bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Preservation Chemicals for Extended Shut-Ins Following Hydrostatic Testing of Gas and Service Pipelines
Authors: Hali A. L. , Lehmann M. N. , Cook S. E. , Russell R. D. , Hartley S. J. , Finan S. M.
Published: March 2016

This paper considers some of the challenges and learnings associated with the application of chemicals for preservation of coated pipe/flow line for a major LNG project in Australia. This includes a comparison of the effectiveness of biocide and oxygen scavenger chemistries for treating seawater. It also discusses monitoring philosophies and the unique approach taken in designing and optimizing the chemical injection system to address the environmental and technical challenges of this project.

The gauge testing of flowlines and pipelines in large-scale LNG projects of Australasia is an important compliance stage required prior to commissioning. Due to the extended timeline necessary to complete downstream infrastructure, pipelines and flowlines are usually deployed well before the treatment facilities are constructed, and may be shut-in awaiting connection for relatively long durations, following the hydrotesting procedures. If left unprotected, the pipeline becomes susceptible to corrosion predominately due to the presence of bacteria, but also due to the presence of dissolved oxygen and the saline nature of the hydrotest fluid which is typically seawater. Chemical treatment strategies for preserving these lines can consist of a bacteria control agent (biocide), and an oxygen scavenger, and occasionally a corrosion inhibitor which is added to mitigate corrosion in case all the oxygen has not been removed. Treatment strategies are often dependent on the required shut-in duration, local environmental regulations, and the asset integrity management specifications defined by the operator.

For the project presented in this paper, the integration of data obtained from the various stages of testing and computational modeling supported the design of an effective treatment program for this application. This was achieved despite of a number of unique challenges arising from stringent environmental constraints and the tight operating specifications required in this project.

A case history is provided describing the novel approach adopted in selection of pipeline preservation treatment chemicals through the assessment of various parameters, including laboratory studies (conducted to verify product performance under different operating conditions), as well as Computational Fluid Dynamics (CFD) modeling studies aimed at optimizing the chemical injection location, residence time, and flow regime. It is anticipated that such a systematic approach in design and optimization of treatment programs can provide a multitude of benefits in similar projects operating in environmentally-sensitive locations.
Acoustic Transmitter Active Vibration Control for Sonic Logging
Authors: Zhao Yiming , Song Xingyong , Dykstra Jason
Published: March 2016

Sonic logging tools are commonly used in wireline logging and logging-while-drilling (LWD) operations for determining formation lithology along the wellbore. Having an understanding of the near-wellbore rock with high certainty can significantly reduce risk when planning well stimulation and completion. The quality of sonic logging data is critical for decision making, especially in offshore applications for which mistakes can be costly. While much of the progress towards improving sonic logging data quality has been pursued via mechanical and electrical design along with post-process signal analysis, little has been done with using advanced control systems to boost performance of the sonic logging tools.

In this paper, the authors demonstrate noticeable improvement in the sonic logging tool's performance by producing high-quality acoustic waves from the acoustic transmitter using a novel control system design. While with proper mechanical and electronic design a transmitter can generate acoustic waves with high-quality frequency characteristics for measurement, there can exist sustained resonance vibration that degrades the data. This paper introduces a control method that mitigates excessive transmitter vibrations, releasing the full potential of the transmitter mechanical design. The robustness of this control system allows for peak performance over the range of high-pressure/high-temperature (HP/HT) environments the tool might experience downhole.

The control method described in this paper operates on similar principle as noise-cancelling headphones; however, because there is no external microphone or other sensing device, the control system is challenging to design. Essentially, it cancels out undesired vibration by generating a second waveform of equal strength but opposite direction and superimposing it to the existing waveform. The challenge of generating the proper cancelation waveform is overcome by a multistep learning algorithm. To sense the vibration, it uses the back-electromotive force (back-EMF); a voltage signal determined from the actuation device itself. One of the issues with using the back-EMF is it is substantially smaller than the actuation voltage, making reading this value during firing difficult. The benefits of this approach include reducing sensor costs and improved robustness by reducing sensor failure modes. The only modification required for the implementation of this advanced control system is a firmware update, making it an effectively zero-cost solution for a step-change boost in performance. Both laboratory test results and field data are presented to demonstrate the effectiveness of the novel control algorithm.
How Can Suction Pile Foundations Help to Maximise Profitability of Marginal Fields?
Authors: Spanjaard T. , Romp R. H.
Published: March 2016

As per January 2014, Petronas estimated Malaysia has some 106 marginal oil fields with approximately 580 million barrels of oil. Development of these fields require platforms almost similar to commercial fields, while total production is typically lower due to smaller reservoirs. Therefore, the total revenues are smaller and thus development is often questionable. More efficient technical solutions can contribute to cost reductions and hence turning marginal fields into commercial fields. This paper outlines a cost-efficient technical solution that contributes to profitability of marginal field platforms.

