BAKER HUGHES - Drilling Fluids Reference Manual

HORIZONTAL AND EXTENDED REACH DRILLING
to TVD ratio in excess of 2:1. Relative difficulty is a function of both reach/TVD ratio and absolute
TVD, commonly referred to as Aspect ratio.
Constraints to successful ERD include downhole drill string and casing movement, applying
weight to the drill bit, possible buckling of casing or drill string, and running casing successfully to
the bottom of the well. Tension may be a primary concern in vertical wells, but in ERD, torsion
may be the limiting factor. Running normal weight drill pipe to apply weight
TVD BRT (ft)
0
5,000
10,000
15,000
20,000
25,000
30,000
Industry ERD Wells
Departure (m)
0 2,000 4,000 6,000 8,000 10,000 12,000
0
1,000
2,000
3,000
4,000
Industry ERD Envelope
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000
Departure (ft)
5,000
6,000
7,000
8,000
9,000
TVD BRT (m)
Courtesy, K&M Technology
Figure 11 - 1
Medium-Radius Applications Industry ERD Wells.
to the bit in ERD can lead to buckling of the drill pipe and rapid fatigue failure. Conventional
drilling tools are prone to twist-off, because of unanticipated failure under the high torsional and
tensile loads of an extended reach well. Torque can be significantly reduced with the use of nonrotating
drill pipe protectors. Advanced equipment for an ERD well may include wider diameter
drill pipe, additional mud pumps, enhanced solids control, higher capacity top drive, more
generated power and invert emulsion drilling fluids. ERD requires longer hole sections, which
require longer drilling times. The result is increased exposure of destabilizing fluids to the
wellbore. The superiority of invert emulsion drilling fluids versus water based-fluids in ERD is
widely recognized. Conventional water based fluids may not provide the inhibition or confining
support of invert emulsion drilling fluids.
Extended reach drill string design involves a) determining expected loads, b)selecting drilling
string components, c) verifying each component’s condition, d) setting operating limits for rig
team, and e) monitoring conditions during drilling. Economic issues in drill string planning include
availability, logistics, and cost. Rig and logistics issues include storage space, accuracy of load
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006. 11-2