Selection of hydrocarbon gas for huff-n-puff IOR in shale oil reservoirs
Selection of hydrocarbon gas for huff-n-puff IOR in shale oil reservoirs
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DOI：
10.1016/j.petrol.2020.107683
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发表时间：
2020-07
影响因子：
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通讯作者：
W. Ozowe;Shuang Zheng;M. Sharma
中科院分区：
文献类型：
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作者：
W. Ozowe;Shuang Zheng;M. Sharma
在页岩油藏中，循环注入CO2已被证明可以有效地回收大量石油，然而，由于CO2的腐蚀性以及与乙烷和丙烷等烃类气体相比，其混相压力较高，因此使用CO2存在某些不利因素。本文利用地质力学组合水力压裂和油藏模拟器(Zeng et al.，2019a，2019b)对Eagle Ford油藏的岩石和流体性质进行了模拟，重点研究了相态对注入单组分气体：N_2、CO_2、C_1和C_2的影响，以及不同C_1、C_2和C_3组成的烃类气体的组合，作为选择比CO_2更有效的注入剂的依据。单组分注气采油结果表明，注C2采收率与CO2相当，气油比较低。在注入的所有气体中，由于与油藏流体的混相性较差，N_2的采收率最低，GOR最高。用不同组成的碳氢化合物气体进行的模拟表明，采收率高于注入C2。结果表明，在吞吐初期，C2含量高于C2的烃类气体，由于其较高的压缩系数提高了开采阶段降压后的体积膨胀，采油速度较快。相反，C2和C3含量较高的碳氢化合物气体在较后的周期中采收率较高，因为这些气体的高密度改善了在浸泡阶段与油藏流体的混相性。这项研究的结果为操作员选择具有最佳组成的碳氢化合物气体提供了必要的信息。这种在不同注气周期内调整注入液组成的策略，对提高吞吐油田先导员采收率具有重要作用。
In shale oil reservoirs, cyclic CO2injection has proven to be effective at recovering significant amounts of oil, however, certain downsides to the use of CO2exist owing to its corrosive nature and its higher miscibility pressure compared to hydrocarbon gases such as ethane and propane. This paper presents simulation results focused on the impact of phase behavior on the injection of single component gases such as; N2, CO2, C1and C2, and a combination of hydrocarbon gases with varying C1, C2and C3compositions, as the basis for selecting an injectant, that is more effective than CO2for cyclic gas injection.The simulations presented were carried out with rock and fluid properties from the Eagle Ford reservoir using Multi-Frac-Comp, an integrated Equation-of-State geomechanical compositional hydraulic fracturing and reservoir simulator (Zheng et al., 2019a, 2019b). Oil recovery results obtained for single component gas injection shows that C2injection yields comparable oil recovery to CO2and lower gas-oil ratio. Of all the injected gases, N2yielded the lowest oil recovery and highest GOR because of its poor miscibility with the reservoir fluid. Simulations carried out using hydrocarbon gases with varying compositions of C1, C2and C3show recovery factors that are higher than C2injection. The results show that hydrocarbon gases with a higher C1content over C2, results in faster oil recovery during the initial cycles of huff-n-puff because the high compressibility of C1enhances the volume expansion obtained upon depressurization during the production phase. In contrast, HC gases with higher C2and C3content yield higher recoveries during the later cycles because the high density of these gases improves miscibility with the reservoir fluid during the soak phase.The results from this study provide operators with information required to select a hydrocarbon gas with an optimum composition of C1, C2, C3and C4. This strategy of tuning the injected fluid composition during different cycles of gas injection can play an important role in improving oil recovery from huff-n-puff field pilots.