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Selection of hydrocarbon gas for huff-n-puff IOR in shale oil reservoirs
Journal of Petroleum Science and Engineering ( IF 5.168 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.petrol.2020.107683
Williams Ozowe , Shuang Zheng , Mukul Sharma

In shale oil reservoirs, cyclic CO2 injection has proven to be effective at recovering significant amounts of oil, however, certain downsides to the use of CO2 exist 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, C1 and C2, and a combination of hydrocarbon gases with varying C1, C2 and C3 compositions, as the basis for selecting an injectant, that is more effective than CO2 for 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 C2 injection yields comparable oil recovery to CO2 and lower gas-oil ratio. Of all the injected gases, N2 yielded 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, C2 and C3 show recovery factors that are higher than C2 injection. The results show that hydrocarbon gases with a higher C1 content over C2, results in faster oil recovery during the initial cycles of huff-n-puff because the high compressibility of C1 enhances the volume expansion obtained upon depressurization during the production phase. In contrast, HC gases with higher C2 and C3 content 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, C3 and 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.



中文翻译:

页岩油藏吞吐正压IOR的烃气选择

在页岩油储层中,已证明循环注入CO 2可以有效地回收大量油,但是,由于CO 2具有腐蚀性,并且与烃类气体(如乙烷和甲烷)相比具有较高的混溶压力,因此使用CO 2存在某些不利因素。丙烷。本文介绍了模拟结果,重点放在相行为对单组分气体注入的影响,例如:N 2,CO 2,C 1和C 2以及具有不同C 1,C 2和C 3组成的烃类气体的组合作为选择喷射剂的基础,比CO 2更有效 用于循环注气。

所提出的模拟是使用Multi-Frac-Comp,Eagle Ford油藏的岩石和流体属性进行集成的,该油藏是状态方程的综合地质力学成分水力压裂和油藏模拟器(Zheng等,2019a,2019b)。单组分气体注入获得的油采收率结果表明,C 2注入可产生与CO 2相当的油采出率,并且气油比更低。在所有注入的气体中,N 2的采收率最低,GOR最高,因为它与储层流体的混溶性差。使用具有不同C 1,C 2和C 3组成的烃类气体进行的模拟显示,采收率高于C2注射。结果表明,C 1含量高于C 2的烃类气体可在吞吐正压的初始循环中更快地采油,因为C 1的高压缩性可提高生产阶段减压时获得的体积膨胀。相反,具有较高C 2和C 3含量的HC气体在随后的循环中产生较高的回收率,因为这些气体的高密度可改善在浸泡阶段与储层流体的混溶性。

这项研究的结果为操作人员提供了选择具有最佳成分C 1,C 2,C 3和C 4的烃类气体所需的信息。在不同的注气周期内调整注入的流体成分的这种策略在改善从哈夫-n-puff油田飞行员获得的石油采收率方面可以发挥重要作用。

更新日期:2020-08-01
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