Back analysis of foundation piles is an important aspect of a project, as it can allow for refinement of soil parameters, leading to pile holding capacity variations, and a more accurate fatigue life assessment. Back analysis of pile driving data to determine the capacity of an axially loaded pile, such as for a jacket structure, is a well-developed process, with the results of pile driving data directly applicable to axial foundation response. However, for mooring piles, where the loads are dominated by lateral forces, determining the capacity is more complex as the results of driving data are not directly relatable. Offshore mooring piles are opened-ended steel tubular piles, with diameters typically ranging between 1 m to 2 m, with a padeye (mooring chain attachment point) located at some point along the pile, usually within the upper third. The piles are driven into the seabed with an underwater impact hammer, or vibratory hammer, and are used for mooring floating structures. This paper presents a methodology to carry out a back analysis of mooring pile capacity based on pile driving data. The process involves two stages, the first is to assess the self-weight penetration of the pile, which will allow clarification of the design shallow soil properties; the second stage is to compare the pile driving data, with the estimated soil resistance to driving, to gain an understanding of the deeper soil properties. The procedure presented within this paper was applied to an assessment offshore South East Asia, a case where location-specific data were not available but were within 500 m of the mooring pile locations. The procedure was used to verify that the piles were suitably designed against the given loading conditions, as the soil data was not co-located with the mooring pile locations. The process forms an important aspect when considering the future of offshore moorings, specifically looking ahead towards floating offshore wind, potentially offering refinement of design factors, verification of pile capacity, reducing offshore exposure time, and optimizing the fatigue life of piles following driving.

In oil and gas wells construction, the cement sheath in the annulus between casing and formation plays a critical role throughout the producing life of the oil and gas well. Under elevated conditions of temperature and pressure, set cement changes its physical, chemical and mechanical properties. Sometimes these changes can lead to strength retrogression of cement. Recently, it was found that calcined clay (CC) and nanoclay (NC) significantly improve the hardened cement matrix properties as both materials have pozzolanic properties. Both additives have characteristics such as acid and sulfate resistance, low heat of hydration, low density, low permeability and the formed phases with the higher thermal endurance. In this study, cement mixes with different percentages (1% & 2%) by weight of cement (BWOC) of calcined clay and nanoclay were investigated and compared with Class G cement slurry. Rheology, fluid loss and compressive strength properties of all cement slurries were measured.Rheological properties were measured at 50°C temperature and atmospheric pressure. The fluid loss test was conducted at 50°C and 1000 psi pressure. The uniaxial compressive strength (UCS) test was conducted for cement samples cured at 121°C temperature and 3000 psi pressure conditions for 24 hours and 5 days in HPHT curing chamber. Microstructural investigations were conducted using SEM analysis of cured samples. It was observed that addition of nanoclay and calcined clay in Class G cement enhanced the rheological properties of cement slurries. The plastic viscosity increased with an increase in percentages of both additives. Higher values of yield point and plastic viscosity were obtained for calcined clay. In case fluid loss, a reduction in fluid loss was noticed for nanoclay. There was no appreciable change in fluid loss with the addition of calcined clay in mixes. Calcined clay-based cement slurries resulted in robust structure and sustained high compressive strength after exposure to high temperature high-pressure conditions. The nanoclay-based mixesgave higher strength compared to Class G cement slurry but lower than calcined clay. The compositional analysis showed that calcined clay gave low calcium/silica ratio and strong bonded structure. This study will pave a way for researchers to study further the application of calcined clay in oil and gas cementing and its long-term durability.

