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Oil industry suffers from flow assurance problems that occur both in upstream and downstream operations. One of the common flow assurance issues arises from precipitation and deposition of asphaltenes in various locations along the oil production path including near wellbore region in the reservoir, production tubing, flowlines and separation unit at the surface. Asphaltene particles precipitate out of oil continuum due to changes in temperature, pressure or composition. Such changes in operating conditions occur during different recovery processes (natural depletion, gas injection, chemical injection, etc.) as well as production and blending of different oils during transportation. There are different experimental methodologies documented in the literature that describe how to determine onset of asphaltene precipitation. In this paper, a comprehensive review is performed on all the available procedures to measure onset of asphaltene precipitation. The advantages and limitations associated with all these methods are also documented. [ABSTRACT FROM AUTHOR]

In this paper, the effects of major asphaltene deposition model parameters, particle-particle collision, and particle-wall sticking efficiencies as well as asphaltene content in a hydrocarbon fluid on asphaltene deposition in both a Taylor-Couette device and production tubing are numerically studied. The possibility of an increase in asphaltene deposition rate as a result of adding asphaltene inhibitors is investigated. The computations show that this critical effect is achievable in a Taylor-Couette device operating in a batch regime only if the particle collision and the particle-wall sticking efficiencies are more than an order of magnitude higher than those identified for asphaltenes present in hydrocarbon fluids. Calculations of deposition in the Taylor-Couette device show also that an increase in the asphaltene content causes an increase in the rate of fluid depletion of particles able to deposit. The deposition calculations for a vertical pipe demonstrate that, due to continuous precipitation of primary particles along the tubing, a hydrocarbon fluid cannot be depleted of particles able to deposit; therefore the maximum deposit thickness always increases with an increase either in the major model parameters or the asphaltene content. Thus, the model parameter values indicating critical deposition regimes are different from those inherent to real hydrocarbon fluids; therefore, these regimes cannot be achieved in practical applications. [ABSTRACT FROM AUTHOR]

Precipitation and deposition of asphaltenes and other organic substances in formation rock causes formation damage and reduces effective hydrocarbon mobility, which can result in significant production losses. The development of reliable experimental, analytical, and modelling methods improves the understanding of asphaltene-induced formation damage and provides tools for preventing and/or controlling formation damage due to asphaltenes in oil-bearing formations. To make further advancements in understanding asphaltene impairment, it is important to analyze the current state of technology and research in this area. In addition to analyses of known experimental data and models of reservoir impairment by asphaltenes, prospective directions of future research in this area are also suggested. [ABSTRACT FROM AUTHOR]

Asphaltene precipitation/deposition have been longstanding issues in petroleum industry which lead to decline in oil production and economical efficiency. Owing to severe undesirable issues associated with this phenomenon, it is crucial to develop a reliable, accurate, and robust approach for quantitative estimation of asphaltene precipitation. In the first section of this paper, amount of asphaltene precipitation from stock tank oil through titration process was estimated using two predictive methods of Support Vector Regression (SVR) as well as Alternating Conditional Expectation (ACE). A novel predictive method, the so-called Power-Law Committee Machine (PLCM) with constituents of SVR and ACE, was then employed for estimation of the amount of asphaltene precipitation. PLCM model assigns weight factors to each individual sub-model of SVR and ACE to specify the contribution of each particular model in the overall prediction of asphaltene precipitation. Optimal values of these weight factors were extracted by means of Genetic Algorithm (GA) since it was already inserted as the combiner in the structure of the PLCM model. To validate this predictive tool, experimental data collected from open source literature were compared against the model predictions. It was observed that PLCM model can estimate the amount of asphaltene precipitation with very high accuracy and it had more satisfactory prediction performance compared to the other models of SVR and ACE. [ABSTRACT FROM AUTHOR]

