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Studying Phase Behavior of Oil/Natural-Gas Systems for Designing Gas-Injection Operations: A Montney Case Study
SPE Reservoir Evaluation & Engineering ( IF 2.1 ) Pub Date : 2020-08-01 , DOI: 10.2118/201109-pa
Son Tran 1 , Sara Eghbali 1 , Hassan Dehghanpour 1
Affiliation  

Advances in horizontal drilling and multistage hydraulic fracturing have unlocked tight-oil resources, such as the Montney Formation in the Western Canadian Sedimentary Basin. However, the average oil-recovery factor after primary production is 5 to 10% of the original oil in place. The aims of this study are to investigate phase behavior and to estimate the minimum miscibility pressure (MMP) of the Montney oil/natural-gas systems.

First, we measure the MMPs of the oil/gas systems using the vanishing interfacial tension (VIT) technique. The gas samples are methane (C1) and mixtures of methane and ethane (C1/C2). Second, we perform constant-composition-expansion (CCE) tests to study the phase behavior of the oil/gas systems using a pressure/volume/temperature (PVT) cell. To complement the VIT and CCE tests, we perform bulk-phase tests to visualize vaporizing/condensing phenomena at the oil/gas interface using a visualization cell. Finally, we use the measured CCE and MMP data to calibrate the Peng-Robinson (Robinson and Peng 1978) equation of state (PR-EOS) and predict the MMP of the oil/gas systems using ternary diagrams. The results suggest that the dominant mechanism for developing miscibility conditions for oil/C1 and oil/C1/C2 systems is vaporizing and condensing gas drive, respectively. According to the results of the VIT and CCE tests, increasing C2 mole fraction in the gas mixtures significantly reduces MMP of the oil/gas system (from 4,366 psi for oil/C1 to 1,467 psi for oil/C1/C2 with 71.3 mol% C2) and increases the oil-swelling factor (from 1.47 to 1.61 by increasing C2 mol% from 0 to 70 mol%). The results of visualization tests show that the presence of C2 in the injection gas significantly enhances oil swelling compared with the pure-C1 case. We observe vaporizing flows of oil components in all tests and strong condensing flows of C1 and C2 into the oil phase in the C1/C2 test with increasing gas-injection pressure. The MMP values predicted by plotting two-phase equilibrium data on ternary diagrams appear to be in good agreement with the measured ones. The results can be used to optimize the injection-gas composition and operating pressure in the Montney.



中文翻译:

研究石油/天然气系统的相行为以设计气体注入操作:Montney案例研究

水平钻探和多级水力压裂技术的进步释放了致密油资源,例如加拿大西部沉积盆地的蒙尼组。但是,一次生产后的平均采油率是原地采油量的5%至10%。这项研究的目的是调查相态并估算Montney石油/天然气系统的最小混溶压力(MMP)。

首先,我们使用消失的界面张力(VIT)技术测量油气系统的MMP。气体样本为甲烷(C 1)和甲烷与乙烷的混合物(C 1 / C 2)。其次,我们执行恒组成膨胀(CCE)测试,以使用压力/体积/温度(PVT)单元研究石油/天然气系统的相态。为了补充VIT和CCE测试,我们使用可视化单元执行体相测试以可视化油气界面处的汽化/冷凝现象。最后,我们使用测得的CCE和MMP数据校准Peng-Robinson(Robinson and Peng 1978)状态方程(PR-EOS),并使用三元图预测油气系统的MMP。结果表明,形成油/ C 1和油/ C 1 / C 2系统混溶条件的主要机理分别是蒸发和冷凝气驱。根据VIT和CCE测试的结果,增加C混合气体中的2摩尔分数显着降低了油气系统的MMP(从含油/ C 1的4,366 psi至含71.3 mol%C 2的含油/ C 1 / C 2的1,467 psi )并增加了油溶胀系数(通过将C 2摩尔%从0增加到70摩尔%而从1.47增加到1.61 )。可视化测试的结果表明,与纯C 1情况相比,注入气体中C 2的存在显着增强了油溶胀。我们在所有测试中都观察到了油成分的汽化流,以及在C 1 / C 2中C 1和C 2进入油相的强冷凝流。在增加气体注入压力的情况下进行测试。通过在三元图上绘制两相平衡数据预测的MMP值似乎与实测值非常吻合。该结果可用于优化Montney中的注入气体成分和工作压力。

更新日期:2020-08-20
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