bluuebunny/crossref_metadata_2025 huggingface dataset:
Riserless Plug and Abandonment of Pilot Holes in Ultradeepwater
Authors: Vølstad J. , Hilliard S. , Aguilar P. , Salehpour A. , Bogaerts M.
Published: June 2014

Offshore East Africa is a new frontier in terms of deepwater exploration. One of the new projects in ultradeepwater offshore Tanzania was located in Block 2 with water depths ranging from 1000 to 3000 m. Seismic data had shown the potential presence of shallow gas, shallow water flow, and gas hydrates while drilling the riserless section. Lack of local oilfield infrastructure, and the lack of pump and displace (PAD) mud availability made the project challenging because the surface section was to be completed within a matter of several days.

Statoil decided to drill the Tangawizi-1 U1 pilot hole to confirm the absence of shallow hazards and avoid the need for overbalance drilling the riserless section with PAD mud. The 8 ½-in. pilot hole penetrated 600 m through the critical zone below the seabed, drilled with sea water, was then plugged back by filling the open hole with cement. The decision was made to perform the cement job through the 8 ½-in. Bottomhole assembly (BHA) containing measurement while drilling (MWD) and logging while drilling (LWD) tools.

The combination of deepwater, riserless, potential shallow hazards and pumping through a BHA with significant restrictions made successfully setting balanced plugs extremely challenging. The slurry was designed following industry standards to prevent fluid influx or destabilizing the hydrates during the setting process by the use of an optimized particle size distribution (OSPD) slurry system. In addition, to successfully be placed through the BHA and avoid plugging the nozzles, this system needed to be stable and have low rheology.

The pilot hole was successfully abandoned by setting two cement plugs. Cement returns were observed at the seabed by a remote operated vehicle (ROV) and no visual flow after placement was observed.
Paleogene Secondary Recovery Analysis
Authors: Hartley Jamie , Smedstad Eric , Widjaja Ervina , Nandakumar Maya
Published: June 2014

The Paleogene has been shown to contain very large reserves. The characteristics of these reserves however present some unique challenges for operators in producing them in the same economic fashion as other plays within the Gulf of Mexico. Artificial lift in the form of downhole electric submersible pumps (ESPs) or subsea mudline boosting pumps are being sought out to improve the recoverables and overall economics of Paleogene field developments.

Small improvements in recovery factor can have a significant impact on the economics given the large size of these reservoirs. Many variables come into play that can impact the overall economic performance of a field development using pumps as a means of increasing recoverables. Downhole ESPs when used in combination with mudline boosting pumps have the potential for delivering the best recovery factors, however poor reliability performance and high intervention costs associated with the use of ESPs in subsea wells can negate the value of those recovery gains. Mudline boosting pumps by comparison, have lower intervention costs, and are generally accepted as having better reliability performance over downhole ESPs.

A production performance analysis was performed for a number of configurations for ESP and mudline pumps for Greenfield developments to determine the improvement in recoverables. An economic performance evaluation was then conducted, comparing the value of the increased recoverables against costs for the hardware, the installation, annual operational costs, and intervention and maintenance costs over a 30 year field life of a Paleogene reservoir.
4D (Time Lapse) Seismic: an Emerging Tool for Underwater Monitoring?
Authors: Hubans C. , Cauquil E.C. , Brechet E.
Published: June 2014

The 4D approach relies upon the use of 3D seismic data acquired at different times over the same area to assess changes in temperature, geomechanical effect, pressure effect, water injection, gas injection, and natural depletion, all these effects inducing density and velocity changes. Nearly thirty years on from its first beginnings, 4D – or time-lapse – seismic monitoring has now come of age as a proven technology, and is classically applied to monitor fluid movement and differentiating between drained and undrained portions of a reservoir. It is now possible to quantitatively monitor pressure injection signals, pressure depletion (compaction) signals, and in many cases, accurately separate the effect of pressure changes and saturation changes. Such changes within the reservoir may impact the whole sedimentary column up to the seabed (i.e. the overburden section). In addition, subsea installations may impact the seabed and the very shallow geology by in situ modification of the geomechanical parameters. With proper quality control during acquisition and processing, it is expected that 4D dataset would provide significant insight regarding the evolution of the seabed and shallow sub-seabed between the exploration phase, the start-up and the production phases.
Marine Magnetic Surveying and Disturbance Field Monitoring by Autonomous Marine Vehicles
Authors: Poedjono Benny , Pai Sudhir , Maus Stefan , Manoj Chandrashekaran , Paynter Ryan
Published: June 2014

Directional drilling uses measurement while drilling (MWD) to infer the inclination and azimuth of the drill bit. The accuracy of the measured azimuth critically depends on the local direction and strength of the geomagnetic field. Lateral uncertainties in the bottomhole location can typically be reduced by 50% if the local geomagnetic field is known accurately. This requires both the mapping of spatial crustal anomalies as well as the continuous monitoring of "space weather" disturbance field variations during drilling operations. Traditionally, these tasks are carried out by aircraft, ships and onshore geomagnetic observatories.

