Describe the process of conventional oil extraction, including primary production, secondary production, and tertiary production.

In primary production, the natural pressure of the oil reservoir drives oil to the surface. This pressure can come from the expansion of gas released from the oil, the overlying pressure of water in the surrounding rock layers, or the initial pressure inherent in the rock formation. During primary production, oil is typically extracted using vertical drilling, with pumps placed directly above the wellbore to draw the oil upwards. Primary production methods are the easiest and least expensive, but they only recover about 10% to 30% of the oil in the reservoir.

Secondary production methods are used when primary production methods can no longer maintain sufficient pressure in the oil reservoir to drive the oil to the surface. In this phase, engineers inject water or natural gas into the reservoir to increase the pressure and push the oil towards the production wells. This process, known as waterflooding or gas injection, can recover an additional 20% to 40% of the oil in the reservoir. Secondary production methods are more expensive and require additional infrastructure but help to extract a greater portion of the oil resource.

Tertiary production, also known as Enhanced Oil Recovery (EOR), is employed when secondary production methods are no longer effective. This phase consists of injecting chemicals, gases, or heat into the reservoir to alter the properties of the oil and make it easier to flow to the surface. There are three main types of EOR: chemical injection (using surfactants or polymers), gas injection (using carbon dioxide or nitrogen), and thermal recovery (using steam or hot water). Tertiary production is the most technically advanced and expensive method of oil extraction but can recover an additional 5% to 15% of the oil in the reservoir. In conclusion, the conventional oil extraction process follows three main phases: primary production, secondary production, and tertiary production. By applying these different methods sequentially, the industry can maximize oil recovery from a given reservoir while considering costs and technical challenges.