Soaking effect on miscible CO2 flooding in a tight sandstone formation
Soaking effect on miscible CO2 flooding in a tight sandstone formation
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DOI：
10.1016/j.fuel.2014.06.024
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发表时间：
2014-10-15
期刊：
影响因子：
7.4
通讯作者：
Gu, Yongan
中科院分区：
文献类型：
--
作者：
Li, Zeya;Gu, Yongan
本文对CO2饱和轻质油的相行为和降粘性能进行了实验研究。利用PVT系统测定了4种不同轻质油和CO2组成的轻油-CO2体系的饱和压力(P-sat)、气油比(GOR)和油胀系数(SFS)。用毛细管粘度计测定了CO2饱和轻质油的相应粘度。结果表明，轻油-CO_2体系中CO_2浓度在38.94~60.46mol.%范围内增加时，P-sat、GOR和油SF分别在4.97~8.44 Mpa、59.0~149.5 cm~(3)CO_2/cm~(3)油和1.14~1.34范围内增加。相应地，在相同的油藏温度下，CO2浓度为38.94%和60.46%的饱和轻质油的粘度分别降至死油粘度的16%和10%以下。在此基础上，进行了6次CO2混相驱替试验，研究了致密砂岩地层混相CO2驱的CO2吞吐效果。结果表明，在不浸泡CO2的冷驱试验中，注入CO2的第一个孔隙体积(PV)产生了大量的原油，而注入CO2的第二个孔隙体积(PV)只有0.77-6.10%的低采收率(Rf)。在CO2吞吐冷驱试验中，将复合砂岩油藏岩心塞中的剩余轻质油和储层卤水在第一次注入CO2后，用剩余的CO2浸泡24 h。在第二次CO2注入过程中，获得了11.05%~14.74%的高含油效率。在6次CO2吞吐试验中，预水驱+CO2三次驱+CO2吞吐的驱油效率最高，这归因于预水驱的流度控制效应和后续的CO2吞吐效应。(C)2014爱思唯尔有限公司。保留所有权利。
In this paper, the phase behavior and viscosity reduction of CO2-saturated light oil were experimentally studied. The saturation pressures (P-sat), gas-oil ratios (GORs), and oil-swelling factors (SFs) of four light oil-CO2 systems with different light oil and CO2 compositions were measured by using a PVT system. The corresponding viscosities of CO2-saturated light oils were measured by using a capillary viscometer. It was found that P-sat, GOR, and oil SF were increased respectively in the ranges of 4.97-8.44 MPa, 59.0-149.5 cm(3) CO2/cm(3) oil, and 1.14-1.34 when CO2 concentration in the light oil-CO2 system was increased in the range of 38.94-60.46 mol.%. Accordingly, the respective viscosities of CO2-saturated light oils with 38.94 and 60.46 mol.% CO2 concentrations were reduced to lower than 16% and 10% of the dead light oil viscosity at the same reservoir temperature. Furthermore, a total of six miscible CO2 coreflood tests were conducted to study CO2-soaking effect on miscible CO2 flooding in a tight sandstone formation. It was found that in the coreflood tests without CO2 soaking, a large amount of oil was produced in the first pore volume (PV) of CO2 injection, whereas only a low oil recovery factor (RF) of 0.77-6.10% was obtained in the second PV of CO2 injection. In the coreflood tests with CO2 soaking, the residual light oil and reservoir brine in the composite sandstone reservoir core plugs were soaked with the remaining CO2 for 24 h after the first PV of CO2 injection. A high oil RF of 11.05-14.74% was achieved in the second PV of CO2 injection. Among the six CO2 coreflood tests, pre-waterflooding plus CO2 tertiary flooding with CO2 soaking resulted in the highest oil RF, which was attributed to the mobility-control effect of pre-waterflooding and the subsequent CO2-soaking effect. (C) 2014 Elsevier Ltd. All rights reserved.