bluuebunny/crossref_metadata_2025 huggingface dataset:
Data-Driven Comparison Between Solid Model and PC-SAFT for Modeling Asphaltene Precipitation
Authors: Abouie Ali , Darabi Hamed , Sepehrnoori Kamy
Published: April 2016

Selecting an appropriate Equation of State to model asphaltene precipitation in compositional wellbore/reservoir simulators is still unclear in the literature. Recent studies have shown that PC-SAFT is a more appropriate model for asphaltene precipitation compared to the commonly used solid model. The main objective of this paper is to compare the solid model and PC-SAFT in both static and dynamic asphaltene modeling. Through fluid characterization, the capabilities of both models are compared to reproduce precipitation experimental data.

The results show that both solid model and PC-SAFT are capable of accurate modeling of asphaltene precipitation. Although matching process using PC-SAFT is much easier, solid model is also able to reproduce the experimental data with the same quality as PC-SAFT, if it is tuned properly. The simulations showed that PC-SAFT is superior to solid model in terms of accuracy for extrapolation when the experimental data are not available for the simulation conditions (i.e. variation in temperature, pressure, and fluid composition in the reservoir/wellbore). However, both models are applicable for interpolation when the experimental data covers the range of simulation condition. The wellbore simulations show that although the trend of asphaltene deposition is similar for both models, solid model overestimates the amount of asphaltene precipitation and deposition in the wellbore compared to the PCSAFT model. On the other hand, since PC-SAFT uses an iterative procedure for finding the density roots, phase equilibrium calculation, and consequently, the simulation procedure takes much more computational time when PC-SAFT is used.
Real-Time Sample Confirmation with Wireless Acoustic Technology During Downhole Sampling
Authors: Mataruco Antônio , Harner Lauren , Castellões Leonardo
Published: April 2016

Having full knowledge of the reservoir is crucial for the development of any hydrocarbon reservoir. Beyond gathering information about skin, boundaries, effective permeability, and production rates, knowing what type of hydrocarbons are being produced is often the key to optimizing the reservoir's production (i.e., reducing costs and raising profits). This paper describes the process of using wireless acoustic technology during downhole sampling to obtain important information to aid in the development decisions for a reservoir.

During the sampling process, valuable insight is gained about fluid sample collection, retention, and basic composition. This information can help the operator gain a better understanding of what is occurring during the lifecycle of the sampling event—before and after sample collection, during sample recovery to the surface, and in the sample transfer. Being able to follow each stage of the sampling process in real time provides important data that confirms whether the sample remained in single phase, as a representative fluid sample, for the entire duration of the well test. It is important to keep the sample at high pressure during the recovery process to ensure a monophasic sample. This is accomplished with a nitrogen pressure-compensation system to maintain pressure during recovery.

In addition, using the pressure from the common nitrogen chamber inside the sampling system in conjunction with the new data interpretation system, it is possible to confirm, in real time, the basic composition of the samples (black oil, volatile oil, condensate, dry gas, water) that are captured inside the sampler chamber housings. Additionally, the number of samples collected and the retention of those samples can be determined.

This type of knowledge about the sampling event is normally obtained once the toolstring has been pulled to surface and after the sampling cylinders have been sent off to the lab for pressure, volume, and temperature (PVT) analysis. Gaining insight into the characteristics of the reservoir in real time allows for operational decisions to be made quickly, ensuring necessary sample collection, thereby saving time and money.
Analysis of Wellbore Stability Management and Surveying Time When Using MWD Survey RPM on Cessation Method in Drilling Operations
Authors: Monterrosa Leida C. , Zegarra Erica , Soto Reinaldo A. , Celis Criss M. , Lowdon Ross
Published: April 2016

This paper explores various case studies to evaluate how an innovative methodology for sending MWD surveys up hole, based on cessation of surface RPM rather than variations of mud flow rate, helps drilling operations become more cost effective, decreasing wellbore stability & HSE risks, reducing surveying time and optimizing connection procedures.

Conventional surveys are taken by recycling the mud pumps. Mud flow is brought to below the MWD turn-on rate in order to switch off the tool and trigger the survey, and then the flow is increased to above the turn-on rate and the survey is sent to surface. Surveys based on RPM cessation use a different technique that allows the MWD tool to take the survey and to transmit it to the surface acquision system when it detects that the rotation has being stopped, allowing the mud flow to remain unchanged and removing the need to recycle the pumps.

Various distinct applications were analyzed in terms of MWD surveying time, wellbore stability and stuck pipe risks to evaluate the impact of this new approach in drilling operations. The cases analyzed deal with the following aspects: reduction of stuck pipe events in projects with high risk wellbore stability issues, ECD and pressure management in MPD projects, anti-collision avoidance and overall reduction of rig time for projects taking MWD surveys before connection.

