松辽盆地页岩油藏可动油特征研究

针对松辽盆地青山口组一段页岩油藏19块岩样,开展高速离心和核磁共振实验,建立了储层可动油评价方法,揭示了目标页岩油藏可动油特征;结合高压压汞实验和扫描电镜实验,从孔隙结构角度分析目标油藏可动油特征的原因。结果表明：随着渗透率降低,实验岩心T2谱右峰比例减少,可动油变少。区块一岩心可动油百分数平均17.88%,区块二岩心可动油百分数平均14.56%;不同渗透率岩心均含有一定量微米级渗流通道,两区块岩心中微米喉/缝控制的可动油分别为9.34%和5.7%;0.10～1.0微米喉道控制的可动油比例较低,区块一平均为4.05%,区块二平均为3.22%;小于0.1微米喉道控制的可动油比例区块一为4.49%,区块二为5.64%。高压压汞表明目标页岩油储层基质喉道非常小,主要喉道分布在5纳米～30纳米之间,6块岩心平均喉道半径为30纳米;扫描电镜结果表明,目标页岩油藏基质致密、喉道小,多数孔隙呈孤立状,部分储层发育裂缝隙、间裂缝等微裂缝,非均质性强;储层发育一定比例微裂缝,因此离心力较小时能驱出一定量的原油,但储层基质整体致密,喉道小,导致其总可动油比例较低。

Study on movable oil characteristics of shale reservoir in Songliao Basin

Based on 19 rock samples from shale reservoirs in the first member of Qingshankou Formation, Songliao Basin, high-speed centrifugation and nuclear magnetic resonance experiments were carried out to establish the evaluation method of reservoir mobile oil and reveal the characteristics of mobile oil in target shale reservoirs. Combined with high pressure mercury injection experiment and scanning electron microscope experiment, the causes of movable oil characteristics of target reservoir are analyzed from the perspective of pore structure. The results show that with the decrease of permeability, the ratio of T2 spectrum right peak decreases and the movable oil decreases. The average percentage of movable oil in Block 1 and Block 2 is 17.88% and 14.56% respectively. The cores with different permeability all contain a certain amount of micrometer scale seepage channels, and the movable oil controlled by micrometer throat/fracture in the two cores is 9.34% and 5.7%, respectively. The proportion of 0.10 ~ 1.0 micron seepage channels was relatively low, with the average of 4.05% in block 1 and 3.22% in Block 2. The proportion of seepage channels smaller than 0.1 micron was 4.49% in block 1 and 5.64% in block 2. High pressure mercury injection shows that the matrix throat of the target shale oil reservoir is very small, and the main throat distribution is between 5 nm and 30 nm, and the average throat radius of the six cores is 30 nm. Scanning electron microscopy results show that the target shale reservoir has dense matrix, small throat, most pores are isolated, and some reservoirs develop micro-fractures such as cracks, interfractures, and strong heterogeneity. A certain proportion of micro-fractures are developed in the reservoir, so a certain amount of crude oil can be driven out when the centrifugal force is small, but the reservoir matrix is dense and the throat is small, resulting in a low proportion of total movable oil.