bluuebunny/crossref_metadata_2025 huggingface dataset:
A Continuous Flow Device for the Purification of Semiconducting Nanoparticles by AC Dielectrophoresis
Authors: Golnabi Rustin , Chi Su (Ike) Chih , Farias Stephen L. , Cammarata Robert C.
Published: September 2014

Single-walled carbon nanotubes (SWCNTs) have attracted significant attention as building blocks for future nanoscale electronics due to their small size and unique electronic properties. However, current SWCNT production techniques generate a mixture of two types of nanotubes with divergent electrical behaviors due to structural variations. Some of the nanotubes act as metallic materials while others display semiconducting properties. This random mixture has prevented the realization of functional carbon nanotube-based nanoelectronics. Here, a method of purifying a continuous flow of semiconducting nanotubes from an initially random mixture of both metallic and semiconducting SWCNTs in suspension is presented. This purification uses A/C dielectrophoresis (DEP), and takes advantage of the large difference of the relative dielectric constants between metallic and semiconducting SWCNTs. Because of a difference in magnitude and opposite directions of a dielectrophoretic force imposed on the random SWCNT solution, metallic SWCNTs deposit onto an electrode while semiconducting SWCNTs remain in suspension [3]. A discussion of these techniques is presented, along with a dielectrophoretic force-utilized microfluidic lab-on-a-chip device that can accomplish purification of semiconducting nanoparticles at high processing rates. The effectiveness of the device is characterized using Raman spectroscopy analysis on separated samples.
Development of Earth-abundant CZTS Thin Film Solar Cells with Sulfurization Technique
Authors: Katagiri Hironori , Jimbo Kazuo , Washio Tsukasa
Published: September 2014

Cu2ZnSnS4 (henceforth CZTS) absorber layers are successfully synthesized by a sulfurization technique of physical vapor deposited precursors. In our previous report, we have clarified that the off-stoichiometry composition of Cu-poor and Zn-rich is desirable to achieve high conversion efficiency. By using CZTS compound target that provide such active composition, we could conduct a simple single sputtering method to prepare CZTS absorber. In our laboratory, a two-stage process of precursor preparation followed by sulfurization is a major fabrication method from the start of this study. We think that this method is suitable for a mass production. An optimization of the sulfurization process is a quite important issue because the active composition was already revealed. In this paper, TG/DTA system available in the H2S atmosphere is introduced to optimize the sulfurization condition. As a result, bump-free CZTS films were prepared successfully and the fluctuation of J-V properties in one substrate was drastically suppressed.
Periodically ordered nanohetero inorganic structures of nanoparticles, nanorods and layers in a matrix from self-assembled block copolymers
Authors: Wakayama Hiroaki , Yonekura Hirotaka , Kawai Yasuaki
Published: September 2014

Periodically ordered nanohetero inorganic structures offer great promise due to their unique electric, ionic, magnetic, and photonic properties. Many studies have focused on the formation of periodically ordered nano-hetero inorganic structures through layer-by-layer adsorption, sputtering, and self-assembly methods. However, the construction of three-dimensional periodically ordered nanohetero inorganic structures with desired sizes and morphologies remains a great challenge. We present a simple method for producing three-dimensional periodically ordered inorganic nanoheterostructures with controlled shape and size by replicating self-assembled block copolymers (BCPs) containing precursors of metals and metal oxides. Precursors were dissolved with BCPs in a solvent. Upon evaporation of the solvent, each precursor was selectively introduced into a separate polymer block. Application of an external magnetic field (10 T) to the BCP-precursor composites resulted in a phase transition of from spheres to hexagonal cylinders. Subsequent pyrolytic removal of the BCPs produced periodically ordered nanoheterostructures that were structural replicates of the precursor–BCP composites. Self-assembled nano-hetero inorganic structures of nanoparticles, nanorods and layers in a matrix were produced. The morphology and domain size can be tailored by controlling the molecular weight and relative block length of block copolymers. The controlled size and morphology of the inorganic nanoheterostructures demonstrate the method’s utility for producing highly functional materials.
Crossover between Ferroelectric and Quantum Paraelectric in SrTiO3 both by Isotopic Substitution and Hydrostatic Pressure
Authors: Wang Ruiping , Itoh Mitsuru
Published: September 2014

Quantum paraelectric SrTiO3 undergoes a transition to ferroelectric by the substitution of 18O for 16O. The Tc vs. x in SrTi(16O1-x18Ox)3 follows Tc = 30.4(x - 0.33)1/2. Application of the hydrostatic pressure on the SrTiO3 and SrTi(16O0.0718O0.93)3 have the effects of decreasing ε and depressing Tc, respectively. Above the critical pressure pc, ferroelectricity of SrTi(16O0.0718O0.93)3 disappears. Fitting the data to the Barrett's formula, ε , elucidated that T0 and T1 for both compounds changes linearly with pressure.
Testing and simulation of 3D effects on progressive collapse resistance of RC buildings
Authors: Qian Kai , Li Bing , Zhang ZhongWen
Published: September 2014

