bluuebunny/crossref_metadata_2025 huggingface dataset:
Fall Detection with Part-Based Approach for Indoor Environment
Authors: Fathima A. Annis , Vaidehi V. , Selvaraj K.
Published: February 2015

In the current scenario, majority of the aged people want to lead independent life, and most of them prefer living at their own home. According to recent case studies, the major cause of casualty among elder people has been due to the accidental falls. Hence, it is eminent to have a fall detection monitoring system at home. The prevailing method for fall detection uses accelerometers to distinguish fall from other day to day activities, these results are more erroneous. In this paper, vision based “Fall detection with part-based approach (FDP)” is proposed to give accurate information about the person activities in the indoor. The proposed scheme uses background subtraction in association with aspect ratio and inclination angle to detect the fall. Moreover, the proposed approach predicts the fall even if the person is occluded by other objects or under self-occluded condition. To detect the person even if only partly visible and occluded by other non-moving objects, part based approach is adapted. To train the system for detection purpose, Cascaded structure of Haar-rectangular features with joint-boosting classifier is utilized. The detection efficiency is measured by precision, recall and accuracy parameters.
Creep Rupture Forecasting
Authors: Chatzidakis Stylianos , Alamaniotis Miltiadis , Tsoukalas Lefteri H.
Published: February 2015

Creep rupture is becoming increasingly one of the most important problems affecting behavior and performance of power production systems operating in high temperature environments and potentially under irradiation as is the case of nuclear reactors. Creep rupture forecasting and estimation of the useful life is required to avoid unanticipated component failure and cost ineffective operation. Despite the rigorous investigations of creep mechanisms and their effect on component lifetime, experimental data are sparse rendering the time to rupture prediction a rather difficult problem. An approach for performing creep rupture forecasting that exploits the unique characteristics of machine learning algorithms is proposed herein. The approach seeks to introduce a mechanism that will synergistically exploit recent findings in creep rupture with the state-of-the-art computational paradigm of machine learning. In this study, three machine learning algorithms, namely General Regression Neural Networks, Artificial Neural Networks and Gaussian Processes, were employed to capture the underlying trends and provide creep rupture forecasting. The current implementation is demonstrated and evaluated on actual experimental creep rupture data. Results show that the Gaussian process model based on the Matérn kernel achieved the best overall prediction performance (56.38%). Significant dependencies exist on the number of training data, neural network size, kernel selection and whether interpolation or extrapolation is performed.
Planning and Management of Distributed Energy Resources and Loads in a Smart Microgrid
Authors: Delfino Federico , Rossi Mansueto , Barillari Luca , Pampararo Fabio , Molfino Paolo , Zakariazadeh Alireza
Published: February 2015

This paper addresses the issue of planning and management of a so-called smart microgrid, namely a group of interconnected loads and distributed energy resources (DER) with clearly defined electrical boundaries that acts as a single controllable entity with respect to the public grid. Special attention is devoted to the microgrid Energy Management System (EMS), which plays a crucial role in governing the power flows from the different generating sources and can resort to optimization procedures and algorithms in order to minimize the daily operating costs. The main features of the EMS platform suitably developed to control the University of Genoa test-bed facility called Smart Polygeneration Microgrid (SPM) are here illustrated and thoroughly discussed.
Study on Matching Relationship of Polymer Hydrodynamic Size and Pore Throat Size for Stratum in Sand Reservoir
Authors: Dan-dan Yin , Yi-qiang Li , Dong-feng Dong Feng , Fu-yong Wang , Jun-xin Gao
Published: February 2015

Considering the existing problems of high injection pressure and lagged oil well response during SP flooding in the low permeability Hong gang reservoir in Jilin oilfield, in this paper compatibility researches are processed between polymer hydrodynamic radius and core pore-throat size under various permeability. Traditional way of determination of polymer hydrodynamic size using the laser particle size analyser is under ordinary conditions of pressure, but this method can only determine the size of the low concentration (below 800mg/l) polymer solution, and polymer solution for ERO concentration is always high. Another method is underpressure of 0.15MPa according to the API. Through experiment under different pressures, we found that polymer hydrodynamic size decreases with increasing of pressure. Due to the pressure drop funnel between the injection and production wells, the polymer coils' patterns and flow properties vary a lot spatially. So the above two methods are not accurate determination of the polymer solution hydrodynamic size in the formation. And for the low pressure gradient in zones far from the well, compatibility has changed between polymer and the pore throats, which results in the increasing injection pressure and hysteresis effects observed in production wells. In this paper, considering the far-well zone pressure gradient and shear force during the preparation and injection of polymer, nuclepore membrane filtration experiments are developed to measure the hydrodynamic radius under different molecular weights and polymer concentration, as well as the flow properties in three cores with different permeability. The results show good matching between the polymer solutions with molecular weight of 2000×104, 1500×104, 800×104 with corresponding concentration of 1700mg/L, 1500mg/L and 1000mg/L, and the nuclear pore membrane filter of 0.49μm, 0.36μm and 0.2μm, respectively. Also, they show a relatively good compatibility to the cemented cores of 180-200×10−3μm2,60-80×10−3μm2,25–40×10−3μm2, respectively. Furthermore, the ratios of the median radium pore throats to polymer hydrodynamic size(R/Rh) are 7.01-8.9,7.28-9.12 and 6.53-8.85, respectively, and for that in the Hong gang field, the ratio as 7–9 shows goodcompatibility.
New Guideline for Seismic Assessment of Fixed Facilities in Malaysian Water
Authors: Mukherjee Kaushik , B Ayob M Sapihie , Khai Lai Tze , Nichols Nigel Wayne
Published: February 2015

