以长庆油田长8区块为例,采用室内静态实验与动态驱替实验,定量研究CO2驱过程中CO2与地层水在不同温度、压差、成垢离子质量浓度条件下产生的沉淀量,以及沉淀作用对储集层物性的影响,建立了相应的数学表征模型。采用数学表征方程对Eclipse数值模拟软件E300模块的数值模拟模型进行了修正,在此基础上模拟了研究区块CO2连续气驱过程中无机盐沉淀物的分布规律,预测了无机盐沉淀物对油田采收率的影响。CO2-地层水反应过程中生成的无机盐沉淀主要是CaCO3,且压差、成垢离子质量浓度与沉淀量呈正比,温度与沉淀量呈反比。CO2驱替前后岩心孔隙度变化率与温度、驱替压差呈正相关性,由于沉淀作用影响,地层水组（CO2-地层水-岩石反应组）的岩心孔隙度增加幅度始终低于蒸馏水组（CO2-蒸馏水-岩石反应组）的岩心。随着CO2的不断注入,最终在生产井附近产生的沉淀最多。由于沉淀物在井组内广泛沉积,导致油田开发效果变差,考虑沉淀作用时CO2驱20年后区块采收率为33.45%,不考虑沉淀作用时采收率为37.64%。图8表4参16
袁舟
,
廖新维
,
张快乐
,
赵晓亮
,
陈志明
. 二氧化碳驱过程中无机盐沉淀对油藏采收率的影响——以长庆油田长8区块为例[J]. 石油勘探与开发, 2021
, 48(2)
: 379
-387
.
DOI: 10.11698/PED.2021.02.14
Static experiments and dynamic displacement experiments were conducted to quantitatively determine the amount of precipitate generated by the CO2-formation water reaction at different temperatures, pressures, and scaling ion concentrations during CO2 flooding in the Chang 8 block of Changqing Oilfield, the influence of precipitate on the physical properties of reservoirs was investigated, and the corresponding mathematical characterization model was established. The mathematical characterization equation was used to correct the numerical simulation model of E300 module in Eclipse software. The distribution pattern of inorganic salt precipitates during continuous CO2 flooding in Chang 8 block was simulated, and the influence of inorganic salt precipitates on oil recovery was predicted. The inorganic salt precipitate generated during CO2-formation water reaction was mainly CaCO3, and the pressure difference and scaling ion concentration were proportional to the amount of precipitate generated, while the temperature was inversely proportional to the amount of precipitate. The rate of core porosity change before and after CO2 flooding was positively correlated with temperature and flooding pressure difference. The core porosity increase in the CO2-formation water-core reaction experiment was always lower than that of CO2-distilled water-core reaction experiment because of precipitation. The area around the production wells had the most precipitates generated with the injection of CO2. The oil field became poor in development because of the widely distributed precipitate and the recovery decreased to 33.45% from 37.64% after 20-year-CO2 flooding when considering of precipitation.
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