High Modulus Polyethylene (HMPE) fiber ropes have been widely employed in a large variety of marine and onshore load bearing applications, but not yet in permanent offshore mooring systems due to their well-known high creep behavior. The Lankhorst Gama98 ® HMPE mooring ropes based on low creep Dyneema ® DM20 fiber were recently introduced and certified by ABS for the offshore WindFloat Atlantic project's mooring system at a depth of around 100m, which is the first time such HMPE fiber ropes have been used for permanent mooring. Compared with the conventional application of fiber ropes, usually employed as middle segments of mooring lines, the application of HMPE ropes as top segments directly connected with the platform in shallow water creates more challenges from the impact of temperature, UV and marine growth. For the permanent mooring of WindFloat Atlantic, the HMPE mooring rope was incorporated in the catenary mooring system by Principle Power to transfer the restoring force generated by the bottom chain weight in an efficient and direct manner to the floating platform. This lightweight mooring line enables lower pre-tensions while maintaining the same station keeping performance and excellent fatigue life. This ultimately drives down the pulling capacity requirements for installation of the mooring system and hook-up of the platform. Lessons learned from this application could result in a more efficient approach to HMPE mooring line installation. With such groundbreaking application, the HMPE rope is being demonstrated as a permanent mooring component and its performance assessed in this wind energy project, which may benefit the offshore wind industry. It may also be useful to oil and gas in a permanent use application context. This paper presents (i) the ABS process details in assessing the proposed HMPE ropes with DM20 low creep fiber for meeting class requirements and WindFloat Atlantic project specific needs, and (ii) address the offshore industry concerns with HMPE ropes such as creep, creep rupture, UV effect, and marine growth.

The main objective of this paper is to present and discuss the Fire and Blast design methodology for offshore platform topsides with reference to the API RP-2TOP Standard. The first edition of the API RP-2TOP standard has been published recently and consists most up to date provisions for the tospides design for fire and blast loads. The paper focuses on the key aspects of the topsides design of offshore platforms for fire and blast loading as addressed in the API RP-2TOP standard, summarizes the design recipe and highlights the differences between the API RP-2TOP and corresponding API RP-2FB provisions. A risk matrix is provided as a means to determine the acceptability of the risks from accidental events of fire and blast and can primarily be used as a means of screening low-risk events that do not need further investigation. In addition, a detailed and structured methodology is provided for structural assessment from fire and blast events. The fire and blast scenarios should be developed as part of the process hazard analysis.

It is well understood that strength to weight ratio is an important driver facilitating extended reach deviated wells, as such engineering corrosion resistant ultra-high-strength light-alloys (LAs) are an absolute necessity. High strength steels and nickel alloys, having yield strengths between 80 and 120 ksi, commonly used in oil & gas completions and production, have 3 to 5X higher specific gravity compared to LAs. In comparison, commercial coarse-grained polycrystalline light-alloys (CGP-LAs) have a much lower strength, typically less than 45 ksi yield strength and are not corrosion resistant. However, if strength of LAs can be increased to match that of steels and nickel alloys while simultaneously augmenting their corrosion and environmental assisted cracking (EAC) resistance through severe plastic deformation (SPD) routes, manifesting an ultra-fine-grained (UFG) microstructure, they will far surpass strength to weight ratios of steels and nickel alloys. As such the quest for a perfect alloy with the right combination of strength, ductility, corrosion, and abrasion resistance is ever ongoing. The advent of nanotechnology and advancements in engineering nanostructures with high strengths and reasonable ductility has motivated researchers globally [ 1 - 7 ]. We have bridged a few of these technology gaps by addressing challenges relating to the compromised ductility of these novel high-strength nanomaterials, however there is limited data on their EAC susceptibility. EAC encompasses stress corrosion cracking (SCC) related events or catastrophic failures due to the loss of ductility of a metal exposed to acid gases, such as hydrogen sulphide (H 2 S) and/or through absorption of hydrogen. To determine if grain refinement in a LA, and resultant Hall Petch strengthening, where strength of the UFG-LA surpasses that of commercial coarse-grained oil-grade steels, is instrumental in enhancing its EAC resistance, focused experiments were conducted. An aluminum-magnesium CGP-LA commonly used in offshore and marine applications was selected and subjected to SPD resulting in an UFG microstructure. Both CGP-LA and UFG-LA specimens were exposed to environmental conditions to compare their corrosion and EAC and resistance. It was observed from polarization measurements and immersion tests that UGF-LA had better corrosion resistance than CGP-LA. Uniaxial tensile tests in a neutral halide environment for various holding times confirmed that strength and ductility was maintained for UFG-LA specimens while catastrophic failures of CGP-LA specimens were observed. It was also evident from orientation images that grain boundaries in UFG-LA were predominantly high-angle in contrast to CGP-LA. The improved corrosion and EAC resistance of UFG-LA was due to a large number of purer grain boundaries with nanocrystalline impurities distributed infrequently along them. These results are very topical as they highlight the possibility of harnessing the enhanced strength to weight ratios of these unique alloys for designing buoyant thin walled flowable shells for deployment in high pressure high temperature (HPHT) oilfield environments, from vehicles being designed for interstellar gas giants to aggressive sour oilfield reservoirs.

