bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme Response Predictions for Deepwater Mooring System
Authors: Cheng Zhiping , Kuang Jinlu
Published: March 2016

As exploration and production of offshore oil moves into deeper waters, mooring lines become longer and heavier, with total weight increasing up to about 10% of the floater's total displacements. The effects of line dynamics on vessel motions and mooring line tensions become much more prominent. Coupled time domain dynamic analysis is used extensively to assess the response of the mooring system. If the responses are narrow-banded Gaussian processes with Rayleigh distributed peaks, the extreme values are readily available. However, the mooring system responses calculated based on coupled time domain dynamic analysis are more likely to be non-Gaussian due to the prominent nonlinear line dynamics effect. Generally, the extreme value computed from a single time domain simulation will vary about the Most Probable Maximum Extreme (MPME) value. Consequently, statistical fitting techniques are recommended by API RP 2SK to establish reasonable confidence in the predicted extreme responses.

In this paper, a fully coupled time-domain dynamic analysis is performed for a typical deepwater mooring system with 20 different seeds/wave profiles using Orcaflex. The most probable maximum extreme (MPME) responses under different wave profiles are predicted with Winterstein/Jensen method, Weibull fitting method and Gumbel fitting method, respectively. This paper investigates the characteristics of these three statistical fitting methods and examines the convergence of these methods under different random seed selections. Winterstein/Jensen method and Weibull fitting method may result in scattered values under certain conditions, while Gumbel fitting method always yields consistent values. Recommendations are provided to eliminate the divergent results from using Winstertein/Jensen method and Weibull fitting method.
Flow Considerations and Pitfalls in Subsea Equipment Design
Authors: Ji Lin
Published: March 2016

In Subsea Production System design, the effect of equipment design on flow and vice versa may not be sufficiently considered by the design engineers. Historically, rules-of-thumb and piping design guidelines have been adopted leading to overly conservative design or conversely poor performance. This paper discusses some of common design practices with regard to equipment sizing, sensor placement and thermal design and attempts to promote a better understanding of the impact of flow on equipment design.
Improvement in Oil Recovery Through Pro-Active Reservoir Management for a High Value Asset – A Case Study
Authors: Kumar R. , Sha Foo Lee , Asykin Nurul , Salleh Zaimi , Othman Mohamad
Published: March 2016

fieldThe field, located 120 km offshore in the Malaysian deep water, was discovered in December 2003 and put on production in November 2012. As per the Field Development Plan (FDP), Reservoir Management Plan (RMP) for G-K field is to inject water and gas from the beginning of oil production in Pink1/2 and UK1 reservoirs. The objective of the study was to optimize the voidage replacement by WI, so as to maximize the up-dip oil recovery.

The study was conducted on a sector model. A compositional PVT model, having 17 pseudo components, was developed. To explain the compositional variation in reservoir, the PVT variation has been incorporated. The SCAL data, same as used in FDP, have been used for the study. Two producers were considered in the sector model so as to study the oil movement between the two wells. One Injector each was placed in GCG and aquifer.

For UK1 reservoir, the plan is to re-inject 60% of the produced gas from UK1. For PINK1/2, it is planned to re-inject all the produced gas from PINK 1/2 plus any remaining gas left after internal usage. The total VRR target for both the reservoirs is 1.0, and the remaining part of the voidage replacement is made up by water injection. The FDP RMP was reviewed, because it was thought that in view of the small gas cap size (m ratio about 0.2 for PINK1/2 and 0.18 for UK1) and limited Gas Injection capacity, making up VRR equal to one by WI may not allow GC to expand rapidly. During the study, the whole process of Gas Injection and water Injection was divided in two parts, viz, Pre-Gas Breakthrough period and Post-Gas Breakthrough period so as to separately assess the impact of limited gas injection capacity after gas breakthrough. For PINK1/2 reservoirs, WI at 25% of the Instantaneous Voidage Rate (IVR) provides the best recovery before gas breakthrough. To avoid gas flaring after gas breakthrough, WI rate has to be increased to 40% of the IVR. For UK-1 reservoir, WI at 35% of the IVR provides the best recovery.

Due to this study, there is an improvement of about 10% oil recovery over FDP study, which is equivalent to over 70 MMSTB of oil. In UK1 even after this improvement, a significant amount of up-dip oil still remains un-swept. This may require additional gas injection or drilling infill wells up-dip to the present location. During FDP the study was conducted on a Black Oil model, the present study was conducted on a compositional model.
Numerical Analysis of Anchor Dragging Impact on Rock-Covered Pipeline Using CEL Method
Authors: Tjahyono S. , Teh T. C.
Published: March 2016