A large part of the fleet of platforms in Malaysian waters are ageing with the increasing demand of enhancement in view of further oil recovery and the additional development in the extended and nearby field. The enhancement process will also require development of new facilities to comply with performance and integrity requirements. The integrity issues imposed thus needs to be dealt with multi-disciplinary efforts that include a fresh regional seismic hazard mapping. To address this, a site specific assessment was carried out in 2009 for Sabah, Sarawak and West Malaysia offshore concessions in the South China Sea. The study concluded that the use of standard ISO spectral maps to be unconservative for the seismotectonic conditions offshore Malaysia. A modified spectrum shape, generally consistent with the ISO 19901–2 had been developed to match expected ground motion in each of the three blocks.

To formalize this, a new guideline has been developed for the seismic assessment of existing platforms as well as newly built fixed structures in Malaysian region.

The impact of the modified spectrum was assessed and recorded for selective platforms in these regions. This, in combination with the newly developed framework of adopting Performance Based Design, will form a complete guideline closely aligned with Petronas performance target and HSE expectations.

Fundamentally, offshore platforms shall have adequate strength against all effects influencing their structural integrity. The seismic requirements are intended to reduce risks to persons, the environment and assets to the lowest level that are reasonably practicable. The technical aspects of the developed seismic criteria can easily be implemented in future designs. However, understanding of the effect on the fitness-for-purpose of the existing structures in line with the ISO requirements are also essential. Particular emphasis to be given to the systematic inspection and subsequent integrity of topside connections of the existing facilities.
Unlocking the Potential of Metal Oxides Nanoparticles to Enhance the Oil Recovery
Authors: Hendraningrat Luky , Torsaeter Ole
Published: February 2015

The development of current technology has enabled manufacturer to create various types of nanoparticles for multi-purposes in various sectors including the oil and gas industry. The use of nanoparticles for enhanced oil recovery (EOR) has been studied in the past decade both in the lab- and pilot-scale projects. Most of the research observed that nanoparticles are very attractive for EOR purposes. However, most of those studies use ??of silica-based nanoparticles. The use of other types of nanoparticles should be investigated as alternative solution.

In this study, two water-based metal-oxides nanoparticles: Al2O3 and TiO2, were employed. The primary size of both nanoparticles ranged of 40-60 nm. Nanofluids was prepared by dispersing 0.05 wt.% metal-oxides nanoparticles with synthetic saline water. Berea sandstones cores are used as porous media with average porosity and permeability of 15% and 60 mD respectively.

Coreflood experiment was conducted by injecting metal-oxides nanofluids as tertiary process (Nano-EOR). Degassed crude oil with viscosity ranged 5–50 cP was also used. To investigate the effect of temperature and rock wettability to oil recovery, coreflood experiment has been performed on various temperature condition and initial cores wettability: water-wet, intermediate-wet and oil-wet.

The detailed process and results are outlined in the paper to reveal the possible application of metal-oxides nanoparticles as alternative EOR method.
Free Span Rectification by Pipeline Lowering (PL) Method
Authors: Thusyanthan N.I. , Sivanesan K. , Murphy G.
Published: February 2015

Surface laid pipelines experience free spans due to various reasons such as uneven seabed, local scour or a storm event. If free span lengths are beyond acceptable limits, vortex induced vibrations (VIV) can cause the pipeline to undergo fatigue damage and severely reduce the pipeline's design life. Thus pipelines need to be periodically monitored to ensure that there are no free spans that are beyond the acceptable length. When such free spans are identified, these need to be rectified immediately to avoid fatigue damage to the pipeline. Rectifying unacceptable free spans in existing pipelines are a constant battle for operators around the world.

Free spans on existing pipelines are commonly rectified by grout bags. While this method is considered to be a standard and cheap solution, it often does not provide a long term solution to free spans. It is often the case that the pipeline whose free spans are rectified by grout bags needs further free span rectification the following year. The onset of more free spans and the need for rectification cycle often continues annually when grout bags are used to rectify free spans.