Re-use of platforms will lower the total investment required. The main technical challenge is to find a foundation method that is suitable for decommissioning and allows for reinstallation. A suction pile foundation is characterized by relatively fast installation and easy decommissioning. Installation is done by a discharge of water from the inside of the suction pile, leading to pressure difference between the inside and outside of the suction pile. This causes a net downward installation force, resulting in a penetration of the soil. The reversed principle is used for decommissioning or relocation of a suction pile founded platform.

Cost reductions in construction, installation and decommissioning phases are combined in the Self-Installing Platform (SIP) concept. The concept comprises of onshore construction of a one-piece platform, followed by transportation to field location without the need of HLV's. Hence, transportation is done either floating, towed or lifted by a sheer leg vessel. At site, the platform is lowered on the seabed and subsequently the suction piles are installed to target penetration. Once the wells are depleted, the SIP allows for relocation and subsequent installation at other marginal fields.

Suction piles are successfully used since 90's for many offshore applications with soils ranging from soft to stiff clays, loose and dense sands and in layered soils. Currently, four (4) SIP-1 concepts and three (3) SIP-2 concepts are successfully installed. This proves the potential economical benefit of future developments of the SIP concept in marginal fields.
Experience on Deepwater Drilling Riser about Hang-off Modes in Typhoon Condition of South China Sea
Authors: Leixiang Sheng , Liangbin Xu , Jianliang Zhou , Shiquan Jiang , Xunke Li
Published: March 2016

Typhoon occurs frequently from July to November every year in South China Sea. It develops fast, moves in high speed, and changes trajectory frequently, especially the typhoon, which is formed in local sea area near the drilling rig. It always threatens the safety of deepwater drilling operation. Typhoon response plan is therefore required to avoid damage to the deepwater drilling operation. According to traditional response plan, all the riser joints should be retrieved onto the rig floor and then the drilling rig should be steered away from the typhoon developing trajectory. However, it is a huge challenge to retrieve all the riser joints in deepwater due to limited response time. For example, the related T-time (typhoon prepare time) of L-1, with water depth over 2500m, is more than 6 days, but the forecast precision of typhoon is only 4-5 days. This indicates that it is not practical to retrieve all riser joints onto the rig in a limited response time, thus contingency plan of hanging off riser system to resist typhoon is more practical for deepwater drilling operations.

A case study example is presented in this paper to discuss soft hang-off and hard hang-off mode. Different hang-off lengths are analyzed in the case study. Also, combination effect of driving speed and drilling vessel heading is considered in the case study. This paper summarises the related experience of CNOOC about how to response to typhoon in hang-off mode.
Effect CO2-H2S on Corrosion of 3%Cr Carbon Steel in High pCO2 Environments
Authors: Abas Ahmad Zaki , Nor Azmi Mohamed , Suhor Muhammad Firdaus
Published: March 2016

The corrosion behavior of 3%Cr carbon steel was investigated under high pressure carbon dioxide environments, containing small amount of hydrogen sulfide, to simulate the condition of high carbon dioxide containing natural gas transporting offshore pipeline. It was systematically studied under high pressure carbon dioxide (range from 80 and 120 bars) with variation in other key parameters (temperature, water partitioning and hydrogen sulfide concentration). The corrosion rates were tested using High Pressure and High Temperature (HPHT) Autoclave and measured using the techniques such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), iron count and weight loss (WL). The surface morphology and the composition of the corrosion product layers were analyzed by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that in the water-rich phase, the addition of 200 ppm hydrogen sulfide instantaneously decreased the corrosion rate of 3%Cr at both 25°C and 80°C (80bar and 120 bar). It was also observed that the corrosion rates of 3%Cr carbon steel at 120bar and 80°C in the water-saturated CO2 phase are negligible. The addition of hydrogen sulfide increased the corrosivity of this phase and within the Minimum Acceptable Corrosion Rate (MACR) of 0.1 mm/year.
Integration/ Assimilation of Workflows to Describe and Characterise Low Resistivity/ Thin bed Reservoirs using Advanced Wireline and Core Data
Authors: Gaafar Gamal R , Altunbay M. Mehmet , Bonnye Yoel , Musa Faizah M , Bal Adriaan. , Belevich Alexander V.
Published: March 2016

Tapping into low resistivity (LR) pay zones in brown fields requires less capital expenditure (CAPEX) than developing new fields or embarking on enhaced oil recovery (EOR). Therefore, the economic significance of commonly overlooked LR thin-bed reservoirs drew significant attention from asset managers, particularly in the current rapidly declining economics of the hydrocarbon (HC) business of today. LR reservoirs however, are difficult to identify. Therefore, they can easily be bypassed unless a comprehensive identification program is employed. Identification, evaluation and quantification of LR reservoirs require integration of different workflows that address different aspects of geophysical, geological, petrophysical and reservoir engineering challenges. In this study, a workflow and case study for selection of key wells with the highest potential of by-passed LR reservoirs and integration of computational workflows, with appropriate algorithms, are demonstrated for the monetisation of LR pay zones.

