Investigating the Effect of High Pressures and Temperatures on CorrosionInhibition for Water-Based Drilling Fluids

摘要

Corrosion is defined as the gradual degradation of materials as a result of reaction with their environment. In gas and oil sector and during the well life, equipment can corrode at any stage causing enormous losses in time and money. Inhibiting corrosion while drilling is considered to be one of the best solutions for corrosion, as chemical inhibition can be acquainted with the drilling fluid itself. The purpose of this paper is to study the effects of corrosion of steel pipes of different sizes (3.5’, 4.5’ and 5.5’) and discuss the possible inhibition treatments.In the lab, the change in thickness as well as weight was recorded. Then, the material properties were compared under the effect of diverse corrosion media conditions (temperature, base fluid, inhibitive fluid). Each sample was exposed to about 100 hours of corrosion. The final results showed that corrosion rate is the highest when only water based mud is present in the medium. However, corrosion rate is less severe under ambient temperature conditions contrary to High Pressure High Temperature (HPHT) medium were corrosion rate was severe (around 4.1 lbs/ft^2- year). It was also noted that the corrosion rate is inversely proportional to pipe thickness: as the diameter increases, the corrosion rate decreases accordingly.When inhibitor (Conqor 404) is presented, it was observed that the rate of corrosion decreased drastically in the HPHT medium. Here, another relation can be established: as more inhibitor is injected into the mud, the corrosion rate reaches an economic margin where high concentration of the inhibitor is not feasible anymore.Introducing inhibitor (OSL 1) to the mud instead of (Concor 404) will cause the corrosion rate to decrease to a low state, but higher than the rate achieved while using Concor 404 in same concentration. Mixing both inhibitors (OSL 1 + Concor 404) together will yield inhibition results better than using OSL 1 alone. Although Concor 404 was proven to be the best inhibitor when presented in considerably high concertation, it is recommended to use a combination of Concor 404 and OSL 1 as it has desirable results under HPHT conditions with feasible cost. The final decision depends merely on the metal type and limiting corrosion rate for that specific metal.