Subsea pipelines located in harbour areas and shipping lanes are subjected to potential damage due to impact of anchor dragging. Such pipelines are usually covered with rock berms for protection. Due to the high costs associated with the installation of offshore rock berms, there is a need to optimise the rock berm size such that the rock quantities are reduced while still providing adequate protection for the pipeline. Analysis of anchor dragging near a rock-covered pipeline involves quantifying the complex interaction between the anchor, the anchor chain, the soil and the pipeline-rock system. In the present study, Coupled Eulerian-Lagrangian (CEL) finite element method is used to simulate the complex soil deformation and flow during the anchor dragging, thereby providing better understanding of the underlying mechanisms of the problem. This paper presents results of CEL analyses of anchor dragging near a pipeline covered by rock berms of different sizes. The simulated trajectories of the anchor during the dragging are shown to be in good agreement with the experimental results of Gaudin et al. (2009). This shows the ability of the present method in giving more rigorous solutions and better predictions of rock berm protective capacities. This paper also illustrates the use of the present analysis for optimizing the rock berm design and hence enabling significant cost savings.
Fit-for-Purpose Qualification for Corrosion Resistant Alloy (CRA) Tubing Selection in High CO2 Field Based on Field Experience and Laboratory Test
Authors: Zin Z. M , Ong G. , Riyanto L. , Jadid M.
Published: March 2016

This paper focuses on tubing material selection study conducted for a high CO2 oil field located offshore of Peninsular Malaysia.

The field's CO2 concentration varied laterally and with depth. The highest CO2 concentration of 66 mol% in gas had been recorded from well test and fluid data. This resulted in severe corrosive environment in the wells. Based on the well surveys, many existing wells which were completed with API-5CT L80-13Cr had suffered from localised corrosion within a span of two (2) years of production. Existing material selection was revisited in order to prevent corrosion in future development wells. An important change made was to conduct material qualification test specific for the field conditions on several corrosion resistant alloy (CRA) materials. The details of the test and findings are presented. To better understand the corrosion severity in existing well completion, well survey results are also discussed.
Qualification of a New Robust and Cost-Effective Polymer for Flexible Pipe Pressure Sheath
Authors: Tronc F. , Bourdel S. , Brun E. , David E. , Guillerme J. F. , Levet A.
Published: March 2016

Flexible pipe polymer pressure sheath is made either of polyolefin materials, polyamides or polyvinylidene fluoride. Each of these three polymer families is characterized by its own advantages and limitations. Polyolefins, particularly polyethylene (PE) and crosslinked polyethylene (XLPE), and polyamides have demonstrated their excellent behavior for containment layer in flexible pipe applications because of a good combination of properties. However the use of polyolefins materials is limited in pressure as they are subjected to blistering and the use of Polyamides is limited in temperature as they are subjected to hydrolysis. When these two polymer families cannot be used because of high pressure and/or high temperature, high grade (and considerably higher cost) Polyvinylidene Fluoride (PVDF) is considered.

For several years, Technip has been dedicated to the development and qualification of a new robust and cost-effective polymer material for flexible pipe pressure sheath. Its domain of temperature and pressure combines the high temperature of current crosslinked polyolefin materials and the high pressure of polyamides. One of the characteristics of this new material is its intrinsic long term stability towards hydrolysis and chemical aggression.

A full qualification program was carried out for this new polymer material. This program includes full polymer characterizations according to API17J [1], industrial extrusion qualification on production lines, mid-scale tests to qualify in temperature the sealing mechanism in the end-fittings and full-scale tests to validate the behavior of this new material during manufacturing, installation phases and during service life.

This new polymer material offers a real step change in the design of flexible pipes for the transport of oil, gas, water and mixtures thereof.
Extended Pipeline Bundle Length for Field Development
Authors: Animashawun Kolawole , Goodlad Martin
Published: March 2016

Towed Pipeline production systems (Pipeline Bundles) are currently fabricated and installed in the North Sea and Norweigian Sea regions from the fabrication facility of a major subsea contractor in Wick, Scotland. The site is located approximately 6 miles north of Wick and extends from the shoreline at Sinclairs Bay landward for approximately 7.8km in an east-west orientation. The current limit for the fabrication of a single Pipeline Bundle is 7.7km.

The company has undertaken a Research and Development study on Pipeline Bundle Extended Lengths (Pipeline Bundle lengths up to 15km) to investigate a means to connect several Pipeline Bundle sections together in order to be able to satisfy the requirements of fields where long tie-backs may be required. Pipeline Bundle length extension can be achieved by onshore tie-in through mechanical connection, Golden welds or fabricated at a different site with a suitable length capacity.

The key benefit of the extended Pipeline Bundle length is to reduce the overall cost of field development by eliminating the requirement for: Interconnecting towheads (Pipeline Bundle end structures),Tie-In spools,Extended hire of tow vessels,Additional Diver/ROV support vessel time for the tie-in of interconnecting towheads.