This paper evaluates the three-dimensional (3D) or slab effects on reinforced concrete (RC) buildings to mitigate progressive collapse, which is caused by the loss of an interior column. Six one-quarter scaled beam–column, or beam–column–slab substructures are tested. These six specimens are categorised into three series (P-, T- and S-series). The test results confirm that transverse beams and RC slabs can reduce the collapse vulnerability of RC buildings effectively. In addition, it is quantified that 3D effects without slab can increase the yield load of the frame by up to 100%, while 3D effects including slab can increase the yield load up by 246·2%. This is because the slabs not only increase the bending moment capacity of beam sections working as flanges, but also provide more alternative load paths for load redistribution. RC slab can upgrade the first peak load of the buildings by developing compressive membrane actions, and upgrade the ultimate load capacity of the building during the large deformation stage by developing a tensile membrane action. As the number of tested specimens is relatively small, a series of numerical and parametric studies are carried out to further quantify the 3D or slab effects on RC buildings in resisting progressive collapse.
Successful Use of Mixed Aluminum-Steel Drill Pipe String in Complex Horizontal Wells: Case Study
Authors: Menand S.. , Lehner Jeffry K. , Evans Nigel , Palmer Aaron , Arthur Metcalfe
Published: September 2014

High strength-to-weight aluminum alloy drill pipe is a powerful torque and drag reduction tool for deviated wells. The aluminum alloy drill pipe enables to achieve strength to weigh ratios equivalent to 160 ksi yield strength steels and is typical 30-50% lighter than similar steel drill pipe. An operator has recently tested aluminum alloy drill pipe in a complex and highly deviated well profile.

This paper presents the key findings regarding the benefits of drilling using aluminum drill pipes in a mixed aluminum-steel string compared to a string using steel pipes only. Firstly, the innovative drill pipe design is presented, followed by lessons learned during rig operations regarding pipe handling practices, rig compatibility and pipe inspection. Then, the paper presents results of an advanced torque, drag and buckling simulations taking into account the rigorous mechanical characteristics of aluminum drill pipe. In well planning phase, sensitivity analysis enabled to optimize the placement of aluminum drill pipe along the mixed aluminum-steel drill string according to the well profile and to predict anticipated torque, drag and loads on pipes while drilling. Through extensive modeling and field data interpretation, the paper presents a comparison of the overall drilling performances between steel only and aluminum-steel drill pipe string, and provides metrics in terms of torque and drag reduction. These results were then used to challenge horizontal and extended reach drilling well profiles where the utilization of steel drill pipes only has shown its limitation.
Ultra-Deepwater Blowout Well Control Analysis under Worst Case Blowout Scenario
Authors: Yuan Zhaoguang , Hashemian Yahya , Morrell Daniel
Published: September 2014

For offshore wells, the regulatory agency requires the submission of a worst discharge analysis and relief well planning report. The ability to control the blow out under worst case blowout scenario shall be documented and is a requirement for the operators to successfully apply for a permit to drill in the US offshore fields.

As the water depths of offshore drilling operations are getting deeper and deeper, due to the increased frictional pressure losses in kill lines and formation fracture strength, bringing the blow out well under control with worst case discharge becomes more challenging. Operational parameters need to be carefully controlled to avoid exceeding the operational limitations such as breaking the formation or exceeding available pump capacity.

In this study, dynamic simulations of multiphase flow are carried out to evaluate the operational parameters during the kill process. The simulations account for transient changes including frictional pressure losses, U-tube effect and fluid density variations. By optimizing the operational sequence with regards to, kill mud density, pump flow rate, pump down staging, relief well drillstring and trajectory, blowout can be controlled without exceeding the operational window.

The paper shows the required volumes of the kill mud, required pump capacity, optimal flow rate arrangement, and minimum time required to get full kill mud return to the sea floor during the well kill operation. Through the aid of advanced transient software models, assessment of the required capacity to kill a blowout enables development of realistic contingency plans to ensure that well control can be re-established in case of an ultra-deep water worst blowout scenario.
Shaped Charge Selection and Underbalance Optimization Using the Perforation Flow Laboratory for Deepwater Subsea Wells in Offshore Africa
Authors: Osarumwense Osarennomase , Satti Rajani Prakash , White Ryan , Ochsner Darren , Sampson Tim , Gilliat Jim , Fraser Graham
Published: September 2014

In recent years, the oil and gas perforating industry has seen the growth of perforating flow laboratories to develop shaped charges for reservoir-specific conditions. Flow laboratories can help measure perforation tunnel characteristics, flow features, productivity and the performance of shaped charges. Such information is critical to perforating job design, particularly in challenging deepwater wells.

