Page 45 - Handbook Of Multiphase Flow Assurance

40 2. Initial diagnosis and solution of flow assurance production problems in operations

Field or laboratory tests for initial solid samples identification

Once a closed valve was ruled out as the possible cause of a suspected blockage,
the separator inlet strainer should be inspected for any accumulated solids. Solids car-
ried by produced fluids to the separator may help understand what processes happen
upstream.

Field laboratory initial tests for solid samples identification

Solids can be analyzed to help identify a flow assurance problem and develop the best
solution. Although a specialized lab testing is preferred, a number of tests can be performed
in the field to analyze the solid deposit using readily available chemicals such as water, table
salt, diesel fuel, and simple instruments such as polarized sunglasses.

Field analysis
Very preliminary analysis may be performed in the field using just water if getting the
sample to the lab is prohibitively far or would take a long time.
Hydrate: use an inverted graduated transparent cylinder to measure the volume of gas
from a known volume of hydrate sample. Place a sample into the graduated cylinder
filled with water. Place the upside-down graduated cylinder containing sample into an
upright glass filled with water. If enough gas evolves from the sample to displace all
water from the cylinder, it is hydrate.
Wax: if the sample floats in water it is likely wax.
Viscosity: use a calibrated cup viscometer with a hole of a known diameter in the bottom
to measure time of sample outflow.
Asphaltene: check sample density. If the sample sinks in water it is likely asphaltene.

Laboratory analysis
Table 2.2 lists a number of simple tests which can be conducted in the field, ordered from
simple to more complex.
Any preliminary analysis information should be shared with the professional laboratory
along with the sample as the initial measurements on solids which rapidly dissociate or melt
can make a difference in the proper identification of the flow assurance issue.
Inspired by The total systems approach process, Baker Hughes Inc., 2013.
Note: As sample can release a poisonous vapor, all tests must be done in a vent hood!
If a partial solid residue remains during any test it may be filtered, weighed and subjected
to additional tests.
100 °C temperature was selected for ease of obtaining this temperature in the field condi-
tions using boiling water (at sea level); at elevation the water will boil at a lower temperature,
but the test results will remain valid.
CPM (cross-polarized microscope) is useful for analysis of paraffin wax and other
solids.