Experimental and advanced computational modelling study of downhole elastomer seal assemblies

Elastomers seals are widely used in various drilling, completion, and production equipment. One such equipment is liner hanger which has become integral part of modern well designs. Failure of liner hanger seal assembly can compromise well integrity, and lead to severe health, safety, and environmental consequences. Concerns regarding reliability of elastomer seals in liner hanger assemblies have been raised by the regulators as well as industry. This dissertation work provides detailed investigation of design, and failure of downhole elastomer seal assemblies using experimentally supported advanced computational modeling techniques. This work is partially supported by Bureau of Safety and Environmental Enforcement (BSEE) and it is set in the context of liner hanger assemblies. However, major outcomes of this research also applies to other downhole seal assemblies. Specific objectives of this dissertation are - (i) investigate performance of liner hanger seal assembly under various design, operational, and failure scenarios, (ii) develop operating envelops and identify critical parameters influencing performance of the elastomer seal assembly, (iii) develop a modelling tool for predicting leakage through elastomer seal interface considering surface characteristics, (iv) generate guidelines for design and qualification of elastomer seals and provide regulatory recommendations. Novel technical aspects of this research work are – (i) studying material behavior of different elastomer material (NBR, EPDM, FKM, FEPM, FFKM, PTFE) under normal and downhole conditions, (ii) using the elastomer material data in true-scale finite element (FEA) models to evaluate equipment level performance of seal, (iii) scaled laboratory tests and analytical calculations to validate FEA models, and (iv) development of a leakage modelling tool that can predict leakage rates as a function of surface topography of seal interface and operating conditions. Results from this dissertation indicate that type and design of seal equipment determines which elastomer properties need to be qualified. Hardness and elastic modulus alone may not be good predictors of fitness-for-service of seal assembly. For example, performance of expandable liner hanger seal assembly primarily depends on seal dimensions and elastomer shear modulus while performance of conventional liner hanger seal assembly mainly depends on elastomer bulk modulus. Selection of appropriate elastomer material for a certain application depends not only on chemical environment and temperature but also on assembly design, operational constraints, and thermal changes. Comparative evaluation demonstrated that conventional liner hanger seal assembly outperforms expandable liner hanger seal assembly in terms of contact pressure generated per unit energization but it is more prone to failure than expandable assembly. Contact pressure at seal-pipe interface, as predicted by macro-scale FEA models, does not accurately indicate fluid pressure that can be effectively sealed. Leakage modelling studies demonstrated that surface characteristics of elastomer and fluid properties determines the contact pressure needed to achieve complete sealability. Leakage modelling approach developed in this work can be an invaluable tool in seal design workflow for determining target seal energization needed for complete sealability

Constrained Motion Analysis of Spacecraft Trajectory in Restricted Three Body Problem

Due to the popularity of libration points, many satellites are being maintained on their desired trajectory. Indian space research organization has planned to launch the Aditya-L1 spacecraft to study about the Sun by 2021. James Webb Space Telescope has also been designed to observe deep space at L2 in the Sun-Earth system by 2021. The combined gravity of the Earth and the Sun keep satellite’s orbit locked at libration points. Though satellites enjoys an uninterrupted view of Sun and Earth all the time, they are affected by the solar radiation pressure (SRP) continuously. Due to the instability of collinear libration points, the certain amount of thrust is required to maintain the desired trajectory. This thesis introduces the Udwadia-Kalaba (UK) formulation of constrained dynamics as applied to the restricted three-body problem of the Sun-Earth-Spacecraft. A dynamic model of the restricted three-body system is presented to analyze the unconstrained motion of spacecraft. The results show the instability due to perturbation from the SRP. Then, the Udwadia-Kalaba formulation is applied to derive the equation of motion of spacecraft with additional constraints such that spacecraft maintains the desired trajectory at libration points. The results of exact amount of control acceleration with the directions are provided for spacecraft for the following three cases: i) maintaining position at the L1 considering the Earth’s circular orbit (i.e. CR3BP) ii) maintaining position at the L1 and L4 or L5 considering the Earth’s elliptical orbit (i.e. ER3BP) and iii) maintaining the three-dimension halo orbit around the L1 and L2 in CR3BP. The UK formulation is modified using Baumgarte’s stabilization method to allow to compute the results for the incorrect initial conditions (i.e. initial state deviations). In this case, the results are analyzed for the underdamped, overdamped and critically-damped systems. In addition, the delta-v is compared for the transient response with time-varying linear quadratic regulator (LQR). For fully constrained system, the control accelerations required to maintain the desired trajectory obtained by the UK technique are shown identical to those obtain via feedforward part of the time-varying LQR, as expected