It was concluded that more and more phases of a well construction have seen the benefit of this methodology as it has greatly contributed to the efficiency of drilling operations and in some of the cases allowing the fulfillment of the well objectives by the significant reduction of drilling risks, in comparison with the conventional way to take MWD surveys.

This is a novel approach to take MWD surveys and send them up-hole; very little has been written in industry literature about how its application enhances the reduction of key drilling challenges such as reduction of stuck pipe events. This will allow operators and contractors to push the envelope even further, in scenarios where extra fluctuations in the mud flow are adding significant financial or HSE risks.
Offshore Wind Farm OWF Installation Best Practices Based on Field Experience
Authors: Ekici Deniz , White Mike , Drunsic Michael
Published: April 2016

Offshore Wind Farm (OWF) operations have a significant growth potential outside of the North Sea, which is the only part of the world at the moment with a significant operational offshore wind farm presence. However, there are multiple pilot projects around the world in progress. Similar to other construction industries, one of the most critical and high risk phases of a project is the installation phase, particularly the marine components. Marine operations are inherently more complex compared to land-based installation operations, due to involvement of more sophisticated machinery to address the hindrances of performing construction activities in the marine environment. This paper highlights some of the critical installation points in a typical offshore wind farm project, as experienced first-hand during recent offshore installation campaigns in Northern Europe.
Logistics and Supply-Chain Management in Offshore Wind Farm (OWF) Applications
Authors: Drunsic Michael , Ekici Deniz , White Mike
Published: April 2016

The offshore wind industry is experiencing significant global growth and with the first offshore wind project in the United States currently under construction, the budding U.S. market is poised for growth. One of the significant differentiators between new entrant markets such as the U.S. and the established European market, is the existence of an established and relatively mature supply chain. Even with the developed supply chain in Europe, there is still significant opportunity for cost reduction and effective supply chain management can be a key factor for realizing these opportunities. Construction of offshore wind projects requires a robust supply chain management system to manage the complex logistics and flows of goods and services. The serial nature of the manufacturing and installation of offshore wind farm components combined with the large sizes of the components necessitates specialized equipment and approaches to supply chain management. In emerging markets such as the U.S., additional challenges associated with vessel restrictions (e.g the Jones Act[1] and the Cargo Preference Act[2]), port infrastructure limitations, and limited domestic manufacturing of key components increase the need for strong supply chain management to ensure successful projects. The installation and transportation infrastructure, equipment, and logistics represent critical areas of the supply chain and there are numerous areas where the U.S. market can build upon experience from European experience. As the offshore wind industry develops in North America, effective supply chain management will be critical to delivering the first projects and ensuring offshore wind can be a competitive contributor to the energy supply mix.
Drilling Technology: Drill Cutting Remediation System (DCRS) for Subsea Top Hole Drilling
Authors: Price William R.
Published: April 2016

During subsea field development, a significant amount of drill cuttings, mud and cement, is discharged on the seabed while the tophole sections of subsea wells are drilled and cased before the BOP and drilling riser are set in place atop each well. Discharging this material at the wellhead can reduce visibility and make ROV operations more difficult. In fields where multiple wells are drilled in a small area, the large volume of discharge can cover the seabed with a layer of material of 90 feet or more, enough to bury manifolds and complicate hardware installation. In some cases, an intervention vessel is required to move the accumulation of discharged cuttings before the installation of the production infrastructure.

A Drill Cutting Remediation System (DCRS) was developed to address these issues during top hole drilling by diverting discharged cuttings and cement away from the wellhead and clear of te areas planned for subsea infrastructure. The system consists of a Wellhead Funnel (WHF) placed on the wellhead to capture the cuttings and cement, and a subsea dredge, connected to the WHF with hose, which transports the material outside the field perimeter to keep the near-well area clean and to keep the water clear.

While it can be applied to single wells, the DCRS provides the greatest benefit in drilling campaigns with multiple wells that are batch set in a small area. The DCRS can be deployed without impacting critical rig time. The system helps maintain water clarity and visibility for ROV operation and other activities. The DCRS removes potentially troublesome cement discharges and prevents their buildup in the near-well area. In addition, the seabed is kept clear to enable efficient installation of manifolds, jumpers and hydraulic and electrical flying leads (HFL and EFL).

The DCRS has been applied in the Gulf of Mexico on two batch-set projects and one single well project, saving time and money. The DCRS has the potential to provide similar advantages in subsea fields around the world.
Widened Safe Mud Window for Subsalt Well Sections: A Workflow and Case Study
Authors: Shen Guoyang , Shen Xinpu
Published: April 2016

This paper presents a 3D numerical study on the mechanical behaviors of natural fracture under injection loading, and further proposes a practical workflow for designing a widened safe mud weight window (MWW) for drilling subsalt well sections with natural fractures. The original safe MWW value for subsalt well sections is usually narrow. More specific, for a subsalt well section with natural fractures, no safe MWW existed because of this unfavorable geological environment. Therefore, hydraulic plug technology was adopted to reinforce wellbore stability and widen the MWW. The value for opening a natural fracture under the given mud-weight pressure was numerically calculated, and then used for selecting the lost circulation material (LCM) treatment size. In addition, stress cage, which is quantified by enhancement of hoop stress at the wellbore surface, was numerically analyzed.

