It has been noticed in well acidification operation that the acidification job quality is not satisfactory, the effective period of the acidification job is short, and the acidified area is limited. In well acidification operations, it has been found that the results of acidifying a gas well penetrating sandstone reservoirs are much better than the results of acidifying an oil well penetrating sandstone reservoirs. This observation has been used in designing oil well acidification program to improve the acidification job quality, that is, a gas can be injected with acid into the well in oil well acidification. The mechanisms and advantages of alternated injection of gas and acid are extensively studied in this paper. In laboratory experiment, the acidification results of undamaged cores and cores damaged by completion fluid under 3 gas injection models were studied, and the effects of different injected gases on the acidification results were analyzed. It is considered that gas injected in well acidification clearly improved the acidification job quality of damaged cores, especially when an acidification mode in which prepad gas plus alternated gas and acid injections was used during well acidification. For undamaged cores, the effectiveness of gas injection with acid in well acidification was not satisfactory. It was also found that the effectiveness of injecting CO2 was better than that of injecting N2. Alternated gas injection with acid in well acidification greatly improves the permeability of the reservoir rocks, and is able to enhance the effectiveness of conventional well acidification job. This technology has a broad development prospect.%针对常规酸化作业逐渐暴露出酸化效果差、有效期短、解堵范围有限等问题,充分考虑砂岩储层气井酸化效果普遍好于油井的现场经验,提出了油井酸化过程中通过注入气体以提高酸化效果的设计思路.研究过程中分析了气液交替注入酸化解堵工艺的作用机理及优势,通过室内实验进一步探索3种不同注气模式下,对未伤害及受钻完井液伤害岩心的酸化改善效果,并对比分析了注入不同气体对酸化效果的影响.研究认为,酸化过程中注入气体能明显提高被污染岩心的酸化效果,尤其采用前置气+气液交替注入的酸化模式,而对未受污染岩心注入气体改善酸化效果不明显,且总体上注CO2气体酸化效果要好于注N2.气液交替注入酸化工艺现场实验解堵效果显著,能够有效地提高常规酸化效果.
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