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Sherar B.W.A.,Blade Energy Partners | Keech P.G.,Nuclear Waste Management Organization of Canada | Shoesmith D.W.,University of Western Ontario
Corrosion Science | Year: 2013

Severe corrosion damage may occur when gas transmission pipelines are exposed, at disbonded coating locations, to trapped waters containing sulfide followed by secondary exposure to air. Aerobic corrosion with sulfide was investigated in a long-term corrosion experiment in which corrosion was monitored by measurement of the corrosion potential and polarization resistance obtained from linear polarization resistance measurements. The properties and composition of the corrosion product deposits formed were determined using scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. A switch from aerobic to aerobic-with-sulfide corrosion doubles the relative corrosion rate. © 2012 Elsevier Ltd.

Sherar B.W.A.,Blade Energy Partners | Keech P.G.,Blade Energy Partners | Keech P.G.,University of Western Ontario | Shoesmith D.W.,University of Western Ontario
Corrosion Science | Year: 2011

A corrosion mechanism has been developed to describe tubercle formation along pipeline steels during successive anaerobic-aerobic cycles. Small concentrations of O 2 under nominally anaerobic conditions can lead to the separation of anodes and cathodes. Under subsequent aerobic conditions localized corrosion is then promoted by O 2 reduction on the general magnetite-covered surface. Subsequently, the conversion of magnetite to maghemite passivates the general surface, and focuses corrosion within one major tubercle-covered pit. On switching from aerobic to anaerobic conditions, corrosion is temporarily supported by the galvanic coupling of lepidocrocite (γ-FeOOH) reduction (to γ-Fe-OH·OH) to steel dissolution primarily within the tubercle-covered pit. © 2011 Elsevier Ltd.

Sherar B.W.A.,Blade Energy Partners | Keech P.G.,University of Western Ontario | Shoesmith D.W.,University of Western Ontario
Corrosion Science | Year: 2011

The influence of anaerobic-aerobic cycling on pipeline steel corrosion was investigated in near-neutral carbonate/sulphate/chloride solution (pH 9) over 238. days. The corrosion rate increased and decreased as exposure conditions were switched between redox conditions. Two distinct corrosion morphologies were observed. The majority of the surface corroded uniformly to produce a black magnetite/maghemite layer approximately 4.5 μm thick. The remaining surface was covered with an orange tubercle, approximately 3-4. mm in cross section. Analysis of the tubercle cross section revealed a single large pit approximately 275 μm deep. Repeated anaerobic-aerobic cycling localized the corrosion process within this tubercle-covered pit. © 2011 Elsevier Ltd.

Da Silva T.P.,Blade Energy Partners | Naccache M.,Pontifical Catholic University of Rio de Janeiro
Society of Petroleum Engineers - SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition | Year: 2016

Hydraulics play an important function in many oil field operations including drilling, completion, fracturing, acidizing, workover and production. In Managed Pressure Drilling (MPD) applications where pressure losses become critical to accurate estimate and control the well within the operational window, it is necessary to use an appropriate rheological model for mathematical modelling of fluid behavior. The standard API methods for drilling fluid hydraulics assume Herschel-Bulkley (H-B), Power Law (PL) or Bingham plastic rheological model. This paper summarizes the results of an extensive study on issues and relevant aspects related to the equipment and methods used to characterize the drilling fluids for MPD applications, as well as the operational implications that diverge from conventional practices. A comparison of Fluid Rheology Characterization will be made by using laboratory high precision rheometers versus conventional FANN35 methods. Subsequently, a comparison of Rheology Model Selection proposed by API 13B opposed to Non Linear Regression (NLR) and the error intrinsically it is also included. Further investigation of shear rates is presented in a MPD "typical" annular geometry will be calculated via Computational Fluid Dynamics (CFD) and the formulas suggested in API RP 13D compared. To conclude it will be presented a discussion of the influences of measurements, data treatment (Curve Fit) and environment (laboratory observations versus field experiences) in the accuracy of fluid rheology characterization. Copyright 2016, SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition.

Suryanarayana P.V.,Blade Energy Partners | Lewis D.B.,Blade Energy Partners
SPE/IADC Drilling Conference, Proceedings | Year: 2016