An illustrative example is performed with information from a well in a deepwater Gulf of Mexico (GOM) field. It is observed that a fracture with initial width of 0.5 mm opening to 0.664 mm will result in an increment of 0.55 lbm/gal mud weight. This solution is obtained with assumption of one pair of natural fractures. In the case of two existing pairs of fractures, a 1.1 lbm/gal increment of mud weight can be directly obtained for this set because of the linear property of the model,.

The case study described in this paper provides a workflow for widening the MWW for safe drilling through a naturally fractured subsalt well section. A best practice for using this type of MWW design is also presented.
Enhanced Nozzle Inflow Control Device Development for Wall Shear Stress Minimization in High-Production Application
Authors: Corona Georgina , Yin Weiqi , Felten Frederic
Published: April 2016

Inflow control devices (ICD) are a proven technology for overall production flux balance. Because they restrict flow, standard ICDs develop regions of high-fluid velocities and high-wall shear stresses. Wall shear stress is a tangential drag force produced by a layer of flow along a wall as a result of friction between the fluid and the wall. Elevated production rates of oil and/or water with CO2 or H2S increase fluid velocities and associated wall shear experienced by ICDs potentially leading to flow-induced erosion-corrosion and mechanical failure. For these environments, corrosion is enhanced by the removal of the passivating layer through fluid flow-induced erosion.

Because of the strong need for ICD completions in a high profile field project in the Middle East, an enhanced ICD design has been developed to withstand high production rates without creating high wall shear, thus reducing erosion-corrosion induced by flow. Computational fluid dynamics (CFD) was used to study several ICD designs and assess the modifications necessary to enhance performance for different flow rates and pressure drop conditions. Worst case scenarios were evaluated to ensure the modified design would be suitable for the environment and meet the operator's criteria for production.

CFD analysis proved the enhanced adjustable nozzle ICD was an improvement over the standard ICD. This modified design showed lower wall shear on the critical surfaces. Throughout the ICD design optimization process, flow behavior was evaluated to minimize regions of predicted high velocity and wall shear. The enhanced design is commercially available in the Middle East. The modified, adjustable, nozzle ICD helps to condition the flow better than the standard ICD, thus reducing the wall shear stress around critical parts (including perforation holes, basepipe surface, and NPT plugs). This reduction is crucial when dealing with required high production flow rate.

Exploring options to minimize wall shear stress on the surfaces of completion components is a relatively recent challenge. It is an important subject for operators attempting to avoid mechanical failures and the associated recompletion costs. The present study provides a methodology to design fluid passages to minimize the flow-induced erosion-corrosion experienced at high production rates as well as high injection rates experienced during workover operations.
Human Factors and Organizational Management - Can We Fix the Mindset? Modernizing Drilling with Human-Centered Designs
Authors: Hoffmann K. J. , Gutierrez J. A.
Published: April 2016

Engineers cannot fix an industry mindset, but they can offer possible solutions to enhance product design and assist with improved operations. One such solution, which has been applied in multiple industries have incorporated Human-Centered Design (HCD) to improve safety integrity, reduce downtime and increase efficiency. HCD incorporates better user interfaces and system design that can assist users when critical decisions must be made. Proper human-centered design or HCD can reduce stress and errors. The application of HCD best practices has helped multiple industries improve safety integrity, reduce downtime, and increase efficiency.

This paper will discuss how employing a HCD process—characterized by the active involvement of users, appropriate allocation of function between users and technology, iteration of design solutions, and a multidisciplinary design team—may result in products for offshore installations that could contribute to a reduction in downtime by utilizing easier to understand formats that may enhance user productivity, and improve operational efficiency.
Applied Geostatistical Reservoir Characterization in R: Review and Implementation of Permeability Estimation Modeling and Prediction Algorithms - Part II
Authors: Al-Mudhafar Watheq J.
Published: April 2016

Modeling and prediction the formation permeability is a decisive step in the reservoir characterization as it concerns the sparseness of the row data with different scales from different sources. Efficiently combining the different sources of rock characteristics, especially core and well logs data, should lead to accurate estimation of permeability for other wells that have no core analysis. That results in accurate reservoir characterization, precise geospatial modeling and solid reservoir modeling.

