Improving Drilling Performance Using Advanced Drillpipe With Streamline Connections
Authors: Jellison Michael J. , Alvord Graham L. , Driskill Todd K. , Wilson Ron , Johnson Vernon Troy , Chandler Raymond Brett 
Published: December 2007

The trend to drill deeper and longer extended reach wells with long, slim-hole 6–1/8 in. horizontal production intervals has revealed serious limitations in the standard 3–1/2 in. drill pipe conventionally used in these applications. ConocoPhillips realized significant drilling performance and economic benefits by utilizing 4 in. drill pipe with advanced design, slim-hole connections in place of standard 3–1/2 in. drill pipe. The streamline drill pipe design configuration resulted in successful drilling of longer slim-hole intervals with enhanced torsional and tensile strength and improved hydraulic performance at a lower overall cost.

Introduction

ConocoPhillips' Alpine field on the western North Slope of Alaska required Extended Reach Drilling to deliver pay zone objectives located at measured depths between 8,800 ft and 21,200 ft with lateral lengths up to 7,830 ft MD. Complex 3-dimensional paths are employed in the field often resulting in tortuosity considerations and associated elevated torsional and compressive load requirements for the drill string.

ConocoPhillips wanted a drill string design that could deliver higher torsional capacity and improved hydraulic performance to enhance drilling efficiencies and lower operational times and costs. The slim-hole 4 in. drill string design permitted use of the same drill bit/casing program as employed previously with conventional 3–1/2 in. pipe.

A high performance, double shoulder connection for 4 in. drill pipe was selected that maintained a tool joint outside diameter similar to conventional 3–1/2 in. drill pipe tool joints. This streamline connection maintains fishing ability in both cased and open hole sections while providing enhanced torsional strength. Other major drilling improvements realized include: higher buckling resistance, more available pressure at the bit, lower standpipe pressure, improved hole cleaning and higher penetration rates. In addition, the 4 in. high-performance drill pipe was suitable for drilling larger diameter intermediate hole sections eliminating a requirement for 5 in. drill pipe. This drastically reduced the amount of time spent picking up and laying down drill strings, resulting in reduced HSE exposure handling drill pipe.

This paper addresses these considerations and provides case histories that clearly illustrate the benefits, savings and limitations that can be achieved with this new drill pipe design configuration.

Alpine Development Overview

As mentioned above the Alpine field is located on the western North Slope of Alaska, see Figure 1. The field has no paved road access; annual ice road access is generally available from approximately the middle of February through May. Recoverable oil reserves are estimated at 429 million for the field. The current production rate is approximately 129M BOPD.

The drilling sites consist of two pads connected by a gravel road. The wells include injectors and producers drilled on a one to one ratio. All the wells, both producer and injector, must be drilled from the twp pads that contain surface templates with well slots on 10 ft spacing, center to center. Insulated conductors are pre-install at each slot.