This paper presents a new approach named the "Pipeline lowering (PL) method" for free span rectification. This unique solution will ensure the free span rectification is a long term solution compared to grout bags that may be affected by scour and wave loadings. The solution involves lowering the crests of the free spans such that the pipeline follows the natural seabed profile while ensuring the pipeline integrity is not compromised at any stage. The lowering operation is carried out solely by fluidizing the seabed soil by a mass flow excavator and the pipeline lowers under its self-weight. A laboratory demonstration and successful field implementation of PL method for free span rectification are presented in this paper.

This paper provides vital technical knowledge on free span rectification by PL methodology for pipeline engineers, contractors and operators who need to ensure free spans are rectified safely and efficiently. This new methodology is a cost effective and elegant solution.
A New Method Of Bhp Measurement In Esp Deadhead Test
Authors: Xian Wei , Wenyu Liu , Yan Pi
Published: February 2015

The Electric Submersible Pump (ESP) intake pressure and well bottom-hole pressure are important factors in reservoir management and well performance optimization. Normally, the bottom-hole pressures for ESP wells are determined by ESP sensors, slick line pressure gradient technique or acoustic sounding technique. However, there're still some wells' ESPs have no sensor (or sensor failed); and acoustic or slick line operations can't be run due to the well bore restrictions.

This paper develops a method of measuring bottom-hole static and flowing pressure by variable ESP speed for these wells. And it is a quick way to get the pressure data without shut-in operation and can be operated at low cost. The theory of the method is the "Affinity Laws" of centrifugal pump. The centrifugal pump heads will change as the square of speed variation. And with a deadhead test under different ESP speed conditions, the bottom-hole pressure can be calculated.

There are around 80 ESP artificial lift wells in the case field at Bohai bay. All of these wells produce with ESP and sensor installed. However around 13% sensors are failed due to misc. reasons. Reservoir management became complicated because unable to get the exact reservoir pressures.

By the method given by paper, after the authors get the deadhead pressure data, comparison has been done with sensors had reading pressure in 12 wells. Authors also tested 11 sensor failed wells' downhole pressure and successfully optimized wells' performance.
Simulation Protocol for Core Flooding: Relative Permeability and Capillary Pressure Analysis
Authors: Kumar S , Awang Mariyamni , Abbas Ghulam , Farouque Khurram , Ahmed Sheraz
Published: February 2015

The relative permeability and capillary pressures are used to characterise large-scale multiphase flow encountered in recovery of hydrocarbons. These parameters are acquired via special core flooding experiments. Reservoir engineers calculate these parameters from special core analysis (SCAL) module of reservoir simulation. However, core flooding is an expensive experiment and involves spending lot of time and efforts before Darcy law assumptions are achieved. Therefore, independent simulation of core flooding is necessary during which reservoir engineers can perform faster and simultaneous analysis of relative perms and capillary pressures of multiphase flow.

This paper presents 1-D black oil simulation of core flooding using Sendra software to get relative perms and capillary pressures. The approaches used in this study are four steps. In the first step, the results of core flooding were estimated at different correlations. In the second step, experimental data of core flooding for differential pressure and production versus time were referenced in the software. Then history matching was performed using estimated and experimental data of core flooding using different correlations. Based on this, the best fits of correlations were obtained for estimating both relative perms and capillary pressures. The benefits of this approach compared with other methods are that it saves time, user-friendly and faster. It is reliable for estimating relative permeability and capillary pressures at steady state or unsteady state, imbibitions or drainage process either in oil or gas recovery.
A Case Study Detailing the Design, Planning, Installation and Cost and Environmental Benefit Analysis of a Reinforced Thermoplastic Pipe Pulled Through the Inside of an Existing Offshore Steel Flow Line in the East Malaysia Samarang Field
Authors: Wright John R , Karim Khairul Anuar , Kennedy Steve
Published: February 2015

There are many older offshore steel pipelines that have been damaged or exhibit excessive corrosion whereby dropping below minimum wall thickness requirements. Conventional rehabilitation or replacement of existing offhshore flow back lines often times has been cost prohibitive for older lower producing wells resulting in the premature abandonment or closing of wells.

By pulling flexible reinforced thermoplastic pipes through the existing steel pipelines and multiple riser configurations, signifcant cost savings can be realized with minimal sea floor disturbance. The reduced capital costs allow wells to continue to be productive through their remaining lives without sacrificing pipeline integrity. This paper provides a detailed case study for a Petronas flow line in the Samarang Field describing the step by step processes required for a successful rehabilitation of a pipeline. This includes proper pipe sizing considerations to compensate for lower flow rates, material selection for the reinfoced thermoplastic pipe to withstand the pipleline flow environment, determination of pull force requirments, regulatory approvals, pre-installation preparation of the existing flow line, step by step installation procedures, testing and integrity requirements and how unforseen issues raised durning the process were addressed. The paper will conclude with lessons learned and what improvements were implemented for future projects as well as the cost benefits versus replaceing the steel lines
Simulation Study for Smart Horizontal Wells Application in Maximizing Oil Reserves for Malaysian Field EOR Thin Oil Reservoir
Authors: Metwally M.M. , Faizal M. , B A Rashid R. , Rizal M.
Published: February 2015