A novel study employed autonomous marine vehicles for geomagnetic surveying. Two autonomous marine vehicles were equipped with towed magnetometers and were deployed for 2 months offshore the Hawaiian Islands. To investigate the accuracy of the measurements, the two vehicles surveyed exact-repeat profiles. The measurements of the two vehicles agreed to within 2nT, exceeding even the stringent 5nT standard for geomagnetic observatories. To avoid entangling the towed magnetometer, the autonomous vehicles had to be in continuous motion. They demonstrated their ability to circulate around a given target. This "base station" mode allows them to monitor the time variations of the disturbance field. After correcting for spatial gradients of the crustal field, the measured disturbance field variations were found to be in excellent agreement with the Honolulu observatory. In the final phase of the study, one of the vehicles acted as a base station, while the other surveyed a regular pattern. A total of 700 line kilometers were flawlessly surveyed by one vehicle within 14 days. The resulting crustal magnetic anomaly map agrees to within 10nT with previous, lower-quality ship-borne magnetic surveys.

This study demonstrates the utility of autonomous marine vehicles to carry out crustal magnetic surveys and monitor disturbance fields in support of offshore directional drilling operations. These new capabilities improve well placement for increased oil and gas recovery. Accurate geomagnetic reference values further enable tighter quality control of MWD equipment, enhancing safety and reducing nonproductive time.
Challenges in a Multi-Disciplinary Approach for Explosion Design of FLNG
Authors: Paris Laurent , Cahay Marc
Published: June 2014

Floating Liquefied Natural Gas (FLNG) units have been under development for decades. They are now becoming a reality, combining the design and installation of LNG units with a traditional " FPSO". Since FLNG facilities handle large flammable gas quantities in a relatively small and congested environment compared to onshore LNG plants, the explosion risk is expected to be higher than some other offshore floating facilities. As a consequence the intensity of the resulting blast loads on the unit can be more severe even if the explosion likelihood is considered low in the design through a frequency analysis.

Even if prevention and mitigation measures are implemented to reduce the risk to ALARP (As Low As Reasonably Practicable), Safety Critical Elements (SCE), such as main equipment and structures, shall be designed to withstand the blast event. Since the explosion events are very specific (high intensity and short duration), the common design rules and tools should be updated to take into account this accidental event. In addition, the associated performance criteria for SCEs should be also modified. Finally the entire design shall comply with safety objectives (personnel protection, prevention of escalation).

This paper focuses on the philosophy of design against a blast event. It will review the critical functions of the unit that must be maintained during emergency evacuation in order to protect people and, identify the key parameters governing the explosion strength on FLNG. It will show that the derivation of effective explosion loads on structures and equipment based on computational fluid dynamics simulations is not straightforward and requires expertise both in explosion modeling and explosion response. In a second part the paper will show how all the engineering disciplines in Technip individually apply these blast loads into their design through non-linear finite element analyses. Finally, it will highlight the interface between the engineering disciplines and how a consistent demonstration through the design can be achieved in order to fulfill the safety goals, taking engineering further.
Lifetime Extension North Sea FPSO, Mooring System Replacement; Integrity and Design Challenges
Authors: Leeuwenburgh R. , Brinkhuis H.T.
Published: June 2014

Bluewater's Haewene Brim Floating Production Storage and Offloading (FPSO), moored by means of an internal turret mooring system in the central North Sea since 1998, ran out of its original 15 years design life. Good field performance and the tie-in of another field resulted in a targeted lifetime extension for the FPSO of 18–20 years. In the late 90s a number of turret mooring systems, with a typical design life of 15 – 20 years have been installed in the North Sea. A number of these, currently or in the near future, might also be subject to lifetime extension programs. The technical challenges experienced during the lifetime extension project of the Haewene Brim FPSO mooring system will be discussed in this paper.

The main objective for the lifetime extension program of the mooring system was twofold: to design a mooring system which allows for continuous operations for the extended lifetime and to maximize the utilization of existing components. A number of the findings, steps of the design process and challenges are described in this paper and solutions are presented. This is complemented with a discussion regarding mooring integrity issues (birdcages in spiral strand wire sections) faced with over the last few years, which made it more challenging to fulfill the original design life and to design a new mooring system within the targeted boundary conditions.
Fluid-Structure Interaction: Lowering Subsea Structure / Equipment in Splash Zone During Installation
Authors: Jia D. , Agrawal M.
Published: June 2014

Successful installation of subsea structures and equipment is critical for offshore campaigns in development of deep-water fields. This paper presents a novel approach using Fluid-Structure Interaction (FSI) to predict wave induced motions, wave loads, dynamic stresses and deformation of subsea structure and equipment in the splash zone during installation. This approach combines transient multiphase CFD simulation including dynamic mesh motion with transient nonlinear Computational Structural Dynamics including tension forces in non-linear flexible slings. This proposed approach has been successfully implemented for lowering of a subsea manifold in splash zone during installation.