We are proposing a systematic approach to identify LR-prone areas of a given basin or field prior to screening petrophysical data for verification and evaluation. The approach first identifies areas where depositional processes are conducive for developing LR reservoirs. For example, areas associated with channels that may have well-developed crevasse splays. These potential LR areas are then selected for more detailed petrophysical investigation to confirm the potential presence of LR pay. If available, bypassed but potentially productive zones can be verified with advanced logging data using integrated algorithms. The elimination of unnecessary testing in parts of a basin, or field, having low potential for LR pay zones, yields the sought-after gains in economics and augments the concept of a "financially less demanding" project.
A Novel Workflow for Modelling Complex Compartmentalised Structures Leads to Enhanced Field Development Strategy
Authors: Iskenova Gulnara , Ram Bhargava , Maldonado Jorge , Kumaran Prashanth , Meyer Juergen , Chabernaud Thierry , Casado Jonathan H. , Sharma Sachin K. , Rahman Mohd Ramziemran Abdul , Moreno Juan Carlos , Ibrahim Ramli B
Published: March 2016

Reservoir compartmentalisation, whether structural or stratigraphic, is one of the most prominent parameter for accurately characterising the distribution of hydrocarbons in the subsurface and it is a key element for optimising hydrocarbon recovery. In order to accurately characterise its compartmentalisation, a new volume-based structural modelling technique have been applied for generating a geocellular model of the complex, highly faulted east flank of the studied field (Sabah, Malaysia). Benefits over existing pillar-based and surface-based techniques are discussed.

The volume-based modelling technique consists of interpolating a continuous 3D property representing the relative stratigraphic age of the formations from all available well and seismic interpretation data. A watertight structural framework composed of faults and horizon surfaces is then extracted from this property, and converted to a geocellular grid in which the faults are stair-stepped. New workflows were developed for early integration of fluid distribution and production data during the creation of the geological framework, leading to an accurate delineation of fault compartments.

The fault network of the new east flank model is composed of over 90 synthetic and antithetic faults, forming X and Y-shaped truncations and subdivided into over 35 geological units. Fault truncations are located within the volume of interest and have key bearing on the understanding of fault sealing potential. The subsequent 3D grids include all interpreted faults and integrate fluid contacts, pressure and production data, capturing essential compartmentalisation characteristics.

The main benefit of the volume-based technique over pillar-based methodologies is that it incorporates all the fault network complexity. Indeed, as their coordinate lines must be parallel to fault surfaces, grids which geometry is extruded along curvilinear pillars can generally not be used to represent fault systems with X or Y-shaped truncations. Besides, grid cells may become excessively skewed in presence of synthetic and antithetic faults, which can trigger inaccuracies when performing flow simulations.

Finally, thanks to early integration of production data during the interpretation phase the dynamic model could easily be history matched by adjusting fluid transmissibility across nearby fault blocks and between adjacent sand layers.
Modifying the Hall Plot for Analysis of Immiscible Gas Injection Wells
Authors: Talabi O. A.
Published: March 2016

The Hall plot is a proven, useful tool for evaluating performance of injection wells. It was originally developed for single-phase, steady-state, radial flow of liquids. It continues to be used to analyse water-injection wells and has also been modified and applied to the injection of polymer micellar solutions for enhanced oil recovery (EOR). However, published studies into its applicability for gas injection scenarios are very limited. This paper discusses the applicability of, and modifications to, the Hall plot for evaluating injection of gas into a reservoir under specific conditions—particularly immiscible gas injection into a gas cap.

Three commonly used expressions of the Darcy equation applied to gas wells exist—the low pressure approximation, the high pressure approximation and the method of real-gas pseudopressures. For this study, a methodology similar to that which was originally used to derive the Hall plot for liquids is applied to these expressions in order to derive modified ‘Hall’ expressions for gas wells, making appropriate assumptions. The validity of the resulting derived expressions was then verified using results from a commercial reservoir simulator. Published correlations were used to evaluate pressure-dependent properties for the plot, where required.

Based on the analysis, it was found that at low pressures, using the original expression of the Hall plot introduces a nonlinearity that could be misinterpreted as a change in injectivity. The modified expression for the Hall plot, based on the low-pressure approximation and published correlations, removes this artificial nonlinearity and straightens the plot, greatly improving its diagnostic value. It was also seen that at high-pressures, the attempts to re-derive a Hall plot expression for gas flow lead to an expression of the same form as the original Hall plot. Therefore the original Hall plot can be used without modification as it produces a straight line with no curvature. The method of pseudopressures gives the most comprehensive solution over the entire pressure range as expected, although it is more difficult to evaluate due to the need for numerical integration.

