Abstract

Well-head production of petroleum can be significantly affected by flocculation, deposition, and plugging of asphaltene, paraffin/wax, and/or diamondoid inside the well. The economic implications of such a formation damage are tremendous. In this paper a comprehensive mechanism and predictive model for such compounds in the oil wells is presented. This model is based on the macromolecular theory of polydisperse polymer and colloidal solutions, kinetics of aggregation, electrokinetic transport phenomena, and phase behavior of multicomponent mixtures.

One question of interest in the oil industry is "when" and "how much" heavy organics will flocculate out under certain conditions. Since a petroleum crude generally consists of a mixture of hydrocarbons and heavy organics it may be necessary to look at this problem from a more fundamental point of view than it has been the practice in the past. In this paper the author presents the cause and effect mechanisms of such depositions and introduces mathematical models to be used for preventive measures in various cases of petroleum production, transportation, and processing.

With the application of the proposed models a number of predictive case studies are made. It is shown that with proper plannings in the production scheme, consideration of the characteristics of the producing petroleum injection fluid, well casing, and the reservoir it is possible to choose a formation-damage-free production scheme.

Introduction

The need for understanding the nature of heavy organics (asphaltenes, asphalts, bitumens, resins, diamondoids) present in crude oil and their role in the production and processing of petroleum is well recognized around the world as manifested by the extensive related research and experimental activities underway at various research centers1–4. It appears certain that the trend in the oil industry, worldwide, will be and has already started towards the exploration, drilling, production and processing of lower quality crude and use of secondary and tertiary methods for recovering more oil from existing reservoirs. Gas injection, re-injection and miscible flooding of oil reservoirs is an economically viable technique. One of the most common problems in such recovery processes is the possibility of poor channeling and viscous fingering. This may be caused by the large difference between the mobilities of the displacing and displaced fluids. Blending or introduction of a miscible fluid in petroleum, in general, will produce a number of alterations in its flow and phase behavior as well as the reservoir rock and conduit characteristics. One such alteration is the heavy organic precipitation, which ultimately affects the productivity of a reservoir in the course of oil production or flow rate of the oil in a conduit (well or pipeline). In most such circumstances heavy organic precipitation may result in plugging or wettability reversal in the conduit and reservoir5–8.

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