Horizontal wells become an important factor in improving well productivity, especially in brown-field development. Smart well completions are becoming the best in development technology with horizontal wells. Inflow control devices (ICD) are used to enhance the performance of the horizontal wells by delaying gas and water breakthrough. However, as smart completions make the horizontal well more expensive, so their use requires justification. Reservoir simulation studies are very helpful tools to optimize and evaluate the number, size and locations of the ICD along the horizontal section. This paper presents a simulation and optimization study which was carried out on the planned three horizontal infill wells in one of Malaysian field. The infill wells will be subjected to enhanced oil recovery (EOR) scheme after almost five years from their initial production. The EOR scheme will include drilling more gas and new water injectors in order to support the reservoir pressure. Application of the EOR scheme emphasizes need of using ICD to balance the expected gas and water production. The main target of the study is to properly model the horizontal wells with ICD completion using the multi segmented well approach. Several simulation runs were evaluated to cover the expected scenarios for the required ICD design. All results were compared to the case assuming production without using ICD. This is to observe the benefits of using ICD and to come up with the optimized ICD design suitable for each well. The study is crucial firstly, in evaluation of the initial simulation results of ICD application before drilling of the planned wells and secondly to have a proper ICD design model for each horizontal well which can be quickly modified in future based on the actual data during drilling operations where there is no more time available for the rig.
The Use of Dope-Free Tubulars in Offshore Operations: Experiences and Benefits
Authors: Actis Goretta Emiliano , Castineiras Tomas , Giacomel Bruno , Merliahmad Mustaffa
Published: February 2015

The use of Dope-Free tubulars in offshore operations have been increasingly adopted by different operators since its debut in the North Sea in 2003.

Dope-Free tubulars replaces the storage and running pipe dope historically used in Casing and Tubing by a dry coating applied on pipe threads in an industrial controlled environment.

The elimination of dope simplifies greatly the supply chain of the preparation of Casing and Tubing for offshore increasing the efficiency, safety and lessening the environmental impact of the process.

The main benefits of this technology are: - Improved Operational efficiency - preparation, running, pulling management of rig returns; - Reliability: connections are installed in a more consistent and repetitive manner as the coating is an industrial process replacing a manual operation; - Improve well productivity: eliminating the damage to the formation created by the pipe dope and Health Safety & Environment.

Operators experience, after a short learning curve, showed great reductions in installation time, reduction on connections re-make ups and rejects, improvement on workers' Health & Safety conditions by eliminating unsafe tasks and creating cleaner work areas, and minimization of the Environmental impact.

This paper describes the experiences and benefits of the use of Dope-Free tubulars in offshore operations in the main offshore oilfields including the North Sea, the Barents Sea, Brasil, Indonesia, Gulf of Mexico and the Persian Gulf.
Small idea, Big Savings - Open Drain Sump Caisson Design Modification to Prevent MIC (Microbial Induced Corrosion)
Authors: Sunnapu Ravi Kanth , Tung Liong Raymond Tie , Maskawi Bolhi B. , Armugam Rema Malar
Published: February 2015

Description of the proposed paper:

The proposed paper describes the innovative design of open drain sump caisson liquid disposal to resolve the Microbiologically induced corrosion (MIC) in the pipe lines of Sarawak operations. The design eliminates the sea water entry in to the pipe lines and minimizes the threat of MIC to ALARP level which is one of the root cause for many pipe line failures.

Background:

Baram Delta is the largest oil field in Sarawak operations (SKO) with a current production of 72 kbpd, actively operating for the last 40 years. In strategic view of production sustainability of BDO fields, 6 new EOR projects have been proposed under the new PSC agreement in 2011, which will be carried out simultaneously to extend the field life to another 30 years with many new platforms coming up.

BDO (Baram Delta Operations) is currently facing numerous integrity challenges with pipelines, and there had been premature leakages/failures of some pipelines. One of the root causes is the effect of SRB caused primarily due to seawater entry into the pipelines through open drain sump caisson system. SKO is now investing approximately RM4 Billion solely on pipelines replacement & rejuvenation projects, and several pipelines have been replaced in recent years.

Application:

It can be applied to not only to Sarawak operations but to all offshore facilities where there is no water treatment/disposal facilities and all the crude oil along with produced water pumped to onshore facilities for further processing before sending to tankers. This design is already incorporated in the Generic Satellite Well head platform design of PCSB.

