BAKER HUGHES - Drilling Fluids Reference Manual

HORIZONTAL AND EXTENDED REACH DRILLING
Chapter 11
HORIZONTAL & EXTENDED-REACH
DRILLING
Horizontal and Extended Reach Drilling techniques are commonly used in the development
phase of oil and gas fields. These types of operations present many challenges in drilling fluid
design.
INTRODUCTION
Horizontal and extended-reach drilling are not new technologies. Variations of these techniques
were in use 50 years ago. With current state-of-the-art equipment, wells that were once considered
marginal and uneconomical potentially become high-return development projects.
Compared to a vertical well, a horizontal hole or extended reach well in a productive formation
increases the total percent of the wellbore drilled through the pay zone, resulting in these benefits.
• Accelerated production rates
• Total recovery improvement
• Through reductions in pressure gradients, water and gas coning problems are limited.
Operators make use of these technologies to improve and accelerate the replacement of reserves.
According to several surveys of oil and gas producers worldwide, over 50% of wells drilled in the
near future will utilize horizontal and extended-reach technologies.
Horizontal and extended-reach terms are often used synonymously, but in fact they are
fundamentally different. One definition of a horizontal well states that a well is considered
horizontal if the producing reservoir is penetrated with the intent of never leaving that stratum.
Therefore, a well does not have to be 90° to be classified as a horizontal well. A prospect can be
defined as an extended-reach well when the wellbore is over 60° to 70° with a horizontal
displacement of 10,000 ft. Such wells are drilled with a single-bend or steerable motor that can be
rotated from the surface. No formal accepted definitions have been established however, and the
above examples are meant to show the differences only.
EXTENDED REACH DRILLING
Extended Reach Drilling (ERD) has evolved from simple directional drilling to horizontal, lateral,
and multi-lateral step-outs. ERD employs both directional and horizontal drilling techniques and
has the ability to achieve horizontal well departures and total vertical depth to deviation ratios
beyond the conventional experience of a particular field. ERD can be defined in terms of reach/true
vertical depth (TVD) ratios. An extended reach well is commonly defined as a well having a reach
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 11-1