Effect of Nanoparticles and Solvent Based Emulsion on Heavy Oil Viscosity

Considering the fact that heavy oil and bitumen constitutes about 70% of world’s total oil resources, it is not surprising that the quest to produce heavy oil has attained industry wide attention. Because of extremely high viscosity, heavy oil reservoirs generally yield low-energy and low-productivity wells. Technical and economic challenges associated with heavy oil production, indicate a need for extensive research and development activities. The objective of study presented in this document is to investigate three different approaches for reducing viscosity of heavy oil. In the first set of experiments, three types of metal oxide nanoparticles (CuO, Fe2O3, and NiO) were employed and their effect on heavy oil viscosity was investigated at different concentrations. The second approach was to mix a solvent-in-water (S/W) emulsion with heavy oil sample in different proportions and inspect rheological changes in resultant emulsion. In third phase of the study, both nanoparticles and solvent based emulsion were added to heavy oil sample and viscosity of resultant nano-emulsion was examined. For all test fluids, rheological measurements are presented at four different temperatures ranging from 100°F to 160°F. This unprecedented experimental work was conducted with two extremely viscous heavy oil samples having viscosity of approximately 77,000 cP and 350,000 cP at room temperature. Addition of nanoparticles resulted in notable reduction in viscosity of both heavy oil samples. For each type of nanoparticles, viscosity reduction of 50 to 70% was achieved. The degree of viscosity alteration was observed to be a function of type of nanoparticles, their concentration, and fluid temperature. Moreover, optimum concentrations for maximum viscosity reduction, were identified for each metal oxide nanoparticles at different temperatures. Using S/W emulsion, depending on volume fraction, viscosity reduction varying from 20 to 93% was achieved. In case of S/W emulsion containing nanoparticles, viscosity alteration strongly depended on type of nanoparticles added. Addition of copper oxide nanoparticles in S/W emulsion resulted in additional viscosity reduction of 10 to 30%. Iron oxide nanoparticles had adverse effect, if any, on the performance of S/W emulsion. Interestingly, nickel oxide nanoparticles either had improving or deteriorating effect depending on its concentration in S/W emulsion. Cost analysis revealed that some of the test fluids cost less than $16 per barrel of oil and provided 40 to 50% viscosity reduction. The results are promising considering the fact that the cost presented were calculated based on purchase quote for a very small quantity and they will reduce significantly for field scale applications. Remarkable results obtained in this study, confirm efficacy of nanoparticles and solvent based emulsion in reducing viscosity of heavy oil. This work rekindles the interest in non-thermal heavy oil recovery techniques such as chemical flooding, and provides a foundation for future core flooding studies

Improved polarimetric analysis of human skin through stitching: advantages, limitations, and applications in dermatology

Polarimetry is a powerful tool for the analysis of the optical properties of materials and systems, such as human skin. However, in many polarimetric setups, the field of view is limited to a few square centimeters. In these cases, it is possible to resort to stitching techniques, which involve combining multiple Mueller matrix measurements obtained from different overlapping regions of the sample. In this paper, we propose a stitching technique for polarimetric data and discuss its advantages and limitations. We also describe the potential of image stitching for improving the accuracy and robustness of in vivo polarimetry in the presence of random patient movement. We conducted our research using a diverse set of samples which included porcine skin, human skin from arms and fingers, cold cuts of chicken and gelatine, alongside synthetically created sample data. Our results demonstrate the effectiveness of this technique for the application in dermatology. Each additional in vivo measurement enhances the field of view by approximately one third, thereby considerably augmenting the total observation area. We show that stitching enables for the polarimetric assessment of large skin patches which is useful for the diagnosis of inflammatory skin diseases