Results, Observations, Conclusions and Significance of Subject matter:

Elimination of Microbiologically induced corrosion and reduction of the risk to ALARP level. Elimination of safety hazards of handling portable tanks/ tote tanks while transferring the tanks to the supply vessels to and fro from offshore platforms. Reduction of Operations Expenditure (OPEX) of more than RM 100million for BDO operations. Simplified design with very minimum incremental cost to the conventional design. Very easy operations and environmental friendly
Advanced Technologies for Produced Water Treatment
Authors: Hussain Altaf , Minier-Matar Joel , Gharfeh Samir , Janson Arnold , Adham Samer
Published: February 2015

Produced Water (PW) is the highest volume liquid waste stream generated by the petroleum industry. Historically, the treatment of PW has been limited to free oil and suspended solids removal, using physical separation technologies, and injection in disposal wells. The petroleum industry is investigating new PW treatment technologies given that the physical separation technologies traditionally used in the past are, in most cases, not capable of producing water of suitable quality to replace fresh water uptakes. This paper presents the results of a laboratory investigation carried out by the ConocoPhillips Global Water Sustainability Center (GWSC), where various treatment processes (membrane processes, membrane-bioreactors (MBRs), membrane distillation (MD) and ozonation) were evaluated as treatment methods for PW from different oil & gas fields. The key conclusions of this paper are:- Membrane processes and Thermal evaporators are currently operating within the petroleum industry in full scale PW treatment and reuse applications.–The preliminary results of investigations performed by GWSC confirmed the potential of Membrane filtration, MBRs and Ozonation to treat PW and produce an effluent suitable for reuse. Membrane Distillation may have potential in the longer term. Further investigation is ongoing.– If successfully implemented, the above technologies will contribute to provide the petroleum industry with a broad range of technologies to cost-effectively treat and reuse PW. Because of new regulations combined with geological restrictions and local water scarcity, the drive to have a greater fraction of the PW more extensively treated and ultimately reused is increasing. Moreover, the growth in the application of water intensive processes to extract unconventional oil & gas resources, in particular in shale plays and oil sands, has increased the need for cost-effective treatment and reuse of PW to reduce fresh water uptakes.
The Comprehensive Application of Both Near-Bit and Surface Vibration Measurement to Quickly Identify Coalbed Boundary
Authors: Gao Wenkai , Dou Xiurong , Sheng Limin , Liu Yongfeng
Published: February 2015

In a cluster and horizontal coalbed methane well drilling environment, one of the most effective methods to enhance the individual well producing rate is to prevent the bit drilling out of the seam top and floor, and the bit is always in the best position to extend along the target layer. The conventional electromagnetic resistivity or gamma measurement while drilling system mounts far away from the bit(more than 7m), however the ROP of CBM drilling is usually high, which lead to time lag and large deviation of trajectory. The use of near-bit and surface vibration measurement while drilling system can identify the seam top or floor as quickly as the bit contact the boundary, to increase drilling efficiency. The paper briefly introduced the work principles, composition and application of the system.

The system is composed of near-bit vibration measurement tool, surface vibration detecting device, wireless transmitting system, signal processing and indicating software system. The downhole measurement system detects and processes the near-bit data, the result is sent to surface in real time, then operators can change drilling parameters in time if harmful downhole conditions are indicated, considering with the surface measurement.

This system has been extensively tested and proved to be effective in identifying the difference of breaking fossil coal and other rocks. Detail of the test and the method to deal with the data will be discussed in the paper.

Quickly identifying the coalbed boundary due to vibration detected both downhole and surface allows operators to take timely remedial action before the bit drills out of seam layer. Thus the drilling efficiency has been remarkably improved.
Real-Time Production Surveillance Overcomes Challenges in Offshore Dual String Gaslift Wells in Baram Field, Malaysia
Authors: Kamis A. , Zulkifli S. , Abdul Rani M.B. , Soni S. , Alvarez J.A. , Tello C. , Chuliwanlee C. , Iskandar O. , Barbarino S. , Konakom K. , Khan M. , Salazar J.
Published: February 2015

PETRONAS and OVS Group team up to optimize gas-lift process in offshore dual string oil wells in Baram field, Malaysia. This paper outlines how the real-time production data and well model approach help to overcome the challenges faced in dual string gaslift wells and improve their performance.

Challenges

To determine the injected gas allocation factor in dual-string wells when both strings are producing. To determine the well inflow performance with limited or no reservoir information such as permeability, drainage area, skin etc. for multiple completions. To improve the well and field performance in absence of daily measured flow rates. To diagnose high producing GOR wells to improve the gaslift performance.

Methodology

Gas Allocation method is developed to compute gas injection rate in each string based on welltests. Composite IPR is built at the solution node (Figure: 1.0) where fluids from all producing completions are commingled in tubing and nodal analysis is performed. Well-model-based Virtual Meter (VM) approach is used to estimate the flow rates and improve the well and field performance. Gas lift diagnostic is used to identify gas-lift performance issues.

