低渗透油藏储层分级评价方法及应用

A grading evaluation method for low-permeability reservoirs and its application

低渗透石油探明储量逐年增加,低渗透油藏未动用储量占未动用总储量的比例较高。笔者在长庆、大庆外围、吉林和华北等油区2 200块岩心分析的基础上,结合几个低渗透油区的开发现状,提出了用主流喉道半径、可动流体百分数、拟启动压力梯度、原油黏度和黏土矿物含量作为评价参数,确定了各表征参数的分类界限,对比了几个低渗透油区储层表征参数数据的差异,深化了对低渗透储层的认识,提出了低渗透油区储层综合评价方法。研究表明,储层分类系数与区块单井产能有较好的相关关系。在此基础上,对长庆、大庆、吉林油田3大低渗透油区进行储层分类评价,确定了各油区不同分类级别所对应的渗透率范围。该项研究将对优选产能建设区块和确定投资具有指导意义,并为确定下步低渗透油藏攻关目标、技术对策及动用界限提供技术支撑。

The demonstrated reserves of low-permeability reservoirs in China increase year by year.The non-producing reserves of low-permeability reservoirs amount to a relatively high percentage of the all non-producing reserves in China.Based on the geochemical analysis of 2 200 core samples collected from the peripheral zone of the Daqing oil region,the Changqing,Jilin and Huabei oil regions and integrated with the current situation of several major low-permeability reservoirs developed by PetroChina Company Limited,we proposed a number of parameters to evaluate low-permeability reservoirs,such as the radius of main flow throat,percentage of movable fluid,threshold pressure gradient,viscosity of oil and content of clay minerals.Meanwhile,the classification limit of various characterization parameters were determined and differences in these parameters for the main low-permeability reservoirs were compared,which has deepened our understanding about low-permeability reservoirs.Thus,a comprehensive evaluation method for low-permeability reservoirs was proposed.The result shows that the correlativity between reservoir classification coefficients and the deliverability of a single oil well is guite good.Based on these data,we carried out a reservoir classification evaluation on low-permeability reservoirs in the Changqing,Daqing and Jilin oil regions,and determined various permeability ranges corresponding to different classification ranks of these oil regions.This work will play a guiding role in optimizing producing regions and investment blocks,and will provide technical supports for oil companies to determine the future exploration targets in low-permeability reservoirs,to set down technique countermeasures for exploiting low-permeability reservoirs and to redetermine frontiers of producing pays.