Corrosivity Studies of Well Completion Fluids Comprising ZnCl2/CaCl2 on N-80 Steel

The pitting corrosion behavior of mixed zinc chloride and calcium chloride well completion fluids used in the high-pressure oil and gas industry were studied. These brines are associated with the problem of pitting type corrosion of tubular goods. The presence of high concentrations of chloride ions leads to severe pitting corrosion but low rates of general corrosion. 

 The corrosion behavior of API 5CT grade N80 in these solutions was investigated by means of weight loss coupons, DC polarization and AC-Impedance (EIS) electrochemical techniques.

 This study identified calcium chloride and zinc chloride mixture solutions with acceptable corrosivity that also satisfies the primary requirements for balancing well pressure and avoiding crystallization. 

 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 different density ranges from 1.20 kg/m³ (10 ppg[1]) to 1.80 kg/m³ (15 ppg) at different temperatures of 25, 60, 90 and120 ^oC, were investigated.

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.

---

[1] Pound Per Gallon

See more of: Advances in Materials for Oil and Gas Production (Session I) - STG 32
See more of: Technical Symposium

<< Previous Abstract | Next Abstract >>