As a consequence of this length increase, this paper asseses the feasibility of Extended Pipeline Bundle length in the following areas; Pipeline Bundle Tie-in,Pipeline Bundle Pre-commissioning,Required weather window launch - to DNV-OS-H01 Ref.[3],Launch force requirement,Control Depth Tow Method (CDTM) Tow Fatigue,Pipeline Bundle manoeuvring during tow,Application for HT fields – Design Temperature of up to 160°C,Pipeline Bundle Installation - Venting and Flooding

The paper will also demonstrate the commercial advantage of towing longer Pipeline Bundles as against multiple Pipeline Bundle tows.
Field Development Cost Optimization: a SURF Contractor's Experience and Perspective
Authors: Seguin Blaise , de Roux Grégoire , Louvet Emmanuelle
Published: March 2016

In the current offshore industry context, ways for significant cost optimizations must be explored and developed to make offshore projects viable. The cost share of the SURF (Subsea Umbilicals Risers and Flowlines) system is increasing, with developments in deeper waters and with more spread reservoirs. The SURF system also presents a wide range of possible options to be considered, thus with many opportunities for overall cost reductions.

This paper presents examples of solutions to reduce costs: early engagement of SURF contractor for the field concept selection, global understanding and optimization of the field architecture, closely linked to installation vessels and methods selection, introduction of new technology, and consideration of interfaces between SURF, SPS (Subsea Production System) and Floater packages to reach a global optimum. The efficient development of these emerging solutions is supported by strong experience in full Engineering, Procurement, Construction and Installation (EPCI) execution of SURF contracts.
Marine Warranty Surveyors - An Underwriter's Eyes and Ears?
Authors: Gnanendran A. , Sharma V. S.
Published: March 2016

Traditionally during the construction and installation phases of offshore construction projects, a Construction All Risks (CAR) policy will be taken out by the operator or their appointed contractor to cover against fortuitous losses during design, handling, transportation, installation and testing & commissioning activities of the permanent components of the project. In most cases the terms of these policies include a "Marine Warranty Clause" within which the Underwriter(s) will require that an independent Marine Warranty Surveyor (MWS) be appointed to the project to act as marine experts on their behalf. This is to ensure the construction phases are completed effectively and safely. Despite Underwriter(s) appointing MWS for the majority of construction projects there appears to be a steady stream of construction losses in the insurance industry.

The scope of MWS task is enormous, from reviewing design documents and installation documents to approving installation activities offshore - so is one MWS representative sufficient to minimise the risk? This paper discusses the real importance of MWS for any offshore construction project and identifies the current shortfalls.
Gaslift Compressor Initial Start-Up Outside of the Design Envelope
Authors: Ab Halim Azuani Haslinda , Samad Johan Alimin Abdul
Published: March 2016

Centrifugal compressors are very sensitive to changes in operating conditions. Operations outside of the design envelope may result in sub-optimum performance and risk serious equipment damage. To accommodate different process conditions, a booster compressor may be required or the existing compressor may be re-rated or re-wheeled. However, this option is costly, time consuming and must be undertaken with due diligence. A good understanding of the compressor's process requirements and field operating limitations is necessary for the full benefits to be realized.

Low gas availability led to development of a strategy to startup a compressor outside of its normal design parameters. The implementation required only modifications to setpoints software, instrumentation and process line-up, thus eliminating the need for a booster compressor and subsequently simplifying the compression system. This strategy was applied on a first time basis without any available analog reference, and proved successful.
Analysis and Design Challenges and Solutions of 3 Sided Passive Fire Protection PFP on Steel Beam Decks for Offshore Installations
Authors: Munoz-Garcia Enrique
Published: March 2016

Passive fire protection (PFP) is consistently used in the oil and gas industry as a method to avoid and or delay global collapse of offshore installations. Current practice is to leave the top flanges of passively fire protected beams on coated, commonly named 3-sided protected beams. The reason for this is to ease the installation of grating on top of those beams. Although discussed in guidance documents such as API 2218 there is, to the author's knowledge, no defined design guidance or standard that allows structural steel designers to calculate the response of such configurations and assure that partially fire protected beams survive the design fire scenarios. It is therefore of interest to gain more knowledge on the heat up process and failure mechanisms of these members. Partially 3-sided protected beams engulfed by hydrocarbon and jet fires are subject to large thermal gradients on their cross-section, high temperatures which in turn cause the beams to be susceptible to a series of possible failure mechanisms such as local buckling, loss of bending or shear capacity and more commonly lateral-torsional buckling.

This paper discusses the thermal and structural response observed on typical 3-sided PFP beams used in the offshore industry. Several heat transfer finite element (FE) analyses were performed on a range of rolled I sections and plate girders, the results provide an understanding of the influence of conduction, convection and radiation in the heat up mechanism of the beams.

This study provides an understanding of the structural response and failure mechanism of 3-sided protected beams. From these results a series of design solutions are proposed and their structural performance analyzed. The pros and cons of each solution are identified as well as their range of applicability. Finally recommendations and conclusions on analysis and design approaches for partially protected beams are made based on the results of this study.
The New Frontiers of Offshore Drilling Activities: Hand-Off Drill Floor and Capability to Talk Continuously With the Bottom Hole
Authors: Calderoni A. , Angeli S. , Colaianni F. , Cantalupo P. , Parnivoda Y.
Published: March 2016

Offshore drilling projects are inherently more challenging to execute due to the increased risks and complexity associated with extreme working condition and unpredictable drilling formation pressure margins.

