Christian Hurtevent

ARN‐Type Naphthenic Acids in Crudes: Analytical Detection and Physical Properties

Calcium naphthenates deposits recovered on site contain massive proportions of high molecular weight tetra acids, so‐called ARN. The detection of ARN acids in crudes is of paramount importance, especially for designing future installations and allowing for mitigation means. The proposed ARN detection strategy involves a concentration step and a high‐pressure liquid chromatography/mass spectrometry analysis. Using this methodology, ARN has been detected in a large number of crude oils, most of which do not show any operational difficulties. A physicochemical model is then proposed for interpreting these results. It incorporates the formation, in specific conditions, of a polymer like structure through ARN association.

Flow Assurance Issues and Control with Naphthenic Oils

Naphthenic oil production is known to be made difficult by stable emulsion formation and possible scaling of calcium naphthenates. From a flow assurance point of view, it is of major importance to foresee these two possible issues at the earliest stage of the project development especially for deep-offshore fields. In this article, a classification of crude oils based on density, acidity and acid types is proposed. Process schemes adapted to the different oil types are also described.

The Use of Fluorescent Tracers for Inhibitor Concentration Monitoring Useful for Scale Inhibitor Squeeze Evaluation

A common problem, in oilfield reservoirs is mineral scale deposition. The build-up of scale inside well bores and the surrounding reservoir causes millions of dollar in damage every year. The most common remedy is to treat the formation of such minerals with scale inhibitor chemicals in a “squeeze” treatment; which is performed periodically. One of the big challenges remains the real-time and on-site control of inhibitor concentration during production. A simple and accurate method to determine the concentration of inhibitors has been developed; this method is based on the use of luminescent tracers. The multiple lifetimes as well as the differences shown in the emission and excitation spectra of the tracers appear to be suitable for the luminescence detection. The increased signal to noise ration due to the suppression of the background resulting from the organic oil residues is used to measure the concentration of residual inhibitors in production waters. Furthermore, the use of a technique as versatile and simple as luminescence spectroscopy allows the online and/or on-site monitoring with very limited drawbacks. This paper describes the use of novel real-time scale inhibitor monitoring; this new technique will help to optimize the treatment rates of the scale inhibitor squeeze treatment.

Evaluation of Anti-fouling Surfaces for Prevention of Mineral Scaling in Sub-surface Safety Valves

Mineral scale formation and deposition in down-hole completion equipment such as subsurface safety valves can cause dramatic and unacceptable safety risks and associated production losses and operational costs. Current scale removal strategies involve both mechanical and chemical technologies, each of them having their own advantages depending on the type of mineral scale and its location. However, these techniques are often costly and of limited efficiency. The current study assesses the ability of a range of chemically and morphologically modified coatings to prevent/reduce mineral scale surface fouling. Building-up on previous work done under static conditions, this paper presents results from scaling tests under laminar and turbulent dynamic conditions using a rotating cylinder electrode under in a complex (mixed) scaling environment (supersaturated w.r.t. calcium carbonate, barium sulfate, strontium sulfate, barium carbonate and strontium carbonate). The study shows that if properly selected, surface treatments represent a promising approach to reduce scale deposition on downhole equipment surfaces that are critical to maintain equipment functionality and thereby well safety barrier integrity. By analyzing the scaling behaviors observed within the set of surfaces tested, suggestions of the controlling factors in anti-fouling on these systems are presented and discussed.

Comparison of characteristic of anti-scaling coating for subsurface safety valve for use in oil and gas industry

A subsurface safety valve is used to shut in a well automatically, if the wellhead equipment or other surface production equipment fails. It is almost always installed as a vital component on the completion. In many industrial systems, scale formation causes significant problems, not when it precipitates in bulk solution but when it deposits on the surface. Surface scaling is a complex phenomenon where several processes such as heterogeneous crystallization or particle adhesion are inextricably linked and occur simultaneously. The sub-surface safety valve can accumulate carbonate, sulphate and sulphide scale. Even a thin layer of scale can impede the smooth operation of the valve and pose serious regulatory and safety risks. In this study twenty coatings from seven different natures have been tested. These coatings are Fluoropolymers, Composite (fluotopolymer matrix), Sol-gel nano-coating, Textured hydrophobic paint, Diamond Like Carbon (DLC), Polished Inconel and Nitro carburated Inconel. Whilst the anti-scaling capability of the coating is the key functional element, it is extremely important that the coating presents other important parameters such as hydrophobicity property, surface roughness, coating thickness and hardness, resistance to erosion, corrosion and temperature as well as coating adhesion. In this paper the controlling factors of anti-scaling coatings are discussed. Promising coatings with anti-scaling properties have been identified.