more introverted and personal performances. The findings of this exploratory study are valuable for both research and artistic practice and pedagogy.
Melatonin as a Candidate Therapeutic Drug for Protecting Bone Cells From Chlorhexidine‐Induced Damage
Authors: Proksch Susanne , Strobel Sabrina Lydia , Vach Kirstin , Abouassi Thaer , Tomakidi Pascal , Ratka‐Krüger Petra , Hellwig Elmar
Published: August 2014

Background: Melatonin was proposed for use in periodontitis and peri‐implantitis therapy due to its bone‐supportive effects. This issue is of interest because standard adjuvant antiseptics, namely chlorhexidine (CHX), prove damaging for osteoblasts. Thus, the aim of this study is to investigate if melatonin is suitable as an auxiliary agent for protecting osteoblasts from CHX damage.

Methods: MC3T3 osteoblast response was determined following administration of various CHX concentrations in the absence or presence of melatonin. Osteoblast morphology was evaluated, total reactive oxygen species (ROS) and superoxide levels were quantified, ratios of apoptotic and necrotic cells were identified by flow cytometry, metabolic activity of remaining cells was assessed, and effects were calculated with repeated measures analysis and post hoc P value adjustment.

Results: CHX led to poor morphology, increased total ROS and superoxide levels, and rigorously diminished the number of vital and metabolic active osteoblasts in a concentration‐dependent manner. However, simultaneous melatonin supply supported cell morphogenesis and growth, reduced ROS and superoxide generation, shifted the percentage of CHX‐damaged cells from necrotic/late to early apoptotic events, and modulated metabolic activity in osteoblasts.

Conclusion: These data reveal that melatonin protects osteoblasts in the CHX context, thereby implicating melatonin as a promising drug in periodontitis and peri‐implantitis treatment.
An Engineered Approach to Address the Need for Long Term Integrity in Cement Subject to Critical Stress Cycles in Deepwater Production Fields
Authors: Rojas R. Giron , Millan A. , Leon S. Gonzalez , Hernández J. Torres , Pando F. Salas
Published: August 2014

The life cycle of a well is not static; throughout the stages, several changes in downhole conditions occur that can affect the integrity of the well. Common activities performed during the construction of the well (e.g. changes in density of the drilling fluids or an increase in temperature while drilling) may have an impact on the achieved cement isolation. During completion activities including stimulation and fracture treatments and even during abandonment activities, the well is exposed to diverse stresses that can damage the hydraulic isolation achieved with the cementing jobs. This document reflects the main steps for a general design process to achieve long-term isolation developed for deepwater development fields in the Gulf of Mexico, specifically at the production stages. This study includes an interdisciplinary study of geomechanics data from the formations, current drilling techniques, and data from downhole sensors at exploratory wells in the area that allowed for better understanding of how the resulting stresses can affect the interaction between formation, cement sheath, and casing, and provides information to design the required cement systems for the development fields.
Improved Drilling Performance in Carbonates Build-Up Section with Innovative Aggressive PDC Bit Design
Authors: Agawani Waleed , Al-Khaldy Meshal Dawood , Taha Mohammed , Al-Failakawi Khaled A , Omar Marwa Gamal , Al Saadi Dhari Mohammed , Abdelhamid Atef , Al-Osaimi Mohammad K
Published: August 2014

Striking a balance between aggressiveness and steerability has always been a challenge in engineering new bit designs. The purpose of this paper is to highlight the engineering steps and challenges faced with designing a more aggressive bit that will drill faster while improving directional control and limiting vibrations to suit the application.

North Kuwait's 8.5″ build up section's geology comprises of layered carbonates, shale and sandstone. The section is known to induce vibrations in conventional RSS BHAs and can be challenging for directional work.

As a rule, less blades in a PDC bit makes a more aggressive bit that is therefore harder to steer with. Historically Kuwait's 8.5″ sections are drilled with a 6 bladed bit design. While proving stable, such a medium-set bit design limits performance in these formations.

The engineering process involved:

In depth analysis of current bit designs involved studying wear patterns, comparing designs that drilled faster sections and those that minimized downhole vibrations Analyzing different drive system specific requirements and the designs found most stable. Selecting the most appropriate PDC depth of cut management technology that would allow the bit to sustain higher parameters without generating extensive torque Drilling and hydraulics simulation software to optimize flow and simulate depth of cut management Extensive field trials

The result was the first 5 bladed PDC bit run in Kuwait; which improved drilling rate of penetrations by 24% while minimizing vibrations and maintaining precise steerability on RSS and AKO mud motor BHAs.