In this study, we are focused on a deepwater subsea sandstone field (1000-1700m water depth) in offshore Africa. The fields typically consist of sinuous turbidite sandstone channel systems of Turonian age. The wells are completed as cased and perforated completions with no active sand control. Typically, deepwater cased and cemented completions are frac-packed, which reduces reliance on perforating performance for efficient flow path from the reservoir into the wellbore. The completion design in this case relies heavily on effective perforations for an efficient flow path, including perforating past drilling damage and minimizing the risk of sand production through selective perforating and reduced shot density.

The formation properties were evaluated to select an analogous rock for implementing a comprehensive testing program. In the first phase, a series of API RP19-B Section IV tests were conducted using various shaped charges to obtain a baseline understanding of shaped charge performance. The rock was stressed to simulate reservoir conditions of overburden, reservoir and wellbore pressures. The testing program aimed at selecting an optimal shaped charge and ensuring the maximum clean up/productivity that can be achieved based on the underbalance method. In addition, the test results provided insight into tunnel geometry, inflow performance and dynamic pressure data to develop an informed perforating strategy. Subsequently, the second phase of the program evaluated the effects of mud invasion on perforation geometry and the higher magnitude of static underbalance on perforation cleanup. This study demonstrates how the perforating flow laboratory can be utilized to design perforating jobs in a deepwater environment. The flow laboratory serves as a unique tool to measure and optimize shaped charge performance in a wide variety of downhole scenarios.
Wellbore Strengthening in Sandstones by Means of Nanoparticle-Based Drilling Fluids
Authors: Contreras Oscar , Hareland Geir , Husein Maen , Nygaard Runar , Alsaba Mortadha
Published: September 2014

Drilling operations of both conventional and unconventional oil and gas accumulations are becoming more challenging especially in deep-water operations. Due to the narrow mud weight window in offshore wells, a proper wellbore stability analysis is required for a cost-effective execution. Wellbore strengthening is an approach used to increase the fracture pressure of the rock, widen the mud window and consequently enhance the well integrity and mitigate mud losses. This paper demonstrates the feasibility of wellbore strengthening in permeable formations using oil-based mud (OBM) containing in-house prepared nanoparticles (NPs) combined with graphite. A significant increase in the fracture pressure was achieved and the predominant wellbore strengthening mechanism was identified.

Fracture pressure increase was quantified by carrying out hydraulic fracturing tests on 5 3/4″×9″ Roubidoux sandstone cores. A 9/16″ wellbore was drilled, cased and cemented to simulate well conditions. Overburden and confining pressure were applied on the cores while testing to simulate a normal-faulting regime. Two injection cycles were applied allowing 10 minutes of fracture healing between the cycles. The fracture pressure was increased by 65% when calcium-based NPs (NP2) blends were used, whereas it increased by 39% in the presence of iron-based NPs (NP1). Optimum NPs concentrations were established after a comprehensive experimental screening. A strong relationship between wellbore strengthening and mud filtration at high-pressure high-temperature (HPHT) using a filter press on ceramic discs was found. Optical microscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses were conducted on the hydraulically fractured cores. The fractures were seen to be completely sealed from tip to wellbore. Therefore, tip isolation by the development of an immobile mass was identified as the predominant wellbore strengthening mechanism. A 40 micron-seal containing homogeneously dispersed NPs and graphite was observed. In addition, a 300 micron-filter cake was developed around the wellbore also containing homogeneously dispersed NPs.
Using High-Strength Dissolvable Metals to Increase Flow Assurance in High-Temperature and High-Pressure Environments
Authors: Carrejo N.. , Kellogg B. R. , Gaudette S. L. , Barnard J. J.
Published: September 2014

Increased completion of ultra-deep, high-pressure, and high-temperature wells has been driven by the growing demand for hydrocarbons. Extreme pressure frac screens (XPFS) have been developed to handle the higher loads and conditions. An XPFS is a high-pressure-rated sand control screen, capable of withstanding up to 15 ksi burst and collapse. The XPFS utilizes engineered, high-strength disintegrating materials (HSDM) to operate as a fluid-loss barrier that can be run-in on the liner. This new technology combines ease of use with a controlled delay in the activation that opens the screen to flow. The HSDM covers and seals over a bonded bead matrix that, when the HSDM dissolves, acts as a screen equal in filtration performance but better than current sand control alternatives in its erosion resistance. The beaded matrix can be customized to ensure filtration through a wide range of particulate sizes and currently prevents passage of 85 to 90% of all particulates larger than 53μm. The HSDM covering the beaded matrix is formulated to corrode in the presence of brine and/or acid and provide access to the sand control media, enabling normal well production. The system increases the efficiency of hydraulic fracturing treatments, and can be installed in a steerable drilling liner. Alternatively, the beaded matrix can be replaced with a solid HSDM plug, thus acting as a fluid-loss friendly, solid-base pipe during run-in and leaving a pre-drilled liner after the HSDM dissolves, eliminating the expensive need to later perforate the pipe. This paper studies the pressure rating dependability and sand control capabilities of a liner that provides operators with an intervention-less ability to complete ultra-deep, high-pressure, high-temperature wells.
Managing Suspension Characteristics of Lost-Circulation Materials in a Drilling Fluid
Authors: Kulkarni Sandeep D. , Jamison Dale E. , Teke Kushabhau D.
Published: September 2014

Lost-circulation materials (LCMs) are often used to mitigate the loss of drilling fluids into subterranean formations. Well-known LCMs include ground marble, graphitic carbon, and cellulosic particulates. The carrier fluid's ability to suspend the LCM material is critical in high-pressure/high-temperature (HP/HT) or inclined wells. This paper provides methods to help determine and manage suspension characteristics of LCMs in the fluid with the aid of certain suspending agents (e.g., fibers).

