稠油注气二次泡沫油形成机理及数值模拟

摘要

The paper attempted to propose a new method of improving later stage performance of cold production from heavy oil reservoirs in respect of forming secondary foamy oil through gas injection.A foamy oil unconventional swelling experiment was designed and carried out to verify the feasibility of generating secondary foamy oil by gas injection and reveal its mechanism of enhancing oil recovery.And then based on the experiment,a sandpack experiment was performed to study the formation of foamy oil during natural gas huffs and puffs,and continuous and intermittent gas flooding processes.The possibility of establishing a numerical model with gas injection characteristics of foamy oil reservoirs incorporated was explored so as to serve for simulating the mechanism of foamy oil formation and later evaluation of EOR results of secondary foamy oil with different ways of gas injection in fields.The results showed that gas injection formed secondary foamy oil with better EOR results in that the oil facilitated the volume expansion,viscosity reduction and light component increase in heavy crude.Compared with natural depletion,the natural gas huff and puff process,with a rich foamy oil fluid generated,was 7.24% higher in terms of recovery percent of reserves;but the continuous and intermittent gas injection processes yielded negative result as they weakened or totally destroyed the foamy oil.Numerical modeling also indicated that the natural gas huff and puff performed better with a cumulative oil production increased by 14.7% after 8 rounds of huff and puff processes in 12 wells;while the continuous and intermittent gas injections as well as edge gas injection were unable to generate secondary foamy oil fluids because of massive gas channeling.%从油气形成二次泡沫油的角度出发,研究改善稠油油藏冷采后期开发效果的新方法.首先,设计泡沫油非常规注气膨胀实验,验证注气二次泡沫油形成的可行性,揭示其提高采收率机理.在此基础上,通过填砂管实验研究天然气吞吐、连续和间歇气驱过程中二次泡沫油形成过程,并建立考虑泡沫油注气特征的油藏数值模拟模型,模拟注气二次泡沫油形成机理,评价实际油藏中不同注气方式下二次泡沫油提高采收率效果.实验研究表明,注入天然气可以形成二次泡沫油,其主要的提高采收率机理为体积膨胀、粘度降低以及轻组分含量增加.天然气吞吐较衰竭开发提高采出程度7.24%,而连续与间歇气驱导致泡沫油现象减弱或消失,进而使得采出程度低于衰竭开发实验.油藏数值模拟研究表明,由于注气二次泡沫油的形成,平台12口井8轮次天然气吞吐累积产油量较衰竭开发增加14.7%.行列连续、间歇和边部气驱气窜现象严重,无法形成二次泡沫油.