Oil and gas research is dependent upon the most in-depth understanding of the primary characteristic of reservoir rock. Such characteristics include porosity, permeability, and wettability. Numerous approaches have been developed for measuring such characteristics through the use of core samples. Approaches used for studying core samples for research often include log and core analysis.
Core samples in the shape of a cylinder are removed from the well during the first phases of production. These samples are typically removed from the side of a drilled gas or oil well. The relevant sample may then be cut into multiple core plugs, a process that require custom stone cutting. Each cylindrical sample often measures approximately 3 inches in length and 1 inch in diameter. Once the core plugs are dried, they can then be measured and studied.
Core sample measurements are used for defining the permeability as well as the porosity of the reservoir rock. In addition, core samples are often used for obtaining information regarding grain density and fluid saturation. Each of these various types of measurements is beneficial to engineers, geologists, and drillers in terms of understanding well conditions and prospective productivity.
Porosity determined with the use of a tool known as a porosimeter. Porosity refers the amount of space contained within the rock that is not occupied by solids. This measurement is vital as it measures the reservoir rock’s capacity for retaining fluids, a characteristic that is important during the drilling process.
A tool known as a permeameter is used for determining the ease that fluids are able to flow through the reservoir rock. Such measurements are made in darcies. This type of measurement is made by studying the speed at which nitrogen or air is able to pass through a dried core plug. Permeability and porosity are typically associated.
Special core analysis may also involve a variety of other measurements, including the reservoir rocks’ capillary pressure. In addition, oil and gas researchers may also wish to understand the reservoir rock’s formation factor.
Conductivity is another important measurement often taken using core samples. This refers to the rock’s ability to transport an electrical current. A geological formation’s conductivity is often reliant on the direction of measurement, a state that is referred to as anisotropic. This is typically the result of numerous paper thin sheets of oil-bearing rocks becoming trapped between layers of thin shale. While the structure could be thousands of feet in thickness, it could also contain a massive amount of oil.
Due to the wealth of knowledge offered by core samples, it is vital that such samples be reserved for future reference. While the demand for oil and gas continues to increase around the world, oil and gas producers are scrambling to make the most of available fields. The preservation and study of core samples for oil and gas research offers vital insight into the nature and structure of rock layers for future production.