利用色谱柱制备了普通砂岩岩心和不含黏土的砂岩岩心,通过室内岩心驱替实验研究砂岩储集层低矿化度水驱提高原油采收率的机理,并分析黏土对采收率的影响。首先向岩心中注入矿化度为100 000 mg/L的高矿化度盐水,以模拟地层水,然后在不同温度下注入矿化度为1 000 mg/L的低矿化度盐水,记录色谱柱流出物中Ca2+、CH3COO-的浓度和pH值。研究表明,低矿化度水驱过程中,不含黏土的砂岩岩心也出现羧酸与砂体分离现象,只是不像含黏土的砂岩岩心那样明显,且Ca2+解吸现象显著,这表明在不存在黏土的情况下,低矿化度水驱也能获得更高的采收率;与高矿化度水驱相比,低矿化度水驱过程中流出物pH值显著增加,且随着温度的升高,流出物pH值和Ca2+浓度变小;低矿化度水驱时砂岩岩心的亲水性比高矿化度水驱时更强。图6表1参20
AL-SAEDI Hasan
,
FLORI Ralph
. 砂岩储集层低矿化度水驱提高采收率机理及黏土对采收率的影响[J]. 石油勘探与开发, 2018
, 45(5)
: 869
-873
.
DOI: 10.11698/PED.2018.05.13
Sandstone core and free clay sandstone core were prepared in chromatography columns, and core flooding experiments were done on them to determine the EOR mechanisms of low salinity water flooding and analyze the effect of clay on recovery factor. First, brine with high salinity of 100 000 mg/L was injected to simulate formation water. Then, low salinity water of 1 000 mg/L was injected at different temperatures. Concentrations of Ca2+ and CH3COO- and pH of the fluid flowing out of the chromatography column were recorded. The study showed that during flooding of the free clay core with low salinity water, the carboxylic acid detached from the sand, albeit not as great as that of the clay-containing cores. It showed a noteworthy desorption of Ca2+ from the free clay core surface, which indicated that low salinity water flooding got high recovery in sandstone reservoirs without clay. Compared with high salinity water flooding, in the low salinity water flooding, the pH of produced fluid increased significantly; as the temperature increased, the pH and Ca2+ concentration of the produced fluid decreased; and the hydrophilic property of the sandstone was stronger.
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