bluuebunny/crossref_metadata_2025 huggingface dataset:
Horizontal Appraisal Well Placement Best Practices to Develop New Oil Prospects in Clastic Reservoir of Cuu Long Basin
Authors: Duy C.L. , Phong L.D. , Pottier X. , Anh T.T. , Permanasari D. , Yusuf N. , Thanh P.N. , Santoso G.I. , Fulton C.L. , Miguel D.L.
Published: February 2015

Initially, oil production in the Cuu Long Prospect field within Cuu Long Basin, comes from the primary fractured basement reservoir target and secondary targets in the overlaying Oligocene and Lower Miocene thick clastic reservoirs. Currently the field production is rapidly declining over the years. To reverse the trend, minor reservoir pay zones in the Lower Miocene and Upper Oligocene have been identified as new oil prospects to be appraised and developed. This paper presents three case studies of drilling horizontal appraisal wells with fit-for-purpose geosteering methods to address the challenges in different oil prospects while reducing the number of pilot holes. The lessons learnt and best practices from the earlier drilled well such as well design, technology selection, real-time geosteering data monitoring and communication process were applied in the subsequent wells to improve the result.

Geostopping technique during landing with resistivity-at-the-bit measurement was used to land the well precisely at the top reservoir with minimum sand penetration and avoid pilot hole. Proactive well placement method using deep directional measurements and boundary mapping capability was applied to optimize the lateral length in the sand. An integrated project team involving geosteering specialists, sub-surface team, drilling engineers, and well-site personnel were brought together to ensure efficient decision making process. As a result, production rate from each of the three wells was more than 50% above the anticipated rate with zero water cut and the number of pilot holes was reduced to one out of potentially three. After these well placement successes, more horizontal wells targeting the undeveloped oil prospects are being planned for future development in the field.
High Strength Low Alloy Steel for HPHT Wells
Authors: Cancio Maria Jose , Giacomel Eloff Bruno , Kissner Gustavo , Valdez Martin , Vouilloz Francisco
Published: February 2015

Carbon OCTG selection for HPHT wells has become a very challenging task for well design engineers, due to combination of high pressure with H2S requiring the use of high strength material to achieve the required safety factors avoiding Sulphide Stress Cracking (SSC) at the same time. This requirement prompted a study based on proprietary laboratory testing data in correlation with existing normative systems (API 5C3 and NACE 15156) for selection of high yield strength material in H2S HPHT wells.

With the information provided, the design engineer could better link existing normative systems with proprietary testing to define the best applicable window of high strength material in H2S wells for HPHT environments.

The paper summarizes the public studies done so far by the industry for the material selection of carbon OCTG for HPHT wells comparing with typical ISO 15156 guidelines. Detail explanations of the characteristics of each testing method are also included; the paper also contains additional study of high strength Sour Service material under different testing conditions to define the Sulphide Stress Cracking (SSC) behavior compared to ISO 15156 material selection guidelines. Two steel grades were tested: Sour Service 110ksi and Sour Service 125ksi, the SSC limits were defined using NACE TM0177 Tensile Tests and DCB Tests.

The paper intends to provide supplementary guidelines to help the well design engineer on the material selection process by expanding API 5C3 fracture mechanics formulas and concepts to address H2S selection concepts, explanation of NACE 15156 for high strength materials for Region 1–2–3, and clarification of different methods used to test materials with H2S as per NACE 15156.
Well Test Characterization of Naturally Fractured Vuggy Reservoirs, with a Global Optimization Method
Authors: Gomez S. , Camacho R. , Vasquez M. , Ramos G. , del Castillo N. , Mesejo J.A.
Published: February 2015

Description:

The implementation of well testing models for dynamic characterization of Naturally Fractured Vuggy Reservoirs (NFVR) commonly involves inverse modeling. Thus, this work introduces new results about dynamic description of NFVR by using a triple porosity-dual permeability model. The values of the inter-porosity flow parameters, storativity ratios, permeability ratio between fractures and vugs, wellbore storage coefficient, skin and total permeability, are automatically identified in Laplace Space by using a gradient Newton-type global optimization method named The Tunneling. This method offers more reliable results in comparison to the local optimization methods commonly used in parameters estimations. Applications: The precision and computational efficiency of the Tunneling Method are demonstrated through the reliable results obtained from the automatic analysis of synthetic examples, where a very comprehensive and large set of synthetic noisy data was used. In all cases, the Tunneling Method obtained optimal solutions. Likewise, the analysis of several field well test data cases recorded in NFVR are shown to confirm the benefits above mentioned. Results, Observations, and Conclusions: The parameters determination in the problem here addressed is non-unique due to the ill-posedness problem forcing the local optimization methods to stop in non-optimal solutions. Likewise, local methods require many realizations until converge into an optimal solution. Thus, the superiority of the Tunneling Method for overcoming these challenges is demonstrated through the reliable analysis of several synthetic and field data cases. Performing the optimization in the Laplace space makes the procedure very efficient in computing time. To moderate or eliminate the non-uniqueness problem, information about storativity ratios obtained from core or well log analysis, can be used through the optimization process. Significance of Subject Matter: Currently, the well test data analysis is the only available procedure to estimate the dynamic parameters which characterize NFVRs. Likewise, the approach introduced in this work allows obtaining more reliable estimations of these parameters than local optimization methods.
New Experimental Correlations to Predict Water-Oil Relative Permeability Curves Affected from Asphaltene Deposition
Authors: Khanifar Ahmad , Onur Mustafa , Darman Nasir
Published: February 2015

