Wax and Asphaltene Deposition Tendency of Malaysian Crude Oils

Summary Tremendous strides have been made recently in asphaltene science. Many advanced analytical techniques have been applied recently to asphaltenes, elucidating many asphaltene properties. The inability of certain techniques to provide correct asphaltene parameters has also been clarified. Longstanding controversies have been resolved. For example, molecular structural issues of asphaltenes have been resolved; in particular, asphaltene molecular weight is now known. The primary aggregation threshold has recently been established by a variety of techniques. Characterization of asphaltene interfacial activity has advanced considerably. The hierarchy of asphaltene aggregation has emerged into a fairly comprehensive picture, essentially in accord with the Yen model with the additional inclusion of certain constraints. Crude oil and asphaltene science is now poised to develop proper structure-function relations that are the defining objective of the new field: petroleomics. The purpose of this paper is to review these developments in order to present a more clear and accessible picture of asphaltenes, especially considering that the asphaltene literature is a bit opaque. Introduction The asphaltenes are a very important class of compounds in crude oils (Chilingarian and Yen 1978; Bunger and Li 1981; Sheu and Mullins 1995; Mullins and Sheu 1998; Mullins et al. 2007c). The asphaltenes represent a complex mixture of compounds and are defined by their solubility characteristics, not by a specific chemical classification. A common (laboratory) definition of asphaltenes is that they are toluene soluble, n-heptane insoluble. Other light alkanes are sometimes used to isolate asphaltenes. This solubility classification is very useful for crude oils because it captures the most aromatic portion of crude oil. As we will see, this solubility defintion also captures those molecular components of asphaltene that aggregate. Other carbonaceous materials such as coal do possess an asphaltene fraction, but that often will not correspond to the most aromatic fraction. Petroleum asphaltenes, the subject of this paper, can undergo phase transitions that are an impediment in the production of crude oil. Fig. 1 shows a picture of an asphaltene deposit in a pipeline; obviously, asphaltene deposition is detrimental to the production of oil. Immediately it becomes evident that different operational definitions apply for the term asphaltene in the field vs. the lab. Indeed, the field deposit is very enriched in n-heptane-insoluble, toluene-soluble materials, but this field asphaltene deposit is not identically the standard laboratory solubility class. It is common knowledge that a pressure drop on certain live crude oils (containing dissolved gas) can cause asphaltene flocculation, the first step in creating deposits that are seen in Fig. 1. Highly compressible, very undersaturated crude oils are most susceptible to asphaltene deposition problems with a pressure drop (de Boer et al. 1995). In depressurization flocculation, the character of the asphaltene flocs is dependent on the extent of pressure drop, suggesting some variations in the corresponding chemical composition (Hammami et al. 2000; Joshi et al. 2001). Comingling different oils can result in asphaltene precipitation that can resemble solvent precipitation. Asphaltenes are hydrogen-deficient compared to alkanes; thus, either hydrogen must be added or coke removed in crude oil refining to generate transportation fuels. Thus, asphaltene content lowers the economic value of crude oil. Increasing asphaltene content is associated with dramatically increasing viscosity, especially at room temperature; again, this is of operational concern. The strong temperature dependence of viscosity of asphaltic materials is one of their important properties that make them useful for paving and coating; application of asphaltic materials is facile at moderately high temperatures, while desired rheological properties are obtained at ambient temperatures.

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Impact of Water Cut on Asphaltene Deposition Tendency

10.4043/25411-ms ◽

2014 ◽

Cited By ~ 2

Author(s):

J. Wang ◽

T. Fan ◽

J.S. Buckley ◽

J.L. Creek

Keyword(s):

Asphaltene Deposition ◽

Water Cut ◽

Deposition Tendency

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Performance of asphaltene stability predicting models in field environment and development of new stability predicting model (ANJIS)

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01407-8 ◽

2021 ◽

Author(s):

Abdus Saboor ◽

Nimra Yousaf ◽

Javed Haneef ◽

Syed Imran Ali ◽

Shaine Mohammadali Lalji

Keyword(s):

Crude Oil ◽

Colloidal Stability ◽

Stability Index ◽

Crude Oils ◽

Asphaltene Precipitation ◽

Oil Composition ◽

Stability Parameters ◽

Predicting Model ◽

Hydrocarbon Production ◽

Asphaltene Deposition

AbstractAsphaltene Precipitation is a major issue in both upstream and downstream sectors of the Petroleum Industry. This problem could occur at different locations of the hydrocarbon production system i.e., in the reservoir, wellbore, flowlines network, separation and refining facilities, and during transportation process. Asphaltene precipitation begins due to certain factors which include variation in crude oil composition, changes in pressure and temperature, and electrokinetic effects. Asphaltene deposition may offer severe technical and economic challenges to operating Exploration and Production companies with respect to losses in hydrocarbon production, facilities damages, and costly preventive and treatment solutions. Therefore, asphaltene stability monitoring in crude oils is necessary for the prevention of aggravation of problem related to the asphaltene deposition. This study will discuss the performance of eleven different stability parameters or models already developed by researchers for the monitoring of asphaltene stability in crude oils. These stability parameters include Colloidal Instability Index, Stability Index, Colloidal Stability Index, Chamkalani’s stability classifier, Jamaluddin’s method, Modified Jamaluddin’s method, Stankiewicz plot, QQA plots and SCP plots. The advantage of implementing these stability models is that they utilize less input data as compared to other conventional modeling techniques. Moreover, these stability parameters also provide quick crude oils stability outcomes than expensive experimental methods like Heithaus parameter, Toluene equivalence, spot test, and oil compatibility model. This research study will also evaluate the accuracies of stability parameters by their implementation on different stability known crude oil samples present in the published literature. The drawbacks and limitations associated with these applied stability parameters will also be presented and discussed in detail. This research found that CSI performed best as compared to other SARA based stability predicting models. However, considering the limitation of CSI and other predictors, a new predictor, namely ANJIS (Abdus, Nimra, Javed, Imran & Shaine) Asphaltene stability predicting model is proposed. ANJIS when used on oil sample of different conditions show reasonable accuracy. The study helps Petroleum companies, both upstream and downstream sector, to determine the best possible SARA based parameter and its associated risk used for the screening of asphaltene stability in crude oils.

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