Since the time we have begun to drill with mud circulating in the hole, the mud pumps have to be turned off every time a pipe or a stand have to be added to the drilling string.

The time spent for those simple operations is not short and the crew involved is often exposed to potential risks: the mud acts as the first safety barrier in the well, without mud circulation drilling accidents, like connection kicks, stuck pipe, etc, could occur. Moreover, repetitive tasks with rig staff and heavy machinery operating in the same tight space is often very dangerous.

The offshore packages discussed in this paper introduce a new frontier for the offshore drilling activities, where everything is designed to satisfy HSE standards and the needs of improve efficiency in offshore activities.

These solutions are composed of a modular hydraulic hoist unit, of an innovative online and offline automated carousel and of a innovative drilling package directly integrated with the other rig equipment.

Not only footprint and weight reduction will be the targets of the next future; in fact, drilling continuously in a fully automated way, without interrupting the mud circulation in the hole even while adding or removing pipes, is crucial in the next future to be safe and competitive in all offshore activities.
Case Study - Hull Block Heavy Lifting Challenges for a Tension Leg Platform TLP
Authors: Ab. Majid Mohamad Azhar Bin , Mohd. Nor Mohd. Shahrizal Bin , M. Hanafi Hisham Bin
Published: March 2016

This paper is to provide the technical overview of the challenges encountered during the hull block heavy lifting for Malikai tension leg platform (TLP). This paper covers the methodology for the integration of the upper column block during the construction phase.

The 500 MT upper column hull block is required to be installed at a height of about 30 meters from ground. The lifting operation required usage of two (2) nos. of 1600 MT crawler cranes, which is the biggest crawler crane available in the market. A lifting procedure was prepared covering the operation, design criteria and analysis for assessments on the structural integrity of the block. The cranes and lifting gears to be used were determined and evaluated based on worst case scenarios.

Site preparations involved clearing and barricading of the operation area, ground works, cranes and other supporting equipment, facilities, lifting and installation aids such as padeyes, back-up structures, strong-backs, corbel, guide and dog plates. The lifting operations have two (2) stages. The first stage is lifting of the block from temporary supports and the second stage is shifting and installation onto the final position. The heavy lifting and integration operations for four (4) upper column hull blocks were carried-out safely and successfully within January 2015 to March 2015.

Since this is the first Tension Leg Platform (TLP) Hull constructed in Malaysia, the heavy lifting of the upper column hull blocks was treated as a critical operation. The multiple challenges and lesson learnt by production engineering and construction team during the lifting operations would be beneficial for future projects of similar structure within this region.
Multi Column TLP McT - Advanced Tension Leg Platform Technology for Marginal Field Development
Authors: Tahar A. , Nurtjahyo P. , Suardin J. , Chaniadi F.
Published: March 2016

Over the years, technology in marginal shallow-water development evolved and surface facility alternatives flourished. The Multi Column TLP (McT) has now been developed to respond to the challenges in shallow-water and marginal fields. This proven design is based on the same design principles that have been used successfully in deepwater for many years, and applying them to overcome some of the main challenges with exploitation of shallow-water platforms.

Innovative solutions for marginal field development should focus on cost reduction, shorten development schedules and exploit previously uneconomical fields. It is well understood that the economic viability of a marginal field development is not only dependent upon the quality of reservoir but is also dependent upon the development cost of offshore facility starting from engineering, procurement, construction, installation until decommissioning.

For oil and gas operators, consideration for cost reduction is of strategically imperative to fully realize the commercial value of offshore projects. Cost savings may derive from the use of the platform for several fields so that platform cost can be distributed, or through the use of other lower specification vessels for transportation and installation when compared with those required for a jacket. Other potential cost reductions may be achieved from fabrication method, engineering requirements and decommissioning plan.

This paper present a technical capability and global performance results of McT for use in the offshore marginal field functioning as utility platform. Design philosophy of McT which is derived from proven and succesfull Cell Spar, TLP and Buoyant Tower technology is presented. A case study are provided to confirm the motions, accelerations, wire tendon tensions and stability. The economic assessment of McT is presented in a separate paper [Ref. 1].
Pioneering HPHT Field Development in Malaysia
Authors: Sofian Anas M. , Noreffendy Jayah M. , Farris Bakar M. , Fadzliana Azmi N. , Syahmi M. , Yusof M. , Rahman Iz'aan Irfan A. , Nizam Baharuddin M. Haidir , Kamil Ishak M. Izham
Published: March 2016

Recognised as the first high pressure and high temperature (HPHT) development ever embarked by PETRONAS as well as the first of its kind in Malaysia, KN-UUD Development had also marked a significant step change in well engineering design approach for Asia Pacific region.