Asphaltene precipitation and deposition may occur during natural depletion, displacement of reservoir oil by CO2, hydrocarbon gas or WAG application. They can affect reservoir performance and cause formation damage such as porosity and permeability reduction, wettability alteration, and relative permeability changes. Moreover, asphaltene deposition may lead to plugging of wellbore and production surface facilities. The dynamic displacement efficiency in porous media is controlled by relative permeability, and asphaltene deposition can alter the original characteristics of the relative permeability. To the best of our knowledge, there exists no correlation available in the literature that can be used to predict the relative permeability alteration due to asphaltene deposition which considers the amount of asphaltene as an independent variable. Although the exact physics on how this alteration occurs is still a research topic, it has been reported that some of its effect may be captured by wettability change and relative permeability shift from a water-wet to an oil-wet (or a mixed-wet) system. In this paper, new experimental correlations are presented to predict the effect of asphaltene deposition on irreducible water saturation, residual oil saturation, and relative permeability for water-oil systems. The correlations are obtained by history matching the experimental data from the several dynamic displacement experiments (conducted on the different core-plug samples, but having the same rock properties under reservoir conditions) with the corresponding data from a two-phase one-dimension black-oil simulation model.
Calculation and Analysis of Operability Envelopes for Deepwater Drilling Riser System
Authors: Chang Yuanjiang , Chen Guoming , Zhang Lei , Liu Xiuquan , Liu Kang
Published: February 2015

This article focuses on calculation and analysis of operability envelopes for deepwater drilling risers system. A solver is developed by modeling the drilling riser as a finite number of beam elements based on finite element method, and it is capable of performing static analysis to obtain connection operability envelopes, hang off operability envelopes and running/retrieval operability envelopes of the drilling riser system.

A practical example of 1500m drilling riser system in south China sea is presented to illustrate the application of the proposed method.

The main conclusions are:By modeling the drilling riser as a finite number of beam elements, the stiffness matrix, mass matrix, damping matrix, and load matrix in the static and dynamic governing equation are derived. A solver is developed by using direct stiffness method to model and calculate the operability envelopes of deepwater drilling riser system.For connection operation, the normal drilling envelope is determined by the LFJ and UFJ angle limit. When surface velocity is small it is affected by LFJ angle, and it is affected by UFJ angle when surface velocity is large, while the connected non-drilling and disconnection envelopes are determined by allowable stress of the conductor and the bending capacity of the wellhead.Hang-off and deployment/retrieval operability envelopes of the drilling riser are determined by the heave RAO and wave height in the analysis. Generally, the hang-off envelope is larger than the deployment/retrieval envelope because of the BOP being involved in the analysis model, which increase the weight of the suspended riser column, and therefore increase the stress level of the riser during the heave motion of the vessel.

The related methods and conclusions have been put into drilling practice in south China sea in 2012, such as LW6-1-1, LH26-2-1, LH29-2-1 et al, those wells have been drilled successfully.
Successful Application of Platform Based Hydraulic Fracturing in High-Pressure/High-Temperature Tight Gas Sand in North Malay Basin
Authors: Abdelaziz Sherif , Ogueri Chidi , Armentrout Leslie Jane , Salleh Zaimi , Fernandez Mariano , Ward Brian
Published: February 2015

During 2012, a single zone low permeability sand in an offshore HPHT gas well in the North Malay Basin was succesfully stimulated with hydraulic fracturing treatment utilizing skid mounted hysdraulic fracturing equipment from a supply vessel. This is the first offshore Malaysia HPHT frac operation peforming treatment from a supply vessel combining with the use of wellhead isolation tool and high temperature hydraulic fracturing fluid. Historical offshore Malaysia fracture treatments were performed with a drilling rig present.

The zone is a dry gas sandstone reservoir, 30% CO2, pore pressure of 0.87 psi/ft, fracure gradient of 0.92 psi/ft, permeability of 0.1-0.5 md and temperatures approaching 400 deg. F at 10,000ft TVDSS. The wellhead isolation tool, fracturing fluids were designed to safely establish the viability of HPHT hydraulic fracturing in the North Malaysia Joint Development Area.