This paper has many potential applications, such as, installation of manifold, subsea tree, PLET/PLEM, suction pile, pump station, or other subsea structure and equipment.

In this coupled FSI approach, pressure loads on the structure due to wave slamming from CFD model is mapped to FEA model of structure-sling assembly, which provides motion and deformation to CFD model. The results clearly show the advantage of this FSI approach to capture the coupled physics of wave slamming and its interaction with the structure and subsequent motions of structure which is being lowered in the splash zone that other approaches cannot capture. Structural integrity of the subsea structure and equipment as well as the sling forces is well evaluated and predicted with this approach.

Traditional approaches for prediction of the motions and loads of subsea structure/equipment during installation rely on simplified formulations or empirical equations or model test to determine the wave loads on structures. It cannot simulate wave-structure interaction, nor the dynamic stress and deformation of structure/equipment due to wave-structure interaction.

The approach proposed in this paper provides a state-of-the-art FSI tool which enhances understanding wave-structure interaction in splash zone during installation. The dynamic stress obtained by using this approach can be used for quantifying fatigue damage of every component on the structure/equipment due to wave loads in splash zone during installation.
In-situ Temperature Measurement of Gas Hydrate Dissociation during the World-First Offshore Production Test
Authors: Kanno T. , Takekoshi M. , Wang X. , Chee S. , Fukuhara M. , Osawa O. , Yamamoto K. , Fujii T. , Takayama T. , Suzuki K.
Published: June 2014

The world-first offshore production test of gas hydrate was just performed in the deep water Nankai Trough along the Pacific coast of Japan in March, 2013. A week-long flow test successfully produced methane gas by depressurizing method from the subsea methane hydrate reservoir.

While methane gas was successfully extracted from natural hydrate, there is a strong urge for understanding the dissociation behavior and characterizing production process of hydrate through the depressurization method. This is a crucial knowledge for the future commercial production of gas hydrate.

The dissociation of methane hydrate is an endothermic reaction, and the drop of formation temperature is expected to occur as the dissociation progresses. By capturing the phenomenon of temperature decrease in-situ, the data attributed to the dissociation of methane hydrate can be obtained during production.

Two monitoring wells, uniquely designed for minimizing thermal disturbance and better thermal coupling were drilled in the vicinity of the production well, and the two types of temperature sensors using DTS (Distributed Temperature Sensing) and array-type RTD (Resistance Temperature Detector) were deployed in the monitoring wells and recorded the data not only during the flow test period but also before and after the test. DTS covered the entire wellbore interval while the array-type RTD sensors were strategically placed across the gas hydrate reservoir with higher temperature resolution and accuracy.

In both monitoring wells, the temperature decreases were observed distinctively with both sensors as the flow test progressed over a week. The data quality check confirmed both measurements were conformable to the design specification and demonstrated the strong advantages of having both sensors in this monitoring system for further interpretation to investigate the dissociation behaviors.

The framework for temperature data analysis was defined to perform thermal characterization of gas hydrate reservoir during the production test stage. The preliminary analysis on the temperature transients was performed, and the results that could explain the dissociation behaviors were obtained.
An Experimental Study for Flow Assurance of the Methane Hydrate Production Test System
Authors: Sakurai S. , Nakatsuka Y. , Edwards T.J. , Hoskin B.J. , Manning D.K.
Published: June 2014

The world's first offshore methane hydrate production test was carried out in March 2013 in the Eastern Nankai Trough. The dissociation of methane hydrates in sediments was produced by depressurization. In this situation, flow assurance (FA) and prevention of hydrate re-formation in the wellbore is an important issue because water mixed with methane is transported through the well and seabed facilities, and subject to the well bore flowing pressure while being cooled-down by the surrounding seawater (around 4°C near the seabed).

A particular concern results from incomplete downhole gas separation of methane and water: this leads to the methane production line containing a small amount of water, and the water production line containing a small amount of free methane gas. In this water dominant flow line there is then the possibility of flow blockage due to gas hydrate re-formation and accumulation, but knowledge about behavior of hydrates under such water dominant conditions was not well known.

