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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.

Brand P.,Blade Energy Partners
SPE/IADC Drilling Conference, Proceedings | Year: 2016

The increasing use of Managed Pressure Drilling (MPD) has been proven to enhance drilling operations in conventional, narrow margin, High Pressure-High Temperature (HPHT) and, in particular, deepwater operations. Its success does not come easily, as the technique challenges the conventional drilling paradigm along with drilling contractors' and operators' policies and standards. Conventional drilling practices for connections, flow checks, tripping, and well control have been long understood and standardized both onshore and offshore. The addition of an MPD system to a drilling operation, inclusive of the recommended practices, makes necessary bridging the gap between conventional policies and standards and those of MPD. This bridging document will produce a formal standard, specific to each project and/or operation. When a new drilling campaign is initiated, the operator typically begins designing a well plan and high-level drilling program by referencing their current standards and policies. Once a drilling contractor is selected, the challenge of bridging the drilling contractor's policies with the operator's standards begins. If the drilling campaign is to include MPD wells, the inclusion of MPD then adds an additional layer of complexity to the established bridging document by challenging standard operating procedures and forcing operators and contractors to create step-outs from their policies. It is often seen as an operational requirement that a MPD bridging document supplements the standard drilling contractor's and operator's bridging document, standing apart from the already established policies. Instead, MPD should be viewed as a way to enhance the currently acceptable policies and practices and should form an integral part of a combined operational policy document. MPD challenges conventional drilling practices, and both MPD and drilling personnel must work closely together during operations. However, regarding well control, the drilling contractor remains ultimately responsible. The driller will continue to monitor the well using standard drilling contractor operating procedures, and observe key drilling parameters with enhanced MPD indicators. The MPD system provides enhanced well control event detection in addition to standard conventional down hole and surface event detection methods while also allowing rapid and accurate control of bottom hole pressure (BHP). This does not replace the drilling contractor's or operator's well control polices. Further examples of how MPD impacts conventional operations include: · What is considered an adequate flow check in both duration and monitoring? · What additions are there to the primary barrier envelope? · What volume and intensities of influxes can be safely managed through the Riser Gas Handling (RGH) system and/or MPD system, maintaining the primary well control barrier? Without formalizing a bridging document between the drilling contractor's, operator's, and MPD service provider's policies to address issues like these, gaps will remain, thereby exposing the operation to the risk of failure and mitigating the potential gain that can be realized from utilizing MPD. The intent of this paper is to highlight the specific areas where conventional policies are challenged by MPD operations and to attempt to offer guidance when implementing and managing this technology. It is also to be used as a tool to raise awareness to ensure that operations are carried out in a safe and efficient manner according to the agreed upon policies, procedures, and standards currently in place, as well as to minimize the potential risk to personnel, environment, and equipment. Copyright 2016, IADC/SPE Drilling Conference and Exhibition.

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.

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.

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.

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