The results from this work indicate that modified versions of the Hall plot can be used qualitatively by engineers to identify injectivity problems during injection of gas into a reservoir under specific conditions—immiscible gas injection into a gas cap—as long as the appropriate approximations and correlations are used.
Geomorphology and Karstification of the Southern Field High Carbonates in Central Luconia Province
Authors: Wei Kiat Chung , Menier David , Jamaludin SN Fathiyah , Ghosh Deva
Published: March 2016

The development of the Central Luconia carbonates in offshore Sarawak has been governed by the orientation of the Luconia Platform, syn-depositional features generated by the rifting and oceanographic parameters, such as sea level fluctuations, hydrodynamic, climate changes, salinity, and oxygen levels. The studied carbonate platform is developed over a southern field high of Central Luconia Province. The prevalent high frequency sea level fluctuations during the Miocene (Burdigalian to Serravallian stages) developed an extensive array of karst by rapid sub-aerial exposure and re-submergence of the carbonate platforms. Multi-attribute was applied to the 3D seismic volume of one of the selected carbonate platforms in Central Luconia Province to recognise karstic feature developed within the platforms. Though it is explicit that karstification occurred mainly along fractures and faults, the karst distribution in the Central Luconia carbonates remains to be an enigma due to their heterogeneous nature, which in turn provides a challenge in drilling and exploration. The studied platform exhibits patchy growth distribution during the Burdigalian stage. This growth is deemed as the initial stage of carbonate growth followed by a combination of build-out and backstepping for the second growth stage. A major karstification stage is highlighted on the second stage build-up, which correlates with a major sea level drop and the distinctive collapsed-paleocave topography. Drowning is evident on the final stage of the platform that can be correlated to the final surge of sea level rise in the Serravallian.
Innovative Multi Technologies Collaboration for Ultra-HP/HT Offshore Fracturing Stimulation
Authors: Christiawan Arya B. , Buelvas Manuel L. , Shukla Sourabh
Published: March 2016

The ultra-high pressure and temperature (HPHT) lower Cretaceous sand-shale layer in Krishna-Godavari basin (KG basin), in eastern India offshore shallow water, in the Godavari River interdeltaic region, is currently the world's highest-temperature petroleum reservoir being explored in the marine environment. It is a part of the fluvial sedimentary KG basin, which is recognized as holding India's largest gas reserves. Its area is approximately 50,000 km2 and it extends from land to the shelf-slope and adjacent deep-sea area along the eastern passive continental margin of India. The bottomhole static temperature of the reservoir ranges from 350 to 450°F at 16,000 to 18,000 ft true vertical depth (TVD), with pore pressure gradient up to 0.85 psi/ft. The hydraulic propped fracturing technique is integral to the completion and well testing program in this typical tight reservoir

Krishna-Godavari basin, seismological cross section, source from Sorkhabi et al, Geotimes, and Sahu et al.

The design and delivery of hydraulic propped fracturing in such a complex reservoir and operational environment requires advanced technologies and meticulous planning and execution, including reservoir and geomechanical characterization derived from latest HPHT formation evaluation logging tools, implementation of integrated production simulation and fracturing modeling software, and application of ultra-HT completion and fracturing products. In addition to technical complexity, the limited drilling unit capability also required equipment planning that involved an integrated fracturing and testing wellhead-string-packer system, a project-specific modular HPHT stimulation boat and post-fracture flowback testing plan and equipment that included surface well testing and a coiled tubing nitrogen fleet.

Several successful hydraulic fracturing operations were performed in this tight ultra-HPHT reservoir for multiple operators. This paper will describe the case history of the hydraulic fracturing completion campaign for one operator in the basin, in particular describing ultra-HPHT techniques and products that were key to the project delivery:

Basin modeling, reservoir, and geomechanical characterization workflow as an integral part of hydraulic fracturing design in complex frontier reservoir

Installation and preparation of modular HP/HT stimulation vessel custom built for this project

Implementation of synthetic fracturing fluids developed specifically for ultra-HT application up to 450°F in a high-pressure and high-shear environment.

This fracturing project has been compared to previous similar treatment in the same basin, and lessons learnt from this campaign has been summarized for similar future ultra HPHT projects globally.
Integrated EOR Approach via Application and Installation of Distributed Fiber-Optic Technology
Authors: Chin M. W. S. , Woon G. C. , Wood K. , Gorgi B.
Published: March 2016

This paper describes the successful permanent installation of the first distributed-temperature-sensing (DTS) system in an enhanced oil recovery (EOR) field and processes used in the workover completion. Successful installation was achieved through a combination of effective planning and field execution before and during the completion period. This paper also describes engineering challenges and unique solutions applied to overcome them. The DTS data analysis techniques used for the initial injectivity test are briefly discussed.

