Views: 12 Author: pqwt Publish Time: 2022-10-07 Origin: PQWT
Encountering fracture water during drilling is a very troublesome matter. The groundwater buried in bedrock fractures is called fracture water. This kind of water movement is complex, the amount of water varies greatly, and is closely related to the development and genesis of fractures. According to the causes of bedrock fractures, the fracture water is classified as follows
(1) Weathering fracture water
Most of the groundwater distributed in the weathering fissures is laminated fissure water, because the weathering fissures are connected with each other, so the groundwater formed in a certain range is also a connected water body, with uniform permeability in horizontal direction and decreasing permeability in vertical direction with depth, mostly diving, sometimes there is also upper dead water. If the upper layer of weathering crust has poor permeability, the lower fissure has a certain pressure, weathering fissure water is mainly recharged by atmospheric precipitation, there is an obvious seasonal alternating cycle, often discharged into rivers in the form of springs.
(2)Rock-forming fissure water
When rock formations with rock fissures are exposed to the surface, they are usually given to rock fissure diving. Rock-forming fissure water in magmatic rocks is more developed. Basalt often develops columnar joints and horizontal joints. The fissures are uniform and dense, with good openness and continuity, often forming a diving aquifer with abundant water storage and smooth water conduction. Rock-forming fissure water mostly exists in the form of layers and is interconnected in a certain range. Rock with rock-forming fissures for the late stratigraphic cover, can also constitute a pressurized aquifer, under certain conditions can have a lot of pressure.
(3)Tectonic fracture water
Due to the tectonic movement of the earth's crust, the rocks form extrusion, shear and other stresses under the action of tectonic fissures, the degree of development depends on both the nature of the rock itself, but also depends on the boundary conditions and tectonic stress distribution and other factors. The development of tectonic fissures is extremely uneven, and the distribution and movement of tectonic fissure water is very complicated. When the distribution of tectonic stress is relatively uniform and the strength is sufficient, dense and uniform, interconnected open tectonic fissures are formed in the rock body, and the laminated tectonic fissure water is endowed.
When the distribution of tectonic stress is quite uneven, the distribution of open tectonic fissures in the rock body is not continuous, and they do not communicate with each other, and are endowed with vein-like tectonic fissure water. In the case of the same rock formation lithology, due to the different tectonic stress, some places may be endowed with laminated fracture water and some places may be endowed with vein-like fracture water.
On the contrary, when the tectonic stress is about the same, the degree of fracture development is different due to the change of lithology; the dense part of the open fracture is endowed with laminar fracture water, and the rest is endowed with vein fracture water. Laminar flow fracture water can be submerged or pressurized water.
When the flexible rock layer and brittle rock layer are stacked with each other, the former constitutes a water barrier with closed fissures, and the latter becomes an aquifer developing open fissures. The brittle rock layer under the flexible rock layer is given compressed water.
Veined fissure water, mostly in open fissures. Since the distribution of fractures is not continuous, the formed fractures have their own independent system, recharge sources and drainage conditions, and the water level is not consistent. There is a certain pressure, uneven distribution, small volume of water and great variation of water level. However, whether it is laminar flow fracture water or vein fracture water, the permeability tends to show anisotropy.
This is because the nature of tectonic stress in different directions is different, with some directions having better fracture opening and some directions having poor fracture opening or even closure.
To sum up, fracture water is encountered during drilling, and the existence, type, transport and enrichment of fracture water are controlled by the degree of fracture development, nature and genesis, and only by studying the changing law of fracture occurrence and development can we drill the well better. Therefore, it is recommended to use PQWT natural electric field ground water detector to detect well before drilling.
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