Drill long horizontal section and clean up filtercake without
An operator in the UAE initiated a drilling program offshore Abu Dhabi.
The first two wells were to be drilled to approximately 20,000-ft [6,096-m] MD
with roughly 10,000-ft [3,048-m] maximum reservoir contact in the horizontal
sections. The 8.5-in openhole sections would be drilled using the FLOPRO NT
fluid and completed with a 6 5/8-in preperforated liner with swellable packers.
A third well was to be completed with inflow control devices (ICDs). The
openhole sections would be acid stimulated over the entire 10,000-ft interval
using 2 3/8-in CT. The plan for the fourth well, which had a shorter horizontal
pay zone of approximately 5,641 ft [1,719 m], called for using a similar casing
program to that used in the first three wells.
Based on a maximum reservoir contact program, an alternative completion
fluid program was proposed for this well. The reason for this alternative
program is to simulate the completion and filtercake removal for the wells with
extreme horizontal displacement. For drilling these extended-reach wells, CT
acidization was not expected to be successful because TD was beyond the length
limits of CT units; therefore, an intervention-free in situ filtercake removal
breakdown solution that would be instead driven by time and temperature was
Completely break down filtercake polymer and starch components
To achieve complete filtercake dissolution, M-I SWACO performed
extensive laboratory testing to optimize breaker design and lubricant
compatibility in addition to evaluating the internal breaker and postspot
breaker performance when dissolving the FLOPRO NT fluid filtercake. M-I SWACO
recom-mended that the operator include the D-STROYER breaker in the FLOPRO NT
fluid when drilling the openhole sections, which would deposit inert breaker
particles in the filtercake while drilling. During completion operations, a
filtercake breaker treatment with low pH would be spotted in the open hole to
dissolve the coating of the D-STROYER breaker and release the internal
oxidizer, enabling it to attack and break down the polymer and starch
components of the filtercake.
A low-pH chelant-base breaker treatment, the BREAKDOWN HD system, was
also recommended to be postspotted to clean up the calcium carbonate component
of the FLOPRO NT fluid filtercake. The D-SOLVER HD high-density chelating agent
included in the system dissolves the SAFE-CARB ground marble bridging agent in
the filtercake while the low pH achieved by adding the D-STRUCTOR organic-acid
precursor breaker activates the coated internal oxidizer.
Reached record-breaking depths and produced above expectation
As part of the MUDSOLV NG service deployment, the D-STROYER breaker was
incorporated into the FLOPRO NT fluid to help the operator reach the target TD
in the four wells without any major issues. Afterward, the downhole completion
assemblies were deployed successfully. All of the wells drilled using this
technique produced significantly above expectation even when acid or a
filtercake breaker treatment was not pumped.
Acid stimulation was cancelled in the second well and only a slightly
acidic completion brine (pH 5) was pumped to activate the D-STROYER breaker. In
the third well, acid stimulation was planned; however, acid completion brine
was instead pumped to activate the D-STROYER breaker. Production from both of
these wells exceeded expectations without the need for acid stimulation via CT.
In the fourth well, the BREAKDOWN HD system was used for a more comprehensive
filtercake cleanup. This well met production expectations while also avoiding
the need for acid stimulation.
Following the proven success of this technology, the operator adopted
the FLOPRO NT fluid with D-STROYER breaker and BREAKDOWN HD system combination
as its standard reservoir drill-in fluid and filtercake breaker treatment for
its extended-reach wells. To date, 26 extended-reach wells with horizontal
sections have been drilled using the combination. The operator has set and
reset multiple times, on subsequent wells, the record for the longest drilled
and completed horizontal section in the UAE, which is now more than 10,000