Li Xianjie, Zhang Jian, Zhang Yaqian, Guan Cuo, Liu Zheyu, Hu Ke, Xian Ruokun, Li Yiqiang
State Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 100028, China.
CNOOC Research Institute Co., Ltd., Beijing 100028, China.
Polymers (Basel). 2025 Jan 20;17(2):244. doi: 10.3390/polym17020244.
The Bohai oilfield is characterized by severe heterogeneity and high average permeability, leading to a low water flooding recovery efficiency. Polymer flooding only works for a certain heterogeneous reservoir. Therefore, supplementary technologies for further enlarging the swept volume are still necessary. Based on the concept of discontinuous chemical flooding with multi slugs, three chemical systems, which were polymer gel (PG), hydrophobically associating polymer (polymer A), and conventional polymer (polymer B), were selected as the profile control and displacing agents. The optimization design of the discontinuous chemical flooding was investigated by core flooding experiments and displacement equilibrium degree calculation. The gel, polymer A, and polymer B were classified into three levels based on their profile control performance. The degree of displacement equilibrium was defined by considering the sweep conditions and oil displacement efficiency of each layer. The effectiveness of displacement equilibrium degree was validated through a three-core parallel displacement experiment. Additionally, the parallel core displacement experiment optimized the slug size, combination method, and shift timing of chemicals. Finally, a five-core parallel displacement experiment verified the enhanced oil recovery (EOR) performance of discontinuous chemical flooding. The results show that the displacement equilibrium curve exhibited a stepwise change. The efficiency of discontinuous chemical flooding became more significant with the number of layers increasing and heterogeneity intensifying. Under the combination of permeability of 5000/2000/500 mD, the optimal chemical dosage for the chemical discontinuous flooding was a 0.7 pore volume (PV). The optimal combination pattern was the alternation injection in the form of "medium-strong-weak-strong-weak", achieving a displacement equilibrium degree of 82.3%. The optimal shift timing of chemicals occurred at a water cut of 70%, yielding a displacement equilibrium degree of 87.7%. The five-core parallel displacement experiment demonstrated that discontinuous chemical flooding could get a higher incremental oil recovery of 24.5% compared to continuous chemical flooding, which presented a significantly enhanced oil recovery potential.
渤海油田具有严重的非均质性且平均渗透率高，导致水驱采收率低。聚合物驱仅对特定的非均质油藏有效。因此，仍需要进一步扩大波及体积的补充技术。基于多段塞不连续化学驱的概念，选择了三种化学体系，即聚合物凝胶（PG）、疏水缔合聚合物（聚合物A）和常规聚合物（聚合物B）作为调剖剂和驱油剂。通过岩心驱替实验和驱替平衡度计算研究了不连续化学驱的优化设计。根据凝胶、聚合物A和聚合物B的调剖性能将其分为三个级别。通过考虑各层的波及条件和驱油效率来定义驱替平衡度。通过三岩心平行驱替实验验证了驱替平衡度的有效性。此外，平行岩心驱替实验优化了段塞大小、组合方式和化学剂的切换时机。最后，通过五岩心平行驱替实验验证了不连续化学驱的提高采收率（EOR）性能。结果表明，驱替平衡曲线呈现出阶梯式变化。随着层数增加和非均质性增强，不连续化学驱的效果变得更加显著。在渗透率为5000/2000/500 mD的组合条件下，化学不连续驱的最佳化学剂用量为0.7孔隙体积（PV）。最佳组合模式是以“中-强-弱-强-弱”形式交替注入，驱替平衡度达到82.3%。化学剂的最佳切换时机发生在含水率为70%时，驱替平衡度为87.7%。五岩心平行驱替实验表明，与连续化学驱相比，不连续化学驱可获得更高的原油采收率增量24.5%，具有显著增强的采收率潜力。