By managing the bits aggressiveness, a more aggressive PDC bit design was proposed and trialed on several wells proving consistent performance improvement on field average rate of penetrations while maintaining accurate steerability to successfully land the wells.
7” Multizone Single Trip Gravel Pack Aids in Reducing Costs and Enhances Completion Flexibility in Offshore Indonesia
Authors: Ping Wei , Lavoix Frederic , Muryanto Bonifasius , Nurrachman Firman , Chaloupka Vladimir , Landry Jed , Li Chun Ming
Published: August 2014

Multizone Single Trip Gravel Pack (MZ-STGP) completion has been the mainstay in Mahakam River Delta and North Java Sea in Indonesia since 2007. The system has been used as a sand control solution for its cost efficiency, the ability to complete multiple sands in a single trip and to provide zonal isolation for production selectivity.

Initial completions have used the 9 5/8” system offering large bore and pumping capacity required for deeper zone gravel packing. Additional requirements has driven the need for a use of a smaller system under various scenarios such as cases where 9 5/8” casing cannot reach planned depth, retrofitting gravel pack in existing wells or completing unexpected additional reserves below 9 5/8” casing shoe.

The paper reviews successful history of a 7” MZ-STGP system including its first worldwide installation in 2009. Introduction of the new system has been very smooth including another world's first combined 7” and 9 5/8” multizone gravel pack completion. The paper presents application concerns when considering multizone systems, as well as lessons learnt from the presented cases.

To date, eight wells have been completed successfully using this slimmer system within expected time frame confirming rig time reduction of 8-10 days per well compared to stacked gravel packs. Not only has the 7” MZ-STGP proven to reduce costs for operators, but it has also permited significant flexibility in drilling and completion operations. The system is now considered as a standard contingency for many operators in cases where a 9 5/8” shoe must be set higher than planned or when openhole completion cannot be run inside of an 8 1/2” open hole.
High Compression Expandable Liner Hanger Case History in the Bakken Shale: Pre-job Planning, Real Time Monitoring and Post Job Analysis
Authors: McCormick John , Brown Casey , Walters Gary
Published: August 2014

Shale plays have become a dominant source for oil and gas production in the United States and in other global areas. There also has been a dramatic increase in the number of horizontal wells being drilled in these plays as well as in the lateral lengths. Unfortunately, horizontal wells can create massive compressive and bending forces that increase the likelihood of damage to downhole tools. Challenges in running completion equipment to the target depths in the Bakken Shale when multi-stage fracturing operations are planned has also been challenging. This paper will discuss the use of expandable liner hangers (ELHs) and how they have been capable of meeting some of the Bakken Shale challenges.

Challenges when completing long horizontals are centered around large compressive loads, including the ability to get the string to bottom and the performance of downhole tools such as liner hangers. Expandable liner hangers have resolved some of these problems, since the ELH systems integrate the liner hanger, packer, and tieback receptacle into a single unit and can provide simpler operations with fewer trips into the hole. The ELH does not rely upon cement above the liner top to provide an efficient seal, since no slips are used to hang the liner. Instead, multiple elastomeric bands support the liner weight and supply redundant gas-tight seals. Although not yet a widely understood technology, high compression ELH completions have increased reliability, safety, and profitability in the Bakken shale, and this has led to the significant increase in its use.

High-compression expandable liner hanger (ELH) runs in the Bakken Shale have shown consistent superior performance, specifically the ability to handle massive loads when pushing strings to TD. This paper disseminates technical information to increase operator awareness of how this technology can improve completions in the still relatively new area of drilling in US shale plays. This paper also discusses how this technology provides needed solutions for safely delivering the completion string to TD and accurately placing completion equipment with flexibility and reliability.
Achievement of Maximum Mud Weights in K-Formate WBM with Micromax and Its Successful Implementations in Deep HPHT Wells
Authors: Al-Muhailan Mohannad , Al-Foudari Saud Jumah , Debroy Amalendu , Rajagopalan Arun
Published: August 2014

The Jurassic reservoirs of deep wells in Kuwait have traditionally been drilled with OBM. Barite is utilized as the weighting material in the OBM resulting damages to these reservoirs, thereby reducing the productivity to a significant extent. The higher oil to water ratio (95/5) of OBM limits the possibilities of identifying the micro fractures in reservoirs due to the limited conductive medium in OBM. Potassium formate WBM, with Manganese Tetraoxide as weighting material was successfully applied in HPHT wells overcoming these limitations.

