How is vitrinite reflectance used as an indication of maturity of source rocks?

How is vitrinite reflectance used as an indication of maturity of source rocks?

The key attraction of vitrinite reflectance in this context is its sensitivity to temperature ranges that largely correspond to those of hydrocarbon generation (i.e. 60 to 120 °C). This means that, with a suitable calibration, vitrinite reflectance can be used as an indicator of maturity in hydrocarbon source rocks.

What is vitrinite reflectance?

Vitrinite reflectance is the proportion of incident light reflected from a polished vitrinite surface. Vitrinite is a maceral (an organic component) of coal. As vitrinite is heated in the earth during burial, it systematically changes its reflective properties.

What is maturity of coal?

The process of organic matter transformation in sedimentary basins with increasing temperature is called maturation. Other maturation parameters used for coals include (organic) carbon content, yield of volatile matter, moisture content and calorific value.

What is organic thermal maturity?

Thermal maturity is the extent of heat-driven reactions that alter the composition of organic matter (e.g., conversion of sedimentary organic matter to petroleum or cracking of oil to gas.)

What is the difference between kerogen and bitumen?

Kerogen—the organic matter that is solid and insoluble in organic solvents—is a key component of organic-rich mudstones. Kerogen is consumed during thermal maturation, whereas bitumen is an intermediary formed at low maturity from kerogen and consumed at higher maturities in formation of oil and gas.

How is coal rank measured?

The rank of a coal is determined primarily by the depth of burial and temperature to which the coal was subjected over time. With increasing temperature, peat is converted to lignite, a very soft, low-rank coal.

What is rank of coal?

Coal is classified into four main types, or ranks: anthracite, bituminous, subbituminous, and lignite. The rank of a coal deposit is determined by the amount of pressure and heat that acted on the plants over time. Anthracite contains 86%–97% carbon and generally has the highest heating value of all ranks of coal.

What is Thermal Alteration Index?

Thermal Alteration Index. TAI is a maturity indicator based on observations of the progressive change in the color of spore and pollen particles in kerogen with increasing maturity (e.g., Gutjahr, 1966; Correia, 1969; Staplin, 1969).

What does thermally mature mean?

Thermal maturity is the extent of temperature–time driven reactions, which are responsible for the conversion of sedimentary organic matter to oil and gas (Mani et al., 2015a).

What are the four types of kerogen?

Kerogen quality

Kerogen type Predominant hydrocarbon potential Amount of hydrogen
I Oil prone Abundant
II Oil and gas prone Moderate
III Gas prone Small
IV Neither (primarily composed of vitrinite) or inert material None

What is the sample maturity of vitrinite reflectance?

Based on vitrinite reflectance, the sample maturity increased from high-volatile bituminous ( Rvmax = 0.77%) to anthracite ( Rvmax = 5.02%). The process is characterized by two fast reaction phases and two slow reaction phases.

How big of a data set do I need for vitrinite reflectance?

A valid data set should consist of 10–20 vitrinite reflectance sample analyses spanning a depth range of a minimum of 4000–5000 ft (approximately 1200–1500 m). Mean reflectance values of the in situ vitrinite population from each sample should be plotted on a log scale versus depth on a linear scale.

What is the Ro random value for vitrinite?

The Ro value is generally a mean value of 50 to 100 measurements. Ro random is the value most often used in vitrinite reflectance measurements. Ro min: The minimum vitrinite reflectance is a measure of the minimum reflectance when the stage is rotated 360°, using polarized white light. Coal begins at low rank as a uniaxial, isotropic material.

Why is vitrinite reflectance important in hydrocarbon analysis?

Regional maturity mapping demonstrates some important detailes in location of ” petroleum kitchen ” and related hydrocarbon findings. So, the main task of the paper (using well data, computer models and maturity summary) is to underline the importance of vitrinite reflectance method (%Ro) and show some characteristic trends in North Bulgaria.