The most conventional approach for combining the core measurements, well log data into permeability modeling is the Multiple Linear Regression, which considers the least-square equation to estimate the coefficient of parameters in the linear modeling. However, there are many other algorithms that can be used for more accurate modeling and prediction of formation permeability. The other methods include: Multivariate Multiple Linear Regression, Generalized Additive Modeling, Multivariate Adaptive Regression Splines, Least-Angel Regression, Bayesian Generalized Linear Modeling, and Robust Linear Modeling.

In this paper, review of all the aforementioned algorithms were provided along with full implementation on the permeability modeling given the well log and core data in a well from Rumaila dataset, from South Rumaila oil field in Iraq. The comparison between these agorithms were performed based on the root mean square prediction error of the predicted permeability after conducting data sampling and cross-validation.

These algorithms can be carried out through several commercial software packages with limitations in terms of availability and computation time consuming. In this paper, we introduce a simplified implementation of all these algorithm through R, the most powerful open-source statistical computing language. Detailed R-codes were prepared for all algorithms.
Integrating Rock Physics Modeling, Pre-Stack Inversion and Bayesian Classification: A Gulf of Mexico Case Study
Authors: Russell Brian
Published: April 2016

In this talk, I will directly link the detailed rock physics modeling of a condensate reservoir from the Gulf of Mexico to the pre-stack elastic inversion results from this reservoir and the Bayesian classification of these results. The goal of this study is to provide a quantitative link between these three very important aspects of seismic reservoir modeling: rock physics, elastic inversion and classification. The first step in this procedure is to perform pre-stack inversion of a 3D seismic volume recorded over the condensate reservoir using available well data, Biot-Gassmann modeling and the interpreted seismic picks as a starting model. Next, I identify the various lithological units from the inversion results and cross-plot these results using VP/VS ratio versus P-impedance. I then compare the cross-plot of the inverted results to the cross-plot of the well log after Biot-Gassmann modeling, in the same parameter space. I next build a detailed rock physics model of the reservoir and perturb the parameters in this model to obtain a good fit to the extracted inverted results. Finally, I use Bayesian classification to identify the probabilistic extent of the reservoir. The significance of this work is that a workflow has been developed, and applied to a Gulf of Mexico dataset, which allows us to iteratively tie together all aspects of quantitative seismic reservoir analysis, from rock physics modeling through elastic inversion to Bayesian classification.
An Innovative Packaged Gas Solution to Optimize Supply Chain
Authors: Mangeot-Gehin N. , Robertson S. , Arnaud G.
Published: April 2016

An innovative solution to help optimize operations for industry and to deliver improved performance and efficiencies across all its activities enhancing asset efficiency and safety, for Industrial gases used Offshore.

Safety is a top priority for the oil and gas industry, and Air Liquide has extended above and beyond industry safety standard compliance with the creation of its latest product.

Operators deploy industrial gases on a daily basis across all aspects of both upstream and downstream activities. This includes pipe fabrication and laying, construction, commissioning and decommissioning of offshore infrastructures, commercial diving for inspection maintenance and repair of subsea structures and well services such as inerting, coil tubing, pigging, and underbalanced drilling.

The oil and gas industry is renowned for its commitment to technological innovation to increase efficiency and optimise performance. These factors, aligned with customer demand, were the guiding principles behind Air Liquide’s decision to create the definitive quad, incorporating extreme performance, enhanced ergonomics and the most advanced safety features in the world.

A new packaged gas solution was launched in September 2015 following rigorous design, and safety and compliancy testing processes. It is already attracting significant attention from major operators who can see the benefits of being able to store and distribute gas in a safer and more efficient way.

The technology serves the major activities of construction and maintenance, subsea works and well services and combines a 40% gas capacity increase, an intuitive human-machine interface (HMI) and advanced safety features such as a built-in pressure reducer with an on/off lever.
Measurement Procedures and Analysis of Fluid Invasion Drivers During Cement Hydration
Authors: Silva Emilio C. C. M. , Jandhyala Siva Rama Krishna , Bardapurkar Sameer , Palla Venkata Gopala Rao , Ravi Kris , Singh Sheetal , Pearl William
Published: April 2016

Fluid invasion during cement hydration is governed by, among other factors, differential pressure between the formation fluids and the annular fluid. The primary phenomena influencing pressure in the annulus are evolution of cement slurry physical and chemical properties with time, filtrate lost to the formation, and changes in cement slurry volume during hydration. A successful procedure to design slurries to mitigate fluid invasion shall model these phenomena and provide viable methods to measure model parameters. At the same time, it should be feasible to formulate cement slurries to obtain the parameters necessary for a successful design.

