51316-7802-Development of Novel Inhibitor Chemistries to Protect Metal Surfaces from Saturated Completion Fluid

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Product Number: 51316-7802-SG

ISBN: 7802 2016 CP

Author: Thenuka Ariyaratna

Publication Date: 2016

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Drilling in heavy brine environments including saturated calcium chloride calcium nitrate calcium bromide and various combinations can prove to be extremely corrosive on completion equipment and production tubing. Novel chemistry approaches are required in order to effectively combat the effects of corrosion especially in high temperature environments. Clariant Oil Services has undertaken a range of tests to identify suitable corrosion inhibitor products for application in various completion fluids under these corrosive conditions. The initial inhibitor selections were focused on calcium nitrate heavy brines followed by inhibitor selections for other heavy brines such as calcium chloride mixtures of calcium nitrate and calcium chloride.Chemicals were screened by determining the products that showed superior solubility in these heavy brines and then several chemicals were tested using rotating cylinder electrode linear polarization resistivity testing. The inhibitors which passed initial screenings were further tested in high temperature/high pressure static autoclaves. The best performing chemicals exhibited a balance of heavy brine solubility and corrosion inhibition performance.In addition to measuring general corrosion rates surface analysis of the coupons was essential to determine the presence of localized corrosion. Static autoclave tests were conducted to determine and confirm strong performing chemicals. A high magnification enabled microscope was used to differentiate between chemical performance and identify any potential areas of local corrosive attack.Poor performing products demonstrated metal surface morphology with high pit density and numerous deep pits while the new chemistries with a novel approach yielded performance of either no pitting at all or very limited pits andextremely low general corrosion. A review of the new products show that their performance can rarely be matched especially in an oxygen rich environment. This paper details all the testing and selection criteria and gives insight into the mechanism of corrosion attack as well as details of the synergies exhibited by the various chemical formulations.Keywords:Corrosion Inhibitor Heavy Brine Completion Fluid Calcium Nitrate Calcium Chloride Mixed brines Oxygen Corrosion HTHP Autoclave Rotating Cylinder Electrode (RCE) Heavy Brine Solubilty