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Abstract Although iron sulphide (FeS) scale is not as common as carbonate and sulfate scales, it is difficult to inhibit, especially at high temperature conditions, due to its low solubility and fast precipitation kinetics. Moreover, the complexity of FeS solution and solid phase chemistry makes FeS deposition and related issues difficult to be solved. This study is to identify more efficient and effective dispersants and inhibitors for FeS scale. Polyacrylamide (PAM), polyvinyl pyrrolidone (PVP), polyoxazoline (OX) and carboxymethyl cellulose (CMC), which are frequently employed during oil and gas production activities for various purposes, successfully prevented FeS particles from settling. CMC was the most effective to disperse FeS particles in brines and it can disperse FeS particles under the conditions of as high as 4M of ionic strength. The size of FeS stabilized with polymers remained in nano-scale. Polymers did not work as threshold inhibitors, but prevented particle growth. Phosphonates and carboxylate chelating agents were also tested for FeS scale inhibition. Diethylenetriamine pentamethylene phosphonate (DTPMP), ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) successfully inhibited FeS nucleation greater than 90% in a given reaction time of 2 hours at 70 °C, based on the measurement of Fe concentration in filtered solution with 0.22 μm syringe membrane. NTA showed the best inhibition performance at pH 5.0 and all three inhibitors stopped FeS nucleation at a substoichiometric concentration of inhibitors to iron(II). EDTA performed better than NTA and DTPMP at pH 6.7 at about 10% excess of EDTA molar concentration over iron(II). As pH and saturation index (SI) increased, greater concentrations of inhibitors were required to inhibit FeS scale.
Nighswander, J. (WCP-Oilphase, Schlumberger) | Joshi, N. (WCP-Oilphase, Schlumberger) | Jamaluddin, A.K.M. (WCP-Oilphase, Schlumberger) | Mullins, O.C. (SDR, Schlumberger) | Creek, J. (Chevron/Texaco) | McFadden, J. (BHP Billiton)
During primary oil production, when the thermodynamic conditions within the well tubing lie inside the asphaltene-deposition envelope (ADE) of the produced fluid, flocculated asphaltene particles could start being deposited on the tubing wall, causing a restriction in the tubing inner diameter that results in loss of production. This paper presents a methodology that begins by determining the ADE in the laboratory. At some thermodynamic states, asphaltenes exhibit a behavior called flocculation--that is, asphaltene particles or micelles aggregate or flocculate into larger particles or flocs. The locus of all thermodynamic points in a phase diagram at which flocculation occurs is called the ADE. Accurate measurement of asphaltene solubility at in-situ conditions inside the ADE is extremely difficult.
Paul, Ferm (Nouryon) | Jeff, Germer (Nouryon) | Kurt, Heidemann (Nouryon) | Stuart, Holt (Nouryon) | Andrew, Robertson (Nouryon) | Jannifer, Sanders (Nouryon) | Klin, Rodrigues (Nouryon) | John, Thomaides (Nouryon) | Nick, Wolf (Nouryon) | Lei, Zhang (Nouryon)
Abstract The controlled release of scale inhibitors (SI) and other treatment chemicals in the near-wellbore region is a key strategy to improving water management and extended well production. In addition, during some completion and stimulation operations, it is desired that robust particles providing controlled release be placed in gravel and sand packs. A novel controlled release scale inhibitor particle is presented which provides beneficial properties due to its unique chemistry and polymer processing methods. This technology provides extended feedback of scale inhibitor with tunable release rates.
Abstract The continuous pursuit to discover new hydrocarbon reserves is driving oil and gas exploration companies to explore in more challenging environments, such as in deep water. One of the major challenges in these environments is to understand the characteristics of hydrocarbon solids deposition and its potential for production disruption. Asphaltenes are one of the hydrocarbon solid materials that have the potential to form, flocculate, and deposit in the production circuits. This process can come about as a result of changes in pressure, temperature, and/or composition. In this paper, we present a systematic approach to characterize asphaltene materials using state-of-the-art technologies. In summary, a fixed-wavelength near-infrared light-scattering technique (NIR) is used to prescreen the thermodynamic onset of asphaltene flocculation. Subsequently, a variablewavelength spectral analysis system (SAS) is used to estimate the asphaltene particle size and the growth kinetics. Finally, a high-pressure microscopy (HPM) technique is used to better understand the morphological behavior of the asphaltene materials. These laboratory techniques can greatly enhance the understanding of asphaltene flocculation and the risk of potential deposition at the beginning of field development. As a result, operators may have the option to proactively prevent deposition or design remediation methods during the planning phase of the deepwater development that will reduce the risk of flow disruption. Introduction Development activities in the deepwater face significant challenges. Of particular concern are the effects of produced fluid hydrocarbon solids (i.e., asphaltene, wax, and hydrates) and their potential to disrupt production throughh deposition in the production tubulars. There is a systematic approach to characterize reservoir fluid for all three flow assurance issues. Of the hydrocarbon solids, the thermodynamics and kinetic aspects of wax and hydrates are reasonably well understood, and results of various studies have been published in the literature. On the other hand, the understandings of the thermodynamic and kinetic aspects of asphaltenes formation and deposition are not yet well developed. Limited amounts of experimental data on the thermodynamic behavior of asphaltenes have been reported in the literature.. Various laboratory techniques such as gravimetric, filtration, fluorescence, spectroscopy, conduction, acoustic resonance, and light scattering have been used in determining the onset of thermodynamic instability resulting in asphaltene flocculation. A detailed description of these various methodologies has been presented in Reference 8. Only recently, the kinetic aspect of asphaltene flocculation has been reported by Nighswander et al. In this work, a systematic approach is presented for understanding the thermodynamic and kinetic aspects of asphaltenes using various state-of-the-art laboratory techniques. The identification of thermodynamic conditions at which asphaltenes start to form and the rate at which they grow are the first steps forward in evaluating economic feasibility. If asphaltenes are anticipated, the next step is an understanding of the effect these asphaltenes will have on the hydrodynamic conditions during production. Knowledge of asphaltenes will allow the production engineer to devise a suitable flow assurance strategy and assess the economics of a potential field development with less uncertainty.