To investigate the potential for hydrate re-formation downstream of the downhole separator (including subsea pipes and equipment), Japan Oil, Gas and Metals National Corporation (JOGMEC) and Oilfield Production Technologies (OPT) developed a unique flow loop maintained at low temperature and high pressure. The flow loop was some 20 m in length. Notably, 6 m of the flow loop was constructed in optically clear cast acrylic, which allowed image capture in horizontal and vertical flow lines, and at flow stagnation points, ofmethane/water flows outside the hydrate regionthe formation, development and flow characteristics of hydrate slurries

In this paper we describe the flow loop design, show images of flow taken by a high speed camera, and our measurements of temperature and pressure in this water dominant system, and the potential of FA problems caused by hydrate re-association. The results and observations were used in the design of the test plan and test procedures implemented in the East Nankai production testing.
Mapping gas Hydrate Systems in the Gulf of Mexico Using Marine CSEM
Authors: Weitemeyer Karen , Constable Steven , Key Kerry
Published: June 2014

An extensive marine controlled source electromagnetic (CSEM) data set was collected in the Gulf of Mexico targeting gas hydrate deposits at four geologically distinct areas within water depths that varied from 900 to 3000 m. The Joint Industry Project 2 drilled two of these locations, Green Canyon 955 and Walker Ridge 313, providing ground truth for the CSEM data. A third survey location, Mississippi Canyon 118 (MC118), is a designated hydrate observatory. We collected both traditional ocean bottom electromagnetic receiver data as well as continuous profiling data using a novel towed three-axis electric field receiver. The towed receiver measured data at a fixed offset of 300 m behind the transmitter, while the ocean bottom receivers recorded data over a range of offsets as the transmitter passed by each receiver. We inverted the CSEM data using a newly developed parallel goal-oriented adaptive finite element-modeling algorithm for efficient 2.5D imaging of the CSEM data. 2D inversions from MC118 are consistent with 1D apparent resistivity pseudosections and reveal resistive areas associated with the carbonate/hydrate mound. An extensive conductive region exists below this, associated with conductive brines sourced from a deeper more resistive salt body. Away from the mound the resistivity structure is a fairly uniform and homogeneous. We present new 2D inversions of the CSEM data that consider electrical anisotropy and constrained inversions that leverage structural control using key seismic horizons along the profiles.
Optimized Riser Architectures for 20 ksi Drilling Operations
Authors: Saeedi N. , Persent E. , Averbuch D. , Guesnon J.
Published: June 2014

Oil and gas companies are considering drilling operations in offshore locations where high pressure formation is anticipated. To be totally safe, such operations will require the use of a 20,000 psi BOP stack and associated pieces of equipment, such as the drilling riser.

This new requirement brings severe constraints for the riser design, which can currently be solved with existing technologies, only in shallow water depth. The load sharing arrangement being the key to 20 ksi drilling risers, it is important to understand in depth this mechanism and its benefits for the riser architecture.

This paper presents a thorough analysis of the behavior of load-sharing risers. The distribution of the loads and stresses between the main riser pipe and the auxiliary lines have been calculated and analyzed for different combinations of design parameters, including effective tension, pressure and load-sharing configurations.

A number of drilling riser options has been evaluated to withstand internal operating pressures of 20,000 psi within the Choke & Kill lines in a water depth of 10,000 ft with heavy mud. According to the study, the conventional technology is discarded because of the thick-walled pipes, the huge mass of the riser and the amount of buoyancy, that are required to withstand high pressure encountered at great depths.

A new generation of drilling risers is proposed based on a new implementation of the load-sharing technology on the Clip-RiserTM. This technology, currently under development, provides the riser with much higher performances for tension, pressure and dynamics.

The evaluated technologies introduce major improvements in the riser design with respect to the conventional one, including a large reduction of the riser mass and of the required buoyancy for riser joints.

Further benefits in terms of weight savings can be achieved by combining this technology with the previously developed steel/composite hybrid Choke and Kill lines.
Deep Water Pipeline Repair In The Gulf Of Mexico
Authors: Brown Lance , Dayani Adrian , Lazenby Shaun , Miller Jackson
Published: June 2014

The ability to repair pipelines remotely becomes critical as water depths of offshore field developments continue to increase beyond diving limits. While there have been several proposed solutions available, very few repairs have been carried out remotely. In October 2012, a Houston based team comprising of Subsea 7, Quality Connector Systems LLC and Stress Engineering Services, Inc. successfully completed a repair in 3, 200 FSW from a light construction vessel (M/V Grant Candies).

The extent of this operation was to assess the damage to the pipeline, remove pipeline coatings, and to install a QCS diverless repair clamp connector; with the limitation that all work had to be carried out only using work class ROVs. Detailed engineering, planning, ROV tool interfacing and a complete system integration test including equipment trials were critical to minimizing vessel downtime and meeting an aggressive schedule. Repair of the pipeline being critical to the long term integrity, and life expectancy following the discovery of a defect.

This paper reviews the current state of remote intervention based pipeline repair technology and provides an overview of the challenges faced when dealing with regulatory agencies (BSEE/BOEM), lessons learned in implementing this repair and considerations to be able to transfer this technology to greater water depths and harsher environments.
Wind-powered Subsea Water Injection Pumping: Technical and Economic Feasibility
Authors: Slätte Johan , Sandberg Johan , Flach Todd , Dekker Gerben , Sixtensson Carl
Published: June 2014

New technologies and solutions are increasingly more critical in the oil industry to develop marginal fields and maintain the oil production rates of more mature fields. In recent years several successful raw seawater injection systems have been implemented and new subsea water treatment technologies are under development, enhancing the methodologies and techniques used.

