How is Petroleum Wax Produced?

1. Introduction of petroleum wax

The main component of petroleum wax is paraffin with a melting point of 30℃~35℃. It is mainly used as moisture-proof and waterproof packaging material for food and other commodities. It can also be used as a raw material for cosmetics. Petroleum wax is a solid hydrocarbon, and the main component is paraffin. It exists in crude oil, fractionated oil, and residual oil and has a wax-like molecular structure with a melting point of 30℃~35℃.

2. Production of petroleum wax

Crude oil contains wax and has been a headache for the petroleum industry since humans began extracting oil. Accumulation of wax in oil pipelines is a major problem. According to incomplete statistics in the late 1980s, the cost of removing wax from oil wells in the US alone was as high as 6 million dollars per year. Therefore, wax has been a long-term topic of discussion for petroleum technology workers.

Before oil fields are developed, crude oil is buried underground and exists mainly as a single-phase liquid under high-temperature and high-pressure conditions. Wax is completely dissolved in the crude oil. During the development of oil fields, when crude oil flows from the oil reservoir to the bottom of the well and is lifted to the surface along the wellbore, the wax separates from the crude oil due to a reduction in pressure and temperature, and forms crystal particles, which accumulate and adhere to the wall of the pipeline under certain conditions, known as wax deposition.

Scientists have investigated the world's discovered oil fields and found an interesting phenomenon. High-wax crude oil is rarely produced in the world's richest oil-producing areas, such as the Middle East, the Gulf of Mexico, Mexico, and Texas in the United States. However, specific regions of all continents on earth, including the third series of oil fields in China, have a high wax content in their crude oil.

Layers that produce high-wax crude oil have the following characteristics:

1. Almost all of them are sandy mud rock formations;

2. All rock formations were formed in low-salt or semi-salt environments;

3. Most of the rock formations contain coal seams, oil shale, or other high-carbonaceous sedimentary rocks;

4. Hydrocarbon-generating layers are mostly formed in lakes, bays, and delta regions near the edge of the land;

5. Wax and sulfur are incompatible with each other, that is, the layer that produces high-wax crude oil has a low sulfur content, and the layer that produces high-sulfur crude oil has a low wax content.

It is now recognized that high-wax crude oil reflects the influence of a certain type of hydrocarbon-generating material, which is mainly produced in fresh water, low-salt water bodies, and coastal sedimentary environments. For example, most oil fields in eastern China are formed in this type of sedimentary environment, so most of them have a high wax content. High-wax crude oil is almost not produced in normal marine sedimentary rocks in vast oceans. This has also been verified in low-level oil reservoirs in the Paleozoic era in northwest China.

High-wax crude oil is mainly generated in layers from the Tertiary, Cretaceous, and Carboniferous periods when land-based organisms were abundant. Therefore, it is reasonable to believe that at least some of the hydrocarbon-generating materials in the region's history are from terrestrial plant materials, which greatly increases the original wax content.