Over the last decades, a number of mooring incidents have been reported in the public domain by conference papers and safety alerts. Mooring chain corrosion and fatigue have been reported as dominant incident triggers for these mooring incidents. Corrosion development is closely related to the locations of the mooring site. Fatigue is related toenvironmental conditions as well as mooring configuration for the mooring line load. This paper provides a review of the environmental conditions and water quality at offshore mooring sites. Important factors affecting mooring line load and load bearing capacity (mooring line degradation) are investigated. The ship-shaped FPSOs,as a dominant type of floating installationsand with more than two hundred of them currently in service,are the focus of this paper. The performance and uncertainties associated with the mooring system of the ship-shaped FPSO are evaluated.The paper provides recent industry advances onmooring performance simulations, monitoring and mooring incident identification techniques. It is recommended that risk-basedmonitoring and inspectionof mooring system can play an important role in improving mooring reliability and operational efficiency. The key elements includeidentifying critical directions of environmental loads, most loaded mooring lines, and the segments of the mooring line thatsubject to heavy corrosions. Systematical data collection, data sorting,data sharing and optimization of algorithm for anomalyidentification play important roles in effective monitoring.

For subsea structures placed on soft seabed comprising fine-grained sediments, geotechnical design may be equally governed by the foundation settlement and stability requirements. For this reason, the soil stress history parameter, i.e. yield stress (σ y ), becomes as important as the strength parameter, i.e. undrained shear strength (s u ). Common practice in characterisation of fine-grained sediments focuses more on deriving the s u profile than on evaluating the σ y profile. More often, the underlying connections between these two important parameters are overlooked in the interpretation process. As a result, the selected design line of σ y may be incompatible to that of s u . This paper presents a balanced characterisation of fine-grained soils, focusing on interpretation of in-situ s u and σ y using a coherent and simple framework underpinned by the Stress History and Normalised Soil Engineering Properties (SHANSEP) relationship. Interpretation procedure, performance and advantages of the proposed framework are demonstrated by a real application to an offshore site dominated by fine-grained carbonate sediments. In this framework, the two SHANSEP parameters, including normally consolidated normalised strength ratio (S) and empirical constant (m), need to be quantified for the site of interest. This is achieved by performing a series of laboratory strength and consolidation tests on undisturbed samples, with the strength tests being performed respectively under in-situ and elevated stress conditions for determining in-situ s u and the values of S and m. Once the SHANSEP parameters and the s u profile are derived, the σ y profile can be calculated. These two profiles can then be refined further by comparing against the measured s u and σ y at discrete depths respectively from the strength and consolidation tests. Since this proposed framework allows the user to consider the results from the in-situ and laboratory tests (including both strength and consolidation tests) holistically, more reliable and coherent interpretation of the s u and σ y profiles can be achieved. In addition, the framework allows for an easy estimation of consolidation-induced strength gain due to the permanent load applied by the subsea structures by simply using the derived σ y profile and updating the vertical stress in the parameterised SHANSEP relationship. This may reduce the conservatism in the foundation design and provide optimisation opportunities.