This paper describes the potential use of floating wind turbines for powering subsea water injection facilities, stand-alone systems', and discusses these systems' technical and economic feasibility compared to current solutions. High-level indicators of economic and technical performance show an interesting window of opportunity for applications that can tolerate unprocessed seawater for injection in oil fields. Other configurations can also be attractive.

The simplest use case considered for this article is powering a subsea pump with a local, offshore floating wind turbine to inject unprocessed seawater into an oil reservoir. Other related cases for floating wind turbine powered injection pumping are identified and discussed. Recent experience on a subsea water injection project on the Norwegian shelf has demonstrated the technical viability of injecting unprocessed seawater into an oil reservoir with suitable properties. Further, successful floating wind turbine demonstration projects have proven this new technology's feasibility.

In the conventional solution for a subsea injection manifold, the costs associated with connecting a subsea power cable to the host platform, where the electrical power for the subsea injection pump is generated, can be substantial. Under the right circumstances and conditions, it may be possible to reduce costs significantly by powering the subsea pump with 1-2 offshore wind turbines that are placed in close vicinity (in the order of hundreds of meters) of the subsea manifold. The reduced costs of this solution are enabled by the shorter subsea power cable, the elimination of incremental power generation on the host platform and, in the case of Norway, reduced taxes related to the incremental emissions of natural-gas turbine power generation for the subsea injection pump.

A study has been performed where the main technical challenges of the wind-powered subsea injection pump have been considered and are judged to be fully manageable. The most significant of these are related to the intermittency of the wind turbine power generation. Wind turbine output characteristics can be designed to produce power even at low but non-zero wind speeds. The optimization problem statement for choosing a wind turbine for this application is therefore very different to the more common challenge of maximizing energy output from wind turbines installed at a particular onshore site.
Seismic Processing Techniques for Geohazard Identification and Risk Reduction in a Frontier Exploration Area
Authors: Noll Christian , Liu Hui , Poole Alan , Helfrich Cody , Scherschel Craig
Published: June 2014

The main objective of Geohazard Investigation is to reduce operational risk in Drilling and Developments. While this is paramount during all operations, it is especially so for exploration drilling in frontier areas where only sparse data are available. Geohazard analysis is often carried out using conventional exploration 3D seismic data on a standalone basis. As these data are primarily acquired and processed to image deeper targets, they do not contain the high frequency content in the shallow section that would be achieved by high-resolution 2D or 3D acquisition.

To ensure operational integrity in areas where there is poor well control, and, or, where geologic complexity is high, it is necessary to pursue techniques beyond the traditional evaluation of available data to deliver high quality risk assessments.

Application of processing and analysis techniques to gain additional insight to conditions, by extracting additional attributes from existing geophysical data are, therefore, attractive. These techniques can be used to build a more robust geologic model, to understand the complexities of the geological system, in the absence of direct sampling, and are even more useful when complemented by ground-truthing.

This paper describes how exploration 3D seismic data were reprocessed into a "high-resolution" 3D seismic volume. The reprocessing was carried out to improve frequency content by focusing on the shallow section for use in site investigation. Work was undertaken to deliver improved understanding of the shallow velocity field by generating a Full Waveform Inversion velocity model. This was then used as the starting model for a pre-stack Kirchhoff depth migration which was able to provide further improved stratigraphic and structural imaging to allow an even more accurate interpretation.

Having delivered an improved seismic volume, advanced coherency algorithms were applied to understand discontinuities, at multiple scales, and spectral decomposition analysis was performed to better understand the distribution of seafloor and subsurface lithologies.

The combined effect of the application of these processing and analysis steps lead to a better understanding of the geologic complexities of the area and how these might translate to potential geohazards, allowing them to either be directly avoided, or mitigated, through engineering design prior to the start of drilling operations.
Underwater monitoring network: Using the deep-sea Drill MARUM-MeBo for installing Subseafloor Sensor Systems for monitoring Seafloor Intervention Operations
Authors: Waldmann Christoph , Freudenthal Tim , Kopf Achim
Published: June 2014

Any intervention into the seafloor will have an impact on the structural integrity of the material in the affected region and will hence result in variation in stress, pore water pressure, and temperature. As a consequence fluids maybe mobilized and may in turn affect the intervention process. To closely track such processes or monitor safe operations in areas of e.g. hydrocarbon exploitation, seafloor mining or marine renewables, new measuring strategies have to be developed to allow a spatio-temporal coverage via a sensor network. With the deep-sea drill MARUM-MeBo that has been developed at the University of Bremen/MARUM new opportunities are opened up to deploy sensors in shallow boreholes (<80 m sub-seafloor depth). MeBo is characterized by its versatility and high mobility with deployments down to water depths of 2000 m. Materials recovered via wire-line coring technique included both soft sediments and hard rocks. After drilling a 2.35 m section the core is recovered using a wire that is latched to the inner core barrel with an overshot. The outer drill string stays in the drilled hole during the entire drilling process. Recently, simple self-contained borehole instruments were developed that are placed in the hole, in which the outer drill string serves as casing. We propose to employ MeBo to deploy a network of instrumented boreholes in the region of deep-sea interventions to monitor the environmental conditions continuously over long time intervals. Data can be exchanged via acoustic modems and may serve to archive time series and use in hazard assessment and early warning.
Future Changes in Gulf of Mexico Hurricane Wave Climatology
Authors: Done James M. , Ge Ming , Holland Greg J. , Bruyère Cindy L
Published: June 2014