Learning from experience of HPHT operators in the North Sea and the Gulf of Mexico, a detailed focus on lifecycle well integrity aspect had been thoroughly emphasised throughout the well design phase. Innovative design thoughts, meticulous process in selecting cost effective solutions and strong collaboration between operator and service providers proved to be the key ingredients for success.

This paper highlights the sophisticated journey of KN-UUD HPHT development well delivery, covering the initial scoping work, design phase, equipment (and material) planning and testing, execution phase as well as the lessons learnt from the campaign.

Challenges and experiences discussed include:

Depletion on shallow reservoirs, its impact towards pore pressure and fracture gradient profile and subsequently, overall well design. First implementation of big bore well design with liner and cemented tieback philosophy in Asia Pacific. HPHT lifecycle integrity aspect and considerations on worst case scenario i.e. reservoir compaction study, cement stress analysis, tubular connection and material testing. Challenges in dealing with non-availability of equipment (including material) and lack of service capability within the region. Complex process of identifying and procuring fit-for-purpose equipment solutions and unique contracting strategy. Annulus management philosophy for HPHT development. Lessons learnt from the actual well construction phase.

The well was successfully delivered to meet all of its objectives, producing from layers close to 16,000 ft. beneath the seabed. The complex process, obstacles and vital experience in overcoming the challenges has pioneered a path for future application of its kind within Malaysia and Asia Pacific region.
Understanding Noises from Different Flow Mediums in Near Well Bore Region: A Novel Approach for Detection and Characterisation of Sub-Vertical Natural Flow Paths in North Kuwait Gas Fields
Authors: Acharya M. N. , Al-Mershed A. , Narhari S. R. , Al-Azmi M. , Dashti Q. M. , Chakravorty S. , Abdulkadir R. I. , Prosvirkin S.
Published: March 2016

Kuwait Oil Company is developing deep tight fractured carbonate and kerogen rich shale gas plays in northern part of Kuwait. Understanding the flow medium is important to resolve ingress of offending fluids such as water and salt during production history in the vertical/deviated wells of this play.

These unconventional reservoirs have been established to be hydrocarbon producing in several prolific vertical producer wells, without having such early water breakthrough. The tight fractured limestone reservoir is sandwiched between salt-anhydride sequence above (Gotnia cap rock) and Kerogen rich carbonate below. A dedicated casing is set at the top of limestone reservoir with the main objective of isolating the Gotnia section prior to opening the reservoir, as some sequences of anhydrites with calcite stringers in Gotnia are high pressured and prone to high water, CO2 and H2S. Based on the current understanding, main source of offending fluids is suspected to be the overlying Gotnia formation, which has limestone stringers.

Fracture studies from several conventional cores and image log data could not conclusively infer through going fractures into Gotnia, although many sub-vertical fractures of different nature have been observed and interpreted in the reservoir section in these logs.

This paper highlights the approach for detection and characterization of flow mediums, in the near well bore region (NWR) within a diameter of investigation of 3 meters or 10 feet. Results of spectral noise log (SNL), high precision temperature (HPT), pressure and natural radioactivity (GR) of a vertical well logged in shut in and flowing mode helped in understanding different flow mediums such as channel flow, fracture flow and reservoir flow. Thus the detection and characterization of different flow path systems with respect to their spatial dimension and their interactive flow contribution could be ascertained with high confidence.
UBD Fractured Basement Pilot Project Case Study in Malay Basin: Transforming a Quartile 3 to Best in Class Performance
Authors: Hafiz M. , Makri M. , Ismail M. Mukhriz , Syafiq M. , Shah M. , Jawing Sherene
Published: March 2016

This paper highlights PETRONAS's journey and experience in the Underbalanced Drilling (UBD) fractured basement pilot project, a 2 wells campaign in the Malay Basin. An integrated UBD team, has set best in class performance, applying lessons learnt in the 1st well to the 2nd well. Major highlights are the key learnings implemented, challenges turned to opportunities, overall project management, well delivery process, well assurance safety processes, achievements and future enhancements for UBD operation.

The process started with a comprehensive UBD Fractured Basement Pilot Project Feasibility study, assisted by risks assessment process which turned into a full engineering and execution plan. Well planning, well constructions and execution of this project will be highlighted. Relevant operational excellence process in PETRONAS such as DWOP, AAR, HAZID, and HAZOP has contributed to excellence in HSE and well delivery performance. Internal assurance process including Wells Peer Review and COP has facilitated a safe and successful project delivery. A multidiscipline and integrated wider scale project execution successfully yielded a noticeable performance improvement in the 2nd well in comparison to the 1st well.

