Research On Design Method Of Special Horizontal Wellbore Orbit

While horizontal well is using for the development of tight oil and gas, conventional methods of wellpath design are unable to meet some special requirements, mainly in terms of long lateral sections horizontal well and "Well Plant" horizontal wells, etc. Does it exist deviation of the wellpath design because of difference reference system between wellpath design and geodesy? How to design target wellpath of multiple control points, which is used for development of anticlinal and fold structural reservoir? And how to optimize the design of "Well Plant" horizontal wells.Earth's surface is an ellipsoid, the geoid, which is similar to a shape of the earth ellipsoid, is the reference system of Geodesy. A point on the wellpath that corresponds to the position of the geoid and wellhead coordinate is not in the same plane, which may mean deviation between the design of wellpath position and the actual position. Therefore, I establish a model of deviation including vertical and horizontal displacement deviation, which affect form latitudes, horizontal displacement and depth. After analyzing the deviation of different regions, it exists difference that long lateral section horizontal well wellpath design. Furthermore, this bias with increasing of latitude and horizontal displacement, and horizontal displacement deviation is affected by the depth, the deeper depth the larger horizontal displacement deviation. Especially, long lateral section horizontal is used to develop the thin oil layer at high latitude area, the wellpath may pierce the reservoir. For the reason, it should affiliate vertical deviation and subtract horizontal displacement deviation during designing. Which will obtain wellpath meeting the actual reservoir, and reducing the drilling adjustments.Using a long lateral section horizontal well for the development of tight oil and gas reservoir, control points is always added into target to keep effectively wellpath in the fluctuating reservoir. At present, it is a trial method that is used to design the multi-control points target wellpath of horizontal well. But it is difficult to control trajectory and improve rapid drilling because of lots of deflective segments. Therefore, considering the low-cost drilling mode of the compound drilling combination of a PDC bit and a screw drill tool, we come up with a new way what control segments is used to replace control points during this horizontal well is designed. In other words, we turn control points to control segments by line, and then we select an appropriative curve to connect the adjacent segment, which is called as two-dimensional or three-dimensional control segment. The examples show that there is large total length of hold segment, which is conducive to the application of compound drilling methods, by this way. Moreover, three-dimensional horizontal segment which is designed by this way can keep tool surface angle constant while directing, which is benefited to improving drilling efficiency. Finally, it will be a theoretical basis for the multi-control points target wellpath design method of long lateral section horizontal well.While "well factory" mode of operation of horizontal wells is using to develop tight oil, there are a large of dead oil zone, oil can't be an effective use of resources, between the two rows target area of wells which are designed by conventional three-dimensional. Therefore,Spoon-shaped borehole which is used to solve this problem in foreign is reverse drilling from kickoff point, and drill a period well section, then turn around to the target area. Drilling earlier reservoir can reduce the dead oil area. By characteristics of spoon-shaped borehole, combined with three-dimensional wellpath design theory, the key of spoon-shaped borehole is suitable closure distance. Because of small distance among wells and the characteristics of spoon-shaped borehole, it may be collision risks where vertical section, whipstocking initial section and the previous segment before the target between adjacent wells in different rows. Therefore, we come up with an optimize wellpath design of "well factory" horizontal wells mode, which is the way of the optimum of well site layout, staggered deflection point and the target position. Examples show, compared to the conventional design method, the proposed method can significantly reduce the dead oil zone. At the same time, after analysis of anti-collision and friction torque, the optimum design method can reduce the risk of borehole collision, moreover, spoon-shaped borehole will not additionally increase the track friction torque, and the horizontal section will also extend normally.According to the theory of wellpath design and the theoretical model of special horizontal well, I carried on the programming about special horizontal wellpath database, which is based on SQL Server 2008 database platform, and developed special horizontal well wellpath design software, which is based on WPF framework and C# in Visual Studio 2013 development platform. The software can't only meet the conventional horizontal well wellpath design requirements, but also fulfill the special requirements of horizontal well design. After testing, the software is stable and reliable.