K-Formate brine was utilized up to maximum density of 12.5 ppg to reduce the impacts of solids in the mud. For the first time, maximum mud weight of 17.8 ppg was achieved operationally using micromax (Mn3O4) in this WBM. Also, for the first time in Kuwait, this kind of fluid was used to drill the section with the inclinations above 60° in deep wells.

As a result of using K-Formate WBM in the reservoir sections, production increased significantly when compared to the wells drilled with OBM and barite. Wells were simulated easily without the presence of barite. Water based conductive medium gave better quality of image logs. Unlike other WBM's, K-formate WBM was stored for long periods, over a year in the mud plants without any damage to the mud properties. Recycling reduced the overall fluid costs in the subsequent wells drilled with K-formate WBM. Environmental damage due to the OBM spills and cuttings were completely avoided; K-formate WBM is highly bio-degradable under atmospheric conditions and is environmentally friendly.

The experience and success gained with its use on the initial wells led to the planned usage of this WBM on all deep exploratory wells. This paper explains the experiences gained and the achievements made over the years with K-formate WBM used for drilling the deep HPHT wells.
ECD Management Solves Lost Circulation Issues in Cementing Narrow Pressure Window: A Case Study
Authors: Isgenderov Islam , Bogaerts Martijn , Osayande Victor , Kurawle Irfan , Kanahuati Alia Iza , Aghaguluyev Javid
Published: August 2014

Zonal isolation in narrow pressure windows has traditionally been challenging. This is due to cement slurry losses or potential fluid flow after cement placement. Accurate pressure data are essential for well control and successful primary cementing. Higher fluid densities and pumping rates can lead to induced fracture and lost circulation. Often, to mitigate the potential for dynamic losses during cement placement, low-density Newtonian fluids (preflush) are pumped ahead of weighted spacers. It is recognized in the industry that Newtonian fluids achieve a turbulent flow regime much easier than non-Newtonian fluids. The impact of Newtonian fluids on the stability of nonaqueous fluid (NAF) systems and weighted spacers are often disregarded during cement job design and testing.

During cement placement, especially in extended reach wells, depending on the volume of preflush needed to maintain adequate wellbore security, a long column of preflush/mud interface may be created. With the Newtonian phase in turbulent flow, the erodability of the mud interface increases significantly. Though preferred for cementing, Newtonian fluids have a detrimental effect on the stability of the fluid interface. Whenever the yield point of the interface falls below the critical value for solids suspension or the slip velocity, weighting material sags out of the mud; this results in hydrostatic imbalance in the fluid column. When the overall hydrostatic pressure falls below the formation pressure at any point in the wellbore, the cement slurry will be invaded by formation fluid influx and a flow pathway created while cement is setting. This channel can become a flow path for hydrocarbons to the surface, leading to sustained casing pressure or a hydrocarbon seep to surface or seabed.

In the Caspian region, an engineering approach was implemented to manage cementing equivalent circulating densities (ECD) when designing cement jobs using lighter and Newtonian fluids ahead of weighted spacers. It has led to successful zonal isolation for recent wells and an evaluation of design considerations for cementing ERD wells.
Aligned Materials and Design Development of High ROP Drill Bits
Authors: Deen C. Aron , Kitagawa Casey , Schneider B. , King G.
Published: August 2014

At their advent, PDC bits were aimed at soft formation, fast drilling applications. However, as PDCs have come to dominate market share over roller cones, PDC bit development has shifted focus toward other goals such as durability and longevity which is often in conflict with high ROP. Returning focus to aggressive, high ROP drilling applications has required development of materials, design and manufacturing processes in alignment with that goal set.

