东方1-1气田高温高压下封隔液抗CO_2腐蚀研究

Study on CO_2 corrosion resistance of packer fluid under high pressure and high temperature in Dongfang 1-1 Gasfield

东方1-1气田中深层属于高温高压气藏且天然气中CO_2含量较高,在完井作业过程中需要加入封隔液以保持油管与套管间的液柱静压力,同时还要防止CO_2气体窜漏而进入环空,加剧对油管、套管的腐蚀。为了确保井筒的长期安全,开展了在模拟东方1-1气田腐蚀环境下,不同盐水封隔液体系对13Cr和13Cr S两种油管材质的腐蚀程度研究。结果表明:高温高CO_2分压下,密度为1.46 g/cm^3甲酸盐封隔液对13Cr材质的腐蚀严重,极易发生腐蚀穿孔;由HLTC复合盐配制的封隔液对13Cr的腐蚀程度明显小于甲酸盐封隔液,对13Cr S腐蚀更小,其腐蚀速率均小于0.076 mm/a,可以满足井筒的长期安全要求,具有进一步推广价值。

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 corrodedseriously and even leaked easily by the formate packer fluid (density 1.46 g/cm3). Compared with the formate packer fluid, the packerfluid 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