Field Proof of the New Sliding Technology for Directional Drilling

Abstract

Abstract This work shows how sliding to make a trajectory correction can significantly improve directional drilling with a mud motor and measurement while drilling (MWD) system using a new surface only technology called Slider. Slider deploys a small robot to interface with the trop drive control panel that automatically rocks the pipe to the right and left following a rigorous analysis of torque by a computer/software that receives the surface torque and stand pipe pressure values as feedback. Improvements from this sliding technique included the following:Increasing sliding rate of penetration (ROP) by more than three-fold in some cases.Reducing motor stalls to zero (sometimes seven stalls per slide were recorded for the conventional method on a slide distance that ranged from 5 ft to 15 ft).Reducing time to orient tool face by an order of magnitude. Tool face orientation was obtained in about 11/2 to 2 minutes without coming off bottom, as compared to enormous difficulties while trying to do this manually for the larger horizontal departures.Providing a means to release the bottomhole assembly (BHA) when becoming differentially stuck without having to come off bottom and with minimal disturbance to the tool face.Removing the tedious work the directional driller had in "rocking" the pipe, which also reduces the risk of torque breakouts. Introduction Steerable motors have been used for about 20 years to drill directional wells. These motors include a bend at the motor bearing housing so the bit points at an angle relative to the borehole centerline. The bend (typically 0.5° to 2°) can be selected to allow the borehole trajectory to be changed by several degrees per 100 ft when the drillstring is advanced without rotation. This bend is sufficiently small so the entire assembly can be rotated for drilling a tangent section. Large portions of most directional wells drilled with motors are drilled while rotating the drillstring; drilling proceeds without drillstring rotation - sliding - when it is desired to change the borehole trajectory. An MWD tool detects and transmits the orientation of the bend (tool face) so the directional driller can orient it in the desired direction by slightly turning the drillstring. The mud motor powers and rotates the bit so the drillstring can be advanced without pipe rotation. The geometrical configuration of the motor assembly determines the curvature of the drilled section. Although this process is conceptually very simple, it can often be difficult and inefficient to implement. Rotary steerable directional tools were introduced in the mid- 1990s to address limitations of steerable motors.1,2 Rotary steerable tools are now routinely used for the directional work on most high-cost drilling operations. They are readily available for wellbores larger then 7 7/8 in. and significantly improve directional drilling efficiency. They are not currently economically practical for most onshore operations and some marginal offshore operations. The daily charge for a rotary steerable system may be twice as much as the cost of the rig used on an onshore well. Limited availability in small sizes also restricts their use in these onshore wells. Rotary steerable tools are just now becoming commercially available in a limited supply for use in 6 1/8-in. wells, and none are yet available for 4 3/4-in. wells. The high cost and limited size of commercial rotary steerable tools provided the impetus for the development of technology to improve steerable motor efficiency for cost-constrained directional wells. Warren3 highlighted the deficiencies of steerable motors at the time rotary steerable systems were being introduced. These deficiencies can now be addressed economically by using the technology discussed below.