The adjustable elbow joint refers to an underground steering tool whose bending angle and direction can be adjusted in real time according to needs. It is one of the key technologies in directional drilling and is also the key to the discussion in this chapter. The core technology of the simultaneous drilling program with centering and deflection correction. At home and abroad, research on adjustable joints has paid more attention. Many related products have been introduced to the market abroad. Generally speaking, adjustable bending joints can be divided into four categories according to their working methods: static offset push bit working method , the working mode of static offset pointing drill bit, the working mode of dynamic offset pushing drill bit, and the working mode of dynamic offset pointing drill bit, as shown in Figure 6.1.
Figure 6.1 Classification of guide tools (adjustable bending joints)
6.2.1 Current status of foreign research
Foreign research on controllable bending joints has started relatively early Early on, in the early 1990s, technicians from Schlumberger Anadrill Drilling Company proposed a "surface closed-loop automatic control drilling system" solution, thus opening a new chapter in the development of adjustable steering directional drilling technology. At present, foreign research on adjustable bend joints has entered the era of intelligent control. The most representative ones are the Auto Trak non-rotating outer cylinder closed-loop automatic steering drilling system launched by Baker Hughes and the Power Drive full-rotating steering system of Schlumberger Anadrill. Drilling system and the Geo-Pilot rotary steerable automatic drilling system launched by Sperry-Sun Products and Services.
(1) AutoTrak rotary closed-loop system
The downhole offset steering tool of the AutoTrak rotary closed-loop system consists of a non-rotating outer sleeve and a rotating mandrel connected through upper and lower bearings to form an opposite Rotating structure. The rotating mandrel is connected to the drill string on the top and the drill bit on the bottom, which plays the role of transmitting cobalt pressure, torque and transporting drilling fluid. The non-rotating jacket is provided with an underground CPU, a control part and supporting ribs. Figure 6.2 is a schematic diagram of the actual and schematic diagram of the downhole offset steering tool. When the three support ribs evenly distributed in the axial direction are supported on the well wall with different hydraulic pressures, the non-rotating jacket will not rotate with the drill string. At the same time, the reaction force of the well wall will produce a bias resultant force on the downhole offset steering tool. . Therefore, by controlling the hydraulic pressure of the three support ribs, the magnitude and direction of the offset force can be controlled to control the steering drilling.
Figure 6.2 AutoTrak steering tool
(2) PowerDriver rotary steering drilling system
The Auto Trak RClS system relies on an independent hydraulic system to support the cost of the ribs The difference in power source is that the power source for the support ribs of the Power Driver SRD system is the difference in drilling hydraulic pressure between the inside and outside of the drill string that naturally exists during the drilling process. As shown in Figure 6.3, there is a control shaft extending from the control part stabilizing platform to the lower wing rib dispensing control mechanism. The upper disc valve is fixed at the bottom, and the control part stabilizing platform controls the rotation angle of the upper disc valve. The lower plate valve is fixed inside the downhole offset tool and rotates with the drill string. The hydraulic holes on it are connected to the rib support hydraulic chambers. When working downhole, the control part stabilizes the platform to control the relative stability of the upper plate valve; the hydraulic holes on the lower plate valve that rotates with the drill string will be connected to the high-pressure holes on the upper plate valve in turn, so that the internal pressure of the drill string The high-pressure drilling fluid enters the relevant wing rib support hydraulic chamber through the temporarily connected hydraulic channel, and the wing rib is pushed out under the action of the difference in drilling hydraulic pressure between the inside and outside of the drill string. In this way, as the drill string rotates, each support rib will be deployed at the designed position, thereby providing a lateral force for the drill bit and producing a guiding effect.
Figure 6.3 PowerDriver steering tool
(3) Geo-Pilot rotary steering automatic drilling system
The Geo-Pilot rotary steering drilling system is also a steering tool. However, unlike the AutoTrak system and the Power Driver system, the Geo-Pilot rotary steerable drilling system does not rely on an offset drill bit for guidance, but relies on a set of offset mechanisms between the rotating jacket and the rotating mandrel to offset the mandrel. This provides the drill bit with an inclination angle that is inconsistent with the wellbore axis, producing a steering effect.
Its biasing mechanism is a set of eccentric mechanisms formed by a combination of several controllable eccentric rings. When the underground automatic control is completed, the mechanism will be fixed relative to the rotating jacket, thus always biasing the rotating mandrel in a fixed direction. , providing a fixed-direction inclination angle for the drill bit, as shown in Figure 6.4.
Figure 6.4 Geo-Pilot guidance tool
According to the previous classification method, the guidance tool of the AutoTrak system belongs to the static offset pushing drill bit working method, and the guidance tool of the PowerDriver system belongs to the dynamic offset method. The guiding tool of the Geo-Pilot system belongs to the static offset pointing drill bit working mode. The characteristics of the push-type rotary steering system are: large lateral force and high deflection rate, but the wellbore drilled by the rotary steering has a large dogleg, large trajectory fluctuations, and is not smooth, and the drill bit and drill bit bearings suffer serious wear. Characteristics of the directional rotary steering system: it can drill a smoother wellbore, with less friction and torque. It can use a larger drilling pressure and a higher mechanical drilling speed, which helps to maximize the performance of the drill bit, the drill bit and its bearings. The lateral load endured is smaller, the ultimate displacement increases, but the slope rate is lower.