This paper presents the application of reliability-based approaches to the survival design of critical wells, in particular deepwater and high pressure/high temperature (HPHT) wells. First, the concept of survival design is discussed. As in other structural design disciplines, a distinction is made between operating (service) loads and survival loads. In essence, survival loads are extreme magnitude loads with low probability of occurrence, but with potentially severe consequences if failure occurs. Survival scenarios falling into this category in critical wells are presented. It is shown that the current practice of using standard Working Stress Design (WSD) approaches for survival scenarios, even with reduced design factors, fails to quantify risk of failure, and can lead to design practices and outcomes that are not risk consistent or optimal. Reliability based design (RBD) explicitly quantifies the risk of failure of a given design. This paper describes RBD and the prevalence of its use in other structural design codes and shows how it can be used for survival design in critical wells. It is argued? that a probabilistic approach in which a deterministic load at its extreme survival magnitude is compared to stochastic strength (from data on strength parameters), is a rational approach to survival load design. Regardless of how low the probability of occurrence of the load is at its survival magnitude, well integrity is demonstrated by assuming that such a load occurs. The method can be easily implemented by constructing resistance distributions using limit state equations such as the Klever-Stewart Rupture Limit, and the Klever-Tamano Collapse Limit equations, with strength parameter data from API TR 5C3 (ISO TR 10400), manufacturer reports or direct material and dimensional measurements. Statistical approaches to constructing such distributions are presented. The deterministic survival load is then compared to this resistance distribution, and a probability of failure calculated. This probability of failure then becomes the basis for design. The goal in survival design is to demonstrate survival rather than continued operability. Based on this, acceptable probabilities of failure for typical survival loads are recommended, and contextualized with other design codes. Particular attention is given to Worst Case Discharge and Well Containment loads, which have become design-dictating survival loads in many deepwater well designs, and are driving design choices of tubulars and connections. The applicability of this approach to connection selection and brittle failure is also demonstrated. Deepwater and HPHT well examples are presented to illustrate the use of the approach. It is shown that designing to an acceptable probability of failure leads to more robust and risk-consistent designs in critical wells. Further, such an approach allows designers to focus on the specific design or well construction changes that enhance survival. The approach described in this paper provides a quantitative basis to examine design adequacy of wells under survival scenarios. The approach is in keeping with the traditional practice of allowing the use of all available strength in designing to survival loads. Using stochastic strength data rather than deterministic strength estimates provides a probabilistic basis for design, thus quantifying risk. The authors believe this is a much needed, and rational approach to optimize design of critical wells under increasingly demanding loads. Copyright 2016, IADC/SPE Drilling Conference and Exhibition.

Wu Z.,Blade Energy Partners | Vasantharajan S.,Blade Energy Partners | El-Mandouh M.,Blade Energy Partners | Suryanarayana P.V.,Blade Energy Partners
SPE Journal | Year: 2011

In this paper, we present a new, semianalytical gravity-drainage model to predict the oil production of a cyclic-steam-stimulated horizontal well. The underlying assumption is that the cyclic steam injection creates a cylindrical steam chamber in the upper area of the well. Condensed water and heated oil in the chamber are driven by gravity and pressure drawdown toward the well. The heat loss during the soak period and during oil production is estimated under the assumption of vertical and radial conduction. The average temperature change in the chamber during the cycle is calculated using a semianalytical expression. Nonlinear, second-order ordinary differential equations are derived to describe the pressure distribution caused by the two-phase flow in the wellbore. A simple iteration scheme is proposed to solve these equations. The influx of heated oil and condensed water into the horizontal wellbore is calculated under the assumption of steady-state radial flow. The solution from the semianalytical formulation is compared against the results from a commercial thermal simulator for an example problem. It is shown that the model results are in good agreement with those obtained from reservoir simulation. Sensitivity studies for optimization of wellbore length, gravity drainage, bottomhole pressure, and steam-injection rate are conducted with the model. Results indicate that the proposed model can be used in the optimization of individual-well performance in cyclic-steaminjection heavy-oil development. The semianalytical thermal model presented in this work can offer an attractive alternative to numerical simulation for planning heavy-oil field development. © 2011 Society of Petroleum Engineers.

Sathuvalli U.B.,Blade Energy Partners | Suryanarayana P.V.,Blade Energy Partners
Society of Petroleum Engineers - SPE Western Regional Meeting | Year: 2016

During production in prolific high temperature (HT) platform wells, the forces exerted by the inner strings can cause noticeable Wellhead Motion (WHM). The thermal forces created by the inner strings are balanced by the conductor (structural casing), and finally by the friction between the conductor and the formation. Depending on the shear stress profile at the conductor-soil interface, the point of fixity (POF) of the structural casing may lie below the mudline (ML), and gross motion in the subterranean section of the conductor can occur. When the shut-in well cools back to the undisturbed state, the thermal forces disappear. Due to the anisotropic nature of the frictional forces, the wellhead does not always return to its original position, and a fraction of the overall wellhead (WH) displacement is locked in at the mudline. This phenomenon recurs during subsequent production and shut-in cycles and it can lead to ratcheting. Ratcheting becomes a critical issue when the net thermal force on the wellhead is an appreciable fraction (or exceeds) the pullout capacity of the pile. Current models to assess WHM regard the inner casings as elastic springs that are attached between the wellhead and the POF. The conductor-soil interaction or the casing-cement interaction below the POF are traditionally addressed by a finite element analyses (FEA). In this paper we discuss the importance of the anchoring shear stress at the conductor-soil interface and provide methods to assess its orders of magnitude. We present solutions to frequently encountered problems in operational and design situations where sections of casing below the assumed TOC come loose or when the subterranean motion of the conductor is appreciable. These solutions can be used in lieu of FEA. By coupling the results of this model with the t-z response of pile driven conductors (as per API RP 2GEO), we present semi-analytical models that are applicable in a wide variety of wellhead loading situations. Copyright 2016, Society of Petroleum Engineers.

