基于微观孔隙结构的低渗透砂岩储层分类评价

针对已有的低渗透储层分类评价方法难以满足北部湾盆地流沙港组低渗透油藏精细评价与油藏开发需求的问题，通过恒速压汞、高压压汞、核磁共振等实验手段开展低渗透储层微观孔隙结构与渗流特征分析，优选储层品质指数、孔隙结构分形维数、主流喉道半径、平均孔喉道半径、可动流体百分数、启动压力梯度变化率共6个参数，基于灰色关联权重分析法建立北部湾盆地低渗透储层综合分类评价标准，进而开展低渗透储量分类评价，为北部湾低渗透储量开发潜力和攻关方向提供依据，分析结果表明:Ⅰ类与Ⅱa类为相对优质的低渗透储量，目前已投入规模开发；Ⅱb类与Ⅲ类为较难动用储量，需采取合理的开发策略与开发模式进行试验性开发；Ⅳ类储量在现有条件下难以有效开发。 

Classification and evaluation of low-permeability sand reservoir based on micro-pore structure

The undeveloped low-permeability oil reserves of the Liushagang Formation in the Beibu Gulf Basin are large, but the reservoir quality is poor. The existing classification standards for low-permeability reservoirs cannot meet the needs of fine reservoir evaluation and offshore development.Based on the experiments of constant rate mercury injection, high pressure mercury injection, NMR and seepage mechanism, this paper comprehensively analyzed the micro-pore structure and seepage characteristics, and optimized six kinds of reservoir evaluation parameters: reservoir quality index, fractal dimension of pore structure, mainstream throat radius, mean throat radius, percentage of movable fluid and change rate of threshold pressure gradient, meanwhile, the classification limit of various characterization parameters were determined by integrating with the reservoir quality index, reservoir seepage ability evaluation factors and specific productivity index constraint parameters. A comprehensive evaluation criterion for low-permeability oil reservoirs is established based on the Grey Relational Analysis method, which is divided into Ⅰ, Ⅱa, Ⅱb, Ⅲ and Ⅳ from good to bad.Carried out the grading evaluation of low-permeability reserves and the research results provide a theoretical basis for the analysis of the development potential, the research direction of the low-permeability reserves in Beibu Gulf Basin.The results show: types Ⅰand Ⅱa are relatively high-quality low-permeability reserves and have been put into large-scale development.Types Ⅱb and Ⅲ are extra-low-permeability reserves and are difficult to develop, which need to be formulated for experimental development by reasonable technical measures and development models.