One of the most concerning areas for asphaltene deposition is the near-wellbore region, where such deposition may cause formation damage. The reservoir fluid of the Lake Maracaibo region is known to cause operational problems such as production losses due to asphaltene deposition. In this paper, we focus on the systematic evaluation of the asphaltene formation damage using stacked composite core samples and live oil samples from Lake Maracaibo area and study the formation damage due to asphaltene deposition inside the composite core stack. A special coreflood system was designed for an asphaltene formation damage study using reservoir core samples and sour–live reservoir fluid samples. The phenomenon of asphaltene precipitation and deposition in porous media and subsequent permeability impairment was evaluated while the fluid pressure decreased below the asphaltene onset pressure (AOP). Live fluid samples were collected and flooded through the stacked composite core plugs under reservoir conditions. Progressive pressure reductions were performed to induce asphaltene precipitation and deposition in the composite core. Changes in the absolute permeability of the composite core assembly due to asphaltene precipitation and deposition were calculated in the context of the pressure depletion process. Significant permeability impairment occurred from the depressurization of the reservoir fluid below the AOP. The upstream inlet pressure of the composite core stack was maintained just above the AOP while the outlet pressure was regulated approximately 50 psig above the saturation pressure throughout the coreflood experiment so that the onset of asphaltene precipitation occurred along the length of the composite core. Following the coreflood experiment, the core stack was depressurized and the remaining fluid was extracted from individual core plugs. Various analytical techniques such as asphaltene content measurement, simulated distillation and optical density were used to perform detailed post-trial analyses of the residual fluids extracted from each individual core plugs. Analyses of the thin sections extracted from various core plugs were also performed to investigate the microstructure of the residual hydrocarbon as well as the distribution of the flow pathways plugged with asphaltene aggregates in the pore structures. The results associated with these post-trial analyses confirmed that the observed permeability impairment was indeed due to the plugging of the flow pathways of the core plugs by asphaltene aggregates, and that the asphaltene-induced permeability loss was somewhat more extensive in the tighter plugs associated with the stacked core assembly. We present the systematic approach to perform asphaltene formation damage study using composite core and live reservoir fluid samples above the saturation pressure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • This study introduces an experimental and modeling approach to obtain asphaltene precipitation. • The new technique is more accurate for light to heavy oils, compared to previous models. • The new approach considers vital oil and process characteristics in asphaltene precipitation. • A sensitivity analysis is conducted to make better operating and policy decisions while dealing with asphaltene precipitation. • The most influencing parameters in asphaltene precipitation are pressure and dilution ratio. Abstract Asphaltenes are heavy fractions of petroleum mixtures, which precipitate out of homogenous bulk fluid phase due to changes in pressure, temperature, and composition. Asphaltene precipitation and subsequent deposition in porous media can adversely affect Enhanced Oil Recovery (EOR) processes as well as impede surface transportation of crude oil. It is therefore beneficial to develop accurate techniques for determination of asphaltene precipitation as well as reliable predictive modeling approaches to remedy potential production impairments. In this study, a laboratory work is performed using three different oil samples (light, medium-viscosity, and heavy crude oil) to measure the mass of precipitated asphaltenes in a series of titration experiments. The effects of various parameters such as precipitant type, pressure, dilution ratio, API gravity of oil, and resin-to-asphaltene ratio of crude oil on the amount of precipitated asphaltenes are studied. A deterministic tool, so-called Response Surface Methodology (RSM), is then proposed to estimate the mass of asphaltenes precipitated from these three oil types in a titration process as a function of input parameters selected through a systematic parametric sensitivity analysis. The Analysis of Variance (ANOVA) technique is also employed to assess the validity of the proposed predictive methodology. Among all the contributing parameters, pressure and dilution ratio are found to be the most influencing factors when predicting the mass of precipitated asphaltenes. The developed simple predictive tool appears to be an effective methodology to forecast the mass of precipitated asphaltenes over a wide range of input parameters for various oil types. [ABSTRACT FROM AUTHOR]