English Edition (6 MB pdf) - Saudi Aramco

Application of Hydrajetting Technology
Achieves Significant Productivity Increase in
Saudi Arabian Gas Producers
Author: Emad A. Al-Abbad
ABSTRACT
Stimulating gas reservoirs, particularly in horizontal producers,
has presented a considerable challenge to Saudi Aramco; as
wellbore accessibility is difficult in wells drilled in deeper
formations, with relatively low permeability and high-pressure
and temperature. Therefore, conventional perforating and
stimulation methods have not been as successful as expected
when applied in single and dual-lateral completions.
Alternative techniques, based on hydrajetting technology, have
been recently applied in a number of underperforming
horizontal gas producers with excellent results. The technology
is used to create slots along the horizontal section and then
perform pinpoint acid stimulation treatments. The acid is
displaced in the zones in most need of stimulation, resulting in
significant well productivity and economic enhancement. This
article details the methodology that has been used to apply
hydrajetting technology, and highlights the successful results
and benefits achieved in a number of field trials.
INTRODUCTION
The majority of Saudi Aramco’s gas producers, targeting
reservoirs in deep and tight formations, are being drilled
horizontally to optimize field development, achieve maximum
reservoir contact and reduce overall cost. Stimulation
treatments are required on a number of these producers,
because their productivity is frequently impaired by either
drilling damage or poor reservoir quality. The conventional
stimulation methods applied early in the field development
history, which included bullheading acid at high-pressure and
rate conditions, and performing coiled tubing (CT) acid
washes, did not improve well productivity at the expected
level 1 . This was not entirely surprising given the difficulty of
placing treatment fluids — in targeted zones in need of
stimulation along lengthy open hole horizontal completions —
in the presence of thief zones, washouts and highly hetero -
geneous reservoir conditions. The problems — associated with
initiating and extending hydraulic fracturing treatments in
vertical wells, drilled in some of the tightest formations and
perforated with conventional methodologies — led to the
search for nonconventional methods, capable of overcoming
the high fracture initiation pressure experienced in these wells.
An innovative hydrajetting tool was developed and field tested
for the first time in a vertical gas producer; with reservoir
characteristics similar to other wells where attempts to
perform proppant hydraulic fracturing treatments resulted in
premature screenouts. The same technique, in combination
with other innovative approaches, was later successfully used
to perform acid stimulation treatments in a number of
underperforming horizontal open hole producers with
excellent results.
HYDRAJETTING OVERVIEW
Hydrajetting is a technology that applies a high-velocity
stream of fluid, carrying small abrasive particles, to create
slots into the hydrocarbon bearing reservoir, Fig. 1 2 . Details of
a typical fluid mixture used during hydrajetting operations are
shown in Table 1, and steps of a typical pumping sequence of
a hydrajetting stage are shown in Table 2. The typical bottomhole
assembly (BHA), Fig. 2, is commonly run on CT during a
slotting operation, and the BHA is usually comprised of the
following: a hydrajetting tool, a CT connector, a motor head
assembly, an anchor to prevent axial movements, a multicycle
Fig. 1. Illustration of three different targets of hydrajetting and the respective sizes
of the jetting cavities 6 .
Additive Unit Concentration
Descrition
(per 1,000 gal)
Getting Agent lbs 46
Surfactant Gal 22
Proppant lbs 1,000
Brine Gal 990
Table 1. Example of jetting fluid mixture comprising the main erosive slurry used
in hydrajetting
SAUDI ARAMCO JOURNAL OF TECHNOLOGY SUMMER 2010 41