Registration of polarimetric images for in vivo skin diagnostics

SIGNIFICANCE: Mueller matrix (MM) polarimetry is a promising tool for the detection of skin cancer. Polarimetric in vivo measurements often suffer from misalignment of the polarimetric images due to motion, which can lead to false results. AIM: We aim to provide an easy-to-implement polarimetric image data registration method to ensure proper image alignment. APPROACH: A feature-based image registration is implemented for an MM polarimeter for phantom and in vivo human skin measurements. RESULTS: We show that the keypoint-based registration of polarimetric images is necessary for in vivo skin polarimetry to ensure reliable results. Further, we deliver an efficient semiautomated method for the registration of polarimetric images. CONCLUSIONS: Image registration for in vivo polarimetry of human skin is required for improved diagnostics and can be efficiently enhanced with a keypoint-based approach

Investigation of Elastomer Seal Energization: Implications for Conventional and Expandable Hanger Assembly

Elastomer seals are extensively used in various wellhead and casing/liner hanger equipment as barriers for isolating fluids. Seal assemblies have been identified as one of the major cause of well control incidents. Majority of hangers utilize conventional weight- or mechanical-set slip-and-seal assembly. The objective of this paper is to conduct a detailed investigation of seal energization in conventional and relatively newer expandable type hanger seal assembly. To achieve the objective, the finite element modeling approach was employed. Three dimensional computer models consisting of concentric casings and annular elastomer seal element were constructed. Seal energization process was modelled by manipulating boundary conditions. Conventional seal energization was mimicked by applying rigid support at the bottom of elastomer element and compressing it from the top. Expandable hanger type seal energization was modelled by radially displacing the inner pipe to compress annular seal element. Seal quality was evaluated in terms of contact stress values and profile along the seal-pipe interface. Different amounts of seal energization were simulated. Both types of seal energization processes yielded different contact stress profiles. For the same amount of seal volumetric compression, contact stress profiles were compared. In case of conventional seal energization, contact stress profile decreases from the compression side towards support side. The seal in expandable hanger generates contact stress profile that peaks at the center of contact interface and reduces towards the ends. Convectional seal assembly has more moving parts, making it more prone to failure or under-energization. Finite Element Models were validated using analytical equations, and a good match was obtained. The majority of research related to elastomer seal is focused on material properties evaluation. Limited information is available in public domain on functional design and assessment of seal assembly. This paper adds novel information by providing detailed assessment of advantages and limitations of two different seal energization process. This opens doors for further research in functional failure modes in seal assembly.Funding: Work was partially funded by Bureau of Safety and Environmental Enforcement (Project No: E17PC00005). Open access fees fees for this article provided whole or in part by OU Libraries Open Access Fund. Acknowledgments: The authors would like to extend their sincere gratitude to the University of Oklahoma for providing necessary resources and granting the permission to publish this work.Ye

Analysis and synthesis of conical coil springs

Springs are mechanical devices that are employed to resist forces, store energy, absorb shocks, mitigate vibrations, or maintain parts contacting each other. Spring strips are commonly coiled in the forms of helixes for either extension or compression. Helical springs usually have cylindrical shapes that have constant coil diameter, constant pitch, and constant spring rate. Unlike conventional cylindrical coil springs, the coil diameter of conically coiled springs is variable. They have conical or tapered shapes with a large coil diameter at the base and a small coil diameter at the top. The variable coil diameter enables conical coil springs to generate desired load-deflection relationships, have high lateral stability, and low buckling liability. In addition, conical compression springs can have significantly larger compression or shorter compressed height than conventional helical compression springs. The compressed height of a conical compression spring can reach its limit that is, the diameter of the spring wire if it is appropriately synthesized. The height of an undeformed conical extension spring can have the height of its spring wire if the spring pitch is chosen to be zero. The shape of an undeformed conical extension spring can be flat if it is needed. The variable coil diameter of conical coil springs provides them with unique features but also raises their synthesis difficulties. Synthesizing conical coil springs that require large spring compression or short, deformed spring height or constant spring rate is challenging. This research is motivated by surmounting the current challenges facing conical coil springs. In this research, different conical compression and extension springs will be modeled. Their performances will be simulated using the created models. The force-deflection relationships of conical coil springs will be analyzed. The results from this research will provide useful guidelines for developing conical compression and extension springs

