Well P&A Tubing Compaction Method Evaluation and Modelling

Master's thesis in Petroleum engineeringThe number of aged fields in the North Sea is increasing, and in few years, and there will be a significant increase in number of wells that need to be permanently plugged and due to low oil prices and other reasons, there is a push from the industry to reduce the cost of P&A operations as much as possible, and using rig-less equipment for P&A has proven to be a reliable alternative to drilling rigs, but this solution requires the development of new technologies to overcome the challenges that come up with it. The presence of tubing in the area where the permeant plug should be set is still a thorny issue for P&A rig-less operation for many reasons. Recently there are many approaches for removing tubing in place without pulling it to surface, one of these alternative ideas is downhole tubing disposal (DHTD). The main scope of this thesis is to give an insight into DHTD method, its advantages and the challenges to translate this idea into practice. In this work as well, different approaches are incorporated to estimate the required tubing crushing force, including FEM, analytical estimation and experimental work. Results are reported for an analytical estimation and FEM (ABAQUS) analysis of a slotted tubular subjected to compression axial load. The results showed different kinds of correlations with experimental test data. On the other hand, they showed that FEM is a powerful method to solve this kind of problems

Numerical modelling and field experimental validation of the axial load transfer on the drill-strings in deviated wells

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper studies the axial load transfer along the drill-strings in deviated wells by developing a finite element model based on the Euler beam theory and the augmentation Lagrangian contact algorithms. The model can simulate the entire drill-strings showing nonlinear contact model between drill-strings and casing. Special attention is given to the axial load loss, the pipe-casing contact force distribution and the slender pipe deformation. The efficacy of the proposed model is validated experimentally using a packer releasing procedure. Various drill-string factors, such as deviation angle, dogleg severity, hook load magnitude and buckling configurations, are considered for evaluating the efficiency of axial load transfer. Our analysis shows that the dogleg severity has a significant influence on the transfer, and the helical buckling of the drill-strings due to excessive loading could make it worse. This study provides a theoretical understanding of the variation of the contact force and the axial load transfer for the drill-strings in deviated wells. It can be used to better understand the working condition of downhole and guide field drilling.China Scholarship CouncilNational Natural Science Foundation of China (NFSC

Nonlinear Drillstring Modeling with Applications to Induced Vibrations in Unconventional Horizontal Wells

A new mathematical model is developed for the nonlinear-static, linearized-dynamic, and fully nonlinear-dynamic behavior of drillstrings in arbitrary wellbore profiles. The formulation is based on a three-dimensional nonlinear finite beam element and accounts for the fully coupled flexibility of the drillstring, geometric nonlinearity (large displacement, small strain), automatic determination of wellbore contact points, friction acting between the drillstring and the wellbore, stabilizer clearance, three-dimensional wellbore profiles, added fluid mass and damping effects from the hydrodynamic forces generated between the drillstring and surrounding fluid, complex tool geometry (including steerable mud motors, rotary steerable systems, and eccentric stabilizers/components), shear beam deformations, lateral rotary inertias, and gyroscopic effects. The resulting model is numerically validated through comparisons with analytical formulas and previous nonlinear models, showing that it can readily be applied to a wide range of drilling engineering problems and used for practical analysis. Additionally, individual contributions of shear deformations, lateral rotary inertias, and gyroscopic effects are definitively shown to be insignificant when calculating the static and dynamic behavior of horizontal drilling assemblies within the rotational speed range of most drilling applications. An initial comparison with field data is also provided, which shows the practicality of the developed algorithms in predicting the characteristics of real drilling scenarios. The model is then adjusted and applied to the specific case of inducing lateral vibrations in unconventional horizontal wells. It is proposed that exciting a lateral resonance in the drill pipe lying on the low side of a horizontal wellbore can induce enough movement to help overcome parasitic axial drag acting on a drillstring. This, in turn, would help to increase weight transfer to the bit while slide-drilling with a steerable mud motor in long lateral sections of a wellbore. The change in this lateral resonant behavior due to variations in weight-on-bit (WOB), inclination, well path curvature, wellbore diameter, fluid properties, and tubular dimensions are clearly shown through linearized-dynamic sensitivity studies. Nonlinear time-domain simulations are also performed to better understand the limitations of linearized-dynamic modeling and to provide a more detailed assessment of how inducing lateral vibration influences the WOB while drilling. It is shown that induced lateral vibrations provide a noticeable dynamic WOB of up to ± 250 lbf about the static value, and a slight increase in the average WOB value of up to 150 lbf. The effects on WOB are dependent on the excitation frequency of the induced lateral vibrations, with the greatest benefits being seen at resonant conditions

Casing structural integrity and failure modes in a range of well types: a review.