Results, Observations, and Conclusions:Integration of databases helped to find out missing/wrong data in well tests and prioritize well tests which are overdue.Ensuring the consistency of Total GOR at reservoir and well level improved the inflow performance for production surveillance, optimization and forecast.VM enhanced the surveillance and understanding of wells, highlighted opportunities and improved the allocation method.Recommendations were made to review production strategy due to gas conning or gaslift design to improve the production and gaslift performance in high producing GOR wells.

Significance of Subject Matter:When limited or no downhole information is available, pressure gradients analysis in both casing and tubing helps to estimate the gas injection rate using surface measurements.In case of multipoint injection (Figure: 2.0), well performance is carried out based on deepest injection point if it is possible. Necessary recommendations are made to avoid multipoint injection for efficient gas lift operation.

Application

It can be applied to any single or dual string gas lift well.

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Overcoming Lost Circulation While Cementing Riserless Tophole in Deepwater
Authors: Goncalves R. , Tajalie A.F. , Meyer A.
Published: February 2015

In Deepwater environment, cementing the surface casing properly is critical to ensure support of the BOP stack, and allow drilling subsequent hole sections. The tophole sections are prone to loss circulation while drilling through the unconsolidated formation and geological fault zones. After switching the well fluid from seawater to heavier pad mud, no drilling fluid returns or very little is observed at sea bed. This scenario makes the cementing operations challenging, as any fluid heavier than seawater may cause lost circulation and compromise the well structural support. Failure to cement the riserless casing properly has been the root cause of many NPT events and one of the top contributors to incidents where the well has been re-spudded. This paper will present the solution to the lost circulation encountered in deepwater wells in Malaysia. The solution uses an engineered dual fibers technology to regain circulation through the thief zones and achieve structural integrity of the riserless casing.

The dual fiber technology with optimized solids package and high solid-content cement has been effectively applied to overcome losses in the deepwater riserless section. This technology can also be used on any cementing operation where loss circulation is expected, as a pill or spacer ahead of the cement slurry, given that proper assessment of the well geometry and thorough engineered design have been performed.

It was absolutely critical for the operator to get cement returns to sea bed. The dual fibers technology and high solid-content cement were synergically utilized, helping to achieve circulation through the unconsolidated and faulty zones and achieve proper cementation of the surface casing. Circulation of fluids to the sea bed was verified by ROV. The job pressure profile shows that the final displacement pressure was as expected and the top of cement calculated to be at planned depth, despite the loss circulation scenario prior to the cementing operation.

The technology presented in this paper provides solution to effectively cement the tophole in deepwater, overcoming lost circulation, helping to achieve structural integrity of the casing that will support the BOP stack and to minimize potential NPT events associated with loss circulation.
CFD Study of Deep Draft SemiSubmersible VIM
Authors: Lee Sing-Kwan , Chien Hung-Pin , Gu Hai
Published: February 2015

In deepwater oil and gas development, a stable floating platform is critical to the safe and reliable operation of the topside production/drilling facilities. The motion characteristics of the platform are a significant factor in the service life of the mooring system and risers connected to the platform. Among different floating platform configurations, deep-draft semisubmersible (DDS) concepts are known to exhibit better vertical motion characteristics in wave environments than conventional semisubmersibles because of the smaller wave exciting forces on the pontoon structure.

In a DDS design, vortex-induced motion (VIM) stemming from vortex-induced lift force remains one of the challenges in offshore engineering. Compared to a single column floating platform such as a spar, a semisubmersible attracts a more complex VIM phenomenon due to its multi-column configuration. Because of the elongated submerged column and enlarged projected area to the current, both in-line drag forces and transverse vortex-induced lift forces are larger, resulting in increased in-line and transverse horizontal motions in a current environment.

In this study, an overset grid Computational Fluid Dynamics (CFD) approach is adopted on DDS to facilitate the computation of an arbitrary large VIM displacement. Due to the high grid resolution requirement for vortex shedding flow simulation, the best practice O-type grid topology with grid points located up to the near wall boundary sub-layer level is used around the semisubmersible hull. The results show the calculated drag forces are in good agreement with measurement data. To further consider the deep draft semi-submersible VIM, an appropriate spring-type constraint is added based on a real application case of a mooring line system.

Systematic CFD simulations show there are complex phenomena for VIM responses due to different inflow current speed and heading angle relative to the DDS. In addition to the common large VIM lock-in motion at the DDS natural sway frequency, simulations also show a combined motion of galloping and VIM that manifests as transverse motion beyond the natural sway frequency range. Spectra analysis also is performed for the VIM time history to provide more comprehensive information, which is useful for the fatigue life estimate for mooring lines and risers.
Optimised Fatigue and Reliability RBI Program for Requalification, Life Extension and Integrity Management of Offshore Structure
Authors: Nezamian A. , Clarke E.
Published: February 2015

There is an ever increasing need to extend the life of aging offshore structures beyond their original design life. Whether these structures are fixed offshore rigs or floating facilities, operators are continually looking for new inspection and mitigation techniques aimed at ensuring the integrity of the structure. Improved inspection techniques and mitigation when combined with a sophisticated Risk Based Inspection (RBI) program can serve to requalify and extend the life of offshore structures.

