Development and Application of the Downhole Drilling String Shock-Absorption and Hydraulic Supercharging Device

Hindawi Publishing Corporation Shock and Vibration Volume 2016, Article ID 2041671, 10 pages http://dx.doi.org/10.1155/2016/2041671 Research Article Development and Application of the Downhole Drilling String Shock-Absorption and Hydraulic Supercharging Device Yongwang Liu, Zhichuan Guan, Hongning Zhang, and Bo Zhang China University of Petroleum, Qingdao 266580, China Correspondence should be addressed to Yongwang Liu; Received 29 February 2016; Revised 7 August 2016; Accepted 18 August 2016 Academic Editor: Salvatore Strano Copyright © 2016 Yongwang Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. It is a hot topic for deep/ultradeep wells to improve rock-breaking efficiency and drilling speed by available downhole energy. Based on different downhole energies and working conditions, specialized plunger pump is proposed to convert longitudinal vibration of drilling string into rock-breaking energy. Technical design is developed to generate high-pressure water jet. And then a simulation model is built to verify feasibility of the technical design. Through simulation, the influence law of key factors is obtained. On this basis, this device is tested in several wells. The result indicates this device can increase drilling speed as much as 136%. Meanwhile the harmful vibration can be absorbed. The energy from drilling string vibration is of high frequency and increases as well depth and formation anisotropy increase. By reducing adverse vibration, this device is able to increase the drilling speed and the service life also meets the demand of field application. The longest working time lasts for more than 130 hours. The performance of this device demonstrates great application prospect in deep/ultradeep resources exploration. To provide more equipment support for deep/ultradeep wells, more effort should be put into fundamental study on downhole drill string vibration and related equipment. 1. Introduction As more and more effort is put into deep petroleum resources exploration, deep/ultradeep wells are drilled in both new and old oil and gas fields [1–5]. Moreover, the well depth becomes deeper and deeper. However, the slow drilling speed limits the drilling of deep/ultradeep wells. To overcome this challenge, researchers have developed a number of tools to increase drilling speed, including downhole motor device, rotary percussion drilling tools, downhole hydraulic pulsed cavitation jet generators, and downhole torsional drilling tools [6–17]. Although these tools differ in working mechanisms, their energies are all from drilling fluid. Field practices proved that drilling fluid pressure loss increases as the well depth increases. In extreme cases, drilling fluid is only able to carry cuttings in ultradeep wells [18–20]. It is obvious that tools based on drilling fluid energy would not achieve good performance in such wells. Therefore it is essential and important to find new downhole energy to develop new speedup techniques and related equipment. Research and field practice prove that increasing water jet pressure of drilling bit can improve drilling speed greatly [21–29]. So, two methods are proposed. First is to supercharge drilling fluid on ground. Second is downhole supercharging [30–33]. Supercharging on ground is complex and expensive. Therefore it is not widely applied. Downhole supercharging does not change current drilling technology and equipment. A supercharging device is installed above drilling bit. Part of the drilling fluid can be supercharged to over 100 MPa. Such high-pressure can help to break rock. The available downhole supercharging devices are powered by drilling fluid. These devices transport the whole drilling fluid energy to part of the drilling fluid. Limited by this mechanism, these devices need complex hydraulic transformation system. However, the downhole space is restricted and condition is not so good; complex hydraulic transformation system can hardly work. So up to now, there is still no downhole supercharging device that can increase jet pressure to 100 MPa when the drilling technology and equipment do not change although much effort has been put [34–39]. This paper analyzes the downhole energy resources and proposes specialized plunger pump to convert longitudinal vibration of drilling string into rock-breaking energy. Technical design is developed to generate high-pressure water jet. 2 2. Available Downhole Energies The characteristics of different downhole energies are important for finding an optimal downhole energy to propel device. Currently, available downhole energies include energy carried by downhole media and downhole natural energy. 2.1. Energy Transmitted by Cable. Cable is one of the most effective methods to carry energy into well. Downhole tools based on this energy include downhole motor drilling bit, downhole motor rotary percussion drilling bit, and laser drilling tools. Energy transmitted by cable has three advantages. First, the energy is not subjected to well depth or drilling fluid. Second, the downhole tool can be controlled from surface by adjusting energy. Third energy is stable and without limitation on the working hours. However, the failure probability will increase when this energy is applied. Also, the relatively high cost makes it hard to apply. 2.2. Downhole Battery. Downhole battery is a portable energy. Tools based on portable energy include rotary steerable drilling systems and new downhole motor rotary percussion drilling tool. This energy is mostly used to change the drilling fluid distribution and speed and eventually propel the downhole tool. This energy is convenient and can provide relatively stable energy, but it has some shortfalls. First, the energy provided is too small to provide for large-power downhole tools. Second, its limited working time prevents it from working long hours in the well. Third, it is sensitive to the working conditions and hardly able to work regularly when encountering high temperature formations. 2.3. Energy from Drilling Fluid. This method is one of the most widely used methods. Many tools have been developed upon this energy, including downhole screw drilling tool, turbine drilling tool, hydraulic rotary percussion drilling tool, and torsional impact drilling tool. However, the drawbacks can also not be ignored while it has many advantages. The main drawback is the significant reduction of available energy as well depth increases. Figure 1 shows the pipe pressure loss varies with the well depth under different fluid capacities. As shown in Figure 1, the pipe circulating pressure loss increases linearly with the well depth. So it is also restricted to increase the deep well drilling speed by using the drilling fluid energy. 2.4. Geothermal Energy. The geothermal energy has been exploit (...truncated)