Meeting industry demand for assessments of future changes in Gulf of Mexico hurricane impacts is a challenge that extends well beyond simply improving climate prediction. Once the climate predictions have been made, there remains a huge gap regarding how this affects industry. The National Center for Atmospheric Research is actively engaged in a collaborative project with the Research Partnership to Secure Energy for America, Chevron Energy Technology Company and Willis Re to align the latest climate research with the requirements of industry.

This paper explores methods to simulate and predict future changes in hurricane impacts on the offshore energy industry. We first expand the concept of the Saffir-Simpson hurricane categorical scale to include important characteristics of the wind field for damage including maximum wind speed, storm translation speed and size, in a new Cyclone Damage Potential index. The index is applied to simulated current and future hurricanes to assess future changes in hurricane damage potential.

Loading on structures in the Gulf of Mexico is a complex function of not only characteristics of the wind field but also ocean characteristics including currents and waves. Simple empirical relationships between wind, wave and current miss some of the essential physics, particularly for extreme events. To improve upon the damage potential assessments we need to account for the full physical interactions between wind, wave and current. This paper explores the ability of fully coupled atmosphere-ocean dynamical simulations to capture metocean hurricane conditions through a case study simulation of Hurricane Katrina. This preliminary case study simulation establishes the simulation technology that will then be used to build robust assessments of the 100-year load and its future change using a combined theoretical and dynamical-statistical approach.
A Pressure Coring Operation and On-board Analyses of Methane Hydrate-bearing Samples
Authors: Yamamoto Koji , Inada Norihito , Kubo Satoshi , Fujii Tesuya , Suzuki Kiyofumi , Nakatsuka Yoshihiro , Ikawa Terumichi , Seki Makoto , Konno Yoshihiro , Yoneda Jun , Nagao Jiro , Mizuguchi Yasuhiko
Published: June 2014

As a part of the offshore production test program, in June and July of 2012, Japan Oil, Gas and Metals National Corporation (JOGMEC) conducted coring operation in the Eastern Nankai Trough where the first offshore production test of methane hydrates was to be conducted. By using a pressure coring device, Hybrid PCS developed by Japan Agency of Marine Science and Technology (JAMSTEC), Aumann and Associate Inc. (AAI), and JOGMEC, pressure conserved cores were recovered from methane hydrate-bearing sandy formations although some technical difficulties encoutered. The samples were analyzed onboard by Pressure Core Analysis and Transfer System (PCATS, GeoTek). Some samples were sent to onshore laboratories for further analyses. Continuous 60m intervalin a methane hydrate concentrated zone was cored and fairly good core recovery and pressure conservation rates were achieved. The obtained data are used for reservoir characterization of methane hydrate concentrated zone from where gas was produced during the actual production test conducted in March 2013.
Hydrate Modeling & Flow Loop Experiments for Water Continuous & Partially Dispersed Systems
Authors: Vijayamohan P. , Majid A. , Chaudhari P. , Sloan E.D. , Sum A.K. , Koh C.A. , Dellacase E. , Volk M.
Published: June 2014

A major industry concern is to reduce the severe safety risks associated with hydrate plug formation, and significantly extending subsea tieback distances by providing a cost effective flow assurance management/safety tool for mature fields. Developing fundamental understanding of the key mechanistic steps towards hydrate plug formation for different multiphase flow conditions is a key challenge to the flow assurance community. Such understanding can ultimately provide new insight and hydrate management guidelines to diminish the safety risks due to hydrate formation and accumulation in deepwater flowlines and facilities. The transportability of hydrates in pipelines is a function of the operating parameters, such as temperature, pressure, fluid mixture velocity, liquid loading, and fluid system characteristics. Specifically, the hydrate formation rate and plugging onset characteristics can be significantly different for water continuous, oil continuous, and partially dispersed systems. The latter is defined as a system containing oil/gas/water, where the water is present both as free water and partially dispersed in the oil phase (e.g., entrained water in the oil). This paper presents the results and analyses of flowloop experiments on partially dispersed systems as a function of water volume fraction and velocity/mixing. These experiments indicate that the partially dispersed systems tend to be problematic and are more severe cases with respect to flow assurance when compared to systems where the water is completely dispersed in oil. We have found that the partially dispersed systems are distinct, and are not an intermediate case between total water, and totally water-dispersed systems. Instead the experiments indicate that growth of hydrate sheet/deposit on the pipe wall because of the wetting of pipe walls by the free water layer coupled with bedding of the hydrates that are formed in bulk liquid seems to be the governing phenomena for hydrates growth in such systems. The data from the tests performed provide the basis for a mechanistic model for hydrate formation and plugging in partially dispersed systems. Lessons resulting from this work should be incorporated into flow assurance models, as well as operating company production strategies to reduce or mitigate hydrate plugging risks in complex multiphase systems.
Hydrate Deposition Mechanisms on Pipe Walls
Authors: Grasso G.A. , Sloan E.D. , Koh C.A. , Sum* A.K. , Creek J.L. , Kusinski G.
Published: June 2014

