Study on CO2 corrosion resistance of packer fluid under high pressure and high temperature in Dongfang 1-1 Gasfield

In Dongfang 1-1 Gas Field, the gas reservoirs in the middle and deep strata are of high temperature and high pressure with higher CO2 content. In the process of well completion, therefore, it is necessary to add packer fluid to keep the hydrostatic pressure between the tubing and the casing. And furthermore, it is necessary to prevent CO2 from channeling and leaking into the annulus as it may aggravate the corrosion of tubing and casing. In order to guarantee the wellbore safety for a long term, the corrosion degree of two pipe materials (13Cr and 13CrS) by different saline packer fluid systems was studied in the simulated corrosion environment of Dongfang 1-1 Gas Field. It is shown that under high temperature and high CO2 differential pressure, the 13Cr pipe material is corroded seriously and even leaked easily by the formate packer fluid (density 1.46 g/cm3). Compared with the formate packer fluid, the packer fluid containing HLTC composite saline has much lower corrosion degree, and its corrosion effect on 13CrS is much less with corrosion rate lower than 0.076 mm/a. Therefore, it could meet the requirements of long-term wellbore safety and should be popularized further.