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.
Directional Drilling Optimization by Non-Rotating Stabilizer
The Non-Rotating Adjustable Stabilizer / Directional Solution (NAS/DS) is the imitation of a mechanical process or an object by a directional drilling operation that causes a respond mathematically and graphically to data and decision to choose the best conditions compared to the previous mode. The NAS/DS Auto Guide rotary steerable tool is undergoing final field trials. The point-the-bit tool can use any bit, work at any rotating speed, work with any MWD/LWD system, and there is no pressure drop through the tool. It is a fully closed-loop system that automatically maintains a specified curvature rate. The Non–Rotating Adjustable stabilizer (NAS) can be controls curvature rate by exactly positioning and run with the optimum bit, use the most effective weight (WOB) and rotary speed (RPM) and apply all of the available hydraulic energy to the bit. The directional simulator allowed to specify the size of the curvature rate performance errors of the NAS tool and the magnitude of the random errors in the survey measurements called the Directional Solution
Point-the-bit rotary steerable system : Theory and field results
Many existing rotary steerable systems rely on non-rotating, stationary pads or stabilizers to provide changes in borehole direction. An inherent weakness with this technique is that it relies on contact with the borehole wall to achieve predictable and consistent directional control. Hole washouts and borehole rugosity can negatively impact the directional performance of these systems. A new rotary steerable system has been developed that does not depend on wall contact by non-moving parts. This new technology uses what is being termed a point-the-bit technique to enable precise, consistent and predictable changes in well trajectory. This paper presents the design objectives and theory behind the point-the-bit system and contrasts it with existing rotary steerable systems. A case history from a successful field trial completed in Alaska is provided and includes well objectives and operational results.