As the oil and gas industry moves towards offshore developments in deeper waters, the risk management of plugging pipelines due to hydrate formation increases in difficulty, which may lead to operation/safety hazards (Sloan, 2005). To tackle this challenge, the flow assurance community requires predictive tools to account for hydrate formation in flowlines (Zerpaet al., 2011). Although significant knowledge has been gained from mechanistic models for hydrate plug formation, there are still components missing for a comprehensive model, such as hydrate deposition on pipeline walls. Currently, field and flowloop data suggest the need to include and quantify hydrate deposition in the hydrate formation model (Lachanceet al., 2012). Agglomeration of hydrate particles by itself cannot account for large pressure drop observed during hydrate formation. Because hydrate deposition is difficult to decouple from other hydrate related phenomena (e.g., agglomeration), little to no research has previously been done addressing this phenomenon, particularly in gas-liquid systems. This paper details the initial effort to study hydrate deposition mechanism as part of a DeepStar funded project (CTR11203). Here, we present results that provide insight into hydrate deposition mechanisms based on experimental investigations designed to isolate this phenomenon from other hydrate issues. We have identified that water (hydrate former) reaches the deposition surface by direct contact of water with the surface, by condensation of water on the cold surface, and finally by liquid capillarity. Once the water reaches the deposition surface hydrate deposits form. We have also found that the rate of hydrate deposition increases by decreasing the surface temperature and these results are repeatable. We have shown that hydrate deposition on pipe walls is a key component for hydrate plug formation. The understanding gained with this investigation contributes to the efforts of the flow assurance community to develop a comprehensive hydrate formation model that could account for all the risks pertinent to hydrate formation in multiphase flow systems.
Structural Integrity Assessment of FPSO Life Extension and Relocation
Authors: Wang Xiaozhi , Sun Haihong , Lee Soontaek
Published: June 2014

Since the first FPSO was built in the 1970s, FPSOs have been a very popular Floating Production Installation (FPI) concept, especially in deep-water application. The mobility of ship-type FPSOs makes them easy to transit, operate in a marginal field and relocate to other fields. Self-propelled FPSOs with a disconnectable turret can sail to safe harbor during a hurricane or other emergency. Oil transportation by shuttle tankers eliminates the need for oil transportation to shore by long-distance pipeline. Because of their flexible features and mature shipbuilding experience, FPSOs are good candidates for life extension at the same field and relocation to different fields at the end of its designed life. However, most FPSOs have been in operation for an extended life, some being converted from existing tankers. A rational and reliable procedure for the assessment of FPSO structures with designated scantling to validate structural integrity after FPSO life extension and relocation is called for, taking into account the expectation of safety and economic aspects. Special consideration is to be made between life extension at the same field or same operating area with updated environmental conditions, and relocation to a new field with different environmental conditions.
Do the new broadband acquisition techniques allow us to improve subsurface geohazard detection?
Authors: Saint-André C. , Compoint A. , Cauquil E. , Pivot F.
Published: June 2014

Geohazards are a major threat which can affect drilling, platform anchoring, and the integrity of subsurface installations. Therefore the assessment of geohazards using geophysical data require the best achievable resolution. Geohazards need to be precisely detected, delineated and understood in order to validate geohazard free areas and safe environments for drilling and production operations. Major subsurface geohazards are gas-charged sediments, gas hydrates and over pressured sands which are generally associated to amplitude anomalies. Dutta et al. (2010) illustrated that shallow hazards detection from 3D dedicated seismic volumes (SHAZ) is perfectly valid. Saint-Andre et al. (2011) highlighted the importance during conventional seismic workflow definition, of a dedicated shallow hazards 3D processing (SHAZ cube) which can systematically be performed using adapted wokflows and would enhance spatial and temporal resolution, hence detectivity in the shallow parts. The recent developpement of broadband acquisition techniques brings out new perspectives concerning shallow hazards detection. The broader frequency spectrum of the data obtained with these new acquisition techniques may become a turning point in terms of geohazards characterization. As a result, this raises the question: Do new Broadband acquisition techniques allow to improve or replace the dedicated 3D seismic volumes for geohazards detection?
Seismic Investigation of Gas Hydrates in the Gulf of Mexico: 2013 Multicomponent and High-Resolution 2D Acquisition at GC955 and WR313
Authors: Haines Seth S. , Hart Patrick , Shedd William W. , Frye Matthew
Published: June 2014

