What Is a Directional Well?

A directional well is a drilling term that refers to a well that is drilled in accordance with a pre-designed orbit with well deflection and azimuth changes.

Directional well technology is one of the most advanced drilling technologies in the field of petroleum exploration and development in the world today. It is a drilling process that uses special downhole tools, measuring instruments and process technology to effectively control the trajectory of the wellbore and allow the drill bit to drill down to a predetermined target underground in a specific direction. technology. The use of directional well technology can make economic and effective development of oil and gas resources with limited surface and underground conditions, can greatly increase oil and gas production and reduce drilling costs, is conducive to the protection of the natural environment, and has significant economic and social benefits. A directional well is a well designed along the well

Directional drilling has become the main method for the development of onshore and offshore oil fields. Directional wells have been widely used in petroleum exploration and development. In areas where it is difficult to establish a well site and install drilling equipment for drilling on the ground, the only way to explore and develop underground oil and gas resources is to drill directional wells near the area. For exploration and development of petroleum in the waters of the ocean or lake, it is best to establish a fixed platform, or use a mobile drilling platform, or drill directional wells and cluster directional wells from the shore. When there are complex formations that are difficult to penetrate in the formations that are drilled to reach the oil and gas formations, these complex formations can be bypassed with directional wells, which are called barrier directional wells. In the case of severe accidents such as broken drilling tools, stuck drills and blowout fires, the use of side drilling and rescue wells is an effective method to deal with such accidents. In recent years, the emergence and development of various types of horizontal wells, extended reach wells, multi-branched wells, and two-dimensional and three-dimensional multi-target wells have pushed the application of directional wells to optimize reservoir development plans, increase production, and increase yield. Range. In addition, in the field of non-petroleum exploration and development, such as the exploration and exploitation of coalbed methane, brine, geothermal, natural gas hydrate, solid minerals, etc., as well as sampling of underground nuclear tests, directional drilling technology also has a very wide range of applications. ^[2]

With the development of directional drilling technology, there are more and more types of directional wells. ^[3]

(1) The tight supply situation of oil and gas resources and the problems encountered in oil and gas production currently provide a broad space for development of directional drilling technology.

At present, the main problems encountered in oil and gas development can be summarized into three aspects: first, how to increase the recovery ratio of the old and new oilfields, how to optimize the well deployment plan of the new oilfield, how to open up more remaining oil in the old oilfield, and secondly, offshore How to develop oilfields can reduce costs and increase production. Third, how to develop more special reservoirs such as low-permeability reservoirs, heavy oil reservoirs, fractured reservoirs, thin reservoirs, and marginal reservoirs. Directional drilling technology is very promising in solving these problems.

(2) The accuracy of the target and the trajectory coincidence rate will be greatly improved. The track design curve, trajectory control mode and trajectory calculation method will tend to be highly unified.

The development of tilting tools, measurement-while-drilling, and orientation-while-drilling technologies has greatly improved the accuracy of the harrow and the trajectory coincidence rate. In the future development, the trajectory coincidence rate will definitely be listed as an important assessment item of the directional well trajectory quality. The high trajectory coincidence rate means that the trajectory is optimized and is conducive to oil production operations. There are currently four types of track design curves, but there is only one "constant device angle mode" in the trajectory control mode. In theory, only constant device angle curves can be drilled, and the other three tracks with curved designs cannot be accurately drilled. The further improvement of the trajectory coincidence rate will inevitably require a high degree of uniformity between the trajectory control mode and the trajectory design curve.

(3) The focus of future directional drilling will be shifted from the target well section to the target zone section. The shift of work focus may lead to new types of directional wells.

The current directional drilling work is mainly focused on the well section before the target. The focus is on not only hitting fast and well, but also hitting the target accurately. Except for the horizontal wells, the well sections in the target area are relatively short, without much workload and difficulty. However, from the perspective of development trends, the emergence of horizontal wells, multi-branch wells, and three-dimensional multi-target wells means that after entering the harrow area, the extension, development, and layout of the trajectory in the target area have received more and more attention. Especially the three-dimensional multi-target wells are called "Designer Wells" in foreign countries, and it is not entirely appropriate to translate them into "three-dimensional multi-target wells" according to their trajectory characteristics in China. Because the important design ideas embodied in "Designer Wells" have not been translated. In fact, the emergence of "Designer Wells" indicates the importance of target wells in reservoir development. Designers will consider the extension, change, and development of the trajectory in the target zone to optimize the development plan and increase production. And recovery factor. The development of a new reservoir using directional wells with multiple trajectory types to optimize development plans has already begun to emerge in the paper (SPE 92085). Following this trend, a new type of directional well that is fully adapted to the designer's wishes is likely to emerge in the future.

(4) The development of drilling-while-drilling and steer-drilling technologies will eventually be directed to the direction of enhanced oil recovery. There may be residual oil-guided drilling technologies.

At present, various drilling-while-drilling technologies (exhausting-while-drilling, logging-while-drilling, formation-drilling-while-drilling, seismic-while-drilling, etc.) and various steering (trajectory steering, geosteering, etc.) drilling technologies that are currently being developed greatly The trajectory control ability is reduced, and on the other hand, the real-time acquisition of downhole information is greatly increased, which greatly improves the transparency of the underground. In view of the huge potential and attractiveness of the remaining oil extraction in the old oilfields, the drilling-while-drilling and pilot-drilling technology will inevitably work towards the development of the remaining oil. Using a certain principle, the drill bit is guided to drill in the direction and direction of the remaining oil accumulation. Advance. ^[4]