For a back to back UBD well, the key learnings have been immediately brought forward and implemented in the 2nd UBD well. Results were apparent and can be demonstrated by the well KPI performance and benchmarking against other operators in Malaysia within the same class. This UBD pilot project demonstrated the project feasibility to drill a challenging fractured basement using UBD technique, which can be further enhanced and replicated to a similarly suitable projects. Overall, the 2nd well was completed 27 days ahead the planned days, with significant cost saving and total NPT of only 4.72%; while managing to drill with additional scope as requested by subsurface.

This campaign provided a basic foundation to institutionalize UBD capability and also will open up a new chapter in PETRONAS's involvement in the whole process starting from well planning & engineering, well construction, and post mortem for UBD specific projects in the future. This template will be used, replicated and improvised to suit future UBD drilling campaign particularly in PETRONAS' operations. In line with the dynamism of this Company, and frequent approach for creative & non-conventional technology implementation, it has kept PETRONAS abreast with a niche and most advanced industrial practices for a better & more effective natural resources exploration supporting the ability to maintain the supply of global non-renewable energy demand.
Cost Effective Project Delivery Through Fire and Gas Mapping Study Performance Evaluation Using Improved Risk Based Approach
Authors: Cao Sunny , Yeung Mandy , Wan Jones
Published: March 2016

Traditionally, F&G detectors are positioned based on engineering experience, industry practices, or prescriptive standards. In recent years, Fire and Gas Mapping (F&G Mapping) studies which utilise 3D based computer aided mapping tools have been recognized as an effective way for Fire & Gas detection system design. Such a study has the advantage of quantified detection coverage to ensure prescribed performance targets are met and deliver optimised Fire & Gas detector layouts.

In the Oil & Gas industry, the most widely adopted F&G mapping assessment guidelines are BP GP 30-85 and SHELL DEP 32.30.20.11. Comprehensive F&G mapping requirements are described in these guidelines including: Risk grading of the fire and gas detection areas; Target fire and gas cloud sizes associated with the risk grade; and Performance coverage requirement (i.e. target coverage percentage) associated with the risk grade.

The BP guideline adopts the risk based mapping requirements, i.e. fire and gas detection zones are classified as different categories (high / normal / low fire risk areas, fully-enclosed / partially-enclosed / open areas based on congestion and blockage), and corresponding target fire and gas clouds of various sizes and target coverage percentages are assigned, in order to provide more cost-effective solutions to deploy the F&G detection systems. The SHELL guideline adopts a similar concept in gas detection by differentiating the target cloud sizes based on the congestion and blockage level of the detection areas.

A more recent challenge in the industry involves cost-effective project delivery through F&G mapping assessment to cater for two major concerns: Assurance of safety performance of the F&G detection system, i.e. provide adequate detection coverage; andOptimization of the F&G detection system to minimize CAPEX and OPEX.

The above trend requires improved F&G mapping calculations to reflect the actual performance of the F&G detection systems, meanwhile, taking into consideration the actual scenarios in fire & gas release events thus leading to further improvement of the risk based F&G mapping approach for performance evaluation. A consistent strategy for conducting F&G mapping studies at various project stages is also essential to minimize the discrepancies in conclusion due to changes in different engineering design stages.

This paper illustrates cost effective solutions through risk based approach F&G mapping study developed by ERM following completion of numerous F&G mapping projects. The paper also presents improved approaches to F&G mapping when evaluating the F&G detection system effectiveness.
A Novel Approach to Estimate Severity of Paraffin Deposition Inside Production Tubing for Vertical Lift Performance Matching in Well Models
Authors: Haindade Zishaan M. W. , Mundhe Pramod A.
Published: March 2016

The vertical-lift performance curves are often generated with the aid of computer software for creating well models of producing oil and gas wells. These models are used as tools for optimizing fluid production, generation of production forecast and well problem diagnosis. The well models are further used to plan for future requirement of artificial lift assistance.

One of the important components for development of representative well models is the Vertical Lift performance and Inflow Performance curve matching. The vertical lift performance curve is generated separately using well test data using various correlations and the best matching correlation to actual well pressure gradient is selected for VLP-IPR matching. The VLP depends on various factors such as tubing size, gas-liquid ratio, wellhead pressure, etc.

The producing oil wells having higher paraffin content tend to deposit paraffin wax inside the production tubing reducing the flow area and increasing the pressure drop. The deposition generally occurs near the surface and at greater depths the tubing is free from deposition due to higher temperature because of the geothermal gradient. Due to this an error is induced as the effective inside diameter of tubing is less than the actual diameter entered by the user, this leads to variation in the actual and calculated pressure drop ultimately leading to deviation by more than 10% in many cases.

This paper describes implementation of method to enter the severity of paraffin deposition in a particular length of tubing and dividing the total length of tubing into sections having different internal diameters. The estimation of deposition can be done by carrying out mechanical scraping operation in which the wax is cut mechanically using paraffin cutters of various sizes starting with the smallest and gradually increasing to higher sizes of cutters. The restriction due to wax is evident at the surface by monitoring the weight loss in the wireline weight indicator.