Technology developed to harness extended reach deviated (ERD) wells for deep-water and longer laterals for unconventionals demand the use of reliable "Dissolvable Alloys". Furthermore, an economic prediction mechanism to assess the degree of dissolution of deployed dissolvable hardware is highly coveted. This is one of the bottlenecks preventing the increased adoption of dissolvables in both deep-water and multistage stimulation (MSS). DAMORPHE was founded to take advantage of recent Mechanical-Materials-Electrical (MME) innovations for development and commercialization of "Game-Changing" technologies through the selective use of amorphous and nanocrystalline dissolvable alloys with Artificial Intelligence (AI). Here we discuss a couple of applications where dissolvable materials bring enhanced functionality over traditional methods and present a case for how replacing these with intelligent materials can bring further benefits to the end users.

Oil and gas development needs in the Gulf of Mexico have continued to push into High Temperature and High Pressure (HPHT) applications. Along with the HPHT requirements, the need for sour service resistance has also grown. To meet these needs, large OD and heavy wall pipe with sour service capability have been specified. To answer this need Vallourec has pushed limits of wall thickness with sour service properties far beyond the standard. This was done for both heavy wall accessories as well as for riser application. Outer diameters ranged from 13 inches to over 23 inches, with wall thicknesses of 2.5 inches. These sizes are common in lower strength material, but to meet the high-pressure requirements, Vallourec was able to provide up to 125ksi specified minimum yield strength grade material. Higher grade material allowed supported cost savings and select elimination of some Corrosion Resistant Alloys (CRA) components. It also allowed much lighter weight pipe as compared to 80ksi specified minimum yield strength material that is standard for sour service applications in oversize OD and heavy wall. To develop such heavy wall pipes with sour service resistance, the heat treatment process has been the most critical step. Quenching the material to reach this level of performance requires the heat-treatment lines to be designed with state-of-the-art and robust heat-treatment equipment. This paper will discuss the material properties achieved on several of the large diameter, heavy wall, sour service pipes.

The first phase of the Chain FEARS (Finite Element Analysis of Residual Strength) Joint Industry Project (JIP) aimed to develop guidance for the determination of a rational discard criteria for mooring chains subject to severe pitting corrosion which, based on current code requirements, would otherwise require immediate removal and replacement. Critical to the ability to establish rational discard criteria, is the ability to accurately predict the residual strength of degraded chain, and to have as a benchmark for loss in strength, an accurate estimate of the chain in its as-new condition. With a correlated FEA method for residual strength prediction and a benchmark for as-new condition capacity, it would then be possible to establish a theoretical relationship between different types of degradation and mooring chain capacity loss, from which rational discard criteria would be derived. To this end the Chain FEARS JIP first developed a Finite Element Analyses (FEA) residual capacity assessment method to accurately predict the residual strength of degraded chains. A number of assessments were carried out to establish the sensitivity of the Predicted Break Load (PBL) to both engineering parameters such as friction coefficient, and numerical modelling techniques. The developed method was validated by the correlation of the PBL against a number of physical break tests. This paper presents a review of the break strength test data of pitting corrosion degraded chain links. The FEA modelling methodology based Predicted Break Load (PBL) are compared with the test data Actual Break Load (ABL) along with the sensitivity of engineering parameters and numerical model modelling techniques on predictions. The developed FEA method accurately predicts the location of the ‘failure’ within the chain string and the ductile necking failure mode, determined to be the prevalent mode of failure for the chain links samples considered in this study. The degree of correlation between PBL and ABL confirms that accurate prediction of the effects of corrosion degradation consequent on uniform and large pitting corrosion can be accurately predicted by use of the Finite Element Method. The developed FEA method was also employed to establish a benchmark for the strength capacity of as-new condition links as presented in [ 1 ], the basis for assessing the relationship between corrosion degradation and residual chain link capacity [ 2 ] and a basis for a multi-axial fatigue assessment method to establish the fatigue capacity of as-new and degraded chain links [ 3 , 4 , 5 ].

