English Edition (6 MB pdf) - Saudi Aramco

formation from toe to heel without proper control over the
placement process. In the past, several stimulation treatments
in dual lateral wells have not achieved the objective of
increasing production in spite of placing acid in both laterals
— raising doubts about the effectiveness of the diversion or
the placement of the fluids.
During the stimulation job with conventional CT, there are
several uncertainties proving that there is no control on the job:
• Where are the thief zones
• Are these thief zones hydrocarbon bearing or not
• Where in the hole is the acid squeezed Is it at the CT
bottom-hole assembly (BHA) nozzle depth
• Does it matter where the CT end is positioned while
spotting the treatment fluids
• In the case of additional bullheading, will fluid go to the
CT BHA nozzle depth, even if there is a thief zone at
the heel
• Is squeeze pressure below or above frac pressure
• What is the downhole temperature during treatment
• When should the pump diverter be used Where What
volume should be pumped
• Is the diverter working Is the next acid stage wasted to
the same thief zone
• What type of diversion fluid should be pumped into nonhydrocarbon
bearing and hydrocarbon bearing zones
• Do we have an adequate pumping sequence Should it
be the same for all wells
• Are the fluid volumes enough or too little
• Is there an understanding of the injection profiles
The availability of open hole logs helps in identifying the
intervals with a higher probability of production. It is possible
that one lateral holds a very good quality zone that
predominates over the other, becoming a key target of the
stimulation treatment.
If one lateral contains predominantly higher permeability
and porosity sections, it is also certain that most of the fluid
volume has the tendency to go towards this section. In this case,
it is likely that the damage is not removed and potential
production in the other lateral is not unlocked. It would then be
ideal to have a means to understand if this situation is taking
place. Many of these questions can be addressed with real-time
downhole measurements taken as the CT treatment progresses.
Ultimately, the objective of the stimulation treatment in gas
wells with open hole completions in Ghawar field includes:
• Ensure uniform placement of acid into the targeted
reservoir intervals.
• Ensure efficient diversion to stimulate the targeted zones.
• Avoid treating the same lateral twice.
A case study of utilizing the latest CT advancements, in two
dual lateral horizontal open hole gas producers, that
demonstrates how to optimize a stimulation treatment as it
develops, is described in this article. Using an innovative
workflow — interpretation of distributed temperature survey
(DTS) responses, correlated with reservoir data — it is possible
to selectively place treatment fluids, maximizing the contact of
stimulation fluids with the targeted formation sections.
BACKGROUND
Well A was completed as a dual lateral Khuff-C gas well
producer. The well was completed with a 4½” tubing string.
The well is cased with a 7” liner to the top of the producing
reservoir at 11,623 ft measured depth (MD). The motherbore
(L0) was then drilled successfully to a TD of 13,895 ft MD.
After that, the lateral (L1) was drilled, with a junction at
11,652 ft MD, to 15,331 ft MD. After drilling, the well was
flowed back for cleanup but was not flowing. It was decided
to stimulate the well, targeting as the main priority the L1
section between 12,500 ft and 13,100 ft.
Well B was completed as a dual lateral Khuff-C gas well
producer. The well was completed with a 4½” tubing string.
The well is cased with a 7” liner to the top of the producing
reservoir at 11,471 ft MD. The motherbore (L1) was then
drilled successfully to a TD of 14,858 ft MD (lower lateral).
After that, lateral L2 (upper lateral) was drilled after opening
a window in the 7” liner at 11,477 ft MD to 11,488 ft MD to
14,625 ft MD. The well production was very poor. A decision
to stimulate the two laterals was taken, Fig. 1.
TVD (ft)
TVD (ft)
11200.00
11250.00
11300.00
11350.00
11400.00
11450.00
11500.00
11550.00
11600.00
11650.00
11700.00
11200.00
11250.00
L1: Pilot hole
L2: Lateral
11300.00
11350.00
11400.00
11450.00
11500.00
11550.00
11600.00
11650.00
11700.00
0 1000 2000 3000 4000 5000
V-Section (ft)
Fig. 1. Well A and B trajectories.
0 1000 2000 3000 4000 5000
V-Section (ft)
24 SUMMER 2010 SAUDI ARAMCO JOURNAL OF TECHNOLOGY