Certain temperature and pressure conditions in reservoirs and gas fields allow natural gas to condense to a liquid form. The condensation doesn’t happen just in reservoirs; with the correct temperature and pressure, the phenomenon can also be replicated in pipelines and surface facilities.
This liquid form of natural gas is known as natural gas condensate, a high-API gravity, low-density mix of hydrocarbon liquids. It’s important to the production of petrochemicals and plastics. In fact, in 2014, the U.S. Energy Information Administration (EIA) reported that condensates account for 8 to 16 percent of U.S. crude oil products.
Thomson Reuters reports that unlike other types of crude, condensates can be used in a wide variety of processes. They are a refinery input and an important feedstock for the petrochemical industry, especially in Asia and Europe. Seeking Alpha, a marketing research firm, also notes that it has a lower production cost than other crude products.
It can be difficult to distinguish condensates from peers, though. In fact, in 2014, Thomson Reuters said that because they are all in liquid form, there was no agreed way to tell condensates apart from ordinary crude. Experts identify condensates through API gravity.
Condensates Have High API Gravity
API gravity is a specific gravity scale created by the American Petroleum Institute (API) to measure the density of petroleum liquids. The higher the API gravity value, the lighter the material. Oil that has an API gravity of more than 30° is considered light. Those that fall between 22° and 30° are medium gravity grades, while those with less than 22° are heavy. Compared to other crude oil products, however, all condensates are light.
The matter of classifying API gravity doesn’t end there. Different agencies set varying gravity standards. One oilfield glossary says that condensates have an API gravity value from 50° to 120°, while the Oil and Gas Financial Journal, a digital industry resource, states that some have a gravity value as low as 45°. Seeking Alpha, on the other hand, says that most condensates fall between 58° and 80°.
Experts explain that the different views boil down to how the condensate would be used. API gravity values can indicate a condensate’s composition, after all.
High API gravity: Condensates that have a relatively high API gravity (the lighter ones) contain considerable amounts of natural gas liquids (NGLs). These include ethane (C2H6), propane (C3H8), and butane (C4H10). NGLs have a wide variety of uses. Consumers burn them for heat and cooking, and petroleum engineers blend them into vehicle fuel.
Low API gravity: Condensates with a relatively low API gravity value (heavier ones) look more like crude oil. This means they have a black or near-black color. They also have high concentrations of C7s (a name for hydrocarbons with seven carbon atoms) and C8s.
API gravity is not the only way to group condensates, though. Experts also classify them according to their mode of production.
Condensate Groups by Production
The Oil and Gas Financial Journal says that even though condensates are made up of similar hydrocarbon compounds, experts group them into three categories:
- Lease condensates: Oil and gas companies often recover these condensates from the wellhead at atmospheric temperatures and pressures. This means that they don’t need further processing. Lease condensates are typically a mix of different hydrocarbon compounds like pentane (C5H12) and hexane (C6H12). Some have heavier hydrocarbons, like C7s. These are clear or translucent in color.
- Plant condensates: These go through a gas processing plant (hence the name). Experts consider plant condensates a processed product. Like lease condensates, they contain large amounts of pentanes and hexanes. The Oil and Gas Financial Journal even explains that people use plant and lease condensates interchangeably in some sectors, such as heavy crude and diluent production.
- Light Naphtha: Most of these condensates surface during the first step of the refining process, which is distillation. Engineers could also extract them through condensate splitting, a process that separates the naphtha-range materials from lighter NGLs. This results in a clean naphtha product, which engineers can use as feedstock for petrochemicals production. Thus, light naphtha condensates are a refined product. They are usually made of C5s, C6s, and other heavier hydrocarbons.
Difficulty in Condensate Production
Among all types of condensates, the lighter ones are more difficult to manage because of their high vapor pressure. This means that operators have to stabilize them immediately in the field. They do this by running the condensates through a stabilizer, which is usually a big tank that vaporizes the components of a certain vapor pressure. This leaves behind a stable condensate that has a low vapor pressure and is easier to handle.
The Paraffin Problem
Apart from the vapor pressure problem we just discussed, oil and gas companies also face paraffin problems, says a 2003 study published in the Journal of the Society of Petroleum Engineers. Paraffins are hydrocarbons that follow the formula CnH2n+2 that have a linear, straight-chain structure.
Despite the number of hydrocarbons that meet the definition of paraffins, researchers have found that only paraffins larger than C20H42 are problematic. Some are rock-hard (long-chain paraffins), while others have a soft, mayonnaise-like consistency (soft-chain ones).
Regardless of form, paraffins cause problems in both the reservoir and production facilities because they tend to build up in the fractions in rocks and gas storage wells. They plug flow lines, filters and injection wells; coat solids; and even aid corrosion in facilities. As a result, they slow down processes and drive up production costs.
Thanks to various treating programs, though, engineers can control this variable. Innovations include heated, coated and fiberglass tubing; hot water circulation; various bacteria; magnets; enzymes; and steam injections.
The Next Big Thing in Crude Oil Production
The latest reports from the EIA show that U.S. condensate production will rise again after it lagged in 2015. This year, experts anticipate a solid recovery manifested by an increase in U.S. condensate production. In fact, the EIA, the International Energy Agency, and the Organization of the Petroleum Exporting Countries forecast that the United States will produce more than a thousand barrels of condensates per day.
Export restrictions lifted in late 2015 that expanded export infrastructures paved the way for improved condensate production in the country. Oilprice.com, an oil and energy news site, adds that increasing oil prices would lead to more investment, and, consequently, greater production in the oil sector.
All of these factors would combine to mean operators would be ready to respond to robust global demand, especially in Europe and Latin America. This would increase even more after the interruptions in the Forties Pipeline decreased the Asian supply. Because of the growing demand, Seeking Alpha notes that condensates would command premium prices in the international market.
Reliable Upstream Consulting
Condensate production is currently a lucrative market. But before oil and gas companies take advantage of this opportunity, they should streamline their operations. This starts by gathering sufficient and reliable information about the oil and gas reservoirs they will be working on.
Sierra Pine Resources International has decades of experience in upstream consulting services. We offer reservoir analysis, reservoir modeling and geological interpretations, among other services. We can help you make the most of exploration and production opportunities. We use innovative software to evaluate complex oil and gas plays and allow you to map out production processes accurately.
SPRI is an industry leader in upstream oil and gas consulting. We can help you make the most of your next exploration and production project.
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