CO2对曲塘区块地层油高压物性影响研究

CO_2能有效降低原油黏度、溶解储层中的胶质、提高储层渗透率,对开采低渗、特低渗透油藏有很好的应用前景;而研究CO_2对地层油高压物性的影响具有重要指导意义。针对曲塘区块这一典型低渗透油藏,采用PVT地层流体分析仪,测定了张3B井地层油溶有不同气量CO_2后的高压物性。结果表明:随地层油中溶解CO_2增多,泡点压力及体积系数大幅升高、地层油密度减小。当CO_2溶解度为44 m3(标)/m3时,泡点压力与CO_2溶解度的关系曲线出现拐点呈"凸"型,说明溶有大量CO_2的地层油对后续注入CO2的溶解起到了促进作用。当压力高于泡点压力时,体积系数和密度与压力呈很好的线性关系,体积系数曲线的斜率(绝对值)、截距与CO_2溶解度呈正比;而密度曲线呈反比。此外,CO_2对地层油具有很好的降黏效果,当CO_2溶解度为83 m3(标)/m3时,其降黏率达到了38%。

Study of the effect of CO2 on PVT of Qutang field

CO₂ has a good application prospects to develop the low and extra-low permeability reservoir, for it is feasible to reduce the oil viscosity and increase the reservoir permeability. And it has an important guiding significance to study on the effect of CO₂ on PVT. To the typical low reservoir of Qutang, PVT analyzer was used to test the PVT of Zhang 3B well dissolved different volume of CO₂.The result show that bubble point pressure and formation volume factor are remarkable increasing, and the value of density shifted to smaller with increase of dissolved CO₂ in reservoir fluid. The curve of bubble point pressure to solubility of CO₂ inclined to convex shape when the solubility of CO₂ is 44 m₃/m₃, for the oil dissolved lot of CO₂ contribute to dissolve more CO₂. There is a good relationship between formation volume factor, density and pressure, when the pressure is above bubble point pressure. The curve slope and intercept of CO₂ solubility is proportional to formation volume factor, while inverse to density. Furthermore, CO₂ has a better reduction on the oil viscosity that the viscosity-reducing rate is up to 38% when the solubility of CO₂ is 80 m₃/m₃.