The above three steering structures are mature technologies used in the commercial market. Among them, the Geo-Pilot rotary steering automatic drilling system is widely used in my country’s Bohai Bay. In 2005 and 2006 alone, the system The construction of more than 20 directional wells (horizontal branch wells) has been completed. Whether it is increasing inclination drilling, decreasing inclination drilling or stable inclination drilling, the system has shown good performance.
The common feature of the above three steering tools is that the electronic structure is complex, and the maximum operating temperature is mostly below 250°. In the application of ultra-deep wells, it is also necessary to solve complex working conditions such as high temperature of the system. Applicability issues. In addition, the performance of the bottom hole drill bit and mud pump also greatly affects the application of the above system in ultra-deep wells.
6.2.2 Domestic research status
Research on adjustable guidance tools started late in China, and the gap with foreign countries is large. In the late 1990s, epoch-making "downhole controllable steering tools" were developed in China, such as variable diameter stabilizers, flow field deflectors, controllable eccentrics, etc., which are important for realizing "downhole closed-loop steering intelligent drilling systems". "Provides necessary and sufficient objective conditions. At present, domestic research institutions such as Xi'an Petroleum University, Shengli Oilfield, and China University of Geosciences are engaged in research in this area. Some of the research results have entered the field use stage. Here is a brief introduction to some of the research results.
(1) Ground remote control adjustable bending joint
This achievement belongs to the "Ninth Five-Year Plan" research project of China National Petroleum Corporation, and its structure is shown in Figure 6.5.
Figure 6.5 Schematic diagram of the adjustable elbow joint structure
The working principle of this structure is: when the displacement of drilling fluid is changed, the pressure difference of the drilling fluid inside and outside the drill collar is changed. This changes the force acting on the end face of the upper spline shaft, and with the participation of the force generated by the spring, the upper spline shaft can move downward and upward. Since the ends of the upper spline barrel, upper spline shaft, and lower spline shaft have inclined plane structures, when the upper spline shaft moves downward and upward, the upper spline barrel will rotate relative to the lower spline barrel. Since the rotation center lines of the upper and lower spline barrels are at an angle to their outer surfaces, when the upper spline barrel and the lower spline barrel rotate relative to each other, their outer surfaces will change in angle, that is, the angle will change. required angle. This achieves the purpose of the present invention: using changes in drilling fluid displacement to control changes in the angle of the well bottom bend joint on the surface. The previously related “wellbore trajectory remote control technology” has obtained a national invention patent, but has not been able to enter commercial application.
(2) Controllable bend joint system based on rotary steerable drilling method
The third oil production plant of Zhongyuan Field, School of Mechanical Engineering, Xi'an Petroleum University, is supported by the CNPC Key Laboratory of Drilling Engineering Next, an exploratory study was conducted on the basic principles of the controllable bending joint guide mechanism, a principle prototype was developed, and preliminary results were achieved, as shown in Figure 6.6.
Figure 6.6 Schematic diagram of controllable bend joint guide structure
(3) Dynamic push-type rotary guide tool
This tool is undertaken by Shengli Oilfield under the national "863" program After "Research on Key Technologies of Rotary Steering Drilling Systems", it was jointly developed with Xi'an Petroleum University. The principle is basically the same as Schlumberger's PowerDrive, as shown in Figure 6.7.
This tool has been subjected to more than 20 ground tests with the rotary steerable drilling tools of Xi'an Petroleum University. In August 2006, a joint field test of the entire rotary steerable drilling system was conducted on the Ying 122 inclined well 225, which was successful and is now basically mature. , but has not yet entered the commercial market.
Figure 6.7 Dynamic push-type rotary guide tool
(4) Other domestic research results
1) Controllable eccentric rotary guide tool. The tool was jointly developed by CNOOC Research Center, Xi'an Petroleum University and China Oilfield Services Co., Ltd. The steering principle is basically the same as that of Baker Hughes, and the hydraulic power comes from the drilling fluid. In November 2005, on-site drilling operation tests were conducted in Well Xi 28-022, Well Ning 37-32 in Changqing Oilfield and Well LD5-2-A1 in Bohai Oil Field.
2) Dynamic pointing rotary guidance tool. Dynamic directional rotary steerable drilling was proposed by Offshore Petroleum Engineering Co., Ltd. and Southwest Petroleum University, combining the directional structure of Halliburton's Geo-Pilot and the footwall valve structure of Schlumberger's Power Drive while drilling. The design ideas of tools are still in the theoretical stage.
3) Directional rotary guidance tool. China University of Geosciences conducted research on the dynamics and working performance of directional rotary steering drilling tools, and made an experimental prototype of an offset steering mechanism. The principle is similar to Geo-Pilot, as shown in Figure 6.8.
Figure 6.8 Directional rotary guide tool
Based on the domestic research on adjustable bend joints, it can be seen that the research results of various research institutions are still basically in the stage of indoor research and trial. , there is still a long way to go before a mature product can be used in drilling projects, let alone used in future ultra-deep well projects.