基于核磁共振技术储层物性变化规律

油田经多年注水开发已经进入特高含水阶段,出现注水压力增大,开发效果差等问题。针对此问题,本文利用目标岩心分析了粘土矿物含量和粒度分布,结合二维核磁共振技术开展高倍注水实验,研究储层物性变化规律及原因。实验结果表明:岩心8-2、岩心16-1经激光粒度测试分别定为含中砂质细砂岩、含粉砂中砂质细砂岩,其粘土矿物含量分别为2.41%、2.57%；随着注水倍数的增加,核磁孔隙度表现为先降低后上升的变化规律；随注水倍数的增加,渗透率(水)波动式变化,前期降低幅度较大,后期出现短暂的上升后持续降低；注水前期损害主要发生在中、大孔隙中且岩心8-2的损害程度要大于岩心16-1；岩心的核磁二维谱中自由水信号变化规律与核磁T2谱中孔隙信号强度变化规律一致。研究认为注水过程中受到水的冲刷作用,微粒以及胶结物中的粘土矿物,容易脱落运移至孔隙喉道处发生堵塞,对孔隙喉道产生一定损害导致渗透率(水)降低,所以注水井出现注水困难和注水压力增大等问题,从而影响油田开发效果。

Research on the Change Law of Reservoir Physical Properties Based on Nuclear Magnetic Resonance Technology

After years of water injection development, the oilfield has entered an extremely high water cut stage, with problems such as increased water injection pressure and poor development effectiveness. In order to solve this problem, this paper analyzes the content and particle size distribution of clay minerals by using target cores, and conducts high power water injection experiments combined with two-dimensional nuclear magnetic resonance technology to study the change rules and reasons of reservoir physical properties. The experimental results show that core 8-2 and core 16-1 are respectively identified as medium sandy fine sandstone and silty sand medium sandy fine sandstone by laser particle size test, and their clay minerals contents are 2.41% and 2.57% respectively; As the water injection ratio increases, the nuclear magnetic porosity exhibits a pattern of first decreasing and then increasing; As the injection rate increases, the permeability (water) fluctuates, with a significant decrease in the early stage and a brief increase in the later stage before continuing to decrease; The damage in the early stage of water injection mainly occurs in medium and large pores, and the damage degree of 8-2 is greater than that of core 16-1; The variation pattern of free water signal in the nuclear magnetic two-dimensional spectrum of the core is consistent with the variation pattern of pore signal intensity in the nuclear magnetic T2 spectrum. Research shows that under the scouring effect of water during water injection, particles and clay minerals in cement are easy to fall off and migrate to the pore throat to block, causing certain damage to the pore throat to reduce permeability (water), so water injection wells have problems such as difficulty in water injection and increase of water injection pressure, which affect the oilfield development effect.