The intent of the project was to provide proof of economic concept for development of single stacked tight gas sandstone pay intervals with platform based HPHT hydraulic fracturing through a combination of industry standard tchnologies used in other areas of the world, but rarely in Malaysia. Single zone production rates will allow economic development of additional low permeability zones in this well as well as additional wells that were previously deemed marginally economical to develop. While significant uncertainty still exists with regard to the drainage radius and productivity of the single zone, initial results have proven that hydraulic fracturing has connected multiple channels as seen on the log. This has improved the well capacity above productivity established through pre-frac well test and pressure buildup analysis.
Using Riser Technology in a Mooring Connector
Authors: Shield John
Published: February 2015

With floating facilities increasing in size and tending to deeper and harsher locations; the mooring system design for environmental loading becomes ever more challenging. Higher average line tensions and fatigue loads can present uncertainty when assessing the capacity and qualification of the individual components.

In 2011 and in response to a client request, SRP investigated the availability of compact subsea mooring connectors with high bending and tension fatigue capacity. An absence of results led SRP to explore the potential of cross-pollinating the technology from deepwater drilling and production riser systems to mooring systems. The reasoning being that steel risers can be subject to very high combined loading; weight limitations and fatigue life often motivate the designer to use high strength steels and efficient, fatigue resistant connections.

This paper discusses the process and design considerations arising from adaptation of an existing and proven technology from one application (wellhead connectors) to a new application (subsea mooring connectors).

The design verification and qualification test program being carried out in 2012 and 2013 are detailed as an example of a design team's interpretation of riser, mooring and new technology standards. The results of the qualification test program, including static and fatigue testing, will also be presented as an indicator of technical success of the strategy.
Smart Gas Lift Valves Eliminate Multiple Slickline Trips in Gas Lift Operations
Authors: Xu Zhiyue , Richard Bennett M. , Kritzler James H.
Published: February 2015

In many gas lift systems, dummy valves are loaded in side-pocket mandrels to isolate the annulus from the tubing where pressurization is required to test the tubing, test the annulus, set a hydraulic packer, or activate an isolation device. If the well then requires gas lift to unload the completion fluid or to assist the well to flow, slickline intervention would be required to remove the dummy valves and install the live gas lift string. This can be a long, cumbersome process and can pose risks to existing infrastructure. Production is also delayed while a new live valve unit is installed.

This paper presents a smart gas lift valve with disintegrable nanostructured composite material technology. The valve is installed in the well to function as a dummy valve during completion operations. It is converted from a dummy valve to a live valve through in-situ disintegration of the nanostructured composite plug in brine during the cleanup process. This eliminates multiple slickline trips or well intervention after the completion, and enables unloading and immediate production of these wells under optimized gas lift conditions.

The nanostructured composite material for the smart plug is lighter than aluminum but as strong as some mild steels. The smart plug has pressure rating of 5,000 psi or higher and will disintegrate in sea water within 12 to 50 hours, making it an ideal tool for offshore gas lift applications. So far, more than 1,000 gas lift valves equipped with disintegrable nanostructured composite plugs have been installed in gas lift wells producing offshore Southeast Asia. The nanostructured composite material, the valve design, the lab test data and a successful field case history will be presented.
Design, Fabrication, Delivery and Installation of TLP Tendons for South East Asia
Authors: Tekumalla Vithal R. , Yang CK
Published: February 2015

The tendons are the critical components to keep TLP's on station. The design of the tendons takes into account platform weight, payload, displacement, required pre-tension, water depth, and the metocean data.

The tendons are long seam-welded tubulars joined together by girth welds. Tendon segments are joint together through threaded type intermediate connectors.

This paper examines the key aspects of the design of the TLP tendons to incorporate the effects of axial tension, hydrostatic collapse, bending, VIV, fatigue and fracture mechanics considerations. The interfaces to the TLP and the foundation pile will be detailed. The tension and bending loads of the tendons need to be monitored and the requirements of a robust tension monitoring system will be highlighted.

The key aspect of the fabrication of tendons including the weld procedure qualification, dimensional control/fit-up and NDT will be examined.

The transportation of tendons from the fabrication site to the installation site needs to address the aspects of logistics.

The requirements of the tendon installation will be examined with respect to the Tendon Support Buoys (TSB's). The TSB sizing and the design considerations will be examined for a typical TLP project.

The installation of tendons and the lock-off of TLP and tendons will be examined.
The Risk of Cryogenic Liquid Exposure Could Have Been a Show Stopper for FLNG (Floating Liquified Natural Gas Production and Storage) Projects : How Did the Industry Respond?
Authors: Wade Robin
Published: February 2015

Liquid natural gas (LNG) at atmospheric pressures, remains as a liquid at -162°C. As the temperature increases, gas is evolved which is flammable and under certain mixtures with air is explosive when in the presence of an ignition source.

