Revisiting Asphaltene Deposition Tool (ADEPT): Field Application

Abstract

Asphaltenes tend to deposit in reservoir, well tubing, flow lines, separators, etc., causing significant production losses. Asphaltenes are originally stable in crude oil at reservoir conditions. However, changes in temperature, pressure, and/or composition may cause asphaltenes to precipitate and potentially deposit onto the surfaces of a flowing conduit. There are several publications in the literature that discuss modeling of asphaltene phase behavior in oil as well as development of deposition models to simulate asphaltene deposition profiles along a flow path. In this paper, a previously reported asphaltene deposition tool (ADEPT) is used to study the deposition in a subsea pipeline in the Gulf of Mexico. This is the first demonstration of an asphaltene deposition simulator that has been used in a fully predictive manner. All of the required kinetic parameters used for deposition predictions were experimentally measured. A new methodology to scale up the deposition constant measured from a small-scale capillary deposition experiment to a large-scale subsea flow line is also reported in this paper. The predictions that made use of such an appropriately scaled deposition constant were in good agreement with field observations. The simulator was also able to predict the effects of a decreasing deposit thickness with increasing flow rates as observed in the Hassi Messaoud field. The paper further discusses a modified pseudo-transient simulator that is capable of incorporating the effect of deposit buildup on flow velocities and frictional pressure drop, which, in turn, affects the phase behavior of asphaltene. The differences between ADEPT and the pseudo-transient simulator is discussed. Simulation results show that incorporating the effect of deposit buildup causes a decrease in deposition rates with time, as reported from field observations.

Integrated one-dimensional modeling of asphaltene deposition in wellbores/pipelines

“…Vargas et al [11] proposed a model which simultaneously considered asphaltene precipitation, particle transport, asphaltene aggregation and deposition. Kurup et al [12][13] further simplified the model to one-dimension, and included diffusion due to turbulent velocity fluctuation.…”

Asphaltene deposition in a Taylor‐Couette device and a pipe: Theoretically achievable critical deposition regimes

“…It has been claimed by different authors that asphaltene deposition in production tubing is driven by Brownian diffusion . A model using this deposition mechanism was developed by Eskin et al and demonstrated reasonably high accuracy in forecasting asphaltene deposit mass in a laboratory Taylor‐Couette (TC) device, in which the inner cylinder rotates and the outer one is immobile.…”

Improving the estimation accuracy of titration-based asphaltene precipitation through power-law committee machine (PLCM) model with alternating conditional expectation (ACE) and support vector regression (SVR) elements

“…When dealing with crude oil fractions, most of the attention is focused on asphaltenes mainly due to its adverse influences on the downstream and upstream sectors of petroleum industry. Asphaltenes are known as the heaviest and the most polar portion of crude oil (Kurup et al 2012) and are defined as fractions of crude oil that are soluble in benzene but insoluble in n-heptane (Shirani et al 2012a, b). Under initial reservoir conditions, asphaltenes are equilibrated in crude oil through peptizing by resins (Kurup et al 2012).…”

“…Asphaltenes are known as the heaviest and the most polar portion of crude oil (Kurup et al 2012) and are defined as fractions of crude oil that are soluble in benzene but insoluble in n-heptane (Shirani et al 2012a, b). Under initial reservoir conditions, asphaltenes are equilibrated in crude oil through peptizing by resins (Kurup et al 2012). With changes in thermodynamic conditions such as pressure, temperature, and crude oil composition, stable dispersion of asphaltenes in crude oil would be destabilized; hence, asphaltenes precipitate out of the crude oil solution and settle in the form of solid deposits which can impede the production process (Shirani et al 2012a, b).…”