Steerable Rotary Drilling With an Experimental System

Abstract

SPE Members Abstract Some of the needs in directional drilling of extended reach and horizontal wells are discussed. It is forecast that Steerable Rotary Drilling (SRD) will meet some of these needs, providing economic benefits. Known options for an SRD system are briefly discussed. The system devised uses synchronous polyphase modulation of bias from a mechanism connected to, and rotating with, the drill bit, powered by drilling fluid and controlled by a directional sensor package, the orientation of the latter being independent of 8HA rotation, stabilized and controlled. This scheme meets structural requirements while being capable of development for a wide range of hole sizes The concept was proved by drilling an interval of 638m (2092ft) with an experimental SRD system. Deviation, while rotating, was controlled at rates up to 8.50/30m (8.60/100 ft) to change elevation up/down and azimuth left/right. The system was successful with both PDC and roller cone bits and the deviation rate vector was largely independent of bit weight. rotary speed and penetration rate. The drilling trials have provided data for a product aimed particularly at extended reach and horizontal drilling. Economic benefits are expected by saving time and by improving directional control. INTRODUCTION. Trends in directional drilling. Benefits of Extended Reach and Horizontal drilling. In developing drilling techniques, attention has traditionally been focused onto reducing "cost per foot". This is only one component of the more fundamental economic target of reducing cost per barrel. In recent years, the economic benefits of extending lateral reach capability in deviated drilling have been clearly recognised. In some cases, it is even feasible to develop offshore reservoirs from land, eliminating costly offshore platforms. The potential benefits of fewer platforms are illustrated by examples of savings quoted of $183 million in Wytch Farm, Southern England, and up to $100 million at Pt. Pedernales, offshore California. A related development is that of horizontal drilling. This can also reduce the cost per barrel, despite the higher cost per foot and feet per well. Extending lateral reach capability of deviated (including horizontal) wells depends on several interacting critical technologies. These have been widely reviewed, for example, by Payne, Cocking and Hatch, who also give many other relevant references. P. 435