Development of a Novel Hybrid-Type Rotary Steerable System for Directional Drilling
Unlike conventional resources, unconventional resources, such as shale gas and coal bed methane, are situated horizontally under geological formations. To exploit these resources, directional drilling and hydraulic fracturing technologies are required. In directional drilling, the dog leg severity (DLS), which indicates how much the angle changes while drilling 100 ft, is a major issue with respect to the cost and time of drilling. In this paper, we briefly review different types of directional drilling methods and propose a new hybrid-type rotary steerable system (RSS). DLS calculations based on three-point geometry for these systems are suggested. This hybrid RSS combining two conventional types of RSSs: point-the-bit and push-the-bit systems, achieves better steerability. The hybrid mechanism is implemented using hybrid pads with hydraulic cylinders and a spherical joint. The advantages of the proposed system are demonstrated by performing small-scale prototype and cement block drilling tests.
Compensation Control for Tool Attitude in Directional Drilling Systems
This paper is concerned with tool attitude control of directional drilling systems, which plays a key role in guaranteeing desired drilling trajectory. The coupling of inclination and azimuth motions are taken into account in the motion model, where the azimuth one involves some time-varying parameters. To ensure satisfactory control precision, an output-feedback compensation control scheme is developed based on a motion model established from Taylor expansion. Stability analysis is sequentially made for the resulting inclination and azimuth closed-loop system. At last, some simulations show that the compensation controller can achieve higher control accuracy than a proportional integral controller.
Improving hole quality by automatic control of the drilling process: theoretical and field studies
Some results from studies on hole deviations are discussed. A system which automatically controls drilling parameters during percusion drilling was developed. A procedure for determining the operat ...