A cross-functional team was assembled to understand and focus on the high ROP concerns of the end customer and was tasked to develop a PDC bit platform aligned with these goals. This paper discusses general and application specific challenges posed by high ROP drilling applications and how they have been addressed by the aligned development of a new system of materials, design, and manufacturing processes used in PDC drill bits. Formation to bit interaction simulations and computational fluid dynamic modeling analysis are presented in support of the development hypotheses. Field results from case studies and broad field data analysis summarizing the results of extensive testing are presented as well.

Driving ROP beyond the ceilings observed in many extreme ROP applications requires that energy be efficiently transferred not just to the bit, but focused on the cutters. To achieve this, an essential change to the base material of the bit body was made, exposing drastically new avenues – and hurdles – for design and manufacturing. However, the simulation and field results presented confirm that the new system is able to consistently achieve the goal set in high ROP applications.
A Novel Autonomous Inflow Control Device Design Based on Water Swelling Rubber
Authors: Sang Guangsen , Jiang Zhenhai , Zhang Qingjie , Wei Jianguang , Zhang Tianjun
Published: August 2014

In long horizontal wells, early water or gas may breakthrough into the wellbore due to imbalanced production profile caused by heel-toe effect, reservoir heterogeneity or fracture existing. Once coning occurs, oil production may be severely decreased due to limited flow contribution from the other regions. Inflow control devices (ICD) are usually installed to maintain the flow across production zones uniformly by creating an additional ICD pressure differential which cancels out the imbalanced production profile. This will lower startup production, however, unwanted fluids from breaking through are significant delayed, and total oil production is maximized. Unfortunately, once low viscosity fluid (water/gas) does break through, they will take over the well, significantly reducing oil production.

In this paper, a novel autonomous inflow control device (AICD) design is proposed based on the combination of nozzle-based ICD and water swelling rubber (WSR). The WSR installed in the nozzle swells once water breakthrough occurs, and the swell increment will be adjusted automatically according to water content, thus changing the minimum flow area and flow resistance rating (FRR) of the device. This autonomous function enables the well to continue producing oil for a longer time while limiting water. To highlight the excellent performance of the novel design, three other designs (nozzle-based, helical channel, and tube-type) with a same FRR of 0.8 were compared, with fluid property sensitivity, and structural parameter optimization researched. The results show that the device has a good performance for both oil producing and water restricting, which enables the well to continue producing oil for a longer time, and maximizing the total production.
Sustainable Safety Performance in Drilling Operation
Authors: Okoli Ejike , Amadi Amadi
Published: August 2014

This paper presents learnings and experiences gained in incident prevention within a Goal Zero framework where no one dies, no one gets hurt, and no leak to environment. Key HSE processes deployed that underpin sustained safety performance in SPDC Wells operations are highlighted in this paper for learning.

The ramp-up of rigs from two to eight in 2011, in an environment with restricted opportunity of optimally attracting skilled-labour from pool of global workforce due to operating environment, was a cause for concern.

Nigerian Content Development (NCD) regulations which mandated the use of contractors and employees from local communities, created a pool of first timers mainly Nigerians and Asian entrants. Work locations and terrains were difficult for rig moves involving narrow, poorly built/maintained roads, bridges, overhead cables, communities and meandering through unmaintained snaky creeks. Overall, the poor safety performance at that time could be attributed to above.

SPDC Drilling team operated for three (3) calendar years without lost time injury (LTI), without leaks to the environment, sustained strong focus on Wells Process Safety and BSi ISO14001 & 14064 certification. Example, five contractors moved from Amber rated (i.e. weaknesses in safety management) to Green (strong safety management).
Abandonment of 19 Subsea Wells in the Jabiru/Challis Fields
Authors: Clyne Iain , Jackson Neil
Published: August 2014

This paper describes the pre-planning and execution of Australia's largest subsea well abandonment campaign to date. The Jabiru/Challis Fields are located in the Timor Sea 640km from Darwin, Australia. The fields were discovered in 1983/84 with first production in 1986 and reached the end of their economic life in 2010. The fields consisted of 13 subsea producers and 6 suspended/partially abandoned wells making it a 19 subsea well abandonment programme.

A semi-submersible rig was selected over a jack-up primarily based on water depth and subsea hardware handling capability considerations. Abandonment solely using a construction vessel was discounted due to the age and condition of the wells and associated risks of using coiled tubing.