The full-field offshore application of an immiscible water-alternating-gas (WAG) process involves simultaneous injection of water and gas to the reservoir formation. Using a sweeping mechanism, water displaces hydrocarbon downwards while gas displaces hydrocarbon upwards, thereby, achieving an efficient microscopic and macroscopic sweep. Thus, the requirement for a technology that can provide both injection profiling and geothermal delineation is essential. DTS surveillance is not a new technology; however, its application in production-optimization process is new and provides insight on sweep efficiency. Higher lift costs and lower oil prices make it even more critical that installations are trouble-free and executed on time.

The number of EOR projects has been growing in Malaysia in recent years. Malaysia's first large-scale EOR project was recently completed offshore Terengganu, representing an investment by a local profit sharing company (PSC) and successful collaboration with a service company for execution. It is a priority that specific criteria are set to ensure the execution process does not only provide required reliability but also complies with health, safety, and environmental (HSE) standards. Thereby, as a continuous and progressive step, project management is of utmost importance in ensuring strategic planning is unique and reliable throughout the duration of the project, specifically for each respective operator.
Fracture Analysis Using Multicomponent (3C) Seismic Data
Authors: Subramaniam R. D. , Prajapati S. , Ghosh D. P.
Published: March 2016

Fracture basement is one of the potential targets for hydrocarbon traps. The properties of the fractures are hardly known in complex geological setting. The emphasis of this study is on the possible use of shear wave splitting in fractured or anisotropic media to obtain the most significant parameters. To perform this technique, cross-correlation method is employed in the three-component (3C) seismic data. This approach estimates the (1) time delay (dt) between the slow and fast waves which gives the crack density in the medium, (2) fast polarization direction (?), offering the fracture orientation and correlation between slow and fast component. Here, we present three case studies on shear wave measurements and the results conclude that shear wave splitting is a reliable method to determine the fracture orientation and density.
Challenging Well Completion and Intervention Technique for Multizone Offshore Brown Field Well
Authors: Chandak K. , Anand S. , Patil B. , Sarma P J , Koshy N. , Vadapally S. , Nayak J.
Published: March 2016

XX-1 is a newly drilled well in Ravva field in eastern coast of India deviated to 70 deg and completed with a 6? Open-hole section. The initial completion plan for the sand prone well was to complete with stand alone screens for a single pay zone. During drilling, additional pay zones were encountered which necessitated completing the well with zonal selectivity using sand-screens with SSD. Selective completion required thru tubing intervention to operate the SSDs and produce selectively.

Due to high deviation, intervening with slick line was very challenging whereas coiled tubing operations had its own limitations which are discussed in the paper. Hence it was decided to use Electro-hydraulic stroking tool along with motorable tool sections to convey tools in the high angle well.

While shifting SSDs with hydraulic stroking tool, frequent held ups and stuck points were observed across all SSDs which made it difficult to confirm shifting key location with reference to SSD sleeve profile and hence confirm SSD opening. This resulted in unsuccessful attempts and tool failures. A detailed analysis was carried out to ascertain the probable cause of multiple held ups within the screen SSDs and to find out other ways to shift the sleeve. Trouble shooting was performed by combining video recording of shifting attempts at surface in an unused screen section along with engineering drawings of the screen. Based on trouble shooting results, shifting procedures were modified accordingly to precisely engage the shifting tool with SSD profile and SSDs were successfully opened. The stroker system also proved useful in opening a circulation SSD which enabled the well to be brought on line.

This paper describes operational difficulties encountered and innovative ideas implemented to shift SSDs. It also reviews job planning, trouble shooting and execution, as well as reports the lessons learnt to derive best practices for future similar operations.
Cement Isolation Packer - An Economic Method of Accessing Bypassed Marginal Reserves in Offshore Brown Field
Authors: Koshy N. S. , Anand S. , Patil B. , Singhal A. , Chandak K. B. , Vadapally S. V. , Sabharwal V.
Published: March 2016

Ravva is a mature field located offshore east coast of India with over 20 years of production history from Middle Miocene sandstone reservoirs. During the development phase of the field, Late Miocene (LM) sands were intersected in few wells at shallow depths. Due to the presence of more promising and critical zones below, these sands were not completed and fell above the production packer and behind the production casing. The marginal reserves in these sands did not justify workover operation to complete it. Rigless options were studied and a shut-in well was selected for implementation.