This paper discusses model details with emphasis on parameters, their test procedures, and equipment details. Dynamic filter-cake properties are calculated by applying compressible filtration theory on data from a modified fluid loss test. Shrinkage/expansion is measured under temperature using the API ring mold apparatus. Pressure and displacement response to filtrate loss and shrinkage/expansion is dependent on bulk modulus, shear modulus, and static gel strength (SGS) evolution of the cement slurry during hydration. Properties are measured as a function of time using sonic analysis and a rotational gel strength device. Both material properties and volume changes attributed to fluid loss and hydration showed time dependency.

Furthermore, the pressure response of two realistic wells having different permeability and pore pressure profiles is analyzed. The two analyzed wells had different pressure responses, indicating that the slurry design should be customized for each well. This difference is attributed to varying capabilities of the well to compensate for volume loss by movement of cement placed adjacent to the permeable section, showing that the relative locations of the filtrate loss and potential fluid influx zones are important. Such an observation is possible only because of the ability to measure and model dynamic properties and events. The proposed methods are practical and can be realized using existing equipment with few procedural changes. Analysis based on these measurements guides the customization of slurry designs.
An Integrated Approach for Characterizing a Sandstone Reservoir in the Anadarko Basin
Authors: Ampomah W. , Balch R. S. , Ross-Coss D. , Hutton A. , Cather M. , Will R. A.
Published: April 2016

This paper presents field scale reservoir characterization of the Farnsworth field unit undertaken as part of a Phase III project conducted by the Southwest Regional Partnership on Carbon Sequestration. Farnsworth Unit (FWU) is located on the northwest shelf of the Anadarko Basin. The target unit for CO2 injection, storage, and enhanced oil recovery (EOR) is an upper Morrow sandstone informally named the Morrow B Sand.

The Morrow B reservoir was deposited during early Pennsylvanian time as incised valley fill fluvial sands. Core and thin sections were examined to determine lithology, mineralogy, porosity types, depositional environment and diagenetic history. Data from XRD analysis, optical and scanning electron microscopy, and microprobe analysis were compared with results from an elemental log analysis (ELAN). This information, together with additional core, well log, borehole image log, vertical seismic profile and 3D surface seismic data was used to characterize and subsequently create a fine scale lithofacies-based geological model of the field. Structural modeling was based on integration of 3D seismic and compressional sonic well log data to create a velocity model convertin the seismic z-axis into the depth-domain. Converting domains allowed the 3D seismic data to be correlated to other depth-domain datasets, such as new and legacy well log data and core sections. Seismic attributes were able to illuminate previously unknown faults and structural elements within the field.

During the petrophysical modeling, several deterministic and stochastic techniques were compared and analyzed to ascertain which method best populates the geological properties into the model. These techniques included kriging, sequential Gaussian simulation (SGS) and Gaussian random function simulation (GRFS). A data analysis approach was used as a quality check to reduce uncertainty in the modeling. Studies of depositional environment provided data used constructing porosity—permeability crossplots; this proved to be a useful approach to assigning permeability to the lithofacies-based geological model. The accepted static model was upscaled for dynamic reservoir simulation.

The approach illustrated in this study presents an improved methodology in characterizing heterogeneous and complex reservoirs that can be applied to reservoirs with similar geological features.
Comparison of the Seismic Response of Offshore Slopes Using 1, 2, or 3 Ground Motion Components
Authors: Carlton Brian D. , Kaynia Amir M.
Published: April 2016

Offshore landslides pose a major threat to subsea facilities, and one of the main triggering factors of offshore landslides is strong earthquakes. The state of the practice models offshore slope stability during strong shaking using one horizontal component of a selected representative ground motion. However, slopes and earthquakes are three-dimensional phenomena. Therefore, to provide much needed guidance in this area, this study performed 27 three-dimensional seismic slope stability analyses in a finite element program to investigate the change in the predicted results when applying one, two, or three ground motion components.

The results showed that applying two horizontal components instead of one may increase the predicted total displacements and shear strains on the slope by 25% to 50% and by 10% to 50%, respectively. In addition, it may also increase the total displacements at the seafloor on the shelf above the slope by 20% to 40%. This could have implications when deciding the safe stand-back line for offshore facilities. However, applying three ground motion components has a negligible effect on the results compared with applying only the two horizontal components. The ratio of the response spectra on the shelf, slope, and basin varied by ± 25%, however no clear trend was observed.
Novel Liquid Foam Stabilizer for Cementing Applications
Authors: Doan Angela Anh , Ejike Mosunmola Omuwunmi , Li Li
Published: April 2016

Deepwater drilling and cementing have been a challenge due to the low temperature at seabed, low fracture gradients, shallow water flow, gas hydrates, etc. Foamed cementing is one of the best practices that have been used for deep water wells. Dry foam stabilizers have been used but are limited to the number of jobs achievable with pre-blended cement on the rig. Introducing a liquid foam stabilizer improves logistics and flexibility, so one type of cement can be used for all cementing jobs, including primary and remedial jobs.