The condition of the wells required detailed barrier management. The main challenge was to maintain adequate barriers throughout the abandonment programme when some of the standard barriers did not exist to begin with. A number of the barriers that were in place during the well construction were no longer present. The Drilling Contractor was fully engaged to ensure single barrier operations were acceptable. Drawing on the experience gained in the North Sea, the Oil & Gas UK Guidelines for the Suspension and Abandonment of Wells were adopted.

With numerous known well issues and more potential unknown issues, coupled with significant logistical challenges, contingency planning was vital. By the end of the campaign, problems encountered included corroded casing, corroded/parted/collapsed tubing, iron sulphide scale, naturally occurring radioactive material (NORM), H2S, non-functioning tubing retrievable surface controlled subsurface safety valves (TRSCSSVs) and blocked perforations.

Significant use of construction vessels was made pre and post rig activities. A programme change during the campaign resulted in the storage of subsea hardware assemblies on the seabed for later retrieval by a construction vessel. This was a safer and lower cost option than recovery to the rig.

This paper is of use to engineers and managers commencing the planning of a subsea well abandonment campaign. It describes actual experience in a relatively uncommon operation in the industry and includes learnings which can be applied to future development planning.
LPG-Based Fracturing: An Alternate Fracturing Technique in Shale Reservoirs
Authors: Soni Tanmay M
Published: August 2014

A novel stimulation technique named Liquefied Petroleum Gas (LPG) based fracturing which can be an alternative to conventional water based fracturing technique or hydraulic fracturing.

In conventional hydraulic fracturing treatments, it is observed that effective fracture length contributing to the production is fraction of the propped fracture length. In LPG fracturing effective fracture length is more than conventional fracture length hence increasing productivity. If we use gelled LPG as a fracturing fluid, it is highly soluble with the formation hydrocarbon. If natural gas formations are present, then propane and methane will combine to create unique liquid vapour saturation and returns to the surface at ambient conditions which can be separated easily. LPG fracturing eliminates the need of flowback water disposal, which is currently major problem in hydraulic fracturing. In LPG fracturing, a stream of gelled LPG or a mixture of propane and butane is injected into the well. Proppant is supplied in this stream and carried into the formation at frac pressures causing fractures though some precautions are must for the safety issues. It has been observed that with less viscosity, less surface tension and less density, LPG can rapidly and efficiently clean up while reducing the pressure needed to mobilize fracturing fluids.

In this paper, effective fracture lengths and rapid cleanup are demonstrated with the help of post fracture pressure transient analysis. Comparison of LPG fracturing with conventional fracturing has been explained critically. Complete recovery of the LPG has also been demonstrated here. Major advantages and disadvantages of this technique along with economics are included in this paper. We can use this technique in order to protect the environment and to increase the productivity. This paper briefly reviews the previous work and explains an overview and applications of LPG fracturing.
Understanding Excessive Water Production in Highly Faulted Mature Gas Condensate Field: From Well Operations to Revival of Integrated History Matching
Authors: Fayzullin Maksim , Tippel Philipp , Gonzalez Jose , Egger Stefan
Published: August 2014

This case study illustrates a methodology adopted by an operator to reveal the dominating mechanism behind dramatic watering-out sequence, prevailing production from a mature gas condensate field in Eastern Europe. A production restoration project was triggered to understand and remedy the adverse effect of water. Finally, its source could be solely verified with the help of numerical simulation.

Many attempts to isolate or handle excessive water production fail, because remediation activities are deployed in the trial- and-error manner, without prior water source identification. Possible reasons that operators simplify their approach by reverting to the best practices/analogs, not accounting for individuality of the problem. Furthermore, ineffective water shutoff jobs are not always analyzed for their pitfalls and consequently fed to the next well. Thereby, the process lacks true insight of the nature of water appearance and, in turn, the right remediation strategy from start, if it exists.

