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Aguiar, Janaina I. S. (Locus Bio-Energy Solutions) | Pontifes, Antonio A. (Locus Bio-Energy Solutions) | Nerris, Anthony (Locus Bio-Energy Solutions) | Rogers, Jonathan (Locus Bio-Energy Solutions) | Mahmoudkhani, Amir (Locus Bio-Energy Solutions)
Asphaltenes and waxes can precipitate and deposit in reservoirs, wells and equipment increasing production and operation costs. Previous studies showed the co-precipitation of these heavy organic compounds under field conditions and that the chemical treatment for one fraction can affect the deposition mechanism of the other fraction. These facts led to a key question: Can solvents that are normally used for asphaltenes remediations affect wax deposition? In this paper, we dealt with the impacts of aromatic solvents addition to a waxy crude and studied characteristics of wax deposits obtained from Cold Finger testing at different ratios of solvent/oil. The results showed that depending on solvent concentration the Wax Appearance Temperature (WAT), composition of paraffins and deposition rate have significantly changed. It was also shown that a biodegradable and low toxicity biosurfactant demonstrated a remarkable efficiency as wax dispersant to control and reduce organics deposition.
Summary Efficient removal of deposited asphaltenes on the surface of metallic flowlines by functional molecules is investigated by nonionic and ionic surfactants at low concentrations. Deposition removal by aromatic solvent toluene is measured as a reference. Water is often coproduced with crude oil and may affect deposition of asphaltenes and removal. In this study, we investigate the effect of water in both asphaltene deposition and removal by functional molecules. Two different crudes from different fields that give rise to serious asphaltene deposition are extensively investigated. For these two crudes, we find one ionic and one nonionic surfactant to be effective in deposition removal at 1 wt% concentration in the crude. This concentration is much lower than that of the commonly studied acidic dodecylbenzene sulfonic acid (DBSA) surfactant. Toluene concentration in the crude varies from 40 to 60 wt% for asphaltene deposition removal. Water delays deposition significantly. However, water does not have an appreciable effect on performance of functional molecules on removal of deposited asphaltenes.
Abstract Recent studies revealed that field deposits collected from production tubing of offshore wells often exhibit compositional varieties pointing to a more complex fouling process under field operations than original predictions purely based on asphaltene instability. Asphaltenes are estimated to constitute only 50 - 60% of total field deposit. The objective of this work was to understand the strong affinity between paraffin wax and asphaltenes resulting in co-precipitation of "waxphaltenes" and their impact on overall Asphaltene Inhibitor (AI) performance efficiency. This approach allows more objective and reliable product development and recommendation strategy to be adopted for offshore production with flow assurance management challenges caused by waxphaltenes deposition. Routine screenings and initial chemical treatments were found unsuccessful and not reliable for samples received from offshore deep-water fields. In this study, the oil sample was fully characterized though Fourier Transform InfraRed (FTIR) spectroscopy and High Temperature Gas Chromatography (HTGC). A series of dispersion and deposition tests were then conducted in order to identify potential chemistries for treatment. Dispersion testing was mainly carried out using Asphaltene Differential Aggregation Probe Test (ADAPT) technique, whereas deposition tests were conducted on a customized Asphaltene Dynamic Deposition Loop (ADDL) test. Crude oil characterization indicated presence of unstable asphaltene fraction within the analyzed crude oil sample. Dispersion efficiency with different asphaltene inhibitors revealed possible co-precipitation issue of other crude oil solubility fractions. Futher characterization analyses highlighted heavier paraffinic components to have very high affinity towards the asphaltene clusters and creating waxphaltene precipitation issue. Efficiency of traditional asphaltene inhibitor chemistries were observed to not perform well for waxphaltene deposition. Imporvement in the chemical treatment program and product development based on the knowledge obtained through this work resulted in better inhibitor formulation. The deposition test results using the improved inhibitor chemistry was tested on ADDL and showed better performance than the traditional asphaltene inhibitor. The new approach presents a unique opportunity to revisit the way product development is performed allowing chemical treatment strategy to be adopted and aligned based on actual deposit characteristics. Findings from this work shed light for more innovation in methods and products to tackle unforeseen waxphaltene deposition in offshore production systems.
Abstract Asphaltene precipitation, flocculation and deposition are vital problems that may cause serious damage to reservoirs, wells, and production facilities. Asphaltene precipitation may occur during primary depletion or acidizing jobs as well as after the injection of rich gas or carbon dioxide. The Organic deposition removal is considered a costly workover job with the current oil prices. The solvents that are usually used are toluene and xylene, which are considered carcinogenic and toxic chemicals. The use of dispersion to inhibit the organic deposition is essential and can be expensive, as it is required for the life of the well. The objective of this paper is to compare the effectiveness of two chemical dispersants and deasphalted oil against vegetable oils (coconut oil and andiroba oil) on the inhibition of asphaltene precipitation. A Kuwaiti crude oil sample was used in this study with an API of approximately 38° and asphaltene content of 2 wt%. The crude oil was characterized by a variety of analytical techniques including: Total acid number (TAN), Total base number (TBN), water content, Saturates, Aromatic, Resins, and Asphaltene analysis (SARA), density, viscosity and elemental analysis. Dispersants and vegetable oils were analyzed by Fourier Transform Infrared spectroscopy (FTIR) to determine the functional groups. An Asphaltene dispersants test was carried out at different concentrations of 150, 300 and 500 ppm and temperatures of 25 and 70°C to evaluate the dispersant efficiency and limitations. The results of this study showed that the dispersant should be designed based on understanding the asphaltene structure and interaction mechanism. Temperature greatly affects the blended dispersant performance due to the relation of asphaltene solubility and temperature; therefore designing optimum concentration must be taking into account. Employing the deasphalted oil as solvent to mitigate asphaltene precipitation can be desirable from economical perspective. Coconut oil performs very well as an asphaltene dispersant when paired with DAO at a concentration of 500 ppm or solely at 25°C. The results can be employed in designing and optimizing dispersants that are environmental friendly and cost effective.
Costa Salmin, Davi (Colorado School of Mines) | Delgado-Linares, Jose G. (Colorado School of Mines) | Wu, David T. (Colorado School of Mines) | Zerpa, Luis E. (Colorado School of Mines) | Koh, Carolyn A. (Colorado School of Mines)
Summary Some crude oils contain naturally occurring surfactants that avoid hydrate agglomeration. Natural hydrate antiagglomeration has been linked to different crude oil fractions, including asphaltenes. Asphaltenes can promote the formation of stable water-in-oil (W/O) emulsions due to their amphiphilic properties. The surfactant-like behavior of asphaltenes is related to their aggregation state. Asphaltenes are strong emulsifying agents when in an aggregated state but weak emulsifying agents when either precipitated or well solubilized in the bulk oil phase. The asphaltene aggregation state may be artificially modified, changing its interfacial activity, by mixing crude oil with heptane–toluene mixtures. This work investigated the influence of the asphaltene aggregation state on gas hydrate agglomeration. Results show that the natural hydrate antiagglomerant properties of crude oils can be highly dependent on the artificially induced asphaltene aggregation state. For instance, if asphaltenes were induced to be solubilized into the bulk oil phase, the natural hydrate antiagglomerant behavior was diminished. However, when asphaltene aggregation was induced, gas hydrate agglomeration was avoided. These new findings could have significant implications for the implementation of novel hydrate management strategies that can reduce or eliminate the need for external interventions and hence minimize capital and operational expenditures by taking advantage of the intrinsic natural antiagglomerant properties of some crude oils.