As operators in the oil and gas industry continue to search for larger oil deposits in areas that are considered High Pressure and High Temperature (HPHT) environments, manufacturers of liner hanger/packer systems must conceive and validate designs that can support these projects. The XPak™ liner hanger/packer system is an expandable product that offers metal-to-metal and elastomer sealing capabilities at the liner top in host casing, capable of superior hanging capacity and seal integrity for installing casing strings of various lengths. The expansion process is achieved using a multi-piston hydraulic running tool with pressure application to displace an Expander inside the XPak hanger body. The displacement of the Expander inside the XPak hanger body relies on interference between the components to radially grow the hanger body to contact and interfere with the host casing. This interaction provides the sealing and anchoring capability of the XPak system. The Expander provides tieback capability via a polished bore receptacle and remains installed inside the hanger body for the lifetime of the installation. Operators are implementing robust host casing designs with less variance in wall thickness to utilize tubulars with higher burst and collapse ratings than those manufactured to API standard variances. The combination of higher burst pressure ratings for the host casing and limited variance on the inner diameters provides an ideal partner for the XPak system. Expandable products rely on a narrower host casing inner diameter range to create the interference needed for optimum performance, as opposed to conventional liner hanger systems which work over a broader diameter range. An ISO 14310 V0 qualification of a 7-5/8 × 12-1/4 HPHT XPak liner hanger/packer system for a major operator in the Gulf of Mexico successfully achieved testing milestones of 15 ksi internal pressure with a combined loading of 1,000 kips in tension at 375°F. The system was also qualified at a low temperature of 60°F reaching a successful test pressure of 21.75 ksi internally with a combined tension load of 1,000 kips. These testing requirements were provided in the customer's statement of requirements to handle extreme well loading conditions. FEA modeling is the primary tool for XPak design and focuses primarily on identifying and predicting material strain to help determine the system capabilities under simulated pressure and loading conditions. The distinct geometry and controlled deformation of the hanger body during expansion are simulated using FEA software to provide guidance to meet design parameters to reach high levels of performance. The initial conceptual design is taken through a complete range of potential well scenarios including: casing inner diameter ranges, maximum and minimum setting forces, geometric tolerancing, friction factors, and transient thermal loading. The results are compiled and reviewed to determine the optimal design model to satisfy the customer's requirements. Validation testing and field installation performance for this product line has been successful. The use of analytical tools for design along with improvements in material options and manufacturing processes has been instrumental in the continued growth of the XPak liner hanger/packer system.

Proppant such as sand and ceramics is used in keeping the fractures open for hydrocarbon production in hydraulic fracturing operations. Its ability to withstand reservoir closure stresses and provide high conductivity is one of its key selection criteria. Sand is preferred over ceramics in unconventional plays due to its low cost and abundance. On the other hand, the lower crush strength of sand compared to ceramics limits its application to wells having lower closure stresses. Therefore, it becomes necessary to strengthen the sand as a low cost solution for demanding downhole conditions. Coating sand with resin is a long-practiced method to strengthen and control fines. One fundamental challenge with resin coated sand (RCS) lies in its overall thermo-chemo-mechanical stability at high temperature and high pressure in the presence of fracturing fluid. In this work, a nanocomposite resin has been developed to provide enhanced coating strength and chemical stability. RCS has been characterized from the perspectives of its core and coating. As received sand has been evaluated by (1) single grain crush testing, (2) optical particle size analysis for sphericity and roundness, (3) XRD for mineral content and composition, and (4) petrography analysis for microstructure, texture, and crystalline phases. Sand has been coated using phenolic formaldehyde (novolac) resin systems reinforced with nanomaterials and altered surface wetting properties demonstrating improved crush strength, chemical resistance and long-term conductivity. Loss on ignition (LOI), API proppant crush resistance test, and API long-term proppant conductivity tests have been used to evaluate RCS. Petrographic evaluation of Northern white sand shows the presence of plutonic, and monocrystalline grains having higher crush strength, whereas Texas brown sand shows abundance of polycrystalline and metamorphic grains that are relatively weaker due to impurities, and inner weak planes. The white sands are well sorted and a roundness and sphericity of >0.6 were measured by optical particle size analysis. With resin coating, the API crush resistance stress of the sand has increased by ∼200%; whereas, the API long-term proppant conductivity has increased by 41% compared to uncoated sand. The nano-composite resin coating containing a combination of nano-reinforcement materials and wettability altering agents has increased the API proppant conductivity further by 100% compared to uncoated sand. Nanomaterial used in the coating contains high surface area nanofibers with exceptionally high aspect ratio. The synergistic effect of different nanoparticles increased the strength to an even higher level by providing a barrier to the permeation of fluid in the coating thereby increasing chemical resistance. An economic and up-scalable nano-composite coating technology containing a novel combination of nanomaterials and surface wettability altering agents has been developed with improved proppant crush strength, conductivity and chemical resistance. The performance of the coated sand has not been compromised when exposed to fracturing fluid at elevated temperature making it a suitable candidate for field applications at higher stresses.