This paper focus on factors attributing to casing failure, their failure mechanism and the resulting failure mode. The casing is a critical component in a well and the main mechanical structural barrier element that provide conduits and avenue for oil and gas production over the well lifecycle and beyond. The casings are normally subjected to material degradation, varying local loads, induced stresses during stimulation, natural fractures, slip and shear during their installation and operation leading to different kinds of casing failure modes. The review paper also covers recent developments in casing integrity assessment techniques and their respective limitations. The taxonomy of the major causes and cases of casing failure in different well types is covered. In addition, an overview of casing trend utilisation and failure mix by grades is provided. The trend of casing utilisation in different wells examined show deep-water and shale gas horizontal wells employing higher tensile grades (P110 & Q125) due to their characteristics. Additionally, this review presents casing failure mixed by grades, with P110 recording the highest failure cases owing to its stiffness, high application in injection wells, shale gas, deep-water and high temperature and high temperature (HPHT) wells with high failure probability. A summary of existing tools used for the assessment of well integrity issues and their respective limitations is provided and conclusions drawn

Interaction between a spoolable complliant guide and coiled tubing during subsea well intervention in deep water

Master'sMASTER OF ENGINEERIN

Systematic investigation of cuttings transport behavior in horizontal and inclined drilling operation

Hole cleaning and cuttings transport play a vital role in the drilling operation. Various drilling problems such as a reduction in penetration rate, an increase in the torque and drag, and an increase in the potential of differential sticking are often related to poor cuttings transport from a wellbore. A variety of parameters, including the fluid rheology, mud velocity, cuttings size, and drill pipe inclination generally influence the cuttings transport performance. Although several experimental and modelling research investigations have been conducted in this area, there are controversial findings about the effect of different parameters on cuttings transport. For instance, the interactions among the parameters during cuttings transport which have not been adequately investigated. In this thesis, we systematically study the effect of drilling parameters on cuttings transport, especially interaction effects of the drilling parameters through experiments and Computational Fluid Dynamics (CFD) method. An extensive experimental study was conducted to investigate the flow behavior of solid cuttings based on Newtonian and non-Newtonian Herschel Bulkley fluid models. Experiments were performed to simulate solid transport behavior in horizontal and near horizontal well trajectories. A high-speed imaging technology was used to visualize the cuttings transport behavior in the annulus section. This visualization tool validates the mechanistic three-layer model of cuttings transport and transition from a stagnant solid bed to a homogeneous single layer model of cuttings transport mechanism. An Electrical Resistance Tomography (ERT) system was used to observe the cutting transport which is capable of providing instantaneous cuttings volume fraction in the annular section of the experimental system. ERT data shows cuttings concentration versus with change in fluid rheology, fluid velocity, eccentricity, drill pipe rotation, rate of penetration, and inclination angle. Experimental studies in the horizontal wells show that cuttings transport capability of non-Newtonian fluid increases upon an increase in fluid velocity, and drill pipe rotation. A higher viscous fluid carries more cuttings in the dispersed phase; however, transport capability reduces significantly through suspension mechanism with increasing fluid velocity and drill pipe rotation. A comparison of four different non-Newtonian fluid cases shows that turbulence plays a key role in cuttings transport in the horizontal well regardless of fluid rheology. This experimental study reveals that a higher ‘Minimum Transport Velocity (MTV)’ is required to move a solid dune in the annulus for a highly viscous fluid. CFD modeling approach is employed to simulate the cuttings transport behaviors in the horizontal and inclined wellbore cases. Cuttings transport in the wellbore annulus represents a solid-liquid multiphase flow phenomenon. The Eulerian-Eulerian multiphase flow model is adopted to describe the flow characteristics in the wellbore annular section. A proper Design of Experiments (DOE) is used to systematically study the interactions among the independent variables. A comprehensive parametric sensitivity analysis is then conducted to obtain a better understanding of the relationship between the input variables and the target parameters (cutting transport performance). It is found that the mud viscosity, mud velocity, and drill pipe rotation have a positive impact on cuttings transport, whereas the cuttings size and annular clearance show a significant adverse effect on cuttings transport performance in the horizontal wells. Although both drilling mud viscosity and velocity exhibit the positive effect, the interaction among them shows a negative influence on cuttings transport. Analysis shows that the cuttings with a size of 1 to 2 mm are difficult to be cleaned, compared to larger cuttings. According to the CFD investigation, the critical inclination angle prone to hole clogging is a function of a wide range of flow rates and fluid rheologies. Also, this study investigated two factor interaction of fluid rheology and velocity for the inclined wellbore orientation. Finally, a generalized expression of cutting transport efficiency is proposed for the inclined well considering two factor and three factor interactions

Fibre optic distributed temperature sensors applications and temperature modelling in intelligent wells environments

