Both drilling and completion engineers have come to appreciate the benefits
provided by Scomiís techniques and prototype equipment which are used to design
and develop reservoir drill-in fluid formulations for water based, synthetic
based and formate muds.
Non-gravel packed open hole completions have
become a preferred technique when engineering economical high angle and
horizontal wells. For both conventional and expandable sand screen
installations, selection of screen type and opening is critical to
retain sand and avoid excessive damage to downstream
production equipment. At the same time, plugging of screens by
drilling fluid components or produced sand, must be minimised to prevent
reduction in produced oil. A middle ground of good control of sand and
unimpaired well productivity is sought.
Until recently screen plugging tests were
run primarily at the wellsite. A simple test device, the
production screen tester or PST, was introduced by StatoilHydro 10
years ago as a quick field test to evaluate damage to production screens before
physically running screens in a well. This modified API filtration cell models
mud penetration of screen while running in the hole and can be predictive of
plugging or collapse damage. The test itself records the time required for a
volume of mud to flow at low pressure through an actual sample of the sand
control screen. If flow through the screen is impeded the mud is judged as
damaging to the screen and additional treatment is required delaying the
Today, in Southeast Asia, both field and laboratory tests are used to
quantify mud damage to completion screens early in the well planning and design
At Scomi Oiltools we now routinely apply a proprietary laboratory device
which quantitatively evaluates run-in-hole damage and models potential
production screen damage which often occurs after screen placement.
Scomi's Global Research & Technology Centre ("GRTC")
has designed and developed a novel filtration and flow system using a
specialised screen-holder that models an integrated sequence of cake building,
screen running, and flowback procedures. Thus, a detailed evaluation for both
conventional and expandable screens is possible without repeated assembly and
disassembly causing disturbance of a developed mud cake.
Pressure drop across a screen coupon resulting from precise control
of fluid flow across the screen is measured in realtime while running the test.
Screen damage is evaluated in much the same way that core damage is measured in
return permeability tests. Reports of flowrate and pressure response are
compiled when comparing performance of different mud recipes and their effect on
screen designs provided by Weatherford, Halliburton, and Schlumberger.
The measurement data allows Scomi engineers to design a
fluid that can eliminate screen plugging. The test has supported
successful completions since 2006 and is now requested by regional operators
early in the well design phase.
Mud Cake Build-Up and Flowback Test Setup
[Click on the image for enlarged version]
This new device provides several advantages:
it allows study of mud flow over
a wide range of pressure and flowrates; at run-in-hole through screen flow and
also at calculated flow initiation of reservoir fluids after screens have been
permits mud cake build up
on either reservoir sand bed, reservoir rock sample, or on a standard ceramic
enables prediction of damage
due to flowback of whole mud lost to the reservoir during drilling operation,
allows adjustments for
compliant and non-compliant screen placement during flowback tests.
The new test device is versatile. Prototypes of the current device have been
applied to a range of projects specifying conventional, expandable, and premium
screens with swellable packers in vertical and horizontal wells. Another related
project modeled extended mud cake development of 10 drilling fluids to study
potential damage by flowback of thick mud cake and formation fluids on the
screens used in MDT tools.
The results have been outstanding
wherever this Scomi Oiltools technology has been applied. Screen performance
tests have been used to design drilling fluid recipes and establish treatment
principles for wells in Bangladesh, India, Thailand, and Malaysia. Prototype
development has been ongoing since 2006 when the first work was performed on
expandable Weatherford screens for Cairn Energy. Since then
Scomi has continuously improved the design
and has streamlined testing and improved accuracy with reductions in cake and
Mud Cake and Screen After Flowback
Currently, GRTC is conducting a study using this device with Sarawak Shell
Berhad to formulate a suitable synthetic-based drill-in fluid to produce a gauge
hole, minimum formation damage, and unrestricted production through a range of
sand screen types. The tests were performed with both sieved and unsieved mud
with addition of shale cuttings to model incorporation of drilled solids and use
of shale shakers. Complete procedures have been tested and to date, the device
continues to provide repeatable and useful information.
These tests will be followed by wellbore cleanup studies in the event
synthetic based reservoir drill in fluids are to be replaced by brines for
completing the wells. Core injection with mud filtrate and return permeability
on reservoir rock will also be carried out as part of a thorough completion
evaluation. Core flow tests will be conducted with a cooperating partner, the
Universiti Teknologi PETRONAS.
The team currently working on the project for Shell
Scomi Oiltools prototype equipment has
given confidence in design and development of fluid formulations for
water based, synthetic based and formate muds applying both ultrafine grind and
API barite as well as sized calcium carbonate. Drilling and completion engineers
will appreciate the opportunity to build an unbiased understanding of the
performance of different fluid types in multiple completion scenarios. The work
is performed at the Kuala Lumpur fluid laboratory and applied in successful open
hole completions across Southeast Asia.