Degrading mechanisms such as corrosion and fatigue, overloading, excessive marine growth and accidental damage may affect the integrity of offshore facilities. Early Identification and addressing the degradation mechanisms can prevent a structural failure. Joint weld close visual inspection or MPI can provide assurance in fatigue performance of the joint and to be used in calibration of fatigue life and improve the inspection intervals requirements.

An oil field consisting of many well head platforms, a living quarter platform), a flare platform and a processing platform are the main focus of this paper. In-place, seismic, spectral fatigue and ultimate strength analyses were undertaken for the platforms to determine the criticality of members and joints. These analyses in combination with cathodic protection studies and available inspection data were used for requalification and life extension.

This paper documents the methodology for the development of the RBI program to support the requalification and life extension of the platforms. The RBI program was based on guidance from ISO 19902, with the likelihood and consequence of joint failure used establishing base line and to identify the number and intervals for scheduled inspections. The results of the baseline inspections and additional sensitivity studies were then used to optimise the RBI program.

This paper serves to highlight the finanacialfinancial benefits, efficiency and importance of developing an RBI program based on probability of failure and consequence to manage the inspection programs for platforms and other facilities, particularly where there is a requirement to requalify the facility and/or extend its life.
Spatial AHP Enables Highly Effective Pipeline Routing Evaluations
Authors: White Chuck , Turner Nathan , Bacon Kellie , Palejwala Ashfaq , Mower Kirk , McGee Simon
Published: February 2015

The Analytical Hierarchy Process (AHP) is employed to structure and prioritize the criteria (issues) that most strongly affect pipeline routing decisions for offshore projects. An AHP model is created incorporating these criteria and the pair-wise comparisons technique is used to establish weighting of the criteria. The collaborative pair-wise comparison approach allows all team members to explore and sound out each other's perspectives on the importance of each of the routing assessment criterion in a disciplined way that builds consensus around the model adopted for the cases under investigation.

This AHP model is then tagged to the geomatics database automatically linking expertise in the pipelining disciplines with advanced geomatics capabilities for assessing export pipeline routing schemes to directly account for key considerations like flow assurance, spanning, and seabed hazard avoidance.

The model is then applied to challenging pipeline planning cases for offshore Western Australia. The results track the rankings of each routing option under each of the identified and prioritized route selection criteria as the actual site data is applied along the entire length of the pipeline. Sensitivities to variations in the weightings of the evaluation criteria are investigated in a way that confirms the robustness of the routing recommendations.

The paper clarifies how the issues and key technical information are efficiently captured and applied within full field development planning studies that reflect real-world information (geomatics). The ability to easily accommodate changes in the engineering/technical basis and/or corporate priorities is highlighted, as well as the consensus-building strengths of this advanced decision-support methodology.
Hydrodynamic Response of Spar with Disc
Authors: Jose Jithin , Selvam Rajamanickam Panneer , Sundaravadivelu Ranganathan
Published: February 2015

Description of the Proposed Paper:

The scope is to study the hydrodynamic response of the spar (39m diameter and 198.1m draft) using WAMIT. The analytical expression proposed by Tao et al., is used to estimate the viscous damping for the spar with the disc at the bottom. The disc increases the added mass and damping. The spar with single disc configuration is studied varying the disc diameter. The spar with twin disc configuration is studied varying the spacing of disc. The disc diameter and spacing is obtained for the permissible heave response of 5m and pitch of 4 degrees considering the swell (regular wave height of 2m and wave period of 25s) and sea (regular wave height of 20m and wave period of 14s) states on the east coast of India.

Application:

The results can be used to design the spar with single or twin disc. The disc diameter and spacing of the disc can be determined for the site specific swell or sea wave height and period.

Results, Observations, and Conclusions:

The heave and pitch responses are observed to be within limits for single disc configuration with disc diameter equal to 1.4 times spar diameter and twin disc configuration with disc diameter equal to 1.3 times spar diameter and disc spacing equal to 0.4 times disc diameter.