Abstract unavailable please refer to PD

Constrained Buckling of Variable Length Elastica

University of Minnesota Ph.D. dissertation. 2017. Major: Civil Engineering. Advisor: Emmanuel Detournay. 1 computer file (PDF); 236 pages.The physical understanding of the response of slender elastic bodies restrained inside constraints under various loading and boundary conditions is of a great importance in engineering and medical applications. The research work presented in this thesis is especially concerned with the buckling response of an elastic rod (the elastica) subjected to unilateral constraints under axial compression. It seeks to address two main issues: (i) the conditions that lead to the onset of instability, and (ii) the factors that define the bifurcation diagram. Two distinct classes of problems are analyzed; (i) the classical buckling problem of a constant length elastica and (ii) the insertion buckling problem of a variable length elastica. Their main difference is the generation of a configurational force at the insertion point of the sliding sleeve in the insertion problem, which is not present in the classical problem. The thesis describes two distinct methodologies that can solve these constrained buckling problems; (1) a geometry-based method, and (2) an optimal control method. The geometry-based method is used to analyze the post-buckling response of a weightless planar elastica subjected to unilateral constraints. The method rests on assuming a deformed shape of the elastica and on uniquely segmenting the elastica consistent with a single canonical segment (clamped-pinned). An asymptotic solution of the canonical problem is then derived and the complete solution of the constrained elastica is constructed by assembling the solution for each segment. Nevertheless, the application of the optimal control method is more generic. It can be used to solve any constrained buckling problem under general boundary and loading conditions. Based on Hamiltonian mechanics, the optimality conditions, which constitute the Pontryagin’s minimum principle, involve the minimization of the Hamiltonian with respect to the control variables, the canonical equations and the transversality conditions. The main advantage of the optimal control method is the assumption of strong rather than weak variation of the involved variables, which leads to the additional Weierstrass necessary condition (“optimal” equilibrium state). Based on it, several factors such as the effect of the self-weight of the elastica and the clearance of the walls are investigated

Introduction to Permanent Plug and Abandonment of Wells

This open access book offers a timely guide to challenges and current practices to permanently plug and abandon hydrocarbon wells. With a focus on offshore North Sea, it analyzes the process of plug and abandonment of hydrocarbon wells through the establishment of permanent well barriers. It provides the reader with extensive knowledge on the type of barriers, their functioning and verification. It then discusses plug and abandonment methodologies, analyzing different types of permanent plugging materials. Last, it describes some tests for verifying the integrity and functionality of installed permanent barriers. The book offers a comprehensive reference guide to well plugging and abandonment (P&A) and well integrity testing. The book also presents new technologies that have been proposed to be used in plugging and abandoning of wells, which might be game-changing technologies, but they are still in laboratory or testing level. Given its scope, it addresses students and researchers in both academia and industry. It also provides information for engineers who work in petroleum industry and should be familiarized with P&A of hydrocarbon wells to reduce the time of P&A by considering it during well planning and construction

The effect of well path, tortuosity and drillstring design on the transmission of axial and torsional vibrations from the bit and mitigation control strategies

As well designs become increasingly complicated, a complete understanding of drillstring vibrations is key to maximize drilling efficiency, to reduce drillstring dysfunction and to minimize drillstring, tool, and borehole damage. Torque and drag models exist that seek to quantify the effects of borehole inclination and tortuosity on static friction along the drillstring; however, the effects on dynamic friction remains poorly understood. This dissertation begins with a review of the past fifty years of work on drillstring dynamics models, an overview of the proposed control strategies and a summary deployed vibration mitigation applications within the drilling industry. Derivations from first principles of a series of computationally efficient axial and torsional drillstring models in both the frequency and time domains are then presented and verified with field data. The transfer matrix approach is used to predict the severity of axial vibrations along the drillstring and is verified using a series of case studies using field data. Harmonic axial vibrations within drillstrings are either induced intentionally, in the case of axial oscillation tools midway along the drillstring, or unintentional, in the case of bit bounce. Two case studies of bit bounce are first evaluated to ensure model validity for a harmonic excitation at a the bit and the model is found to accurately predict bit bounce based on surface rotation rates. Induced axial oscillations, generated by axial oscillation tools, are then investigated to quantify friction reduction and drilling efficiency improvements. Optimal placement is found to depend on wellbore geometry, but is usually restricted to periodic regions of the drillstring. These optimizations are then verified using field trials and suggest that improved placement can result in 20% or more reduction in friction along the drillstring. Two applications of torsional drillstring vibrations are then investigated -- stick slip mitigation and drillstring imaging. The time domain form of the torsional drillstring model is used first to evaluate the effectiveness of three types of top drive controllers -- stiff controllers, tuned PI controllers and impedance matching controllers -- in mitigating stick slip oscillations. Then, the transfer matrix method is applied to evaluate the effect of wellbore geometry on drillstring mobility to conclude that higher order modes of stick slip may become dominant in non-vertical wellbores. The feasibility of drillstring imaging using torsional signals from surface is then investigated to identify inputs and methods that show promise in three setups of varying complexity -- a hanging beam, a laboratory drillstring model and a drilling rig. Two techniques show promise -- white noise injection and model fitting of a step response -- in identifying larger features, including drillstring length and BHA location. However, low sampling frequencies and low bandwidth inputs reduce the ability to image small features such as friction points along the wellpath.Petroleum and Geosystems Engineerin