A detailed experimental study was conducted to evaluate the suspension of a range of LCMs in various drilling fluids and investigate the effects of suspending agents (e.g., fibers) on LCM suspension. Based on experimental data, semiempirical models were developed to help predict the influence of fibers on LCM suspension. The design parameters used in these models included fiber concentration, fiber density, number of fibers per unit volume, and average fiber length and diameter. The modeling work discussed in this paper also provides methods for tailoring the suspending agent properties necessary for achieving effective LCM suspension in the fluid.

The uniform suspension of LCM in the carrier treatment or drilling fluid is necessary during LCM pill preparation and during wellbore applications, such as a hesitation squeeze operation. Thus, using fibers to manage the suspension characteristics of LCM in carrier fluids can help ensure efficient use of LCMs for lost-circulation control. This method is particularly important in severe-loss zones where large sized LCMs are used as well as in HP/HT or inclined wells where maintaining LCM in suspension can be challenging.
Flow Rate and Total Discharge Estimations in Gas-Well Blowouts
Authors: Liu R.. , Hasan A. R. , Mannan S..
Published: September 2014

Despite multitier safeguards in any drilling operation, blowouts occur. When such accidents take place, the total discharge of hydrocarbons becomes the focal point for all concerned, including the operator, the service provider, and the regulatory body. Rate estimation becomes a daunting task with scant information about the formation and fluids at the time of the accident. Given that new regulatory guidelines require such estimates for any offshore drilling, systematic investigation is imperative.

This study presents an analytical model coupling the flow in a reservoir/wellbore system of a gas well. The model considers flow in the tubing, annulus and riser, and the attendant heat transfer in this formulation. To gauge safety concerns, plume dispersion is modeled under various wind speed scenarios when ignition sources were not present. In the event of gas ignition, the energy of the explosion of the flammable gas is estimated with an empirical method in terms of trinitrotoluene (TNT) equivalency. The energy released by the jet fire associated with flammable gas is also evaluated.

Two published field cases provided insight into the model's applicability in actual situations and some perspective on solution quality. However, given the large number of unknowns in any setting, we adopted the statistical design of experiments to understand the impact of independent variables. These variables include formation permeability, connected reservoir pore-volume, and restrictions in flow path, among others. Overall, the model results are in agreement with the previous findings. Specifically, we observed that reservoir permeability controls the flow rate; hence, the cumulative production for a given flow cross-sectional area in the well. In addition, the reservoir pore-volume connected to the well has a large impact on the rate of production decline; therefore, the total discharge volume.
Combined Rate of Penetration and Pressure Regulation for Drilling Optimization Using High Speed Telemetry
Authors: Shishavan Reza Asgharzadeh , Hubbell Casey , Perez Hector D. , Hedengren John D. , Pixton David S.
Published: September 2014

Low latency feedback, high bandwidth, and improved sensor placement are key benefits provided by wired drill pipe (WDP) technology. Improved WDP reliability, based on over 100 wells of field experience, enables more aggressive application of the technology, including closed-loop control of drilling processes. Often, there is a requirement to consider multiple variables when attempting to control complex processes such as drilling in deepwater wells. Such is the case when dynamically optimizing rate of penetration in a pressure-critical wellbore environment.

Formerly, rate of penetration (ROP) and borehole pressure (BHP) have been considered separate optimization and automation tasks, respectively. This study combines ROP and BHP into a single comprehensive controller for a managed pressure drilling (MPD) application. The controller adjusts mud pump flow rate, choke valve position, drill string rotation rate, and weight-on-bit (WOB) simultaneously and with coordinated actions. The automated operations are guided by an objective function that includes factors relevant to both BHP stabilization and ROP maximization. A preliminary MPD case study is used to assess the performance during different drilling events, including transition into varying formations causing an unexpected gas influx. For the unwanted gas influx case, the controller better stabilizes the pressure when there are low latency communications by simultaneously adjusting ROP. With WDP and the optimizing controller, there is substantial decrease in time required to control influx events as compared to earlier controllers or manual methods. The high speed data availability affects both the pressure control reaction time and the resulting severity of the kick. When encountering different formations, there is also noticeable benefit by allowing pressure to fluctuate within an acceptable range to optimize ROP.

