Oil and Gas Terms Beginning with “M” — Page 3

A well-servicing unit for slickline, wireline or coiled tubing operations that is equipped with a mast rather than a crane or gin pole. The mast provides a means of lifting and stabilizing tools, and running… Read more →

A valve located on the Christmas tree that controls all flow from the wellbore. A correctly functioning master valve is so important that two master valves are fitted to most Christmas trees. The upper master valve is… Read more →

What Is Material Balance in Reservoir Engineering? Material balance is a fundamental reservoir engineering method based on the conservation of mass: the volume of fluids produced from a reservoir must equal the… Read more →

What Is the Material Balance Equation? The material balance equation (MBE) is the fundamental reservoir engineering tool that quantifies the relationship between cumulative production, fluid expansion, water influx, and… Read more →

Mathematical relationship between the densities and the corresponding volumes of mixtures of liquid-solid slurries and clear fluid blends, such as drilling muds and completion fluids. Assumptions are: (1) masses and… Read more →

The finer grained, interstitial particles that lie between larger particles or in which larger particles are embedded in sedimentary rocks such as sandstones and conglomerates. Read more →

The treatment of a reservoirformation with a stimulation fluid containing a reactive acid. In sandstone formations, the acid reacts with the soluble substances in the formation matrix to enlarge the pore spaces. In… Read more →

What Is Matrix Stimulation? Matrix stimulation is a well intervention technique that injects treating fluids into a reservoir at pressures below the formation parting pressure, dissolving damage, removing pore-plugging… Read more →

The process of a sourcerock becoming capable of generating oil or gas when exposed to appropriate pressures and temperatures. As a source rock begins to mature, it generates hydrocarbons. As an oil-prone source rock… Read more →

The state of a source rock with respect to its ability to generate oil or gas. As a source rock begins to mature, it generates gas. As an oil-prone source rock matures, the generation of heavy oils is succeeded by… Read more →

A widespread marine flooding surface that separates the underlying transgressivesystems tract from the overlying highstand systems tract. The surface also marks the deepest water facies within a sequence. The maximum… Read more →

The highest temperature recorded on a loggingrun. It is usually taken to be the bottomhole temperature for use in log interpretation. However, on the first logging run or runs after circulation, the mud may be hottest… Read more →

The surface-pump pressure limit below which a treatment should be performed. The maximum treating pressure is determined to avoid fracturing the formation or damaging completion components. The maximum treating pressure… Read more →

(noun) A statistical measure of central tendency, calculated as the arithmetic average of a set of values. In petroleum engineering, the mean is widely used in reservoir characterisation to summarise distributions of… Read more →

The point on a logging tool at which it is considered the logging measurement is made. It is the center of the vertical response, or in some cases an alternative, more suitable point. For measurements that must be… Read more →

The length of the wellbore, as if determined by a measuring stick. This measurement differs from the true vertical depth of the well in all but vertical wells. Since the wellbore cannot be physically measured from end… Read more →

Measurements made by measurements-while-drilling (MWD) tools subsequent to the initial bitrun. MWD logs are recorded while drilling the well. However, these tools can also record logs at later times when the drillstring… Read more →

The difference between the true value and that which is reported from a measurement. Read more →

The range of values for a quantity for which the error of a measuring instrument is intended to lie within specified limits. Within this range, the measurement has a well-defined accuracy or applicability. Outside the… Read more →

What Is Measurement While Drilling (MWD)? Measurement while drilling (MWD) describes the downhole instrumentation and surface telemetry system that transmits real-time wellbore survey data, including inclination,… Read more →

The evaluation of physical properties, usually including pressure, temperature and wellbore trajectory in three-dimensional space, while extending a wellbore. MWD is now standard practice in offshore directional wells,… Read more →

A calibrated tank that automatically measures the liquid volume passing through it. Measuring tanks are also called metering tanks or dump tanks. Read more →

The use of mechanical devices, such as ball sealers, packers and straddle-packer assemblies, to divert reservoir treatments to the target zone. Ball sealers and solid-particle diverting agents incorporated into the… Read more →

A type of jar that incorporates a mechanical trip or firing mechanism that activates only when the necessary tension or compression has been applied to the running string. In slickline operations, the term is often used… Read more →

The reduction in permeability in the near-wellbore area resulting from mechanical factors such as the displacement of debris that plugs the perforations or formationmatrix. Such damage in the near-wellbore area can have… Read more →

The limiting or prevention of motion of the drillstring by anything other than differential pressure sticking. Mechanical sticking can be caused by junk in the hole, wellbore geometry anomalies, cement, keyseats or a… Read more →

A mathematical measure of the centrality of a data set. If the data set is arranged in the order of the values, the median is the value of the central data point for an odd number of data, or the mean of the two central… Read more →

Referring to any particle in the size range 74 to 250 microns. Read more →

A particular type of induction log designed to read an intermediate distance into the formation while maintaining good vertical resolution. The medium-induction array of eight coils (IM) is produced by three… Read more →

The electromagnetic force generated across an ion-selective membrane when solutions on either side of the membrane have different salinities. Shales and clays are cationic membranes, since they allow the passage of… Read more →