Chemical additives play an important role in oil production. Chemicals are used to enhance oil production, control corrosion, prevent wax or paraffin deposition, enhance the flow characteristics of the crude oils, aid in water separation, etc. However, oil field chemicals are often suspected of causing diverse problems in refining operations, including corrosion, fouling, desalting upsets, and loss of catalyst activity. One recent example is the appearance of "rogue chlorides" in certain crudes, which has led to severe corrosion problems in crude distillation units and naphtha hydrotreaters. This paper presents a review of the nature and function of chemical additives that are commonly used in oil production, and discusses examples of the type of problems encountered in refining that are caused by some of these chemicals. A clear understanding of the impact of oil field chemicals on refinery operations is critical to both refiners and producers, to avoid these problems and prevent the erosion of value of the crude. Better communications between producers and refiners is a first step to resolve these problems.
Oil Field Chemicals (OFC) are used for various purposes in oil production, including corrosion control, management of hydrate formation, prevention of wax or paraffin deposition, enhancement of the flow characteristics of heavy crudes, oil dehydration, water de-oiling and well stimulation. In particular, economic oil production from ever deeper offshore reservoirs depends heavily on the use of chemicals to maintain adequate flow from the well bore to the separation facilities, by preventing mineral scales and wax deposits from plugging the connecting flowlines. Other chemicals are used to assist in the various techniques that renew the flow of crude oil from older fields (steam, carbon dioxide, polymer flooding, etc.). Many different chemicals are used in the oil field, and their volume seems to be increasing with production from more challenging environments, as shown in Figure 1 (1). The world market for OFC reached 5 billion $ in 2000 and is expected to grow further (2).
FIGURE 1 - Trend in the use of production chemicals in fields operated by a major European oil company (1)
However, some of these chemicals may also cause processing problems in refineries. The most common problems that are often associated with the presence of OFC in the crude are: desalting upsets, corrosion in the overhead system of crude distillation units and in hydrotreaters, fouling of catalysts, foaming of amine treating units, and fouling of heat exchangers. In many cases the actual relationship between OFC and refinery upsets is hard to prove, as other operational or crude oil factors may account for the observed problems. But the perception that a crude oil is "troublesome" can nevertheless have a negative effect on its value. An understanding of the impact of OFC on refining operations is therefore of critical importance not only to refiners, but also to producers since both are interested in minimizing any negative effect of these chemicals on the operation of the refinery.
The impact of OFC on refinery operations, particularly corrosion, has been studied on previous occasions. However, an update of this topic seems timely because a series of incidents related in part to the presence of organic chlorides in the crude has resulted in a renewed awareness in the refining industry that some otherwise "unexplained" processing problems may be caused by OFC. Whether this awareness reflects an actual increase in the severity or frequency of these problems is more difficult to assess, because a systematic evaluation of these issues has not been undertaken, and most of the evid