Combining ROP and BHP control minimizes risk, decreases drilling costs, and reduces operator workload. Improvements in drilling performance include higher ROP, lower risk of uncontrolled kick events, and more uniform cuttings loading. Another benefit of this combined ROP / BHP controller is that the reaction to gas influx is made more consistent and predictable relative to manual operations, reducing the demand for time-consuming remedial efforts.
Reverse Cement Placement Technique: A Case Study from Deepwater Gulf of Mexico
Authors: Bogaerts M.. , Gubanov E.. , Dooply M.. , Pringuey T.. , Sutama C..
Published: September 2014

Reverse cement placement is an existing technology that is being used infrequently, mainly during land cement operations. During reverse cement placement, the cement travels down the casing – open hole annulus and up the casing. Although reverse cement placement is not very common in deepwater cementing, it has many potential benefits compared to the conventional placement.

Simulation of reverse placement is not possible with existing commercial software. Therefore, jobs were designed using specialized prototype software that enabled the design engineer to accurately reconstruct field conditions. Reverse cement placement will result in lower bottom hole circulating pressures as the direction of the flow follows gravity for the majority of the job. The reverse flow path also has an effect on the temperature the cement will see during placement, which needs to be accurately identified for proper laboratory testing. Proper mud removal is very important to achieve the cement job objectives. Careful attention needs to be given to fluid design as the fluid density and rheological hierarchy are reversed during the placement compared to conventional placement.

A deepwater well in the Gulf of Mexico was identified for permanent plug and abandonment. Based on certain design limitations in the well, the operator requested that several cement plugs be set using the reverse placement technique. In total, seven cement plugs in four wells were set successfully using the reverse placement technique.
Successful Placement of an Advancing Sand and Fines Control Chemical as a Remedial Sand Control, using Subsea Flow Lines from an FPSO
Authors: Piemontese Michele , Colombo Marco , Ripa Giuseppe , Dario Pellicanò , Singh Pratyush , Murphy John
Published: September 2014

The ENI Nigerian subsidiary operates a subsea field located in the north western sector of the Nigerian offshore deep-water, is an oil and gas producing field. The production is from subsea wells which are directed to a Floating Production, Storage and Offloading vessel (FPSO). All the wells in this field require sand control measures in the reservoir section from the onset to prevent sand production. Sand control in the field is challenging and various methods (gravel pack, frac pack and expandable sand screens) have been used. Conventional sand control integrity has failed in one of the wells, compromising production rate and exposing subsea asset to risks related to sand production. Compared to heavy workover required for primary sand control application, an advancing chemical treatment bullheaded through the subsea flowline and the production tubing provided a unique, highly economical, and effective solution to this challenging problem. The product effect creates an ionic attraction between the sand grains and fines, using non-damaging water-based fluid. The chemistry mitigates sand production, reduces or stops fines migration and increases the Maximum Sand Free Rate (MSFR). After pumping chemical treatment through a 4.2 km flow line in the failed frac packed completion, well returned to production with minimal sand presence, less than 24 hours NPT and eliminating the need for re-completion. This was the first time the chemical had been pumped from an FPSO and through subsea flow line. This paper discusses the planning, execution, post job analysis and lessons learned.
Plugging Testing Confirms the Reliability of the Fluidic Diode-Type Autonomous Inflow Control Device
Authors: Greci Stephen , Least Brandon , Aitken Liam , Ufford Adam
Published: September 2014

Because of their capability to delay water and gas breakthrough in horizontal completions, inflow control devices (ICDs) are being used widely in completion strategies to delay water and gas breakthrough. These devices add an additional pressure drop to the production fluid, and this additional pressure drop helps to balance the heel-to-toe effect in long homogenous horizontal completions. ICDs can perform a similar function in heterogeneous wells by configuring the ICDs to have an increased pressure drop in the more permeable zones. With the oil influx more evenly balanced, total oil recovery is maximized.

The next generation ICD is an autonomous inflow control device (AICD), which will independently create a greater pressure restriction against the breakthrough of unwanted fluids. AICDs, as well as ICDs, have relatively small fluid passageways required to help create their fluid restriction. A common concern among operators when running a device with a restricted fluid-flow passage, however, is the risk of plugging by drilling mud, produced fines, or any other debris that travels through the device. To eliminate the concern over plugging the AICD, a test procedure was drafted, and a test program was run to mimic the worst-case scenario down hole.