In this study, the performance of the novel liquid foam stabilizer was thoroughly evaluated with different types of cement and mixing fluid at various temperatures. API class H or class G cement with a foaming agent and the new foam stabilizer were mixed with fresh or sea water at different densities. The salt tolerance of the liquid foam stabilizer was investigated by adding a variety of salts at different concentrations. This liquid foam stabilizer also was evaluated at different concentrations and different foam qualities.

The evaluation includes foam stability and density distribution of set cement. Both the set and unset foam stability were tested. The test results show that the liquid foam stabilizer significantly improves the foamed slurry stability and the density distribution of the set cement.

The new liquid foam stabilizer helps foamed slurry and set cement stability with different types of cements, with fresh and sea water at temperatures from 40 to 190°F. In addition, it helps to improve system flexibility and logistics. Land and offshore applications of the new liquid foam stabilizer will also be described in detail.
Development and Qualification of a Subsea 3,000 Barrel Pressure Compensated Chemical Storage and Injection System
Authors: Schroeder Art J. , Chitwood James E. , Krasin Tim , Lee Brian , Krohn Dan , Huizinga Menno , Paramonoff Alex , Schroeder Charlotte , Gay Tom A. , Cercone David , Pappas James
Published: April 2016

This paper presents important findings while executing a detailed qualified design of a large (3,000 + barrel), subsea (to depths of 10,000 fsw) production chemical storage and injection system. The design drivers for the system were safety first, extensive utilization of existing commercially available equipment / tools / methods, and a re-usable shuttle system that allows for delivery of production chemicals as a service versus the current approach where an operator / owner makes a capital investment. The system is designed to be compatible with existing production chemical formulations and features multiple barrier design between the chemicals and the environment. Placement of the storage and injection system directly on the seafloor in close proximity to the point of need eliminates expensive chemical umbilicals, removes significant topside chemical storage and injection kit weight and space requirements at host facility and isolates hazardous chemicals from platform workers. The re-deployable shuttle economically allows inspection, repair and maintenance to take place quayside with the ability to upgrade equipment as technology progresses and / or quickly and cost effectively adjust to ever-changing field requirements.

Subsea wells have been proliferating over the last decade with ever-longer tie-backs to enable commercial recovery of small resource pools that are unable to support a traditional floating system development. Virtually all wells, especially subsea, require various volumes and types of production chemistries during their operational life. For subsea wells, the incumbent technology is chemistry delivery via umbilicals. In rare occasions, small volumes are sometimes delivered via single trip, disposable containers, principally during intervention activities. As tie-back distances have increased, so have the technical challenges with their attendant mushrooming costs. These challenges include the needs for; special corrosion resistant materials, resistance to high pressures differentials, material flexibility and ‘crimp – resistance’, and long term reliability. Additionally, some of these chemicals are high viscosity and as the tie-back distances increase, so does the pressure drop of the flowing fluids. In some cases, the risks of plugging and the magnitude of the delta-pressure drop in ½? – ¾? chemical tubing within the typical umbilical can preclude tie-backs of long offsets from the host / hub facility. The subject system overcomes many of these challenges by locating a large, pressure compensated storage and injection facility directly on the seafloor in close proximity to the point of need, thus qualifying it as enabling technology for extra-long tie-backs and enhancing technology for short tie-backs, de-bottlenecking, or early production system usage.
Microscopic Study of Wax Inhibition Mechanism
Authors: Daraboina Nagu , Soedarmo Auzan , Sarica Cem
Published: April 2016

Usage of paraffin inhibitors (PI) is one of the practices, especially in deepwater operation, to reduce pigging frequency. The PI selection process is challenging as their working mechanisms are yet to be fully understood. The understanding of crude specific interactions and the upscaling capability from cold finger testing in laboratory to full field scale is limited. This work emphasizes a microscopic study of paraffin crystals morphology under the influence of polymer based chemical inhibitors. The experiments were performed with three types of PI (A, B, and C), two types of oil (a model oil with 1%-wt. wax and a condensate with 9%-wt. wax), and three different PI concentrations (100, 250, and 500 ppm)

For no PI cases, the crystal size between the condensate (CS) and the model oil (MO) are visibly different as MO produces bigger crystals with less nuclei number density than CS. The PI-A (linear co-polymer) is observed to promote formation of larger crystals in both oils, except for 250 and 500 ppm concentrations in CS. The PI-B (long chain comb-like co-polymer) and PI-C (short chain comb-like co-polymer) are observed to generate smaller crystals in both oils, most of the times with greater nuclei number density. The PI-B is more effective in reducing crystal size for CS while PI-C is more effective in MO. An increase in PI concentration does not necessarily magnify the changes in crystal size exhibited in lower concentration. The microscopic characteristics (e.g., crystal size, nuclei number density) of paraffin crystals are expected to affect macroscopic characteristics (thickness and hardness) of the deposit.
CFD Investigation on Scale and Damping Effects for Vortex Induced Motions of a Semi-Submersible Floater
Authors: Koop A. , Rijken O. , Vaz G. , Maximiano A. , Rosetti G.
Published: April 2016

Available field measurements of semisubmersibles indicate that the Vortex Induced Motion (VIM) response is typically found to be smaller than what is predicted in model tests. Reductions of as much as 50% seem to be occurring in the field compared to the response found in model tests. Several variations in the model test setup have been made in the past to achieve a better agreement between field observations and model test results, but no conclusive results have been obtained so far to explain the reason for those differences.

