应用CO2吞吐技术改善低渗透油田开发效果的几点认识

CO2作为一种驱替剂曾在国内外石油开采工业中广泛使用。葡萄花油田CO2吞吐室内实验结果表明：在油层条件下，液态的CO2能够快速气化并溶于原油中，使原油体积膨胀达41．2％，储集层孔隙压力增高，油层的弹性能量增加，使现井网注采关系无法完善的孤立砂体中的剩余油得到驱动。现场试验结果表明，CO2溶入原油后会使原油粘度大幅度降低而水的粘度增加，改善油水流度比；储层中剩余油含量高、单层厚度大、射孔层数少、渗透率高，吞吐采油效果好。CO2吞吐效果还与原油的物性有关，原油中饱和烃含量高、溶解气量低吞吐效果好。

Some Understanding about CO2 Huff and Puff to Improve Development Results in Low Permeability Oilfield

CO_2 has been widely used in foreign countries as a kind of sweeping agent. The laboratory results for CO_2 huff and puff in Putaohua oilfield show: under oil layer conditions, liquefied CO_2 can become boiloff quickly and dissolve in crude oil. Then the volume of crude oil will expand by 41.2%, the pore pressure of reservoirs increases, elastic energy of oil layers increases, and the remaining oil in isolated sand body can be swept. The field tests proved, after the solution of CO_2 into crude oil, the viscosity of oil greatly increases, that of water decreases, and oil-water mobility ratio can be improved; CO_2 huff and puff results will be better if the content of remaining oil in reservoirs is high, the thickness of single layer is high, layers penetrated are few and permeability is high. The results are also related to the physical properties of crude oil: the results will be better if the content of saturated hydrocarbons in oil is high and dissolved gas is little. CO_2 huff and puff technique is effective to improve the recovery factor of isolated sand body.