The corrosion behavior of mixed ZnCl2 and CaCl2 well completion fluids was studied. These brines are
used in oil and gas high pressure production and exploration operations. This study investigates the
pitting type corrosion issue which the use of these solutions can cause to tubular goods.
This study identified CaCl2 and ZnCl2 mixture solutions with acceptable corrosivity that also satisfies the
primary requirements for balancing well pressure and avoiding other application issues such as
crystallization.
The corrosion behavior of API 5CT grade N80 was investigated in these solutions, by means of weight
loss coupons, DC polarization and AC-Impedance electrochemical techniques.
Surface observations and analysis were conducted by means of a Scanning Electron Microscope
(SEM) to determine the pitting morphology on API N-80 steel surfaces.
A tri-phase diagram based on ZnCl2, CaCl2 and water at 21 oC was developed to determine the correct
fluid density with different concentrations of each component. In addition, pH-related diagrams were
developed based on different compositions of each component and their mixtures with different fluid
densities. The corrosivity of fluid compositions with densities ranging from 1.20 kg/m3 (10 ppg(1)) to 1.80
kg/m3 (15 ppg) at temperatures of 25, 60, 90 and120 oC, were investigated.
KEYWORDS: well completion fluid, brine corrosion, crystallization point, electrochemical techniques