松辽盆地龙西地区扶余油层特低渗透储层孔隙结构

Pore structure of Fuyu ultra-low-permeability oil reservoir in Longxi area of Songliao Basin

龙西地区扶余油层储量规模大,但由于储层物性差导致了常规开发效果差。如何加大压裂规模、改善渗流通道,微观孔隙结构研究就显得尤为重要。利用薄片鉴定、扫描电镜、恒速压汞等测试资料,分析不同孔喉参数与储层物性的相关关系,研究储层的孔隙类型、喉道类型、孔喉分布及其对储层物性的贡献。结果表明:研究区储层物性差,孔隙类型为残余原生粒间孔和各类溶蚀次生孔,喉道以微、细喉道为主,储层渗流能力主要受狭小喉道的制约;储层孔隙半径分布差别不大,而喉道半径分布差异显著;随着渗透率的增大,微喉道、微细喉道的比例逐渐降低,喉道半径分布范围和渗透率贡献率曲线跨度越宽,峰值喉道半径越大,对渗透率起主要贡献的喉道半径越大;微观孔喉参数对储层物性的影响主要体现在渗透率上,平均喉道半径、最大喉道半径、分选系数及微细喉道所占比例与渗透率之间存在一定的相关性。研究成果为储层大规模压裂改造提供了理论依据。

Although there exist a large scale of the resources in Fuyu oil reservoir in Longxi area, because of the poor physical properties, the conventional developed effects are rather poor. For increasing the fracturing scale and improving the seeping channel, the study on the micropore structure is particularly important. With the help of the following tested data such as thin section identification, scanning electron microscope and constant-rate mercury injection,the correlation relationships between different pore-throat parameters and reservoir physical properties were analyzed, the contributions of the pore type, throat type and pore-throat distribution to the reservoir physical properties were clarified and studied. The results show that the reservoir physical properties are rather poor in the study area, the pore types are residual primary intergranular pore and various types of the dissolved secondary pore, the throat is dominated by micro and thin throat and the seepage capacity of the reservoir is mainly restricted by narrow and small throat;the pore radius distribution of the reservoir has little difference, but the throat radius distribution has significant difference. With the increase of the permeability, the proportions of the micro throat and micro-thin throat decreases gradually, the wider the distribution range of the throat radius and the curve span of the permeability contribution rate, the larger the radius of the peak throat and the larger the throat radius that contributes mainly to the permeability;the influences of the micro pore-throat parameters on the reservoir physical properties are mainly reflected in the permeability. There are a certain correlations between the average throat radius, maximal throat radius, sorting coefficient and proportion of the micro-thin throat and the permeability. The study results have provided the theoretical evidences for the large-scale fracturing stimulation of the reservoirs.