This paper presents a summary of over 25 years of laboratory data on the monotonic and cyclic soil properties of clays in direct simple shear, triaxial compression and triaxial extension tests, at 15 deepwater Gulf of Mexico sites. The majority of the test results were obtained by three different laboratories. The data are summarized in numerous plots and diagrams, and correlations are presented to help derive soil properties relevant for deepwater foundation design. The database and guidance presented in the paper can be used in early design when site-specific soil samples are not available, or to optimize the scope of advanced laboratory testing on site-specific samples during detailed design. Although the soil samples are all from the Gulf of Mexico, the guidance is believed to be valuable also for the characterization of other non-structured, high-plasticity marine clays.

Technology gaps in measuring wellbore parameters and providing the results at surface without using wireline (Production Logging) or slick-line, without using mud-pulse, electromagnetic or acoustic telemetry, or pre-installed or permanently installed downhole sensors remain an area to be bridged. Our ability to engineer light-weight, high-strength, highly-reactive (dissolvable) or corrosion-resistant, nanostructured-alloys and intelligent micro-electromechanical system (MEMS) devices have enabled design of buoyant sensors having thin (millimetric) wall, capable of withstanding 20,000 psi or more differential pressure. These sensors measure and record a complete set of the client’s required wellbore parameters (e.g., Pressure, Temperature, Depth, Casing collars, Flow-rate across perforations or in wellbore, Water cut, Dissolved O2, etc.). These devices are deployed, either nested in an outer shell of salinity independent water reactive alloy to abet pump down to depth or weighed down by a sinker of dissolvable alloy. These devices are free-flowing within a wellbore so that they can be placed downhole to required depth for a specific time, after which the outer shell dissolves or the sinker weight falls, releasing the inner gauge. The now buoyant device flows back to surface with produced fluids where they make their presence known by sonic or inductive signaling. Our company was founded to take advantage of these disruptive innovations in materials science and sensors and synthesis of these technologies to provide superior performance products for both deep-water domains and the multistage stimulation (MSS) market. In this article we address two of our key inventions. First, the development of miniature, self-contained, battery powered, free-flowing sensor devices for reservoir monitoring, passively retrievable through carrier buoyancy. A subset of this game changing approach, to economize operations is, "Measuring in- situ pressure, temperature, and subsequent production during MSS". Second, we present a mechanism to assess susceptibility of oilfield alloys, especially in live reservoir fluids at the production zone. This encompasses a retrievable sensor device to assess environmental effects on materials at target zone in wellbore during production or shut in, can be deployed anywhere from production zone to bubble point, to surface separator. It facilitates testing not in a simulated autoclave environment at surface, but downhole, at the zone of interest.

