Horizontal directional drilling technology is an underground construction technology, and the geological condition of the stratum has a great influence on the difficulty of directional drilling construction. Since the 1980s, due to the research and development of precise positioning systems of directional drilling and the continuous improvement of directional drilling system level, and after the practice of engineering construction, the adaptability of directional drilling technology in each stratum has been gradually expanded.
Difficulty Analysis of Crossing Complex Geology
◆Difficulties in rock stratum traversal
(1) Due to the hard texture, in the process of directional drilling, there will be large particles of rock debris, due to its high density, the mud is not easy to carry out of the hole, which will cause problems for the subsequent back dragging work.
(2) The rock is hard, the drill bit for a guided hole or reaming construction, the drilling tool wear is very strong, the heat generated by the drill bit is large and easily leads to burning the drill, at the same time, the drilling speed is slow, the artificial machinery, mud and other aspects of the consumption of the consequent substantial increase in the increase in construction costs.
◆Difficulties in crossing pebble gravel strata
(1) Due to the pebble gravel particles of different sizes, the guiding drill bit is particularly easy to deviate from the designed left and right directions.
(2) During reaming, a large amount of pebbles existed in the hole, which increased the friction resistance and caused serious wear to the drilling tools. To effectively carry it out of the hole, it is necessary to increase the mud pump pressure and flow rate, but this will lead to the loss of the cement around the pebbles on the hole wall with the scouring of the mud, making the hole wall stable.
(3) If the proportion of pebbles and gravel is high, the corresponding hardness of this section of the stratum will become high, which will lead to directional drilling guide holes and reaming is more difficult to drill: in the case of a low proportion of pebbles and gravel, if the degree of cementation is not high, the directional drilling wall molding will be very poor, prone to the occurrence of the hole wall collapse accidents, resulting in the failure of directional drilling project. At the same time, due to the presence of pebble gravel, during construction, it is easy to large chunks, which is not conducive to mud carrying out of the hole.
(4) Due to the presence of pebble gravel, the formation is more permeable and prone to mud bubbling phenomenon, there is a greater risk of environmental protection. In case of serious mud loss, the hole-washing operation must be repeated, which is not only inefficient but also causes an increase in all construction costs.
◆Difficulties in traversing sandy soil strata
The biggest difficulty in directional drilling operations in sandy soil layers is the formation of directional drilling holes. As the sandy soil layer is soft and easy to lose, it is difficult to form the hole of directional drilling, so stabilizing the hole wall is the key to solving the problem of directional drilling construction in the sandy soil layer. Nowadays, the way to stabilize the hole wall in directional drilling construction is to use the appropriate proportion of mud. But in the sand layer, to stabilize the hole wall, the viscosity of mud, in the hole wall forms a thicker mud skin, but the mud skin directly increases the pipeline back drag force, back drag the longer the greater the resistance and leads to failure of directional drilling for the shallow sand layer, the use of casing to cope with the sand layer is more effective. However, through the sand layer longer pipeline crossing project is not good to realize.
◆Difficulties in Karst terrain crossing
Due to the special geological conditions of karst terrain, the rock layer, pebble layer, and sand layer mentioned above may exist, so the difficulties of crossing each layer mentioned above may appear or appear at the same time.
In addition, due to the result of the water solution, there are cavities and fissures in the rock layer, during the construction of directional drilling, it is easy for the drill bit to hang in the air and lead to deviation of drilling, falling of drill bit, jamming of drill bit and other phenomena. If the fissures extend in series, there will be a large amount of mud loss, resulting in no return of slurry, so the risk of directional drilling construction in karst landscapes is extremely high.
Roller Reamer
◆Advantages and disadvantages
Higher structural strength, easy to replace the roller disk when it is worn out, the disadvantage is that it is self-important, easy to form elliptical holes when reaming in a soft rock layer; when replacing the roller disk in the hole, it is not easy for the reamer to exit; at the same time, because of its structural characteristics, especially the reamer with a diameter of more than 30 requires a large torque of the drilling rig; it is better not to exceed 500m in length through the rock layer.
◆Applicability
Suitable for soft rock and medium-hard rock.
If you need to order roller reamers, we will provide you with solutions, please contact us at info@vigorpetroleum.com.