The U.S. Geological Survey led a seismic acquisition expedition at Walker Ridge 313 (WR313) and Green Canyon 955 (GC955) in the Gulf of Mexico from April 18 through May 3, 2013, acquiring multicomponent and high-resolution 2D seismic data. WR313 and GC955 are established, world-class research sites where high gas hydrate saturations exist within reservoir-quality sands in a long-established petroleum province. Logging-while-drilling (LWD) data acquired in 2009 by the Gulf of Mexico Gas Hydrates Joint Industry Project provide detailed characterization at the borehole locations, and industry seismic data provide regional- and local-scale structural and stratigraphic characterization. Significant remaining questions regarding lithology and hydrate saturation between and away from the boreholes spurred new geophysical data acquisition at these sites. The goals of our 2013 surveys were to (1) achieve improved imaging and characterization at these sites and (2) refine geophysical methods for gas hydrate characterization.

In the area of WR313 we deployed 25 OBS and acquired approximately 450 km of streamer seismic data in a grid pattern with line spacing as small as 250 m and along radial lines that provide source offsets up to 10 km for the OBS. In the area of GC955 we deployed 21 ocean-bottom seismometers (OBS) and acquired approximately 400 km of high-resolution 2D streamer seismic data in a grid with line spacing as small as 50 m and along radial lines that provide source offsets up to 10 km and diverse azimuths for the OBS. These new data afford at least three times better vertical resolution of the structural and stratigraphic features of interest at the sites and enable considerably improved characterization of lithology and the gas and gas hydrate systems. Our recent survey represents a unique application of dedicated geophysical acquisition to the characterization of confirmed reservoir-quality gas hydrate accumulations. These new data and interpretations are important progress toward tapping into the vast global reserves of gas hydrate.
ESP Gas Handling Technology Increases Oil Production Over 100% in a Mature Reservoir in the Gulf of Mexico: A Case History
Authors: Cardona Andres , O'Quinn Raymond , Fry Steve
Published: June 2014

Current increases in the price of oil have led to a renewed exploration of unconventional reservoirs including the deep and ultra-deep waters of the Gulf of Mexico. Historically, these completions were primarily gas lift producers. Due to the depth of the reservoirs, though, there is still a significant amount of hydrocarbon that is unable to reach the surface. These reservoirs, sometimes called "brownfields, " are characterized by low/marginal production and require a comprehensive analysis to make any optimization project profitable. This analysis incorporates meticulous studies to identify candidate wells for the implementation of proven and reliable technology that will rejuvenate the hydrocarbon production. One major component of the rejuvenation is the use of new electrical submersible pump (ESP) equipment.

In the past, ESP technology has been inadequate for high gas applications; however, recent advancements in gas separators, multiphase ESP stages, shroud configurations and completion strategies have catapulted ESPs to the forefront of the pack. One example of the success of this approach can be found by examining the well in "Field-A" where ESP technologies for gas handling increased production over 200% in the wells with gas/oil ration (GOR_ in excess of 1,000 scf/BPD. This paper chronicles the approach adopted for select wells in the subject field identified as "Field-A" including: inflow and fluid analysis studies, challenges, technology selection, and production optimization results.
Deepstar 11901: Subsea Low Salinity Injection Water for Increased Oil Recovery
Authors: Anres Stephane , Delaplace Thomas , Skivington Graeme , Mateen Khalid , Kusinski Greg
Published: June 2014

This paper is based on work performed for Deepstar CTR11901 (for more information on the program see www.deepstar.org).

On average, only a third of in-place oil is recovered in Miocene reservoirs in the Gulf of Mexico. Water injection has been used to enhance the oil recoveries with limited success. Low salinity water injection could potentially further increase the oil recoveries achievable through seawater injection.

For deepwater oil fields and those requiring long tie-backs to the existing host processing platforms, local subsea processing systems providing low salinity water injection could be useful in improving development economics.

A Deepstar study has been carried out to evaluate the existing technologies for such subsea processing system to generate the low salinity from the seawater at 10,000 feet of water depth. Several conceptual process schemes have been defined and evaluated, employing various combinations of technologies, and compared from the point of view of operability, maintainability and technology maturity level. Technology gaps have been identified in the selected technologies and roadmaps have been defined to fill those gaps.

The paper describes the methodology that has been used to review the existing technologies for water treatment and evaluate their potential for subsea application, presents the main results of the state of the art review and gives an overview of four process schemes defined for subsea implementation of a low salinity water injection station. Whole range of technologies for water desalination have been studied including membranes, electro-dialysis and the use of hydrate formation. The defined schemes combine desalination with other function technologies in order to optimize the make-up of the low salinity water to meet the particular reservoir needs.