As designers have looked more at the risks posed by accidental release of Cryogenic Liquids onboard FLNG assets, it has become more apparent that the steel structures used for these facilities could be prone to brittle fracture. This could potentially lead to structural failure. If fire ensues soon after this cryogenic release then further escalation may occur, particularly if the passive fire protection does not function as expected.

The need for effective, tried and tested solutions to mitigate the risks posed by cryogenic liquid gas exposure was identified nearly 20 years ago. In the last 10 years, as the FLNG industry has accelerated, development has intensified for cryogenic spill protection (CSP) systems. Indeed construction of a leading FLNG asset was nearly stopped due to the lack of an effective solution. In response, the owner initiated studies into the most effective CSP materials to ensure progression of the project.

Since then, the industry has developed a better understanding of the risks posed by these LNG liquefaction assets and the consequences of not addressing these risks appropriately. Working closely with owners and design engineers to address these project specific risks and to develop robust solutions, has therefore become of paramount importance in developing this appropriate response.

This paper covers the initial requirements of protection against cryogenic spill. It considers the solutions developed to meet all the industry standards and describes those finally adopted by the first FLNGs under construction.
Design and Optimisation of Riser Configuration Base on the Project EnPing 24-2
Authors: Qi Xiaoliang , Xie Yi , Luo Yong , Zhu Weiquan , Gao Wei , Shen Hui
Published: February 2015

En Ping 24–2 oil field is located in the Pearl River Mouth Basin in the South China Sea En Ping Sag, about 200 kilometers south of Hong Kong in water depth of about 86-96 m. The development of En Ping 24–2 oil field includes a newly built eight-legged drilling and production platform (DPP) with drilling rig, living quarters, sewage treatment facility, utility systems etc. and 2.2km apart, a newly build 150,000 DWT FPSO with power plant, oil and gas treatment facilities, utility system and living quarters etc. The FPSO is kept in station by a single point mooring system of internal turret type. The single point mooing system and riser system design for the FPSO become the key issues in the project because both systems have to face new challenges, such as shallow water depth, wild environments and high fluid pressure.

The paper presents the key design parameters of riser system, and addresses the evaluation of riser configurations to suit the Enping development. The evaluation focuses on the technical aspects in terms of system feasibility in the presence of harsh Enping environment. With respect to the suspended dynamic riser, several widely used configurations are evaluated and conduct the dynamic analysis in order to obtain riser responses such as effective tension, bend radius, contact clearance and seabed touch. Finally the key conclusions are reached.
Concept Evaluation of Concrete Floating Liquefied Natural Gas (FLNG)
Authors: Nezamian A. , Morgan P.
Published: February 2015

The world has a quarter of its natural gas reserves (approximately 2 billion TCF) undeveloped or "Stranded" in offshore fields. Many gas fields were discovered decades ago, but until just recently these reserves were considered to be commercially and technically non-viable. Floating Liquefied Natural Gas, or FLNG, is now seen as a potentially viable solution to monetize these reserves. Technology developments in offshore Liquefied Natural Gas (LNG) liquefaction, containment and transfer have made offshore FLNG production commercially viable.

Although land-based LNG and offshore FPSOs are each successfully proven in operations, combining the two technologies into a FLNG is complicated and faces various technical challenges. These include safety, ship motion, topside processing, hull & containment, offloading, integration and operation. One of the critical aspects of a FLNG facility are the space constraints inherent in any floater.. A concrete hull structure can be a good answer to these challenges. It can provide a floater with larger deck area and high built-in load-bearing capacity. Concrete has excellent durability in marine environments, is not subject to fatigue, and offers far better insulation properties than steel.

This paper serves to highlight the benefits of a proposed concrete hull structure for FLNG production facility. The proposed concrete monohull concept benefits from significant flexibility with regards to topsides weight, equipment lay-out, simplification of operations and maintenance. Concrete has better fire resistance and corrosive resistance than steel structures and it is not susceptible to brittle fracture in the case of an LNG spill. These are considered to be of major importance for a FLNG production vessel. Building cost and time-scale are competitive.
Effect of Lateral Soil Strength and Stiffness on Jacket Foundation Integrity and Design for South China Sea Sites
Authors: Nichols Nigel Wayne , M.J. Rohani , Mukherjee Kaushik , B Ayob M Sapihie , Clausen Carl J.F. , Lunne Tom
Published: February 2015

Petronas Carigali Sdn Bhd (PCSB) manages about 150 existing platforms at various sites across South China Sea. Integrity reassessment on these existing structures using non-linear pushover analyses has frequently indicated lateral foundation failure at collapse. However to date there has been no physical observations of foundation failures.

