苏北盆地石港特低渗储层微观特征及提高采收率对策研究

Microscopic characteristics of ultra-low permeability reservoirs in the Shigang Oilfield of the Subei Basin and strategies for enhancing oil recovery

陈洪才 李哲 金忠康 孙永鹏 陈军 赵光

CHEN Hongcai LI Zhe JIN Zhongkang SUN Yongpeng CHEN Jun ZHAO Guang

1. 中国石化 江苏油田分公司, 江苏 淮安 211600; 2. 中国石油大学(华东) 石油工程学院, 山东 青岛 266580

1. SINOPEC Jiangsu Oilfield Branch Company, Huaian, Jiangsu 211600, China; 2. School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, China

苏北盆地石港油田属低孔、特低渗砂岩油藏，油井自然产能低，采用水力压裂后注水开发可提高产油能力，但油田开发中呈现低采油速度、低采出程度和开发效果差的特点，开发矛盾加剧。因此，需明确低效开发原因，探究提高采收率对策，为提高石港油田开发效果提供理论依据。通过全岩矿物成分分析、气测岩心孔渗参数、岩心敏感性评价等方法，从岩石矿物组成、孔喉结构和岩石敏感性等方面分析了其储层的微观特性；通过油藏数值模拟以及室内岩心实验研究了压裂水驱后剩余油的分布特征；通过核磁共振在线驱替实验探究了提高采收率的对策。结果显示，储层岩心呈现出典型的低孔、特低渗特征，且在开发过程中具有一定的速度敏感性和水敏感性。压裂水驱后，岩心中剩余油主要分布在0.01~1 μm中小孔径的孔道中，使用表面活性剂驱及二次水驱将岩心中剩余油采收率提高了14.81%。储层渗透率特低、微孔隙和微裂缝发育、速敏、水敏等是其低效开发的主要原因。注水开发会导致岩石矿物膨胀、运移，增大流动阻力，所以区块经压裂水驱仅明显提高主流线上剩余油的采出程度，整体动用程度不高，剩余油仍有较多富集。建议采用化学驱及多轮次驱替以增强中小孔道中原油动用程度，进一步提升油田开发效果。

The Shigang Oilfield in the Subei Basin is characterized by low-porosity and ultra-low permeability sandstone reservoirs. The natural productivity of the oil wells is low, but hydraulic fracturing followed by water injection can improve oil production capacity. However, during the development of the oilfield, problems such as low oil recovery rates, low recovery factors, and poor development effectiveness have become apparent, exacerbating development challenges. Therefore, it is necessary to identify the reasons for inefficient development and explore strategies to enhance recovery, providing a theoretical basis for improving the development effectiveness of the Shigang Oilfield. Using methods such as whole-rock mineral composition analysis, gas-measured core porosity and permeability parameters, and core sensitivity evaluation, the micro characteristics of the reservoir were analyzed in terms of rock mineral composition, pore-throat structure, and rock sensitivity. Numerical reservoir simulations and laboratory core experiments were conducted to study the distribution characteristics of residual oil after fracturing water flooding. Strategies to enhance oil recovery were investigated through nuclear magnetic resonance online displacement experiments. The results showed that the reservoir cores exhibited typical low-porosity and ultra-low permeability characteristics, with certain velocity sensitivity and water sensitivity during development. After fracturing water flooding, residual oil in the cores was mainly distributed in pore channels with diameters ranging from 0.01 to 1 μm. The use of surfactant flooding and secondary water flooding increased the recovery rate of residual oil in the cores by 14.81%. The main reasons for inefficient development included ultra-low reservoir permeability, the development of micro pores and micro fractures, and sensitivity to velocity and water. Water injection development could cause rock mineral swelling and migration, increasing flow resistance. Therefore, after fracturing water flooding, only the recovery of residual oil along the main flow paths was significantly improved, with the overall utilization degree remaining low, and a considerable amount of residual oil still concentrated in the reservoir. It is recommended to use chemical flooding and multiple rounds of displacement to enhance the utilization of oil in medium and small pore channels, further improving the development effectiveness of the oilfield.

国家级青年人才支持项目“油田化学与提高采收率”(27RA2302015)资助。

https://doi.org/10.11781/sysydz202403638