The field development showed that, after water breakthrough, the gas rate dropped by a factor of 4 or 5, thus leading to huge production losses. First, water production occurred in the crest of the structure followed by a sequence of wells being watered-out. The past experience to isolate the invading zone accompanied with extensive logging and misleading choking-back, revealed the necessity of thorough water diagnostics. The well-known categories of problems were analyzed tying them to subsurface uncertainties and vast reservoir information. Simple types were gradually replaced by complex processes, or even by the combination of the following: faulting, multilayered channeling, system of fractures etc. The formed concepts were reviewed in the simulation model honoring available buildup/per-interval pressures, casedhole production/saturation logs and repeated openhole logs to obtain the historical water/gas ratio (WGR) evolution. Finally, the strategy was refined giving ideas for deepening of the wells and downdip sidetracking in the less invaded zones.
Novel Lubricant - Bridging Agent Combination Cures Differential Sticking Problems in High Pressured North Kuwait Wells
Authors: Al-Muhailan M. S. , Al-Foudari Saud Jumah , Debroy Amalendu , Rajagopalan Arun , AbouElkhair M. , McNaughton P.
Published: August 2014

Deep wells drilled into the Jurassic formations of North Kuwait pose a drilling challenge due to the existence of low pressure reservoirs separated by an extremely high pressure salt zone. Currently, the seven string casing design in these wells leaves no further option for zonal isolation. As a result, a wide range of pore pressures are encountered while drilling these formations. Depleted zones/reservoirs in these wells suffered multiple instances of differentially stuck pipe and side tracks. The end result has been a significant loss of expensive rig days. These sections are drilled using oil based mud (OBM) with a high oil/water ratio and mud densities ranging from 10 to 17 ppg.

To prevent a reoccurrence of the differential sticking problems, extensive laboratory work was undertaken to determine how to negate the effects of high differential sticking force while drilling depleted zones. Laboratory tests and fracture modelling based on historical data were carried out to develop a suitable fluid formulation to address these challenges. This work indicated that a novel combination of glycolic polymer lubricant and sized marble bridging agent provided the optimum combination of lubricity and filtration control to minimize differential sticking tendency.

A fluid formulation based on the laboratory results was utilized to drill subsequent wells in this field. The depleted intervals were drilled using a similar OBM treated with a combination of unique lubricant and sized marble bridging agent to reduce differential pressure transmission across the depleted zones. The intervals were drilled and logged without the occurrence of any problems of differential sticking. The troublesome sections were completed incident free resulting in huge savings in cost and rig time.

This paper describes the historical challenges in this field and present case studies demonstrating how the solution was successfully implemented in the field.
Improved Calculation of Multiple Annuli Pressure Buildup in Subsea HPHT Wells
Authors: Yin Fei , Gao Deli
Published: August 2014

In subsea HPHT wells, annular pressure buildup caused by thermal expansion of fluid endangers well integrity. The conventional well design is not secure for subsea HPHT wells. It is significant to assess the risk from annular pressure buildup and provide solutions. Considering the interactions and pressure changes of different annuli, the calculation model of annular pressure buildup in multiple casing annuli is established. This model expands the scope of application of existing models. In view of temperature-dependent coefficient of thermal expansion and compressibility, the calculation method based on temperature increment is adopted to improve the calculation precision of annular pressure buildup. Research results show that the annular pressure buildups are various under the condition of different temperature ranges and same temperature change, and the annular pressure buildup in high temperature range is greater than that in low temperature range. The casing load arising from annular pressure buildup reaches or even exceeds the casing load according to conventional design. The research methodology is applied to a subsea HPHT well. The potential risk is discovered in the conventional casing design when annular pressure buildup occurs, and the casings are optimized design to deal with the issue. Furthermore, the mitigation measures for annular pressure buildup are recommended to ensure the well integrity of subsea HPHT wells. The research in this paper provides the reasonable calculation approach and mitigation measures of annular pressure buildup.
Novel Drilling Fluids Enable Record High-Temperature, Deep-Gas Exploration Well Offshore Peninsula of Malaysia
Authors: Witthayapanyanon A. , Nasrudin K. A. , Wahid F. , Pepple M. M. , Abshar M. , Dollah A. B. , Chandramouleeswaran K. , Kongsawast A. , Bland R. G. , Clapper D. K.
Published: August 2014