Foundation design and integrity assessment takes into consideration lateral soil properties to determine the adequacy of structure-foundation combined system. Observation on Gulf of Mexico foundation performance during hurricane events provided PCSB with the insight and motivation to recalibrate both static and cyclic lateral p-y characteristics of soil currently seen to be conservative.

PCSB together with Norwegian Geotechnical Institute (NGI) undertook a study incorporating literature reviews, review of field lateral load data and numerical modeling to recalibrate API RP2A static and cyclic p-y data and derive new modified p-y relationships to suit Malaysian conditions. Further three(3) platforms were reanalyzed using current API RP2A p-y equations and newly modified p-y equations to study the impact of the recalibration made.

Result indicates that the modified static p-y resistances provide positive global improvement to pushover analyses. This improvement provides a better justification for the life extension of the existing structures as required in an enhanced loading scenario. Minor to negative improvements are seen when the modified cyclic p-y resistances were used for the purpose of in-place analyses. This paper will focus on the methodology adopted, assumptions and philosophy that form the basis of the recalibration and development of the modified p-y method. Discussion on results of in-place and pushover analyses will be made to provide recommendations on the further use of modified static and cyclic p-y calculation method.
Volumetric Hardening in Axial Pipe Soil Interaction
Authors: Smith V.B. , White D.J.
Published: February 2015

The Norwegian Geotechnical Institute (NGI) and The University of Western Australia (UWA) has been working on understanding pipe soil interaction for a long time. NGI has performed a series of large-scale model tests investigating the axial pipe soil interaction in soft clays. Variables investigated are the weight of the pipe, velocity of movement, roughness and diameter.

One aspect of axial pipe soil interaction that needs further investigation is the increased axial resistance that is observed with cycling. This is attributed to volumetric hardening. However, there are also observations that this effect is erased by cycles at a higher velocity. In order to use the effect of volumetric hardening in design of pipelines, further investigation of the phenomenon is needed.

The paper will describe the test equipment used in the NGI laboratory. It will investigate the increased axial friction with axial cycling of the pipe for a variation of the pipe weight at an undrained velocity. It will attempt to show, through measurements of water content of the clay around the pipe, that the clay is contracting during undrained cycling. The paper will also look into the mechanisms contributing to erasing this effect and the influence of pipe weight and velocity.

Deep water fields are often developed using pipelines, both infield and for transportation. Through its life, pipelines go through a series of cycles of production and closedown that changes the pressure and temperature and thus changes the length of the pipe. The axial resistance of the soil on the pipe is one of the parameters governing the buckling and walking behavior resulting from the repeated lengthening and contraction of the pipe.
Riser VIV Suppression Device Test
Authors: Ng D.J.T. , Teng Y.J. , Magee A.R. , Ahmad Zukni N.B. , Aramanadka S. Bhat , Abdul Malik A.M. , Abd Kader A.S. , Haji Ismail N. , Abdul Ghani M.P.
Published: February 2015

Vortex induced vibration (VIV) occurs when a body is exposed to a fluid flow that causes an unsteady flow pattern due to vortex shedding at or near the structure's natural frequency leading to resonant vibrations. This phenomenon frequently happens in slender elements such as risers used in deepwater oil and gas developments. Such vibrations may reduce the fatigue life of the riser, potentially causing catastrophic damage to the integrity of the system and the environment. Installation of VIV suppression devices onto risers will affect the vortex shedding patterns and is thus able to mitigate VIV. A model test was carried out to study the effectiveness of a newly developed U-shaped fairing in reducing drag and VIV of risers.

The U-shaped fairing is an alternative to conventional spiral strakes and tear-drop-shaped fairings for riser VIV suppression. The model test findings offer useful information for its industrial application in suppressing riser VIV.

The model test was performed in a towing tank facility in Malaysia located at Universiti Teknologi Malaysia (UTM). Current flow was simulated by towing a vertically submerged scaled-down riser section underwater with a moving carriage. The riser model was attached to a custom-designed test rig to replicate a section of the actual riser and to simulate its 2D motions. The model riser was tested in three different conditions, i.e. (a) bare riser without fairing; (b) riser with weathervaning fairing (normal condition) and (c) riser with fairing stuck at different orientations (abnormal condition). The test results show significant reduction of VIV on the model riser with fairing under normal condition. In addition, it is found that the drag load for the riser with fairing is significantly lower compared to that of a bare riser or a typical straked riser.