This paper will focus on the procedure, testing, and results of a plugging test developed for the fluidic diode-type AICD. Oil was used to obtain base line performance curves through the AICD. Drilling mud was then circulated through the AICD at various flow rates over an extended period of time. Finally, another oil performance curve was generated to compare against the original oil-flow curve. During flow tests, the plots were analyzed to ensure that there were no indications of plugging in the device. Since no potential plugging conditions were found, the testing verified that the AICD passed the plugging test. After running a test such as this, operators now can feel more confident that the AICD will not sustain any plugging issues down hole in similar conditions.
Use of Liner Drilling Technology to Isolate a Depleted Sand - A Case Study in Mississippi Canyon
Authors: Rosenberg Steven M. , Karimi Moji , Manuel Blake , Tan Ming Zo , Salinas Alexandro , Winchell Rex L.
Published: September 2014

This paper will illustrate the collaborative approach an international oilfield services company and Gulf of Mexico operator used for the planning and successful execution of a 9-7/8-in. x 14-in. Drilling with Liner (DwL) operation to isolate a 6.5 ppg depleted sand interval and mitigate expected losses in a deep water block of Mississippi Canyon. Conventional methods would have most likely have required an 11-3/4-in. or 11-7/8-in. contingency liner for the operator to meet their well construction objectives. Early collaboration between the service company and operator identified DwL technology as the core technology to meet the operator's well construction objectives. The DwL process allows a hazard interval to be isolated in a single trip resulting in less risk and exposure compared to the use of conventional drilling methods. Since DwL technology encompasses a multitude of engineering disciplines, these were integrated into the drilling plan in a seamless manner, ensuring the DwL objectives would be met. To accomplish this, the service company formed a dedicated well engineering team which collaborated with the operator early on in their well planning process.

The engineering disciplines with associated modeling during the DwL planning phase provided technical assurance the 9-7/8″ liner string could be drilled to a satisfactory setting depth while also providing a high-integrity wellbore to the operator over the entire life of the well. These disciplines included:

Torque, drag and hydraulics modeling of the liner running and drilling operation, Connection cyclic fatigue analysis, BHA and directional tendency modeling Cementation and centralization Formation drillability analysis Plastering effect evaluation

During the planning phase, regular operator-service company communications along with project scheduling software gave the operator assurance that agreed upon deliverables would be completed in the allotted time frame with the intended well objectives met.

The 9-7/8-in. x 14-in. liner successfully drilled through the depleted sand reaching a competent setting point, eliminating a potential contingency liner. This paper will present the DwL planning process, associated risk assessment modeling to ensure that safety, environmental and DwL objectives were met, and the DwL operation with its successful outcome
Completion Deployed Scale Inhibition Applications in Deep-Water, West Africa
Authors: Jordan Myles M.
Published: September 2014

The injection of seawater into oil-bearing reservoirs in order to maintain reservoir pressure and improve secondary recovery is a well-established, mature operation. Moreover, the degree of risk posed by deposition of mineral scales (carbonate/sulphate) to the injection and production wells during such operations has been much studied. The current deep-water subsea developments offshore West Africa and Brazil have brought into sharp focus the need to manage scale in an effective way.

In a Deepwater West African field the relatively small number of high-cost, highly productive wells, coupled with a high barium sulphate scaling tendency upon breakthrough of injection seawater meant not only was effective scale management critical to achieve high hydrocarbon recovery, but even wells at low water cuts have proven to be at sufficient risk to require early squeeze application.

To provide effective scale control in these wells at low water cuts, phosphonate-based inhibitors were applied as part of the acid perforation wash and overflush stages prior to frac packing operations. The deployment of this inhibitor proved effective in controlling barium sulphate scale formation during initial water production eliminating the need to scale squeeze the wells at low water cuts (<10% BS&W). To increase the volumes of scale inhibitor being deployed in the pre-production treatments and so extend the treatment lifetimes scale inhibitor was also added to the frac gel used to carry the frac sand.

This paper outlines the factors that influence the suitability of pre-production treatments and present field data from treatments applied via stimulation acid, solid scale inhibitor in frac pack and scale inhibitor within fracture gel to illustrate these different methods and highlight the advantages and disadvantages of each approach.

Many similar fields to the case study outlined in this publication are currently being developed in the Campos basin, Gulf of Mexico, and West Africa, and this paper is a good example of best-practice sharing from another oil basin.
Field-Detectable Scale Inhibitor for Severe Oilfield Environments
Authors: Schilter Randi D. , Yang Chao , Hill Matthew E. , Watson W. Philip , Ewan Kimberley Mac , Almond Stephen W.
Published: September 2014

The formation of sulfate and carbonate salts of barium and calcium during oil production and stimulation operations can result in blocked pore throats in the near wellbore region, narrowed production tubing, deposits on equipment, and in more serious cases, formation damage. Polymeric scale inhibitors are commonly used to prevent or slow this process, but one limitation of scale inhibitors is that they must be used at or above the polymer's minimum inhibitor concentration (MIC). Laboratory methods for determining the MIC are well known; however, determining when the scale inhibitor has been depleted below the MIC can prove challenging. One way to combat this is to continuously treat a producing well, but this results in additional chemical consumption and higher operating costs.

Polymeric scale inhibitors have been developed that contain detectable tags, allowing the residual polymer concentration to be monitored and reducing the chance of an underdose or overdose. This approach could potentially reduce operating costs; however, sophisticated and time-consuming offsite laboratory analyses, such as ICP or other spectroscopy methods, are required to detect the tags – time during which flow assurance can be compromised.

