Editor’s Note: Over the next month or so, we will be dedicating Tuesdays to a series of articles focused on ‘Unconventional Oil Exploration.’ Here’s our first article in the series:
Part 1: What Makes Oil Unconventional?
Hydrocarbon exploration is one of the most active sectors of the geological sciences. Petroleum geologists searching for oil and natural gas face a difficult task; oil and gas deposits are difficult to find, and drilling in the wrong spot wastes valuable time and resources. Furthermore, conventional oil production has peaked, while the demand for liquid fuels only increases. A strategy to combat the oil supply and demand problem is to seek out new, unconventional sources of oil. The definition of unconventional oil varies but generally includes oil shale, oil sands, ultra-deepwater oil, extra heavy oil, tight oil, and Arctic sources of oil. In its 2011 World Energy Outlook, the International Energy Agency (IEA) defines conventional and unconventional fuel sources as follows:
- Oil comprises crude, natural gas liquids, condensates and unconventional oil, but does not include biofuels.
- Crude oil makes up the bulk of the oil produced today; it is a mixture of hydrocarbons that exist in liquid phase under normal surface conditions. It includes light tight oil. It also includes condensates that are mixed-in with commercial crude oil streams.
- Natural gas liquids (NGLs) are light hydrocarbons that are contained in associated or non-associated natural gas in a hydrocarbon reservoir and are produced within a gas stream. They comprise ethane, propane, butanes, pentanes-plus and condensates.
- Condensates are light liquid hydrocarbons recovered from associated or non-associated gas reservoirs. They are composed mainly of pentanes and higher carbon number hydrocarbons. They normally have an American Petroleum Institute (API) gravity of between 50° and 85°.
- Conventional oil includes crude oil and NGLs.
- Unconventional oil includes extra-heavy oil, natural bitumen (oil sands), kerogen oil, gas-to-liquids (GTL), coal-to-liquids (CTL) and additives.
- Biofuels are liquid fuels derived from biomass, including ethanol and biodiesel.
Definitions and Challenges
Conventional and unconventional resources are also defined by how they are produced and refined. The U.S. Energy Information Association (EIA) glossary offers the following definitions:
- Unconventional oil and natural gas production: An umbrella term for oil and natural gas that is produced by means that do not meet the criteria for conventional production.
- Conventional oil and natural gas production: Crude oil and natural gas that is produced by a well drilled into a geologic formation in which the reservoir and fluid characteristics permit the oil and natural gas to readily flow to the wellbore.
Unconventional oils are heavier oils, containing more carbon and sulfur. They also contain impurities that make them more difficult to refine. Unconventional oils aren’t easy to extract compared to their more easily-accessible conventional counterparts and require specialized equipment and technology to deal with their location and/or composition. Most unconventional oils were once considered technologically and/or economically impossible to produce.
Now technologies such as hydraulic fracturing and directional drilling are opening up opportunities to access these sources, although they are still more expensive and less efficient than conventional extraction technologies. Conventional oils found in difficult locations, such as Arctic oil, tight oil, and ultra-deepwater oil, may be considered unconventional or transitional oils.
Given the challenges of unconventional oil production, oil companies are increasing spending to explore and develop previously acquired fields. Faced with declining cash flows and increasing debt levels, these companies will likely offset this spending by maximizing drilling and production efficiency. Whole rock geochemistry technique using Portable x-ray fluorescence (XRF) analyzers are emerging as a valuable way to accomplish this. Portable XRF analyzers provide rapid, real-time, on-site chemical analysis of rocks, cuttings, and cores that can be used for identifying rock composition. These characteristics can be used to infer rock properties favorable to oil and gas production so that immediate decisions can be made to optimize production or operations.
This post is the first in a series on unconventional resources. Future posts will explore the issues involved in Arctic oil production, tight oil, oil sands, and ultra-deep oil. Read Shale Gas Plays: Finding the Sweet Spot with XRF.
Read the entire series: