Rock and fluid properties will determine how much oil and natural gas can be recovered from a reservoir. After an exploratory well has been drilled, it is evaluated to determine if there is enough oil and natural gas in the reservoir to make it economically feasible to initiate recovery operations.
Drill Cuttings and Core Samples - As the drilling mud is brought to the surface, it is run through a sieve to removed the drill cuttings (pulverized rock) before the mud is recycled down into the well. Small pieces of rock are selected for microscopic analysis to determine the type of rock being drilled, how porous it is, and whether oil is present. The drilling mud also is analyzed with sensors to see if trace amounts of oil or natural gas are present — an indication of a possible accumulation at depth. In the past, rock cuttings were the principal source of well information.
Well Logging - A special bit can be used to cut a cylindrical piece of rock that can be brought to the surface for analysis. The core is sent to a laboratory where the exact porosity and permeability can be determined. This gives a good indication of how well oil or natural gas would flow through the rock. Fluid samples can be taken and analyzed to determine the amount and type of hydrocarbon present in the rock.
Wells are completed for production if the value of the recoverable oil and/or natural gas is greater than the cost of drilling and producing them and delivering them to market. If not, the well is plugged In accordance with industry standards and federal or state requirements (depending on the location) and the site is restored.»next