Increased global energy demand has forced the oil and gas industry to search for hydrocarbons in increasingly challenging locations such as high temperature, high pressure (HTHP) reservoirs. This paper presents the field performance of a new fit-for-purpose synthetic-based mud (SBM) used to drill an ultra-HTHP deep gas exploration well offshore Malaysia. The well was drilled to a total depth (TD) of 14, 380 ft (4, 383 m) and reached the highest recorded bottomhole temperature (BHT) of 488°F (253°C) in Southeast Asia. To overcome the anticipated drilling challenges in the extreme environments, the operator and service company collaborated to identify a thermally stable, high-density drilling fluid that met the operator's needs. The drilling fluid was formulated for a maximum density of 18 lb per gallon (ppg), but reached the Southeast Asia record of 19.1 ppg mud weight at TD. The use of dual weighting materials (barite and manganese tetraoxide) yielded lower plastic viscosity (PV) for the high-density mud, leading to improved hydraulics and lower equivalent circulating density (ECD). The drilling fluid encompassed excellent temperature stability with no weighting agent sag and no high-temperature gelation observed after remaining static for five days at BHT during wireline logging. In this respect, it eliminated the rig time spent for additional circulating or conditioning of drilling muds and fluid treatment cost. Moreover, the fluid also provided good wellbore stability with no non-productive time (NPT) from drilling fluid performance. Comparison of field data and laboratory results highlighted the benefits of competent drilling fluid design and testing. As a result of thorough planning and comprehensive laboratory testing, desirable drilling fluid properties were maintained despite extreme HTHP conditions, minimizing trips and operational costs.
First Conformance System to Fix Leaking Downhole Packer and Enhance Hydrocarbon Production in Gulf of Thailand
Authors: Wattanasuwankorn Reawat , Limniyakul Vorasak , Dunlop Tyson , Chayraksa Wichanee
Published: August 2014

Well pressure integrity is a primary concern during offshore operations. Without proper control, barriers can significantly impact safety and production activities. Once a well barrier is unable to deliver pressure control, correcting the pressure integrity problem as quickly as possible becomes a priority. This paper describes a case where, in a conventional gas lifting oil well, a downhole packer leaked during production and significantly reduced hydrocarbon production.

A conformance system was introduced to a Gulf of Thailand operator. The conformance system's rigid setting fluids are a new generation solution for plugging or temporarily isolating specific zones. The system was engineered to help ensure conformance would set at the right angle and temperature under specific well conditions. High-pressure resistance, low solution viscosity, and zero shrinkage are advantages of using the system to recover well pressure barriers.

The conformance operation was performed using an electric line (e-line) punched target below the downhole packer inside production tubing to help establish conformance injectivity. Once the rate was confirmed, the conformance solution was squeezed to target the zone using coiled tubing (CT). CT was an important component of the solution necessary for cleaning as thoroughly as possible. Conformance pressure was confirmed under controlled conditions. The design only allowed a few hours for the solution to build up compressive strength, so a pressure test was performed from the "A" annulus, and the well could hold 1,500 psi.

The recovery of well pressure integrity successfully addressed the well control issue for the entire life of the well and restored hydrocarbon production from an inability to produce to production of 200 B/D. Using this system, a workover of the rig was not necessary to recomplete the well by replacing the downhole packer and risking hydrocarbon exposure during workover operations. This conformance solution was ideal for correcting the packer leaking problem.
Openhole Tractor and High-Tension Conveyance Package Reduces HSE Risk and Saves 3 Days of Rig Time for Formation Fluid Sampling in a Highly Deviated Well
Authors: Akue Michel , Delaval Fabien , Crevoisier Lois De , Hermes Amir , Tchieji Yves , Sarian Serko , Bozzolan Philippe , Reid Martin , Andrew Mike , Bahmudov Kamil
Published: August 2014

To better understand their reservoir in a highly deviated offshore well, the operator required advanced measurements in an appraisal well over and above those normally recorded with basic LWD measurements. The data required to better characterize the reservoir were electrical image logs, dipole shear sonic imaging, high-resolution magnetic resonance measurements, and formation pressure tests as well as pressure/volume/temperature (PVT) fluid samples, all to be collected in oil-base mud. The Operator and Service Company were looking for efficient alternatives to a pipe-conveyed logging operation.

After a thorough study of well details, modelling of required tractor force, and close collaboration between the operational teams of both the operator and service company, it was determined that a conveyance system including the latest generation all-terrain tractor and high-strength cable would be suitable for this operation. Compared to running on drillpipe, tractor conveyance offered benefits for this operation in terms of rig time, flexibility, and safety. The 50-m and 4,513 lbm fluid sampling toolstring used for the operation included six pairs of tractor drives, all required logging equipment, and an electronically controlled weakpoint deployed with an 18,000 lbf high-tension conveyance package.