Significance of Subject Matter:

The effect of single disc with varying diameter and twin disc with varying spacing on spar response is predicted. The effect of viscous damping in addition to radiation damping is studied. The effect of swell wave is found to be the significant for survival condition.
3D Seismic and AUV Data Integration for Deepwater Geohazard Assessment: Application to Offshore Northwest Borneo, Brunei
Authors: Dan Gabriela , Cauquil Eric , Bouroullec Jean-Luc
Published: February 2015

A 3D seismic and AUV data integration has been performed for geohazard assessment at an early stage of a field development. The study area is located on the South China Sea, approximately 100 km northwest of the coast of Brunei Darussalam margin characterized by a delta toe fold-thrust belt. Elongated mini-basins are separated by shale-cored ridges created by basin-directed thrusting. The continental slope is characterized steep slopes and affected by large channels, and mass transport deposits (MTD). A regional geohazard assessment was performed on the 3D exploration seismic data highlighting the presence of numerous seabed an sub-seabed features potentially affecting E&P activity. In order to better assess the possible impact of these geohazards on the field development, a detailed AUV survey has been performed on target areas. The study area ranges from 830 m to 2050 m of water depth and is characterized by seabed gradient up to 45°. Several events of buried MTD including more cohesive blocks which result in the hummocky signature on the present-day seabed are observed. The presence of such MTDs may induce vertical and lateral soil variability that may impact both drilling operations or pile/anchor installation and flowlines installation passing through the hummocky seabed. In addition, the slopes are affected by recent instability processes covering 2 km2 to 10 km2. Larger slide scarps with an amphitheatre-like source area are observed and appear to be created by various retrogressive events. The slides initiate on various slope angles, from 2° to 16°, and measured run-out distances show a large range of values, from hundreds to thousands of metres. Evidences of seafloor expulsion features (craters, pockmarks), shallow gas, gas hydrates are also observed within the study area. The 3D seismic dataset has been used to identify at a regional scale particular geohazards areas requiring a more detailed investigation via AUV at an engineering scale. Such engineering scale allows producing favorability maps created from selection criteria and allowing mitigation strategies for safe E&P activities.
Modelling the Shearing Effect of Flowing Fluid and Wax Ageing on Wax Deposition in Pipelines
Authors: Zhang Xiaohong , Queimada Antonio , Szczepanski Richard , Moorwood Tony
Published: February 2015

Wax precipitation and deposition in pipelines is one of the most important flow assurance challenges for the oil and gas industry. Much work has been carried out to model wax deposition as measured by flow loops and other experiments. Models are routinely scaled up to predict the behaviour of full-scale pipelines, but little information is available to verify if such predictions are reliable.

A fully compositional wax deposition model has been developed that combines an accurate model for the thermodynamics of wax precipitation, a model for diffusive wax deposition based on heat and mass transfer analogy and a method for the shearing effect on the wax deposits caused by the turbulence of the flowing fluid. The wax is treated throughout as a fully compositional distribution of n-paraffins, because previous work has shown that simplifying the representation of the n-paraffins leads to results that appear to be physically unrealistic. The model has been shown to be in reasonable agreement with wax deposition rates reported from flow-loop experiments.

This paper describes the application of the wax deposition model to real pipelines and the shearing effect on the deposited waxes. The shearing effect will be illustrated by reference to the real field cases, and the operating experience of a sub-sea pipeline. The deposition model is analysed to assess its agreement with the real field operating experience, and to assess under what conditions the pipeline could be considered at risk of blocking.

The paper also considers the effect of wax ageing on wax deposits. In cases where fluid turbulence may limit wax build-up, the wax deposit may gradually harden with time due to ageing. A hardening deposit could lead to long-term remediation problems. A number of possible wax ageing mechanism are considered, and how they would modify the deposition process. It is found that the effective diffusivity of hydrocarbon molecules inside the waxy gel deposit is a major uncertainty affecting the predictions. Model sensitivities are investigated in the light of this uncertainty, and the possible impact of ageing on the pipeline is assessed.
Effect of Time and Temperature on Crude Oil Aging to do a Right Surfactant Flooding with a New Approach
Authors: Heidari Mohammad A , Habibi Ali , Ayatollahi Shahab , Masihi Mohsen , Ashoorian Sefatallah
Published: February 2015

Dilute Surfactant flooding is one of the significant processes in chemical flooding. Many oil reservoirs became appropriate candidates for surfactant/water flooding when screening criteria developed. Injected surfactant tries to mobilize the residual oil that was trapped in interstice. The main contributing mechanism for oil recovery improvement by surfactant flooding is rock wettability alteration. Wettability is a one of the proper index in choosing the best approach for a successful surfactant flooding which tiny change in wettability alteration will lead to improve oil recovery.

This experimental study investigated the effect of different aging time and temperature on wettability alteration with exact soaking time to find the optimum condition. Afterwards, coreflooding experiments were performed to determine the impact of dilute cationic surfactant slug with huff ‘n’ puff(cyclic 7 days) method on displacement sweep efficiency in the carbonate core from one of the Iranian oil field. Besides, contact angle and interfacial tension (IFT) measurements were done to provide the supplementary data for a surfactant/waterflooding. The optimum concentrations of C19tab, were determined by measuring interfacial tension values of the crude oil in contact with surfactant solutions, which were prepared from synthetic saline water.

The results obtained from laboratory showed a reduction in residual oil saturation by changing contact angle and IFT reduction between oil and water. Aging is known as important parameter for researcher to alter the wettability. Furthermore it proves effect of wettability alteration is more than IFT reduction.