Coal and rock gas! Shale gas, coalbed methane, combustible ice after another unconventional new breakthrough

Recently, China Petroleum News reported a full-page report on Kexin.Exploration and exploration of coal and rock gas in Tuha oilfield represented by 1H well!

fishing for dry goods! ECF International Shale Gas Forum brings you together to see what is coal and rock gas? How is the development of coal and rock gas in China?

Coalbed methane is mainly generated from coal seams in coal-bearing rock series. It is a kind of unconventional natural gas formed in the process of coal formation and attached to coal seams. It is associated with coal resources and is attached to coal pores. The main component is methane. It is a clean, high-quality energy and chemical raw material that has been rising in recent years.

Coal and rock gas is a new type of natural gas resource between regular gas and coalbed methane, which has the characteristics of coexistence of regular reservoir and unconventional reservoir, symbiosis of free gas and adsorbed gas, complementary accumulation and orderly distribution of self-source gas and its source gas. The biggest difference between the two is that the composition of coal and gas is roughly the same as that of natural gas, while the hydrocarbon component of coalbed methane is greater than that of natural gas.98% to 99% (excluding non-hydrocarbon gas statistics), the absolute advantage, generally does not contain heavy hydrocarbons. The two mining methods are also very different. Coalbed methane is mainly adsorbed on coal rock, the main development method is drainage gas recovery, need to implement drainage to reduce the pressure to the critical desorption pressure of coal seam, to promote the adsorption of gas on the surface of coal seam pore desorption, to move to the low pressure area and finally to the wellhead. The extraction principle of coal and rock gas is the same as that of oil and gas fields, the gas flow can be obtained quickly without long-term drainage, and the reservoir pressure needs to be maintained to ensure high yield..Limited to the current level of technology and economic and technical conditions, the depth of CBM burial suitable for development is usually less.1200 meters, while the depth of economic development of coal and rock gas is mostly more than 2000 meters.

Ancient plant sedimentary evolution into coal rock

On October 28, in the core warehouse of Tuha Oilfield, the reporter saw this special piece of coal for the first time. Strictly speaking, it should be a coal rock core. In the eyes of geological researchers, this is a coal shiny core sample.

Rocks are not unfamiliar to people, but in the eyes of geological researchers, rocks are naturally produced minerals or glass aggregates with stable shapes, which are structurally combined in a certain way. Rock is one of the substances that make up the earth's crust and is the main component of the earth's lithosphere.

Chen Xuan, an enterprise technical expert in Tuha Oilfield, said that although the appearance of rocks is ever-changing, from the environment in which they are formed, that is, from the origin, rocks can be divided into three categories: sedimentary rocks, magmatic rocks and metamorphic rocks. The coal rock is a kind of sedimentary rock, mainly by organic matter and other clastic material under normal temperature and pressure after transport, deposition and petrochemical action, and finally formed.

In order to make it easier for everyone to know coal rock, Chen Xuan described a scene that took place in aboutStory from 0.15 billion years ago. At that time, the earth was in the Carboniferous, Permian and Mesozoic Triassic and Jurassic of the Paleozoic, with abundant sunshine, warm and humid climate, forests and lakes, and spore plants. In a low-lying basin, a shallow swamp is endless. Here lush plants, biodiversity, rich species. They live in harmony, one crop after another, generation after generation. Falling leaves, falling branches, fallen dead trees are immersed in the water. Due to the lack of oxygen, over time, except for a substance called lignin, other parts of the plant are eaten by microorganisms and fungi. The remaining lignin forms a thick peat, which is the most primitive coal. After a long, long time, the swamp dried up, but the river invaded from another direction, and a large amount of sand and soil were applied to the upper part of the peat, thus forming a thick delta plain. The peat is deeply buried. Then, due to the role of microorganisms and peat was further compacted, under the action of high pressure and high temperature, after millions of years, peat has undergone great changes, and its thickness is constantly thinning. The thinner the peat, the deeper the degree of metamorphism. It is in the process of compaction and thinning that a series of changes from peat, lignite, bituminous coal and anthracite are completed, and coal rock is formed. Most geologists believe that the formation of 1 meter of coal rock requires about 100 meters of plant debris. Later, the earth went through continuous plate movement and crustal activity. In some special areas, due to geological tectonic movement, some coal rock will be lifted and exposed to the ground. Under the long time of sunlight, the body of coal and rock accumulates a lot of heat. So, first smoke, then spontaneous combustion. This allows people to discover the value of coal rock, which gave birth to the history of coal mining and utilization. Under the action of geological tectonic movement, some coal and rock will be uplifted, and some coal and rock will be buried deep underground. The coal rock core seen in Tuha Oilfield is taken from Kexin 1H pilot hole well. Color black, asphalt luster, with the hand gently break, can be broken. If lit with fire, a smoke choking smell immediately into the nasal cavity.

If no one told you, you wouldn't doubt that this is a lump of coal.

The core was taken from a deep coal-rock gas risk exploration well deployed in the Tuha Basin.-- Kexin 1H Well. This well can be divided into two different structural types: the shallower part of the coal is soft and the coal structure is broken seriously; the deeper part of the coal structure is complete and the gas content of the coal is relatively high, which is more conducive to the subsequent development of coal and rock gas.

                                                                                                                            Source:ECF International Shale Gas Forum