This test marks a significant collaboration between a local research institute and the offshore oil and gas industry, aligned with the initiative of increasing local capabilities. Effective mitigation of VIV of risers using suppression devices could lead to improved riser fatigue life and overall a more economical platform design.
Investigating the Dynamic 3D Loading Effects on Perforating Guns Imposed by Shaped Charges-Downhole Evaluation
Authors: Glenn Timothy S. , Serra Marco , Rodgers John P. , Wight Jim , Zhang Wei , Craddock G.G. , Harive Kevin
Published: February 2015

Modern development of shaped charges has resulted in greater and greater explosive loads on the perforating guns and has stretched the capacity of perforating guns into uncharted territory. Traditional gun design approaches and standards use collapse pressure calculation and swell measurement with overloaded charges as design verification methods. The extremely complicated interactions between explosives, fragmented casings, and the gun wall are evaluated on an empirical basis, and the nature of these interactions is not well understood. In this paper, we present a new design model that augments traditional design approaches and provides gun designers with better data on gun system structural performance including the effects of phasing, shot density, and charge type.

The loads imposed on the gun body by the explosives are multi-dimensional due to the spiral arrangement of most shaped charges. The resulting dynamic response of the gun body is therefore quite complex and requires three-dimensional analysis. High-frequency bending, torsion, and tensile loads are expected. The casings are typically fragmented, and some of the larger fragments can impose large impact loads on the gun wall. A fully-coupled computer model has been developed that incorporates the rapid explosion, casing fragmentation, and multi-dimensional structural responses.

Multiple instrumented surface tests were carried out to validate the dynamic three-dimensional model. Proprietary testing techniques were used to extract gun internal pressure history and gun stress history at multiple locations immediately following detonation. Redundant strain gages were used and shots were repeated to ensure the integrity of the data.

This paper first presents the newly developed three-dimensional simulation model in full details. The second section describes the instrumented gun test set up and results. The final section of this paper presents validation of the model through comparison with test data.
Installation of Subsea Structures Using Mid-Size Construction Vessels in Harsh Environments
Authors: Jacobsen Tore , Naess Tor-Bjorn
Published: February 2015

Subsea structures are traditionally transported to the relevant site either on the deck of a crane vessel or a barge, depending on their size and shape. In both cases the subsea structure has to be lifted off from deck and lowered through the splash zone. The lift-off from deck is a critical phase of the operation in which there is imminent danger of large dynamic loads and collision between the structure and vessel due to relative motions. During immersion, significant wave impact forces (slamming) may also occur. Hence, these potential hazards will imply operational limits for the traditional methods of installation for subsea equipment. Another possible way of transporting and installing a subsea structure is to perform a submerged tow through the moonpool of an offshore service vessel. It may be argued that such an operation may have a wider operational window than traditional methods since offshore lifts are eliminated. However transit time during towing may reduce the profitability of this method. This paper outlines the two methods for structure installation, and states typical installation criteria based on model tests and empirical data from full scale-measurements and analysis. Also lessons learned from offshore operations are outlined and discussed.
Well and Reservoir Surveillance in Mature Gas Field Peciko and Its Application in Well and Reservoir Management
Authors: Nathanael Christian , Masitah Siti
Published: February 2015

Peciko is a giant gas field operated by Total E&P Indonésie which has been in production since late 1999. The field is situated in Mahakam PSC about 25 km offshore. After more than six years of production, the field entered its decline phase after reaching peak production at 1.3 Bscfd in 2005. With the total number of wells exceeding 130, sustaining the field production has become very challenging in this maturation phase. Problems like liquid loading, scale, tubing breach and sand production require immediate remedial action to prevent wells from suffering any further. Gas water contact movements must also be monitored prior to define targets for infill drilling.

Data acquisition is of key importance to spot on problems which may impair the producing wells, and to understand the well and field behavior for any next development phase. From 2010 to 2012, around 120 Production Logging Test (PLT) were done as well as over 20 jobs of caliper log. PLT is widely used to evaluate reservoir performance and to identify source of water, while caliper log is commonly used for quantifying wellbore access restriction or enlargement.

Many wells with high water production are associated with wellbore restriction due to scale build-up. Production logging combined with caliper log has also helped tubing breach identification in a zone completed with sleeve only. Further, more than 70 jobs of pulse neutron logging were run to monitor the movement of gas water contacts. Sand production is also an issue in Peciko field, and to these end 10 jobs of sand detection logging were acquired. Results are conclusive for a couple of wells, whilst ambiguous for the other, and for these wells the challenge for a solution to remedy sand production remains.

This paper explains how reservoir management team of the Peciko field has extensively used surveillance technologies in fighting the decline by solving liquid unloading problem, maintaining wellbore integrity, and horizontal well placement for hydrocarbon recovery optimization.
Stinger Stiffness and Its Effect on Deepwater Lay Analyses
Authors: Suwarno Gunawan , Lim Gerry , Hua Lee Choon
Published: February 2015

The most economic way to install a subsea pipeline in deepwater is using Slay method because of the lay speed, due to number of workstations. But on Slay method, the lay vessel requires a massive structure which we called "Stinger" to guide the pipe down to seabed. A Stinger is an extension structure at the stern of the vessel which used to support pipeline on its way to seabed. This stinger is also used to control the strain level by controlling the stinger radius. The length and the radius of the stinger will govern the pipe departure angles which in the end, it will govern the length of pipe span on catenary as well as the tension require for pipe laying.