MARIN and the University of Sao Paulo (USP) initiated the VIM JIP with the primary objective to enhance the understanding of possible differences between field measurements and model test observations. In this JIP the effects of waves, current inflow conditions, external damping, mass ratios and Reynolds number are investigated using CFD and model tests. Some of these effects are examined using CFD, some experimentally and some by both CFD and model tests.

In this paper the CFD results are presented to examine the effects due to Reynolds number and external damping. The basic step of the JIP is the comparison of the model-scale CFD results to experimental results. Extensive verification steps are undertaken to improve the confidence in both model-scale and full-scale CFD results. The model-scale CFD results show VIM response very similar to behavior observed in model tests. Then, the CFD model is applied to full-scale Reynolds number to investigate the effects of Reynolds number on the VIM response. Furthermore, the effects of external damping are examined as well, both at model-scale and full-scale Reynolds number.

The CFD simulations at full-scale Reynolds number presented in this paper show a shift in the response curve to lower reduced velocities, but no significant reduction in normalized VIM amplitude is observed. Thus, Reynolds scale effects seem not to be the main reason for the difference between model tests and field observations. However, a significant reduction of VIM amplitude is observed when increasing the external damping in the CFD calculations.

According to these observations the importance of external damping on the VIM response is identified. Further investigation is recommended to assess the damping from riser and mooring configurations which occurs at prototype semisubmersibles, so that the correct VIM response can be considered in the design phase.
Mooring Optimization in Time Domain Using Harmony Search
Authors: Schut Xavier , Dam Marius
Published: April 2016

The design of a mooring system is a time consuming task, owing to the large number of design cases, software interfaces and changing requirements. Although frequency domain is a faster method, the behavior of a turret moored FPSO and the loads applied on mooring system in a certain environment are most accurately predicted in the time domain. This does not help in reducing design time. Therefore an automated time domain harmony search based mooring optimization methodology, that uses industry standard software Orcaflex and Ariane7 through a MATLAB interface, has been developed. Harmony search is a phenomenon-mimicking algorithm inspired by the improvisation process of musicians. In the algorithm, each musician (= decision variable) plays (= generates) a note (= a value) for finding a best harmony (= global optimum) all together. The methodology is applied to design a mooring system for a large turret moored FPSO in deep water and harsh environment as a case study. The objective is to minimize the load on the turret chain table with feasible solutions that satisfy all the design constraints without manual intervention. An optimized solution is found within 5 days and the rate at which different mooring configurations are assessed is in excess of 160 per day. This paper outlines the developed process and how it may benefit the industry as an efficient mooring design methodology.
An Historical Perspective of Loop Activity from Nov. 2014 to Oct. 2015
Authors: Cooper C. , Yang X. , Danmeier D. , Stear J.
Published: April 2016

This paper compares the Loop activity during a one-year period beginning November 1, 2014 to the historical record derived from the Gulf Eddy Model (GEM) which covers 27 yrs. During our Study period, five anticyclones were generated (Lazarus, Michael, Nautilus I, Nautilus II, and Olympus) or one eddy every two months, far exceeding the 10-month shedding frequency observed in the historical data. Histograms describing the percent occurrence and intensity of ocean currents observed over the Study period are compared to historical statistics at sites in Walker Ridge, Mississippi Canyon, and Green Canyon and show Loop or Eddy (LCE) currents occurred at roughly twice the average historical frequency. At the two sites in Walker Ridge, the peak observed speed was near the 100-yr extreme calculated from GEM. At the Shell Stones site, observed currents exceeded the 100-yr GEM calculation by about 10% when the site was impacted by the combined currents of the Loop and a strong associated cyclone. GEM does not include cyclones so it is not too surprising that it could underestimate the currents in these situations.
Well Architecture in the Lower Tertiary Gulf of Mexico – Challenges and Potential Solutions
Authors: Fett Darryl , Mateen Khalid
Published: April 2016

