Page 266 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

Formation Damage by Inorganic Deposition 237

it is also recommended to measure dissolved gas content, suspended
solids, and bacterial population at the sample location. Sampling fluid
should fill the sample container, leaving no ullage space to preserve any
dissolved gas remaining at the sample location in solution. During the
sample transportation to the lab, temperature can alter the solubility of
salts and gasses or even lead to salt precipitation that may lead to inaccu-
rate brine ion characterization in laboratory. Therefore, it is also a com-
mon practice in operation to take a series of brine samples in several
sample containers. The first sample container only has the brine. In the
second, the brine is sampled into a known volume of HCl (usually 5% of
the total sample volume) to preserve the calcium ions in solution. In the
third, the brine is sampled into a 10% Ethylenediaminetetraacetic acid
(EDTA) solution to preserves the barium and strontium ions in solution
by chelating them. In the fourth, the brine is sampled into an accurately
known volume (approximately 5 vol%) of a reducing acid such as
erythorbic or acetic present at a 5% concentration to preserve the irons in
solution.
At the laboratory the brine can be flashed to atmospheric pressure,
and the relative volumes of water and flashed gas are measured.
2
Concentrations of key scaling ions such as Ca 11 ; Ba 11 ; Sr 11 ; HCO ,
3
and SO 22 should be analyzed along with other anions and cations, such
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21
as Cl ; Na ; K ; Mg 11 ; Fe 21 and Fe . Additionally, the determination
of volatile fatty acids is important and best run at the same time as the
bicarbonate determination. In the laboratory, bicarbonate is determined
by a titration-based method of a fresh brine sample; however, this method
actually titrates part of the fatty acid present as well, which leads to an
overestimate of the bicarbonate present.
5.4.2 Options for scale prevention and remediation
The main challenge for the management of scales in the oil field is the
control of downhole scaling in the near wellbore reservoir and the pro-
duction wellbore. The two main strategies available for downhole scale
control are prevention and remediation. There are other options to
remove the precipitation of solids once they are deposited on wellbore,
but they are out scope of this chapter that is dedicated to formation dam-
age. For reservoir inside or near wellbore formation damages, there are
three main types of preventative strategies that are discussed in the follow-
ing sections.