By using this method an accurate well model can be created which will represent the actual behavior of the producing well thereby increasing the accuracy of any further predictions.
Quest for Safety and Simplicity -Choosing an Appropriate Liquefaction Process Technology for FLNG Application
Authors: SIM Charles , TEH Erine Siew Pheng
Published: March 2016

Objectives/Scope: Keppel has identified the market need for a simple and safe natural gas liquefaction process to meet challenging offshore environments where production supports are limited. Such need is also amplified in smaller scale FLNG production plants of up to 2-3 MTPA.

Methods, Procedures, Process: Leveraging on Keppel extensive experience in FPSO conversion, Keppel is trusted to convert the first of its kind FLNG from an existing LNG carrier. In the pursuit of FLNG applications, operators desire a safe and robust process with easy operation consisting of low equipment count and low complexity. To respond to this market need and to leverage in its vast knowledge and experience in the FPSO conversion business; Keppel has developed a proprietary liquefaction process named PreNEx (Precooled Nitrogen Expansion), which is based on a widely accepted nitrogen expansion technology. It employs a single Nitrogen Expansion cycle together with an independent biphasic non-flammable refrigeration cycle for precooling, which is widely used in the air separation industries to achieve comparable liquefaction efficiency to that of multiple expander system without compromising safety, process simplicity, reliability, robustness and flexibility. Such innovative process allows for the conversion of old LNG carriers into FLNG facilities, thus providing a safe and simple alternative solution for small and midscale FLNG solutions. This study covers the optimization of the liquefaction process through simple heat flow redistribution with a process knowhow based on proven process cycles that are already in use, industry wide.

Results, Observations, Conclusions: PreNEx provides a simple, safe and sustainable alternative natural gas liquefaction process for deployment of FLNG. Precooling, condensate recovery and handling become independent from liquefaction operation. It has simple configuration of liquefaction heat exchanger and compression expansion of refrigerant, yet giving comparable thermal efficiency as other refrigerant compression expansion process.

Novel/Additive Information: While LNG liquefaction technologies in the market go towards complexity and fine process conditions to achieve efficiency, PreNEx uses the fundamentals of thermodynamic and heat transfer to achieve efficiency through redistribution of heat load in the process.
18"/12" CRA and 42" Carbon Steel Tie-in Spool Design and Installation for High Temperature/High Pressure and Sour Service
Authors: Pandravada K. N. , Kacher A. , Christensen L. , Russell G.
Published: March 2016

Tie-in spools are common features of subsea developments. On the INPEX Ichthys Gas Field development project, the tie-in spools were particularly large and heavy, which make them stand out from other developments.

The Ichthys Gas Field is located 220 kilometers offshore from the North West coast of Western Australia in water depths of 250 m to 270 m.

This paper covers the 18" corrosion resistent alloy (CRA) clad and 12" solid CRA production and the 42" carbon steel (CS) tie-in spools of the development. The production tie-in spools were designed for high temperature, high pressure and all the tie-in spools were designed for sour service and a 40-year life. The tie-in spools at flowline ends were designed to accommodate a typical flowline expansion of 2.6 m to 3 m.

The paper presents the design challenges and installation solutions developed for the tie-in spools.
Evaluation of Fatigue Performance on Semi Premium Connection for Casing Drilling Application to Prevent Connection Fatigue Failure
Authors: Ong G. , Ramli M. Nizam , Ahmad H. , Ando Y. , Yamamoto T.
Published: March 2016

This paper intends to share the approach adopted by Petronas Carigali Sdn Bhd (PCSB) to evaluate the fatigue performance envelope for a selected casing connection to support the ever expanding Casing while Drilling (CwD) technology. This paper elaborates the original testing procedure which included both fatigue testing followed by sealability test after repeated fatigue cycles to best simulate downhole drilling environment as experienced by the casing connections during CwD operation.

Fatigue performance and gas sealability reliability after undergoing fatigue cycles is one of the key selection criteria for casing connection for CwD application. This is of paramount importance to prevent unforeseen downhole fatigue failure which could lead to the loss of pressure containment and/or the severance of casing string if sufficient tensile load is applied.

Currently, there is no established industry recommended practice on the testing procedure to validate the connection's reliability to cater for CwD application. The closest available is API RP 5C5 or ISO 13679 which only focuses on OCTG premium connections' sealability performance.

PCSB, being one of the pioneer operators who have adopted CwD aggressively is determined to ensure that all casing connections used in CwD applications are physically tested and validated to establish a reliable fatigue envelope. In this project which took about 1 year to complete, a semi-premium connection without metal-to-metal seal threaded on 13-3/8 in. 68 ppf L80 pipe was tested in a 2-phase testing program. Phase 1 saw the connection being subjected to cyclic bending to failure while Phase 2 focused on connection gas sealability after going through a pre-set fatigue cycle.

The novelty of this fatigue evaluation test procedure is that it attempted to delve deeply into the effect of test specimen preparation on the resulting fatigue data such as thread interference, thread taper, running compound, make up torque, surface treatment and etc.