In this study, commercially available styrene butadiene rubber (SBR) polymer up to 3% was added to the highly sensing chemo-thermo-piezoresistive smart cement with a water-to-cement ratio of 0.38 to investigate the effects on the sensing properties. Series of quality control, curing and high pressure high temperature (HPHT) experiments were performed to evaluate the smart cement behavior with and without the SBR polymer. Addition of 1% and 3% SBR polymer increased the initial resistivity by 4% and 12% respectively and hence this parameter can be used for quality control in the field. Vipulanandan p-q curing model was used to predict the changes in resistivity with curing time. Addition of 1% and 3% SBR polymer also increased the compressive strength of the smart cement by 18% and 32% after 1 day of curing respectively, The piezoresistivity of smart cement with the addition of SBR polymer after 1 day of curing was over 500 times (50,000%) higher than the regular cement failure strain of 0.2%. The Vipulanandan p-q piezoresistivity model also predicted the experimental results very well. Addition of SBR polymer reduced the fluid losses 30 minutes and 24 hours after curing. The fluid loss was predicted using the Vipulanandan fluid loss model and compared it to the API model. The smart cement with and without SBR polymer detected the gas leak during initial slurry condition and after solidification. Addition of SBR polymer reduced the gas leak. During the gas leak in the piezoresisitive smart cement slurry the resistivity change was positive and for the solid smart cement the resistivity change was negative. During gas leak in the smart cement slurry the resistivity increase was about 45% and it reduced to 30% with the addition of 3% SBR polymer at pressure gradient of 2000 psi/ft. During gas leak in the solidified smart cement the resistivity reduced, opposite to the piezoresistive response to compressive stress, by about 30% and it reduced to 12% with the addition of 3% SBR polymer at a pressure gradient of 2000 psi/ft. Vipulanandan fluid flow model, generalized Dary's Law, predicted the non-linear responses of gas leak velocity (discharge per unit area) to the applied pressure gradient. Also electrical resistivity changes can be used to predict the gas leak velocity in the smart cement with and without SBR polymer.

Disintegrable metal (DM) has proven its market value since the first set of disintegrable frac balls were successfully employed in a shale well in Bakken field about 10 years ago. The DM material technology and tools have changed the downhole tool operation landscape with unprecedented efficiency, reliability, by reducing the operational complexity or simplifying tool installation or actuation procedures. This paper reviews the advancement of DM materials technology, arts to engineer and control the disintegrating performance, various DM downhole tools, and the field operation case studies over the last 10 years. Review of the art of disintegration of disintegrable metals is based literature surveys and author’s own research and development results. Disintegrable metals currently available on the market could be classified into two different metallic systems based on their base metal chemistry: magnesium based disintegrable metal and aluminum-based disintegrable metal. Both systems are light weight, strong as steel and completely disintegrable in typical downhole environments. The paper will review the material design, microstructure, and properties of the two metallic systems, then discuss how to match material properties with requirement of downhole disintegrable tools, and finally share field operation cases. Most of DM materials have micro-galvanic cells built into their microstructures and disintegrate through galvanic corrosion when contacting with wellbore fluid. Key variables affecting the rate of disintegration include material composition, well temperature, tool surface area exposure to a fluid, fluid type, concentration and agitation conditions. The review reveals that it is critical to select the correct DM material to match the application environment for a successful field application of disintegrable tool. In today’s multi-stage hydraulic fracturing market, DM tools would be the preferred technology of choice when DM material selection and tool design and performance match properly to the needs of hytraulic fracture operation of a well. The thermodynamics and kinetics that control the disintegration performance of DM tools, or the art of disintegration, will be reviewed and shared with the readers. The profound arts and engineering of DM materials and field case studies shared by this paper would shed light on how to make sound selection of DM materials, design optimal DM tools for a defined well or field application, develop the best field operation procedures, and execute a MD application efficiently.

Boulders are known to be present within foundation zone depths at some Atlantic East Coast wind energy development areas, which can make it difficult to level a piled jacket or template and can lead to the progressive collapse of the pile toe, causing premature refusal during pile driving. Although detection and avoidance are preferred over mitigation, numerical analysis methods are available to assess the risk of pile refusal, which allows for informed decisions on whether avoidance is required and what types of mitigation to consider during construction. Detailed numerical evaluation (using one-dimensional wave equation analyses and two- and three-dimensional finite difference and finite element modeling) was performed to develop a better understanding of stresses in the pile during driving. The numerical modeling evaluated the effect of strength, thickness, inclination, shoe length, wall thickness, and lateral continuity on pile stresses. A three-dimensional model of the pile and driving shoe subjected to stress-time histories was used to evaluate the stresses at the pile toe and at the transition from the pile to the driving shoe. Example results are presented to illustrate failure mechanisms of hard layers that include boulders, and high-level guidance is provided on operational sequences and potential contingency measures.

