February
2014
OilfieldTechnology
|
71
(XRD), capillary suction time (CST), bentonite inhibition testing
dispersionmeasurements, linear swellmeter (LSM) testing,
immersion testing, bulk hardnessmeasurements, water activity
measurement, fracturedevelopment tests, regainedpermeability
testing and fracture flow capacity testing.
23,25
In general, capillary
suction time (CST), bentonite inhibition tests anddispersion
tests are used to initially evaluate anew shale inhibitor. These
testswere used to compare three common shale inhibitors, KCl,
polyetheramines (oligomeric ether amine salts) and choline
chloride
3
to anovel product thatwas developedon thebasis of
low toxicity and enhanced shale inhibitionperformance.
For CSTmeasurements, anOFI 294‑50 capillary suction timer
was equippedwithWhatman 17CHR filter paper (Figure 3). An
aliquot of 1 ‑ 2ml freshly prepared inhibitor‑claymixturewas
injected via transfer pipet into the timer reservoir and theCSTs
were recorded. Lower CST values indicate a lower interactionof
thewaterwith the shale andbetter shale inhibition (Figure 4).
Bentonite inhibitor rheological testswereperformedwith an
AntonPaar 302 rheometer using concentric cylinder geometry. A
20ml sample of an inhibitor‑bentonitemixturewas poured into
the sample cup, and the samplewas sheared from 100‑1 sec
‑1
at
25˚Cwhile viscositywas recorded as a functionof shear rate.
Lower viscosities indicate a stronger interactionof the shale
inhibitorwith thebentonite, leading to lower levels of bentonite
deflocculation (Figure 5).
Shaledispersion testswere runonMidway shale samples
that hadbeen retainedby a 16‑mesh sieve. The large shale
pieceswere treatedwith 3% shale inhibitor solutions and sealed
inpressure cells pressurisedwithnitrogen. The cellswereplaced
into apre‑heated roller oven and initially rolled for 16 hours at
250˚F.
3
The cellswere cooled in awater bath and the contents of
the cellswere collectedonto the 16‑mesh sieve anddried. The
mass of the inhibitor‑exposed shale after hot‑rollingdividedby
the initialmass of samplemultipliedby 100 gave thepercentage
of shale retained. The higher thepercent shale retained from the
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Figure3.
OFI294‑50capillarysuctiontimer(CST).