The ultimate objective of this test procedure with further refinement implemented is to ensure that the SAF (Stress Amplification Factor) obtained would be sufficiently reliable for future CwD applications in PCSB which will eliminate the risk of unexpected downhole failure in the form of fatigue and/or loss of containment.
Quantitative Risk Analysis of Well Integrity Issues in Deepwater Well Intervention
Authors: Ajimoko O. O. Tayo
Published: March 2016

This paper presents a quantitative risk analysis for well integrity issues associated with ultra deep water well intervention in the Gulf of Guinea (GoG). The basis for the work is the history of well barrier breach, loss of well integrity during completion and or re-completion in the GoG and oil spill. The reliabilities of the subsea completion components and accessories will also be investigated. The study will draw on available industry data base on well integrity failures, barrier breaches and well integrity problems encountered in the course of field development and workover.

A hypothetical ultra-deep water well will be used as the model for problem definition and boundary conditions establishment. The estimated Quantitative Risk Assessment (QRA) of well integrity events will be compared against available real data for verification and correlation check. For the purpose of this work a rig based well intervention will be considered.
Structure Integrity Monitoring with Meteorological Environment Load for a Fixed Platform in Oil & Gas Field
Authors: Lee Michael M. S. , Chung Joseph Chul
Published: March 2016

Development of smart sensors for structural integrity monitoring[1] and damage detection has been advanced remarkably in recent years. Nowadays optical fiber sensors have attracted many researchers' interests for their attractive features, such as multiplexing capability, durability, lightweight, electromagnetic interference immunity.

The other study is ongoing and has investigated new methods to improve deepwater monitoring and addresses installation of advanced sensors on already-deployed risers, flowlines, trees, and other subsea assets. These highly sensitive monitoring systems will provide operators a cost-effective method for detecting and responding to potential failures, flow assurance issues, and catastrophic events.

In the past, a major shortcoming of post-installed monitoring systems has been inadquately coupled between the sensor and structure. A significant achievement was recently made in bonding methods for sufficient coupling in Oil & Gas field environment. There are two challenges in calibration for the post installed sensors to determine "the baseline or zero state of stress" and "sensitivity of the fiber Bragg gratings on the clamped against the actual load changes" on the structure.

One of the effective monitoring system would be enhanced by calibration methods employing fundamental predictive methods to establish both baseline and sensitivity values[2]. The transition layer between surface and deep water levels (thermocline) required to isolate temperature effects from structural data using temperature compensation for the strain sensors with developed and integrated into the software algorithm.

However, a further validation with the empirical measurement based that correlated methorogical environment load for years should be required since is a difficult challenge to identify and select which results would be the correct either "the theoretical analysis program" or "measured data from the field".

In this paper, the results of low frequency response for the structure Integrity monitoring from utilizing statistical data analysis that consisted with big data from meteorological environment data, accelerometer, tiltmeter and strain sensor from fixed platform in Oil & Gas field is presented.
CO-REGISTRATION OF TERRESTRIAL AND UAV-BASED IMAGES – EXPERIMENTAL RESULTS
Authors: Gerke M. , Nex F. , Jende P.
Published: March 2016

Abstract. For many applications within urban environments the combined use of images taken from the ground and from unmanned aerial platforms seems interesting: while from the airborne perspective the upper parts of objects including roofs can be observed, the ground images can complement the data from lateral views to retrieve a complete visualisation or 3D reconstruction of interesting areas. The automatic co-registration of air- and ground-based images is still a challenge and cannot be considered solved. The main obstacle is originating from the fact that objects are photographed from quite different angles, and hence state-of-the-art tie point measurement approaches cannot cope with the induced perspective transformation. One first important step towards a solution is to use airborne images taken under slant directions. Those oblique views not only help to connect vertical images and horizontal views but also provide image information from 3D-structures not visible from the other two directions. According to our experience, however, still a good planning and many images taken under different viewing angles are needed to support an automatic matching across all images and complete bundle block adjustment. Nevertheless, the entire process is still quite sensible – the removal of a single image might lead to a completely different or wrong solution, or separation of image blocks. In this paper we analyse the impact different parameters and strategies have on the solution. Those are a) the used tie point matcher, b) the used software for bundle adjustment. Using the data provided in the context of the ISPRS benchmark on multi-platform photogrammetry, we systematically address the mentioned influences. Concerning the tie-point matching we test the standard SIFT point extractor and descriptor, but also the SURF and ASIFT-approaches, the ORB technique, as well as (A)KAZE, which are based on a nonlinear scale space. In terms of pre-processing we analyse the Wallis-filter. Results show that in more challenging situations, in this case for data captured from different platforms at different days most approaches do not perform well. Wallis-filtering emerged to be most helpful especially for the SIFT approach. The commercial software pix4dmapper succeeds in overall bundle adjustment only for some configurations, and especially not for the entire image block provided.