Tuesday, September 24, 2019

Tight Oil Chapter 2

The challenges associated with the production of crude oil from shale formation are a function of the compositional complexity and the varied geological formations where they are found. These oils are light, but they often contain high proportions of waxy constituents and, for the most part, reside in oil-wet formations. These phenomena create some of the predominant difficulties associated with crude oil extraction from the shale formations and include (1) scale formation, (2) salt deposition, (3) paraffin wax deposits, (4) destabilized asphaltene constituents, (5) equipment corrosion, and (6) bacteria growth. Thus, multicomponent chemical additives are added to the stimulation fluid to control these problems. 

 While crude oil from tight shale formations is characterized by a low content of asphaltene constituents and low-sulfur content, there can be a significant proportion of wax constituents in the oil. These constituents may exhibit a broad distribution of the molecular weight. For example, paraffin carbon chains of C10-C60 have been found and some tight crude oil may even have hydrocarbon carbon chains (wax) up to C72. While this may be a relief from recovery of high-asphaltene heavy oils, the joy is short-lived and the deposition of waxy constituents can cause as many problems as asphaltene incompatibility. To control deposition and plugging in formations due to paraffin, a variety of wax dispersants are available for use. In upstream applications, the paraffin wax dispersants are applied as part of multifunctional additive packages where, for convenience, asphaltene stability and corrosion control can also be addressed simultaneously. 

 Scale deposits of calcite , carbonates, and silicates must also be controlled during production or plugging problem arise. A wide range of scale additivies is available. These additives can be highly effective when selected appropriately. Depending the nature of the well and the operational conditions, a specific chemistry is recommended or blends of products are used to address scale deposition.

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