Petrophysical measurements as well as downhole formation testing and sampling were all achieved successfully using the all-terrain tractor conveyance in four logging runs, with a total tractored distance of 6,800 m in a formation with unconfined compressive strength ranging from below 5,000 psi to as low as 600 psi. The data and samples were acquired in five logging runs across the entire reservoir interval with a maximum tension of 10,500 lbf. The total operational time of 70 hr represented a time saving of approximately 72 hr compared to a pipe-conveyed operation with the same logging equipment in this setting. Successful deployment of this tractor technology offers alternatives to operators in the region for formation evaluation.
Innovative Field Development Strategy Tackles Complexities of Flue Gas Buildup in Reservoir - LWD and “Distance to Boundary” Technology Comes to Aid
Authors: Keot Chandan Jyoti , Datta H.S , Dubey P.K. , Singh R.L. , Singh A. , Lobo K. , Majumdar Chandan
Published: August 2014

Most of the fields in the northern part of Cambay basin, are characterized by heavy crude. To enhance productivity, Insitu combustion had been practiced in this belt over a long period of time. The in-place combustion of hydrocarbon also produces residual gases called Flue gas, which in time migrates and accumulates towards structural highs. The buildup of flue gas pockets towards reservoir top slowly began affecting production in this belt with conventional producers showing premature gas cuts. This created the need for an effective change in strategy that would yield gas free production. The following paper illustrates a very challenging field development strategy deployed in field Z, located in this belt to tackle complexities of flue gas build up in reservoir. The strategy firstly involved changing the planned drainhole geometries in field Z from vertical and near vertical to horizontal. Horizontal producers has reduced coning and cusping effect and enhanced sweep radius. The main challenge with this strategy was to place these producers at safe distance from the gas pockets at top. To handle this challenge, LWD and “Distance to Boundary” technology was deployed for the first time in this field. A combination of gamma ray, resistivity and density-neutron data would help to track the flue gas zone while drilling which could be used to land the build section at a safe distance below gas caps. “Distance to Boundary” technology would be used during drainhole to detect the reservoir bottom and keep trajectory at about 2-3m from bottom. Placing drainhole close to reservoir bottom would ensure a safe distance from gas pockets throughout the drilled interval. This strategy worked effectively with 3 wells been drilled till now in field Z with very good production rates without any gas cut.
Arachnophobia: A Case on Impairment and Accounting Ethics
Authors: Persellin Julie S. , Shaub Michael K. , Wilkins Michael S.
Published: August 2014

This case requires students to apply accounting and ethical decision making within the context of a potential land impairment decision. Students are required to research the relevant professional literature and provide appropriate FASB codification references and IAS cites as they investigate the significant uncertainties that frequently are associated with valuation and impairment analyses. Students also are required to evaluate the ethical implications of the decisions that could be made regarding the necessity of impairment. The case provides an opportunity for students to extend their research and financial accounting abilities, to consider the consequences associated with a set of potentially reasonable accounting alternatives, and to begin to appreciate how the significant uncertainties that are present in many accounting and auditing situations require consistent technical and ethical decision making. The case could be used in Intermediate Accounting I, as well as in undergraduate and graduate Auditing or Ethics classes.
Does Timely Loss Recognition Improve the Board's Ability to Learn from Market Prices? Evidence from Worldwide CEO Turnovers
Authors: Hu Jinshuai , Kim Jeong-Bon , Lin Z. Jun
Published: August 2014

This study investigates how timely recognition of economic losses (TLR) in accounting reports influences the weights assigned to accounting earnings and market returns in a firm's CEO turnover decisions in an international context. Empirical results from a sample of firms from 37 countries show that as TLR increases, CEO turnover becomes more sensitive to both earnings and market returns. Our results are aligned with the view that TLR improves the board's ability to use both accounting- and market-performance information effectively when evaluating CEO performance and making CEO replacement decisions. Our results also show that TLR's effect on enhancing the board's ability to glean performance information from stock prices and to make an informed decision to replace a CEO is more pronounced in countries with low corporate financial transparency and/or high governance transparency. Our results are robust to a variety of sensitivity tests.