In order to safely complete and access the bypassed shallow sands, a vessel based pumping operation was planned to place a cement packer in the tubing – casing annulus. The slurry was circulated into the production casing/tubing annulus through a circulation SSD installed above the production packer.The cement packer was thus placed across the zone of interest. Designing of the cement slurry was based on reservoir parameters and the setting time was optimized to prevent reversing of the slurry back into the tubing. The cement mix had a bonding agent to exhibit good metal-cement bonding providing prolonged endurance of the cement with the capability of holding the expected pressure differential. The cement packer emulated a production packer providing zonal isolation for the new completion.

Size of the platform precluded spotting of the complete Coil Tubing spread on the platform. High cost prohibited catenary coil tubing operations. As an alternative, the pump spread was placed on a DP vessel and the coil tubing unit was spotted on the platform. A high pressure hose running up from the vessel to a standpipe on the main deck of the platform formed the main conduit for fluids being pumped from the vessel into the CT or wells. Onsite mixing of the cement slurry on the vessel required detailed planning and execution. The well was activated & tested at rates of 1500 bopd with no integrity concerns till date.

This paper will emphasize on the operational procedure and challenges of successfully completing the zone and bringing the shut-in well online. The execution of this operation was done at 1/10th of the cost of a rig based workover. This has also opened up new opportunities to access similar bypassed reserves resulting in incremental production from reservoirs which would have otherwise been left untapped.
A Study of a Novel Inter Pipe Coating Material for Paraffin Wax Deposition Control and Comparison of the Results with Current Mitigation Technique in Oil and Gas Industry
Authors: Rashidi M. , Mombekov B. , Marhamati M.
Published: March 2016

Hydrocarbon liquid consists of a range of components with different physico-chemistry characterization. Sometimes there are heavy component with crude oil such as asphaltene, naphthenic and paraffinic wax components and etc. Deposition of wax in both onshore and offshore pipelines presents a costly problem in the production and transportation of oil. There are several parameters contributing to wax deposition in multiphase crude oil flow, e.g. pressure drop, flow rate, pipe internal body surface roughness, surface energy of the pipe, liquid wetting of pipe wall as well as temperature difference between fluid and surroundings [1,2]. Application of internal coating of subsea pipelines can reduce wax deposition. The aim of the present work is to experimentally study the wax deposition in Malaysian waxy crude oil, where the data set studied was gathered from several experiments. Most of the methods can be used to remove the paraffinic wax deposition after it occurs. However, insulation systems yielded in better performance as it was found to help in the prevention of heat loss and solid deposition during flow conditionsThis study utilized flow loop apparatus. This paper compared the wax deposition behaviour with temperature, roughness and flow rate within the tested pipes [Polyvinyl Chloride (PVC), Ethylene - TetraFluoroEthylene (ETFE), and steel as a reference material]. Moreover, the prevention of temperature loss from liquid to surrounding and corrosion control significantly affects pressure drop across the pipeline [3]. The conducted experiments concluded that ETFE had a better effect on the paraffin wax deposition control. Moreover, ETFE as a novel polymer based coating material was economically feasible to be utilized in the oil and gas downstream and upstream systems exposed to wax deposition.
Improved Casing Integrity Evaluation Enables Multiple Strings Metal-Loss Profilling in Aging Wells
Authors: Zaini A. Bin Ahmad , Ali A. Md , Razak M. Abdul , Samaile E. , Busaidy Adil , Wa Wee Wei
Published: March 2016

BNX field is a mature oil field with complex wells targeting multiple reservoirs across the field. The introduction of an Enhanced Oil Recovery (EOR) project has set a new challenge on determining the integrity of aging wells. In the past, comprehensive downhole casing integrity testing was rarely done with the exception of conventional pressure integrity checks. Such methods may have limited effectiveness in analyzing wells with multiple strings and complex completion configuration, and cannot precisely locate or quantify the magnitude of metal loss. Convention is to run a Multi-fingered caliper inspection tool to evaluate the single tubing inner metal loss, but again this has limited value as it could not measure tubing thickness or more importantly the condition of the casing behind the tubing. A solution was needed that could allow the evaluation of tubing and casing to be done offline and simutaniously.

An innovative approach with a combination of slim-hole ultrasonic borehole imaging tool and electromagnetic imaging tool is deployed to provide a new insight in the casing integrity evaluation in the field of study. The idea being that the borehole imager would accurately describe the tubing string while the electromagnetic tool would describe the total metal, both tubing and casing, subtracting the tubing thickness from the total metal measured would then leave an accurate measurement of the casing thickness. Three well candidates were identified, each well was planned for a sidetrack, but before moving a rig onto these old wells the team wanted to know if the 9 5/8? casing was in good enough condition to use. And for the first time, the thickness of multiples strings up to 13.375 inch casing was evaluated simultaneously utilizing a low frequency electromagnetic and a high resolution ultrasonic measurement. The ultrasonic tool provides comprehensive metal loss evaluation for inner most string while the electromagnetic tool provided the total metal thickness of both strings. The combined interpretation of these two through-tubing evaluation outputs provides a viable technique to evaluate metal loss profile for first two strings under study without the need to pull the inner most string. The overall casing evaluation operation is further optimized by the maiden deployment of an e-line light weight unit.