Typically modern stinger consists of one, two or three space frame and hold by stinger holding frame and stinger hitch. On each of the space frame, the pipeline will be supported on few number of roller supports. These supports are called "Roller Box". The Stinger radius are adjusted by setting the "Roller Box" at certain heights and also set the angles between Stinger Sections.

Typically during Pipelay analyses, Stinger was assumed to be fixed, at certain extent, this rigid assumption is valid. Many Pipelay operations have been analyzed based on this assumption. The pipeline is becoming deeper and deeper and the deeper pipeline required longer stinger and typically the un-supported part of the stinger also become longer which make the stinger does not stiff enough or it will deflect much more compare to shorter stinger.

This study is about using Pipelay Analyses Software and Structural Analyses Program to calculate the displacement of the Stinger based on Reaction Load on the Roller Box taken from Pipelay Analyses. And the interaction between the two softwares was used to predict appropriate stiffness of the stinger. In the end of the study, comparison using Rigid Assumptions and Non Rigid Assumption on Pipelay Analyses was drawn to understand the effect of the stain level, tension required and the gap on stinger last roller.
Early Stage Geohazard Assessments in Tectonically Active Areas: Application to Potential Developments in South-East Asia
Authors: Clare M. , Smith C.A. , Dan-Unterseh G. , Spinewine B.
Published: February 2015

A methodology is outlined for performing desktop studies in geohazard-prone areas to estimate feasibility for subsea cables and pipelines. Various global cases studies are referenced with relevance to development areas in South-East Asia. This involves a review of available geological, geophysical and geotechnical data, to provide guidance for routing, planning of surveys, and geohazard mitigation. Seismic hazard is not discussed in detail as it is comprehensively dealt with elsewhere.

Enhanced subsea construction activity results from increased demand for energy supply and communication networks. The need for transportation of these products often necessitates the crossing of tectonically active areas that may be prone to geohazards which may result in pipeline rupture or cable breakage. Implications of tectonic activity may be direct (e.g. earthquakes), as well as shaping the terrain through imposition of structural controls, and providing potential trigger mechanisms for slope instability and density flows.

Seafloor morphology is characterized on a regional-scale to understand structural controls, and local-scale to identify characters indicative of seafloor rupture, past slope instability, or future flow conduits. Interpretation of geophysical data provides information to feed an evolutionary geological model. This rationalizes periods of tectonic activity with geohazard scenarios, e.g. regional-scale catastrophic slope failures during intense rifting, compared with smaller, discrete landslides during periods of relative quiescence. Integration with available geotechnical data provides information to understand sedimentary processes and inform forward-looking analyses, such as debris-flow modeling. Thus, an estimation can made of magnitude and duration of forces impacting on structures. Examples are provided of how slope failures and sediment density flows may vary on slopes that have been modified by different tectonic processes. Conduits laterally offset by faults, or uplifted by toe-thrusts may limit the downslope run-out of flows; however, linear, fault controlled canyons may permit longer travel distances.

A phased and integrated framework is outlined for early stage geohazard assessment in tectonically active areas to inform feasibility and concept routing studies. The intention of this approach is to ensure early stage decisions can be made with respect to route selection and to maximize the efficiency and effectiveness of future data acquisition.
Regulatory and Safety Challenges of FLNG
Authors: Fagan Conn
Published: February 2015

Liquefaction of natural gas is moving offshore as an economic means of developing natural gas fields. This trend is currently in the start phase with a number of projects currently under construction and many more at concept and engineering phases. In addition FLNG projects are being proposed for location in an increasingly larger number of geographical locations, coming under a number of different regulatory jurisdictions.

There is currently little engineering experience associated with such applications and in addition standards and regulation specific to this new technology may lag behind the industry developments. Different jurisdictions may also have varying approaches when it comes to means of ensuring safety on their own continental shelf.

This paper will address the approach adopted by DNV in specifying requirements for design and construction of offshore LNG production units and our view on how this approach relates to the bigger picture of regulatory compliance.

In addition some key technological areas which DNV see as a safety challenge with regard to such units will be discussed.

The paper will therefore bring together experience gained from a number of projects and present some generic lessons related to the issues of safety and regulatory compliance which may be of use in future FLNG designs.
Effective Slug Handling and Sand Separation Using Innovative Separator System
Authors: Zainal Abidin S.A. , Harun Z. , Jothy A.
Published: February 2015

In many oil and gas developments with multiphase flow lines, production instability due to slugging is a major flow assurance concern. Slugging initiates oscillations, puts excessive demands upon the separation and operation, and increases the wear and tear of equipment. Large liquid surges can cause poor performance, separator shut down, high pressure trips, or flaring. An integrated separation system has been developed to provide high separation efficiency through effective handling of sand and slug, energy efficient inlet heating, stable 3-phase separation (gas, oil and water) with efficient liquid droplet removal and with minimal pressure drop.