Doctor of Philosophy

dissertationDesign of synthetic strategies that allow facile access to a stereocenter in a catalytic fashion is highly desirable. This dissertation details the development of a palladium-catalyzed process that enables strategic coupling of alkenyl groups with multisubstituted alkenes in a highly enantioselective fashion to generate tertiary or quaternary allylic stereocenters. Chapter 1 focuses on the existing modern methods that allow incorporation of an alkenyl moiety in a catalytic and enantioselective manner. In Chapter 2, a palladium-catalyzed intermolecular enantioselective coupling of alkenyl triflates with acyclic primary or racemic secondary alkenols is described. Applying this strategy, a wide array of functionalized alkenyl groups can be installed at positions β, γ, or δ to a carbonyl group in high enantioselectivity. It is necessary to use electron deficient alkenyl triflates to direct selective β-hydride elimination and prevent catalyst arrest. To demonstrate the synthetic potential of this process, a two-step derivatization of the resulting Heck product led to the formation of a tricyclic core structure, present in various natural products. The application of the redox-relay Heck strategy to trisubstituted alkenes afforded the construction of quaternary stereocenters and is described in Chapter 3. Specifically, the reaction of terminal (E)-alkenyl triflates, in the presence of a Pd(0) catalyst and a chiral ligand leads to the formation of allylic quaternary stereocenters in high enantioselectivity. iv To further illustrate the synthetic applicability of this transformation, the alkene introduced in a chiral Heck product was readily processed via simple organic transformations to access remotely functionalized chiral tertiary alcohol, acid, and amine products. Finally, Chapter 4 explores the applicability of highly polarized alkenes as potential substrates in the redox-relay Heck reaction. A number of electron-deficient alkenyl triflates underwent selective coupling with acyclic aryl enol ethers in the presence of a chiral palladium catalyst to provide chiral allylic ether products in high yields and excellent enantiomeric ratio. Furthermore, the significance of this process was demonstrated through the formation of chiral allylic alcohol achieved via a simple cleavage of the p-methoxyphenyl moiety

Enantioselective Palladium-Catalyzed Alkenylation of Trisubstituted Alkenols To Form Allylic Quaternary Centers

In this report, we describe the generation of remote allylic quaternary stereocenters β, γ, and δ relative to a carbonyl in high enantioselectivity. We utilize a redox-relay Heck reaction between alkenyl triflates and acyclic trisubstituted alkenols of varying chain-lengths. A wide array of terminal (<i>E</i>)-alkenyl triflates are suitable for this process. The utility of this functionalization is validated further by conversion of the products, via simple organic processes to access remotely functionalized chiral tertiary acid, amine, and alcohol products

Palladium-Catalyzed Enantio­selective Heck Alkenylation of Acyclic Alkenols Using a Redox-Relay Strategy

We report a highly enantio­selective intermolecular Heck reaction of alkenyl triflates and acyclic primary or racemic secondary alkenols. The mild reaction conditions permit installation of a wide range of alkenyl groups at positions β, γ, or δ to a carbonyl group in high enantio­selectivity. The success of this reaction is attributed to the use of electron-withdrawing alkenyl triflates, which offer selective β-hydride elimination followed by migration of the catalyst through the alkyl chain to give the alkenylated carbonyl products. The synthetic utility of the process is demonstrated by a two-step modification of a reaction product to yield a tricyclic core structure, present in various natural products