Suryanarayana P.V.,Blade Energy Partners | Krishnamurthy R.M.,Blade Energy Partners
Society of Petroleum Engineers - SPE Thermal Well Integrity and Design Symposium | Year: 2015

Strain-based approaches that allow post-yield loading are now quite common in the design of tubulars for high temperature service in cyclic steam stimulation and similar applications. The traditional notionally strain-based design approach proposed by Holliday (ASME 69-PET-10, 1969) has formed the basis of design for several decades. In this work, a modified Holliday approach, which provides a rational, easily applied basis of design for thermal service tubulars, is presented. The modifications improve upon several assumptions made in the original approach, especially that of an ideal elastic-plastic, symmetric material. Thermal effects important in design, such as temperature deration of yield, cyclic strain hardening, Bauschinger effect, thermal stress relaxation, and strain localization are incorporated in the design approach, and acceptable design factors for different tubular grades are proposed. While familiar and able to produce reliable and acceptable designs, the modified approach has several limitations, which are discussed in the paper. These limitations largely arise from the fact that cyclic plastic strain is usually unavoidable in a thermal service tubular, and as a result, mechanical failure is rooted in fatigue. In this paper, a new, Low Cycle Fatigue (LCF) approach is presented as an alternative for critical thermal applications. The approach is based on the concepts of Critical Strain, a material property, and Ductile Failure Damage Indicator (DFDI), a plastic damage parameter. The new approach accumulates the plastic damage through the parameter DFDI, and can handle both cyclic and applied monotonic strains in the plastic region. The plastic damage is correlatable to critical strain, and can incorporate the influence of principal stresses and cyclic loads in the plastic region. The paper presents the basis of these parameters, and their use in assessment of plastic damage failure in other tubular and structural design approaches. The method offers some advantages over the more traditional, Coffin-Manson based LCF models, including reduced experimental burden, ability to incorporate connections and sour service considerations, and the ability to handle non-zero mean strain. Limitations of the method, and ongoing efforts to address them, are presented. The paper also presents an example illustrating the application of the new LCF approach. Copyright 2015, Society of Petroleum Engineers.

As production conditions in the oil field become progressively more severe in temperature, pressure, and acid gas content, the experimental evaluation of the corrosion and cracking behavior of the materials used in well completions becomes ever more important. Testing of these materials is typically accomplished in pressure vessels (i.e. autoclaves). Generating field relevant environments in a closed system is not trivial. In a 1998 paper, the author formulated an equation of state for closed systems based on ideal gas behavior which was used to determine the amounts of brine and acid gases to be charged into the autoclave in order achieve the desired partial pressures at the test temperature [1]. This approach, based on ideal gas behavior and published gas solubility coefficients, worked well for relatively mild conditions. Since it is not the partial pressures of the acid gases that cause the corrosion and cracking of steel in solution, but rather the concentrations of the acid gases dissolved in solution, and since on the other hand field conditions are characterized only by the partial pressures, a relationship must be defined between the partial pressure, or more precisely the fugacity, of the acid gases and their concentrations in solution. Under mild conditions published solubility data can be used in conjunction with ideal gas behavior. However, solubility constants are a function of temperature, total pressure, salinity of the brine, and gas composition. This leads to relationships which are not easily handled on a routine basis. More recently commercial software has become available which can reliably handle these relationships. This study will highlight the effects of pressure, temperature, and gas composition on the aqueous acid gas concentration, and place this approach in perspective with regards to NACE MR0175/ISO 15156.© 2013 by NACE International.

Blade Energy Partners | Date: 2015-05-18

Systems include a well having a production casing and a production tubing positioned therein, forming an annulus there between. A packer is positioned in the annulus at a position sufficient to separate the annulus into a first portion and a second portion. The well further includes a tie-back conduit positioned in the first portion of the annulus and configured to allow heat transfer between a working fluid flowing through the first portion of the annulus and a production fluid flowing through the production tubing, thus separating the circulating working fluid from fluids in the second portion of the annulus. A working fluid loop is fluidly connected to the first portion of the annulus. Co-production methods, methods of modeling, and computer-readable media including the methods of modeling are disclosed.

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