Oil and gas industry experiences indicate mooring chain corrosion is a major challenge. Observed corrosion rates in the field can be several times higher than the design allowance. In addition, pitting corrosion is not considered in design but can be significant in service. Pre-emptive chain replacements may be required which are typically very costly. In addition to corrosion, some of the other performance factors for mooring chains include strength, wear resistance, toughness and fatigue resistance. Carbon steel is the conventional material currently employed for mooring chains. There are significant incentives to develop new material technologies with improved seawater corrosion and wear performance for mooring chain application. This paper describes one such new material technology – High Manganese Steel (HMS), and its assessment for mooring chain application. HMS is a family of alloyed steels that, when optimized, can offer improved properties over conventional carbon steel. Several HMS chemistries were manufactured, on which small scale performance evaluation testing and weldability assessments were carried out. Based on the assessments, these custom HMS alloys show promising results in terms of the performance factors required for mooring chain application.

Magnetorheological fluids (MRF) have their rheology modified in the presence of a magnetic field. The MRF consist of a base fluid, magnetizable particles, and a viscosifier that supports these particles. The magnetizable particles align in the direction of the magnetic field, creating a barrier, and thus modifying the rheology of the mixture. When a large enough magnetic field is applied to the MRF, the fluid's yield stress increases drastically in a matter of milliseconds. Due to this fluid response, a tunable back-pressure can be generated when the MRF's rheology is modified downhole with the use of a permanent magnet assembly as part of the BHA. One potential application of this technology is to facilitate drilling operations in narrower mud windows. As an analogy, the technology proposed in this paper works under the same principle of the conventional MPD systems, but with the additional capability of being able to apply a backpressure downhole where the magnetic assembly is located, and therefore only modifying the pressure below the tool location. As a result, abnormally pressured formations could be safely drilled without fracturing the formations above, due to the pressure profile above the magnetic assembly remaining unchanged. As a proposed way to demonstrate this principle, the shear stress variation at different magnetic field intensities is evaluated for different samples of MRF in a special rotating bob rheometer equipped with an electromagnet. A higher magnetic field applied to the MRF produces a higher shear stress, and thus a larger pressure-drop. Upscaling this effect, some of these MRF samples were circulated in a large-scale flow-loop with two concentric pipes that resemble the drill pipe and the annulus. On the flow-loop, some electromagnets and permanent magnets were strategically located to apply a magnetic field to the circulating fluid. The pressure changes (back-pressure) along the system was monitored to evaluate the effect of the magnetorheological response on the pressure variation. As an additional application, a potential electromagnetic surface choke that "activates" the MRF could create a flow restriction, and therefore a back pressure. In that sense, this electromagnetic choke could provide a finer aperture of the choke when the magnetic field is modified accordingly and could be less susceptible to erosion of mechanical parts from solids contained in the mud.

Mooring system life extension for offshore floating production installation has become a hot topic for offshore industry as more and more floating units approach the end of their design lives. Some mooring system life extension projects have already been completed successfully, there are still some issues upon which the mooring industry has not reached consensus, such as field inspection capability/accuracy, uninspected items assessment, component degradation assessment, and acceptance criteria for numerical evaluation. This paper demonstrates two mooring system life extension processes located at Liuhua (LH) 11-1 oil field, following ABS rules as well as industry best practices. It also presents the challenging issues met during this long period of operation, initiated in 2016 and to be completed by end of 2019. Nanhai Shengli (NHSL) FPSO and Nanhai Tiaozhan (NHTZ) FPS are located in Liuhua 11-1 oil field. Both of the mooring systems were installed in 1995 with an originally designed life of 10 years, and already upgraded/replaced partially to extend their lives for continual safety operation. Thus, this is the second life extension for them, and some special challenges are presented. The upgrade of the mooring system is proposed based on inspection, testing, and analysis results for the existing mooring components. This paper focuses on some of the work that has been performed. These experiences may be helpful for the life extension of other similar mooring systems.