The compact integrated system is applicable for all facilities performing three phase separation both onshore and offshore, facilities with space limitations, waxy fluid services, facilities with slugging issues, facilities with sand issues and motion sensitive issues such as FPSO.

Several units were successfully installed in various countries such as TGT FPSO for HLJOC, Vietnam, D1 FPSO ONGC, India and PETRONAS Carigali facility in Anjung Kecil & Kayu Manis, Malaysia. The installations have demonstrated CAPEX, weight and footprint savings of up to 50 percent compared to conventional separator system.
Middle East to India Deepwater Pipeline (MEIDP) Crossing of the Owen Fracture Zone
Authors: Nash Ian , Burnett Christopher , Parry Simon
Published: February 2015

The Middle East to India Pipeline (MEIDP) will provide an economic and secure source of gas for India, where the demand for energy will continue to increase over the coming decades. The proposed pipeline will be the deepest major infrastructure pipeline laid with water depths exceeding 3000m for significant sections of the 1200km route.

This paper will give details of the 2013 geophysical reconnaissance survey along the pipeline route. Five areas were highlighted during desktop studies as significant for potential geohazards, namely the Indian and Omani continental slopes, the Indus Fan, the Owen Fracture zone and the Qalhat Seamount. The findings in these areas will be presented with particular focus on the Owen Fracture zone crossing, where the continental plate boundary between the Arabian and Indian tectonic plates meet forming a right lateral strike slip fault movement zone. The movement on the plate boundary will be investigated and examples of survey data will demonstrate the challenges that need to be overcome in crossing this major geohazard feature. The results of the survey will be discussed together with details of the geohazard design process required to identify a feasible route and necessary intervention works at this feature to bring this project closer to reality.
Effect of CO2/H2S on Corrosion Behavior of API 5L 65 Carbon Steel in High pCO2 Environments
Authors: Mohammed Nor Azmi , Suhor Muhammad Firdaus , Abas Ahmad Zaki , Mat Sa'adan
Published: February 2015

The corrosion behavior of API 5L X65 carbon steel was investigated under high pressure CO2 environments, containing small amount of H2S, to simulate the condition of high CO2 containing natural gas transporting offshore pipeline in Malaysia. It was systematically studied under high pressure CO2 (range from 80 and 120 bars) with variation in other key parameters (temperature, water partitioning and H2S concentration). The corrosion rates were measured using the techniques such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) 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 H2S instantaneously decreased the corrosion rate of API 5L X65 at both 25°C and 80°C (120 bar). It was also observed that the corrosion rates of API 5L X65 (at both 25°C and 80°C) in the water-saturated CO2 phase are lower than the Minimum Acceptable Corrosion Rate (MACR) of 0.1 mm/year. The addition of H2S increased the corrosivity of this phase. On the hand, insignificant corrosion was observed in the under-water-saturated CO2 phase, even with the presence of 200 ppm H2S.
Lessons Learned from Pig Rescue Operations During Precommissioning of a 290 km Offshore Pipeline in Persian Gulf
Authors: Tabatabaei A. , Tabassomi H. , Mahmoudi M.
Published: February 2015

Pigs are devices utilized when carrying out various pipeline operations during its lifetime. The most serious threat for each pigging operation is stoppage in the pig movement. "Pig Rescue" operations refer to the activities for making the pig continue its path and move along the pipeline. Normally when the pig gets stuck, the first task is to estimate the location of pig in the pipeline. Situation is even more disastrous for the case of offshore pipelines since locating the position of the pig would be a hard and costly task.

Most reputable pipeline service contractors and operators have gradually built their own knowledge base when dealing with different scenarios of pig rescue operations. However, choosing a cost-effective engineering solution in a reasonable time period is always a major challenge.

This article describes the lessons learned from pig rescue activities done during precommissioning operations of a 290 km offshore pipeline from Siri Island to Asaluyeh Port in the Persian Gulf. The 32-inch natural gas pipeline is considered the longest offshore pipeline in the region. As a series of valuable experiences achieved from the project, this paper presents different procedures for moving the stuck pig based on the pipeline conditions and the type of pig itself. Some of the procedures include pressurizing the pipeline with gas or liquid, performing sudden fluid discharge, inserting other pigs inside the pipelines, etc. Furthermore, necessary engineering and safety considerations when following up the pig rescue procedures are discussed that would be absolutely useful for practitioners in the oil and gas industry.