The successful application of this newly integrated casing integrity evaluation technology has greatly reduced the intervention related risks, costs and time. The case study presented will serve as the critical pilot to extend the same workflow to other wells across the field. In addition it paves the way for the next generaltion of EM and slim ultrasonic tools discussed at the end of the paper.
A Systematic Dynamic Characterization Method for Abnormally High-Pressured Gas Reservoirs
Authors: Li Yong , Li Baozhu , Zhang Jing , Xia Jing , Jiao Yuwei , Peng Hui , Xiao Xiangjiao , Wang Hongfeng
Published: March 2016

Compared to the normal clastic gas reservoirs, abnormally high-pressured gas reservoirs in China have some distinctive characteristics: deeper buried depth, higher productivity of single well, more heterogeneous formation, stress sensitive rock and more difficult to develop. It's not feasible to identify and characterize this kind of reservoirs only based on one method. This paper presents a systematic method of dynamic characterization for abnormally high-pressured gas reservoirs, which mainly involves material balance analysis, rate transient analysis and well test interpretation in combination with geological analysis results.

This paper firstly establishes a new equation suitable for abnormally high-pressured gas reservoir with aquifer support. Then the systematic method mainly using material balance analysis, rate transient analysis and well test analysis are detailed presented. The systematic method can fully integrate the long-term low accuracy data of dynamic production and short-term high-precision data of transient well testing. And the three methods can be combined and constrained to each other, in order to correctly evaluate well and reservoir properties, such as the formation permeability, well skin, oil drainage radius, gas in place and so on. Also the methods have the diagnostic function to aquifer influx, which can predict water breakthrough in gas wells. Furthermore, based on the evaluation results, the "dynamic numeric model" can be built and all three methods can be used to predict the performance of the wells.

M1 abnormally pressured gas filed in China is taken as an example to elaborate the details of this method. The calculated well drainage radius shows that some well production is interfered by surrounding wells, while some wells are not. Also transmissibility of faults are evaluated and used in the numerical model building. Based on the evaluated properties, "dynamic numerical model" of the gas reservoir are established and applied to the well performance prediction, which are validated by actual gas well performance. It can be seen that these three methods are fully integrated and constrained with each other, which can generate a reliable result.

This systematic technique has been successfully applied to "M1 gas field Adjustment and Optimization Plan", which provides a reliable foundation for the effective development of M1 gas field. Furthermore, the systematic method can be used for reservoir evaluation and performance prediction in any other abnormally pressured gas fields.
Step Riser Configuration for Deepwater Application
Authors: Tan Zhimin , Yuan Jiabei , Hou Yucheng , Clevelario Judimar
Published: March 2016

An innovative step riser configuration and its variations are presented for use in deep or ultra deepwater field developments. The configurations are based on existing proven technologies and free-hanging catenary configurations. The step riser configuration is characterized by the utilization of buoyancy tanks/modules array to generate over hundreds of tonnes net uplift buoyancy, directly exerting that buoyancy force to the riser midline connection rather than the riser body. This technology enables significant improvements in the stress utilization and fatigue performance of a flexible riser. In addition, the reduced tension loads greatly decrease installation vessel requirements. The large buoyancy system not only reduces the top tension but also decouples the motion passing from the upper section to the lower section. As a result, high compression and over-bending issues near the touchdown zone can be mitigated.

This paper also investigates step riser configuration performance and its variations, step wave and tensioned step riser configuration, to address the specific issues associated with different deepwater applications. Parametric studies are performed using commercial software to predict and compare the behavior of the stepped riser system in various dimensions. Also discussed is a scaled step riser model test to validate the performance of the step riser configuration. The step riser model was towed horizontally at varying speeds to investigate the riser's tension, curvature and vortex induced vibration (VIV) responses.

The study indicates that the step riser configuration and its variations are a practical cost effective solution for flexible riser systems in deepwater applications with severe metocean conditions.
Sand-Silt-Clay Evaluation Models: Which One to Use - A Case Study in the Malay Basin
Authors: Gaafar Gamal Ragab , Eltunbay Michael Mehmet , Aziz Shaharudin B A , Najm Ehab
Published: March 2016

Clastic-reservoir characterisation of the Malay basin poses numerous challenges resulting from the silty and clayey nature of its reservoirs. To date, different practitioners use shale volume (Vsh) and clay volume (Vcl) in an exchangeable fashion, where the former is rock and the latter is defined as either size or mineral content. Inaccurate quantification of Vcl magnifies the errors inbound in the calculation of porosity and saturation because of the impact of clay density and conductivity in relevant equations.