This paper reports an alternative tagged polymeric scale inhibitor that is easily detected by a simple in-field titration and provides outstanding carbonate and sulfate inhibition within favorable cost constraints. Additionally, the new novel tagged scale inhibitor is anticipated to be more environmentally friendly than phosphate-based scale inhibitors, a growing demand in the oil and gas industry. Analyses such as static jar tests and dynamic scale loop (DSL) testing were used to evaluate the scale inhibition efficiency. The performance of the new scale inhibitor versus commercially available scale inhibitor (SI) was highlighted by the DSL, where the MIC was determined to be 20 ppm versus 80 ppm for two widely used scale inhibitors in a barium sulfate scaling brine. The dual benefits of in-field detection and excellent scale inhibition make this alternative tagged scale inhibitor a promising and cost effective addition to the oil and gas industry.
Assessment of Foamed Cement Used in Deep Offshore Wells
Authors: Kutchko Barbara , Crandall Dustin , Moore Johanthan , Gill Magdalena , Haljasmaa Igor , Spaulding Richard , Harbert William , Benge Glen , DeBruijn Gunnar , Shine Joe
Published: September 2014

The use of foamed cement systems for deepwater applications has been increasing and is often the system of choice for shallow hazard mitigation as in the Gulf of Mexico. However, there is little information regarding foamed cement behavior under wellbore conditions. Research is being conducted to develop a predictive relationship between the mesostructure and physical properties of foamed cements used in offshore applications. Samples of foamed cement have been generated using both atmospheric laboratory and high-pressure field preparation methods. Field-generated foamed cement samples were collected in constant pressure (CP) sample cylinders using the same full-scale field equipment used to generate foamed cements in a well. These samples were scanned while inside the CP cylinders using X-ray Computed Tomography with a scan resolution of approximately 35 μm.

Results of the laboratory testing indicate a correlation between foam quality, bubble size distribution and physical properties such as strength and permeability. Initial results also highlight key differences in laboratory and field-generated foamed cements. The variations in cement structure within the field-generated foamed cement samples appear to indicate a strong relationship between the flow of the cement into the sample vessel and the final porosity and properties of the in-place hardened cement. This research will provide a better understanding of the effects that foam cement production, transport downhole, and delivery to the wellbore annulus has on the overall sealing process.
Paper Title: Ultra-High Pressure Perforating System Development
Authors: McClean Charlie , Myers Bill , Talapatra Didhiti
Published: September 2014

A major oil field operator in the Gulf of Mexico had a well that was posing significant challenges to their perforating strategy, due to the extreme pressures that were expected. The operator required a perforating system that would survive in an environment with pressures as high as to 35,000psi.

Technology that would enable any perforating system to withstand these extreme pressures had not been refined within the industry at the time of the customer inquiry, due to the limited number of projects with such extreme conditions. Therefore, a service company committed resources to develop and ultimately refine this product and identify the best system for the customer to achieve the optimum operational results with no lost or non-productive time from this service. The service company carried out detailed pre-design modeling to identify any concerns that would aid in tailoring the complete system.

This paper reviews the development of this perforating system and identifies concerns that were encountered during the design and manufacture of the system. In addition, this paper describes the value that was brought to the project through the use of a detailed, customer-supported quality plan. The importance of correlation between real-life testing and modeling results in delivering a streamlined and fit-for-purpose system is also discussed.

In summary, the paper describes and quantifies the inherent risks associated with perforating projects in extreme high-pressure environments. Moreover, this paper demonstrates how the service company responded to these risks in the design process to improve the system. Lessons learned are also discussed, along with information on service quality delivery.
Comparative Studies of Compact Triaxial Perforation Stability Tests and Thick Wall Cylinder Tests
Authors: Uchida Yuh , Goto Masayoshi , Morita Nobuo
Published: September 2014

Comparative studies of perforation stability with a standard TWC tester (Thick Wall Cylinder tester) and a new compact TPS tester (Triaxial Perforation Stability tester) were performed using sandstone cores with UCS (Unconfined Compressive Rock Strength) ranging from 500 to 7000 psi. This paper aims two objectives: one for advocating the merits of a new technology and the other for improving the interpretation of the conventional TWC test results. TWC testers are commonly used for evaluating perforation stability to predict the onset of sand production (Geertsma, J. 1985). However, most users are confused how to interpret the results since the TWC testers use cylindrical cores where only uniform confining pressure can be applied, while the real in-situ stress is directional around perforations. The core-cut directions are parallel or perpendicular to the whole core axis and are different between companies. The new triaxial perforation tunnel stability tester uses conditions similar to the real perforations. Note that the TPS tester uses cubic rocks with a 0.5 inch hole and the ratio of the horizontal to vertical stresses in perpendicular to the hole axis can be varied between 0.3 to 1.0. Using these two devices, various rock samples were tested varying the ratio of horizontal and vertical stresses. The results showed that unlike the standard TWC tests, the perforation stability tests with the same in-situ stress ratio as the field one did not require corrections of directional in-situ stress effect. Note that depending on rock non-linearity, complex correction factors from hydrostatic confining stress to directional stress is required for the TWC tests since pre-mature failures are commonly observed for hydrostatic loading. A guideline of interpretation of the TWC results is given based on the comparison of TWC and TPS tests for the correction factor of the TWC tests if the results are applied for directional stresses. Using the new compact perforation stability tester is also advocated since the new tester is as compact as the standard TWC tester and the interpretation of the results is simple and accurate since the directional stress is applied with the same stress ratio as the field stress condition.
Expanding Cement for Improved Wellbore Sealing: Prestress Development, Physical Properties, and Logging Response
Authors: Thomas Jeffrey , Musso Simone , Catheline Sebastien , Chougnet-Sirapian Alice , Allouche Mickael
Published: September 2014

