基于核磁共振技术的疏松砂岩油藏微粒运移伤害机理

Damage Mechanism of Particle Migration in Unconsolidated Sandstone Reservoirs Based on Nuclear Magnetic Resonance Technology

准噶尔盆地阜东斜坡区头屯河组疏松砂岩油藏物性非均质性强,孔喉结构复杂,储层开发过程存在微粒运移现象。为明确微粒膨胀、运移对储层微观孔喉结构的伤害作用机理,基于室内物理流动模拟实验结合低场核磁共振(nuclear magnetic resonance,NMR)技术,定量评价头屯河组油藏储层的微观孔喉伤害程度,明确微粒运移伤害主要控制因素。结果表明:微粒膨胀引起的孔喉结构伤害程度平均为6.84%,微粒运移造成的伤害程度高于微粒膨胀的伤害程度,达到9.16%。其中介于0.01~9.33 ms较小孔喉的伤害程度较高,微粒膨胀、运移对孔喉的伤害程度平均为5.64%、7.60%。孔隙度、渗透率、分选系数与储层微观孔喉伤害程度呈负相关关系,排驱压力与孔喉伤害程度呈正相关。蒙脱石+伊蒙混层含量高是导致阜东斜坡区头屯河组疏松砂岩油藏微粒膨胀的重要因素,砂粒运移则是微粒运移的宏观表现。从微观尺度揭示了疏松砂岩油藏在生产阶段发生砂粒运移对储层造成的伤害机理,研究成果可为生产现场优化开发方案、降低储层伤害程度提供理论依据,实现疏松砂岩油藏的高效开发。

The loose sandstone reservoir of Toutunhe Formation in Fudong slope block of the Junggar Basin has strong physical heterogeneity,complex pore-throat structure and obvious reservoir sensitivity.In order to clarify the damage mechanism of particle expansion and migration on the microscopic pore-throat structure of the reservoir,based on low-field nuclear magnetic resonance(NMR)technology,the damage degree of microscopic pore-throat in Toutunhe reservoirs were quantitatively evaluated,and the main influencing factors were identified.The results show that the damage degree of pore-throat structure caused by particle expansion is 6.84%,and the damage degree of particle migration is higher,reaching 9.16%.The damage degree of the smaller pore throats between 0.01 ms and 9.33 ms is higher,and the damage degree of particle expansion and migration to the smaller pore throat is 5.64%and 7.60%respectively.The porosity,permeability and sorting coefficient are negatively correlated with the damage degree of pore-throat and the threshold pressure is positively correlated with the damage degree of pore-throat.The high content of montmorillonite and illite-montmorillonite is an important factor leading to the particle expansion of the Toutunhe reservoir,and sand migration is the macroscopic manifestation of particle migration.The damage mechanism of unconsolidated sandstone reservoir caused by sand migration during production stage was revealed from the microscopic scale.The research results can provide theoretical basis for optimizing the development plan of production site and reducing the damage degree of reservoir,so as to realize the efficient development of unconsolidated sandstone reservoir.