Deepwater wells in the ‘Lower Tertiary’ play in the Gulf of Mexico are completed through large vertical intervals comprising of multiple high pressure hydrocarbon layers with low permeability. Operators are faced with numerous challenges to economically produce these reservoirs including: low permeabilities requiring multiple hydraulic fractures; highly pressured, deeply buried reservoirs over large intervals to complete and isolate; and high differential pressures during stimulation and production. The technology currently in use tends to address many of these challenges, however the productivity of these wells is still relatively low and the well costs remain high. This paper will review the challenges encountered in these wells, and the technologies currently used to address them. It will also outline potential well design and construction approaches for consideration by industry to improve well productivity and increase reliability.
Practical Guidelines for the Diagnosis and Remediation of Pipeline Blockages
Authors: Bukkaraju Sampath K. , Osorio Nelson F. , Annadorai Karthik M. , Garduño Jorge L. , Golden Nathan K.
Published: April 2016

One of the primary flow assurance challenges in the production of hydrocarbons is the prevention of pipeline blockages. Blockages can occur from a combination of improper system design, improper selection of piping and insulation materials, production chemistry aspects, inadequate or improper commissioning, startup and operating procedures, deviation from the proven operating procedures, changes in the operating conditions, intervention operations and improper maintenance procedures. The nature of the blockages can vary from "not-so-severe" to "hard-to-remediate" depending on the type of blockage.

While prevention is the best strategy, pipeline blockages do occur and it is very important to identify the cause and nature of the blockage along with its location to a reasonable level of accuracy and the operating limitations dictating the best suited remediation strategy. The criticality of blockage resolution largely depends on proper identification of the type and location of the blockage/s.
A Self-Walking Vertical Mining System Concept Using DTH for Seafloor Mining and Its Preliminary Design
Authors: Watanabe Yoshiyasu , Watanabe Keisuke , Yuasa Fumio , Nazuka Tatsuki
Published: April 2016

In the traditional concept of subsea mining field development, a subsea crawler generally has a big drill and scrapes the mineral deposit horizontally. In this "Horizontal Mining System (HMS)", ores vary in size and large chunks should be crushed into transportable particles. So a Subsea Crushing and Feeding Unit (SCFU) must be required for efficient slurry transportation to use the traditional riser system.

The vertical mining system (VMS) introduced in the previous paper1) consisted of a Down-The-Hole Drill (DTH) unit with a moving beam mounted on a jack up platform. The whole mining system consisted of the VMS, an Installation and Relocation Vessel (IRV), a subsea separator with pump, a riser and a mining support storage offloading (MSSO). The VMS had various merits but had a demerit that its relocation was executed by the IRV, which increased the project cost and period.

This paper introduces the concept and preliminary design of a Self-Walking Vertical Mining system (SW-VMS) that eliminates the use of the IRV and reduces the project cost and period. The SW-VMS consists of an upper jack up platform (UP) where the DTH drill unit and a moving beam are mounted, a middle frame (MF) and a lower jack up platform (LP). Each jack up platform has four legs and the platforms and the frame slide with each other. With alternately landing the four legs of each platform on the seafloor, the slides between the UP and the MF make the SW-VMS walk in one direction and the slides between the LP and the MF make the SW-VMS walk in the other direction. Thus the SW-VMS becomes capable of walking two-dimensionally on the seafloor.
Understanding Fluid Complexity and Reservoir Connectivity Using Downhole Fluid Analysis in Wilcox Formation Gulf of Mexico
Authors: Betancourt Soraya.S. , Mishra Vinay. K. , Clinch Simon , Guo Genliang , Malik Mayank , Cañas Jesus A. , Chen Li , Mullins Oliver C.
Published: April 2016

The development of the Wilcox formation in the Gulf of Mexico is constantly pushing technical boundaries in the oil industry. Here, ultra-deepwater wells are needed to target ultra-high pressure sub-salt reservoirs that are up to 32,000 ft below sea level. Innovative evaluation techniques and processes that could reduce reservoir uncertainties are key from prospect evaluation through field appraisal and development. In particular, detailed description of reservoir properties, fluid characterization and connectivity assessment in this challenging environment are extremely valuable.

An operator is extensively utilizing wireline formation tester measurements and downhole fluid analysis (DFA), and has implemented a workflow to assess reservoir connectivity using DFA data, asphaltene nanoscience, and geochemistry in a multi-well context. The coupling of vertical and lateral fluid gradient measurements from DFA and thermodynamic equilibrium analysis of the reservoir fluids represents a powerful new method for connectivity assessment. This includes use of novel asphaltene science and the Flory-Huggins-Zuo equation of state to model equilibrium asphaltene concentration gradients in petroleum reservoirs.

The workflow has been successfully implemented in all the operator's Wilcox fields to appraise both vertical connectivity of reservoir sands within individual wells and lateral connectivity throughout the field, and identify potential production challenges associated with non-equilibrated fluids. These workflows hinge on the application of the latest formation testing technology to help acquire the nearly pristine formation fluid samples required for such DFA field studies and real-time decision-making in characterizing reservoirs.