Expansion of oilwell cement after placement in the annulus is a promising route to improve wellbore sealing. Expansion can potentially provide benefits such as: closing a microannulus, reducing the tendency for cracking/debonding, and improving cement logging evaluation. To properly evaluate the performance of expanding cement formulations in a laboratory setting, the cement should be hydrated under confined conditions similar to a wellbore. We conducted measurements using a new confinement cell developed in our laboratory. The cell provides radial confinement and elevated temperature as in a wellbore. The availability of water to the cement can also be controlled to simulate tight or porous formations. In the axial direction the cement sample contacts a piston that either confines the sample while measuring the axial stress development, or permits linear expansion that is measured. Using blends of oilwell cement with magnesium oxide (MgO), a standard expanding additive, we measured the axial stress development and linear expansion under different curing conditions. To better understand and optimize cement expansion we also characterized the hydration kinetics of the MgO additive alone and in the presence of the cement, using isothermal calorimetry. Finally, we measured the acoustic response of cement formulations with and without a commercial expanding agent with a standard ultrasonic pulseecho technique. This testing confirmed the benefits of expansion for the logging response.
Innovative Heavy Landing System for Ultradeep Offshore: Extended Slip Crush Resistant Tube, Enhanced Slip Design and Heavy Weight Carrier
Authors: Flores Vincent , Franchi Jonathan , Granger Scott , Vierke Andre
Published: September 2014

The offshore industry's current trend is driving towards ultra deepwater wells, combined with deeper total depths. In order to be able to set and run larger and heavier casing strings with hook loads approaching or exceeding 2.5 million lbs, an innovative heavy duty landing system has been developed and put on the market.

Such systems must be capable of landing heavy loads while ensuring slip crush resistance. It includes an extended slip with enhanced design (coupled with a new greasing system), a 2.5 million lbs landing carrier and a pipe with a thick walled high strength material section, a light weight tube, and a rotary shouldered connection.

One of the current operational challenges with existing heavy duty landing strings is linked to the positioning of the slips, in particular when using extended slip designs. The limited length of the slips area requires additional time for proper positioning and set up. To address these issues, a new slip proof section design has been developed: the combination of an extended crush proof section and the absence of a heat affected zone in that particular area decreases running time while completely eliminating the risk of setting the slips on a weak point.

The "Spiri-Reinhold pipe crushing" formula has been used to design this system. However, considering the approximation of this model's results, crushing performance has been assessed using the Finite Element Analysis, as well as physical tests performed with a specifically designed pulling unit. These full scale test results have been compared to the ones obtained with both the Finite Element Analysis and the standard "Spiri-Reinhold pipe crushing" formula.
Drill Pipe Riser Intervention System Successful Experience in Offshore West Africa
Authors: de Fonvielle Henri , Bordet Laurent , Campbell William , Susak Nenad , Marajh Mitra
Published: September 2014

While offshore intervention on subsea equipment is quite common, the increasingly deeper water operations require light weight intervention systems while meeting safe and stringent operating specification. For these new deep offshore challenges, the conventional risers are becoming a more costly and less desirable solution.

Starting with a recollection of the main drivers that motivated the development of drill pipe riser intervention systems (DPRISi), the paper details the technical and economical challenges in West Africa that have led to the design of such a solution. When non-productive time and financial aspects are taken into account, it makes sense to develop a dedicated system in order to provide fast and reliable intervention.

Depending on the field requirements, two different types of drill pipe riser systems using a proprietary double shoulder connection were used by operators. A first solution was developed in 1999 featuring a seal ring close to the external shoulder. Subsequently, a new solution featuring a gas-tight metal to metal seal on the pin nose was developed in order to address increasingly demanding and challenging operations.

Intensively used in West Africa since 1999, the solution using the seal ring has shown robustness and reliability while being used for several projects in Angola such as Girassol and Rosa and now GirRI. The paper draws a summary of these operations and the feedback on the field use and maintenance. Also it emphasises the successful qualification process for the metal to metal seal solution that has been used in offshore Nigeria since 2010 for the USAN project.