Swellpacker™ System Delivers Step Change in Zonal ... - Halliburton

The cluster is being developed in three phases. The objective
of Phase 1 was to determine from a number of data sources
whether a miscible gas injection project would be feasible in
some fields. Phase 2 will involve primary depletion in a
number of fields followed by gas injection in some of them.
Phase 3 will involve formation-wide depletion and gas
injection in the remaining fields. To maximize ultimate
recovery from these fields, gas (and water) shutoff is
required during Phase 2 and Phase 3 of the project.
Therefore zonal isolation over the reservoir is essential.
A substantial effort was made during Phase 1 to determine
whether zonal isolation was being achieved using
conventional cementing techniques. Cement bond logs were
run in every well over the liner section to determine the
quality of cement. These logs showed in practically every
case that a microannulus had been created. During well
completion, cement from the production liner debonded
because of differential pressure, leading to the creation of a
microannulus. Subsequently, the cement cannot re-seal and
a permanent flow path between cement and production
liner may arise, preventing zonal isolation.
Selective perforating during the well testing campaign
showed that this microannulus was conductive to reservoir
fluids. In one incident, reservoir fluids leaked all the way to
surface, providing further evidence of inadequate zonal
isolation.
Expandable pipe was not a technically feasible option owing
to the presence of high levels of hydrogen sulfide. A focused
effort was initiated to find an improvement over
conventional cementing techniques, and attention settled on
the Swellpacker isolation system.
Laboratory testing
To determine if the Swellpacker isolation system would be
able to withstand the anticipated differential pressure levels
in the various reservoirs, laboratory testing preceded a field
trial. Testing aimed to verify the cement assurance principle
of the Swellpacker isolation system with a 2-m-long, 4.82-in
outer diameter (OD) rubber element on a 4.5-in OD base
pipe placed in a 4-m-long, 6.1-in OD autoclave. The sealing
ability of the Swellpacker isolation system was tested by
introducing a microannulus on one side (90°) and allowing
the rubber element to swell and seal off the annulus by
flowing hydrocarbons through it.
The pressure test was aborted at 300 bar (maximum
pressure rating of the test unit) and the Swellpacker
isolation system was able to hold the differential pressure
with no detected leak. The system proved to be effective in
sealing off a simulated microannulus between the cement
and pipe interface and could withstand a differential
pressure in excess of 300 bar. The test also demonstrated
that the Swellpacker isolation system sealed off irregular
surfaces at the cement edge. These results provided
confidence that the Swellpacker isolation system can
effectively seal off a microannulus that develops downhole
between the pipe and cement interface—for example, as the
result of operations during well construction.
Field trial
It was therefore decided to run a field trial of the
combination of a cement slurry with the Swellpacker
isolation system. The objective of the production test was to
expose the Swellpacker isolation system to oil and then to
measure changes in flow rate, fluid composition and static
pressure. The critical parameters to be tested were as
follows:
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