Different models were developed to evaluate sand, silt, and clay reservoirs, which may be applicable in some local areas and not applicable in others. One of the more common caveats in some of the available models is the mix between the silt volume, Vsilt, and the volume of dispersed clay, Vcl_disp, which has an impact on the effective porosity and water saturation calculations, Sw, especially when evaluating lowresistivity/low-contrast (LRLC) zones using the Thomas-Stieber model.

In the presented study, the same data set was treated with three different deterministic models to solve for sand, silt, and clay volumes. These models include: 1) the sand-silt-clay-water model, also known as the Malay or SSC model; 2) a model that uses maximum porosity to calculate the silt volume; and 3) a technique that uses nuclear magnetic resonance (NMR) clay-bound and capillary-bound volumes from the NMR porosity model.

To select the most accurate and reliable petrophysical approach, the results were compared with X-ray diffraction (XRD) analysis results in the area of the study, and a comparison of grain-size distributions of actual data with grain-size distributions obtained from NMR T2 measurements by a recently developed model was made.

The proposed technique helps in selecting maximum sand and shale porosities as one of the essential parameters in the Thomas-Stieber model for typifying and quantifying the shale and for deciding whether the laminated-dispersed or laminated-structural shale model should be used.

The refined sand, silt, and clay volumes and porosities along with tensor resistivity data were then input into the tensor model for a petrophysical evaluation across anisotropic sand intervals.

The proposed model will help to minimise the uncertainty as a fit-for-purpose approach by improving the accuracy in the calculated mineralogy, porosity, saturation, and consequently, reserve estimations.
Agile Activated Circulation Sub: Flexibility Risk Mitigation in Unconventional Wells
Authors: Tahoun Ahmed , Aljaafar Karam , Khalil Abdul Mushawwir , Fauzi Nurfaridah Bt Ahmad , Ahmad Hassan Bin
Published: March 2016

Agile activated circulation sub is presented, with design advantage of being able to open and close numerous times and there is no limitation to the number of tools run in the string. The tools now being field tested are designed to perform complete needed cycles in one trip, with the total number of cycles limited only by the battery life.

The standalone tool system activated by sensing its environment (Flow, Pressure or RPM), working internal logics before being in a position to receive surface signal to operate in desired mode. The tool has application in any well where it operates the first position for partial bottom-hole-assembly (BHA) bypass increasing annular flow and second, full bypass, position for dumping lost-circulation-materials (LCM) or fast wellbore clean up, the final, downhole barrier isolate drill string above the tool from downhole pressure in well control situation.

Restrictive BHA limits the flow rate and annular velocity required to clean the hole during drilling or displacement operations. BHA restrictions can also limit the size and concentration of LCM and wellbore strengthening material needed to seal troublesome zones. The tool helps driller reduce risks associated with hole cleaning by improving annular fluid velocity with the ability of running multiple tools in same BHA in hole cleaning mode. Each tool can be operated independent of all other tools, allowing driller to optimize hole cleaning hydraulics, as well, tools can be configured with suitable side port nozzle to achieve the desired pressure drop and flow split according to well program. The tool presents advantages over the industry's current system is that there are no restricting ball seats, flow chokes or ball catcher subs in the tool. This paper presents the design, engineering, testing, field trial results, application and function of this new circulation valve

The novelty of the tool is in the ability provided for driller to overcome circulating challenges efficiently and effectively irrespective of tool depth or well profile in reasonable time using variation of RPM, or variation of flow rate. When circulation is not possible or when string is stuck, the tool can be operated to assist driller resume circulation using pump pressure without need for flow.
FSI Analysis for Sloshing Structural Assessment of LNG CCS by Multiphase Fluid Model
Authors: Hwang Se Yun , Lee Jang Hyun , Kim Yooil
Published: March 2016

In design process of the LNG (liquefied natural gas) CCS (cargo containment systems), it is very difficult to determine the effects of sloshing impact and the corresponding response of the CCS. The reliable sloshing assessment methods for LNG CCS are important to satisfy the structural strength of the systems. Since compressibility of the sloshing impact may limit the maximum pressure, mixture model of multiphase is required to represent the sloshing physics. A multiphase CFD model has been introduced to simulate the impact of the LNG sloshing by considering the two phases of gas and liquid. The scheme of CFD model is tried based on the Eulerian domain model that employs the CVFEM. It includes the interphase momentum interaction between liquid and gas. For verification of numerical model, sloshing impact in a rectangular insulation box is simulated to compare the sloshing impacts induced by inhomogeneous multiphase model. Also, the numerical model is applied to localized FSI model for strength assessment of LNG CCS.