What are the types of carbonate rocks, carbonate rock types and characteristics

Carbonate reservoirs occupy an extremely important position in the world's oil and gas production. According to statistics, the oil and gas production of the world's carbonate reservoirs accounts for about 60% of the world's total oil and gas production. The Middle East accounts for about 2 3 percent of the world's oil production, with 80 percent of the oil-bearing layers being carbonate rocks.

Carbonate rock production in North America accounts for about 1 2 percent of the entire oil production in North America. In the bio-reef oil fields of the former Soviet Union, oil reserves accounted for about 31% of the entire carbonate rock reserves, and natural gas accounted for 29%. The results show that the world's carbonate reservoirs can be summarized into six types:

1) Limestone and dolomite beneath the unconformity.

Pore type: inner mold pores, pores, cracks enlarged by dissolution, breccia pores.

Genesis: Near-surface dolomitization or dissolution, fractures and brecciation.

Representative examples: Anadarko Basin, Williston Basin, Permian Basin in the United States.

2) Dolomites of the supratidal zone with subtidal zones.

Pore types: intergranular pores, intergranular pores, internal mold pores, pores.

Cause: Dolomite formed by the mixed zone of seawater and freshwater under the freshwater lens on the surface of the reef outcropping; Concentrate the brine back.

dolomite formed from carbonate deposits; dolomite formed by the evaporation of concentrated brine and the upward elevation of metasomatic carbonate deposits; Dolomite formed by carbonate deposits buried deep in the ground.

Representative examples: Dolomite reservoirs in the Silurian Niagara Reef in the Michigan Basin, USA; Dolomite reservoirs of the Ordovician Red River Formation in the Williston Basin.

3) Oolitic grains, clumpy shoals.

Pore type: intergranular pores, internal mold pores, pores.

Cause: Primary intergranular pores or internal mold pores formed by the dissolution of particles.

Representative examples: Saudi Arabia, UAE Upper Jurassic Arab Group, Qatar Upper Jurassic Arab Group.

4) Reefs (including reef-related reservoirs).

Pore type: the pores of the growth skeleton and the pores enlarged by dissolution, especially the pores formed by the leaching of fresh water on the outcropping surface of the reef.

Genesis: primitive pores between skeletons, pores between pre-reef breccias.

Representative examples: Carboniferous-Permian horseshoe reefs in the Permian Basin of the United States, and carbonate facies of reef and platform facies in the Urals region of Russia.

5) Micropores in argillite limestone and chalk.

Pore type: Intergranular pores.

Genesis: Porosity between microcalcite formed during the stable period of stucco sedimentation, suggesting that the original stucco was dominated by calcite.

Case in point: North Sea oil fields in the Early Cretaceous Samama group of the United Arab Emirates, such as the Ekofisk field.

6) Micro-cracks within argillite limestone.

Pore types: cracks, microcracks.

Cause: Tensile crack caused by extrusion force.

Representative example: Tamaulipas Formation, Cretaceous Basin Facies, Mexico.

Rock production accounts for about 1 2 percent of the entire oil production in North America. In the bio-reef oil fields of the former Soviet Union, oil reserves accounted for about 31% of the entire carbonate rock reserves, and natural gas accounted for 29%.

There are limestone and dolomite argillite limestones, which are mainly composed of aragonite, calcite, dolomite, magnesite, siderite, rhodochrosite. Modern calcium carbonate deposits are mainly composed of high-magnesium calcite, aragonite, and a small amount of low-magnesium calcite. Classification:

Classification of composition, using the tritex of dolomite, calcite and non-carbonate minerals**, carbonate rocks are divided into 8 types (see figure). Carbonate rocks.

Classification of structural genesis can be divided into bright crystal anomalous chemical rocks, argillaceous anomalous chemical rocks, argillaceous rocks (normal chemical rocks), in-situ reef limestone, metasomatic dolomite and other types.

Type: limestone, marble.

Characteristics: The limestone is relatively loose, and the marble is hard and dense. Carbonate rocks are susceptible to erosion by flowing water, forming calcareous precipitates. The reaction with acids is more violent, producing carbon dioxide and soluble calcium salts.

There are two types of carbonate rocks: sedimentary rocks and metamorphic rocks. Limestone and dolomite belong to sedimentary rocks, marble.

It is a metamorphic rock. The limestone is relatively loose, easy to dissolve to form the Kashgar landform, the dolomite has a strong anti-erosion effect, the marble is harder, the color is beautiful, and more carved materials, such as white marble railings and lions.

There are mainly two types of "limestone and dolomite", the main component of limestone is "calcite", and the main component of dolomite is "dolomite". Carbonate rocks are mainly found in marine sedimentary environments. The genesis of dolomite is mainly "magnesium ions replacing calcium ions" at the microscopic level, and "dolomite metasomatism calcite formation" at the macro level.

At present, carbonate reservoirs are also an important reservoir research type. Hope it helps.

Carbonate rocks are mainly limestone and dolomite.

The main component of limestone is calcite (caCO3) and the latter is dolomite (camg(cao3)2), compared with dolomite, limestone has low porosity, and it bubbles with hydrochloric acid, while dolomite has no reaction!

Most of them belong to the category of sedimentary rocks, and rock classification refers to the geological body formed by the collection of rock-forming minerals according to a certain structure to become rocks, which can be divided into three categories according to their genesis: magmatic rocks, sedimentary rocks and metamorphic rocks.

Carbonate rocks belong to the sedimentary rocks of the three main groups of rocks.

Carbonate rocks

Sedimentary rocks are crystallized and deposited from dissolved carbonate substances in the water body to form rocks. It mainly includes limestone and dolomite, as well as a variety of transitional types such as gray dolomite caves.

The carbon-nano slag salt rocks are prone to karst and form various karst landforms, and the Guilin landscape is a typical example.

Carbonatite

Magmatic rocks, a type of magma formed mainly by the condensation of magma rich in carbonate minerals.

In Tanzania, Africa, the "Ordoin Yoliangai" volcano is currently the only known modern eruption of carbonated magma

Sedimentary rocks are crystallized and precipitated by dissolved carbonate substances in the water body, and deposited to form the rock Zaozhou. It mainly includes limestone and dolomite, as well as various transitional types such as gray dolomite.

Carbonate rocks are prone to karst, forming various karst landforms, and Guilin's landscape is a typical example.

Carbonatite

Magmatic rocks, a type of rock formed mainly by the condensation of magma benches rich in carbonate minerals.

In Tanzania, Africa, the "Ordoin Yoliangai" volcano is currently the only known modern eruption of carbonated magma

The peak forest in Zhangjiajie is caused by the action of early tectonic movement of quartz sandstone, forming staggered vertical and horizontal joint fractures, a kind of tiny mutual non-moving fractures. Then weathering and caving occurred along the joint joints, and finally formed the peak forest seen today - the quartz sandstone peak forest landform.