Multiphase flow modeling of asphaltene precipitation and deposition

Abstract

Asphaltene precipitation in reservoirs during production and Enhanced Oil Recovery (EOR) can cause serious problems that lead to reduction of reservoir fluid production. In order to study asphaltene tendency to precipitate and change in flow rate as a function of distance from wellbore, an equation of state (Peng-Robinson) based model namely Nghiem et al.’s model has been employed in this study. The heaviest components of crude oil are separated into two parts: The first portion is considered as non-precipitating component (C31A+) and the second one is considered as precipitating component (C31B+) and the precipitated asphaltene is considered as pure solid. For determination of the acentric factor and critical properties, Lee-Kesler and Twu correlations are employed, respectively. In this study, a multiphase flow (oil, gas and asphaltene) model for an asphaltenic crude oil for which asphaltene is considered as solid particles (precipitated, flocculated and deposited particles), has been developed. Furthermore, effect of asphaltene precipitation on porosity and permeability reduction has been studied. Results of this study indicate that asphaltene tendency to precipitate increases and permeability of porous medium decreases by increasing oil flow rate in under-saturated oil reservoirs and dropping reservoir pressure under bubble point pressure. On the other hand, asphaltene tendency to precipitate decreases with pressure reduction to a level lower than bubble point pressure where asphaltene starts to dissolve back into oil phase. Moreover, it is observed that precipitation zone around the wellbore develops with time as pressure declines to bubble point pressure (production rate increases up). Also, there is an equilibrium area near wellbore region at which reservoir fluid properties such as UAOP (Upper Asphaltene Onset Pressure) and LAOP (Lower Asphaltene Onset Pressure) are constant and independent of the distance from wellbore.

Prediction of Asphaltene Precipitation Envelope (APE) Using Empirical Equations and Equation of State Model

“…It has been proven through large number of phase behavior studies that asphaltene precipitation starts to appear at pressure above saturation pressure which is termed as Upper Asphaltene Onset Pressure (UAOP) [8,9]. Then as reservoir pressure decreases further, as a result of hydrocarbon production, the asphaltene precipitation amount increases and reaches maximum at bubble point pressure (BPP).…”

Experimental investigation on precipitation damage during water alternating flue gas injection

“…No matter what type of gas injection is performed, asphaltene precipitation is an inevitable problem during the process. The solid deposition seriously affects oil recovery and increases the cost of enhanced oil recovery [11]. When the content of asphaltene reaches a certain limit, the wettability of the reservoir rock tends to be altered from oil-wet to water-wet [12][13][14][15][16], which will cause more reservoir blockage and reduction of heavy oil production [12,17], and become unfavorable for oil production and recovery process [18][19][20][21][22].…”

Formation damage due to asphaltene precipitation during CO2 flooding processes with NMR technique

“…Asphaltene precipitation could cause serious damages to formations [5][6][7]. This is because the precipitated asphaltene will deposit on to the reservoir rocks, which may cause reservoir plugging and wettability alteration [8,9].…”