中国陆相页岩油储层水平渗透率与垂直渗透率特征——以渤海湾盆地济阳坳陷和江汉盆地潜江凹陷为例

Characteristics of horizontal and vertical permeability of continental shale oil reservoirs in China:A case from Jiyang Depression in Bohai Bay Basin and Qianjiang Sag in Jianghan Baisn

目前,页岩油在北美地区已经实现了商业开发,中国页岩油的勘探开发也有了重大突破。在生产实践中发现水平纹层/层理发育层段产量高于其他层段,推测水平渗透率大于垂直渗透率。针对中国陆相典型页岩油储层渗透率,应用压力脉冲衰减法,对水平渗透率与垂直渗透的变化规律进行定量研究,结果表明:①常压条件下,当层理缝发育时,水平渗透率高于垂直渗透率可达5个数量级;当层理缝不发育时,水平渗透率比垂直渗透率高20~50倍左右;当储层发育切穿层理的构造微裂缝时,水平渗透率与垂直渗透率相差倍数小于1;②围压条件下,与海相页岩油储层相比,陆相页岩油储层的水平渗透率和垂直渗透率变化更为复杂,其中水平渗透率对围压的敏感性更明显;③就水平渗透率与垂直渗透率之比而言,纹层状灰质页岩/纹层状砂质页岩、层状页岩和块状页岩的变化范围分别为1.5~90.0,1.4~46.0和1.3~40.0;④潜江凹陷页岩油储层孔喉半径小,矿物组分复杂,发育硬石膏等特殊矿物,阻塞孔隙,使得江汉油田潜江凹陷页岩油储层渗透率比胜利油田济阳坳陷页岩油储层渗透率低10~100倍。

At present,commercial development of shale oil has been achieved in North America,and a major breakthrough has been made in the exploration and development of shale oil in China.In practice,it has been found that segments with horizontal beddings contribute more in petroleum production compared with those without beddings,probably indicating a larger horizontal permeability compared with the vertical permeability.The study focuses on quantitative analysis of horizontal and vertical permeability variation pattern in typical continental shale oil reservoirs in China by using pressure-pulse decay method.The results indicate that:(1)under atmospheric pressure,the horizontal permeability is 5 orders of magnitude higher than the vertical permeability in shale oil reservoirs with bedding‐parallel fractures,while it is about 20 to 50 times higher than the vertical permeability in those without bedding-parallel fractures.When vertical structural micro-fractures cutting through bedding exist,the ratio of horizontal permeability to vertical permeability is less than 1.(2)Under confining pressure,the variation of horizontal and vertical permeability in continental shale oil reservoirs is more complicated in comparison with marine shale reservoirs,and the horizontal permeability is the more sensitive to the confining pressure.(3)The ratios of horizontal permeability to vertical permeability in laminated calcareous shale/laminated arenaceous shale facies,lamellar shale facies,and massive shale facies,vary from 1.5 to 90.0,from 1.4 to 46.0 and from 1.3 to 40.0,respectively.(4)In comparison,the permeability of shale oil reservoirs in Qianjiang Sag in Jianghan oilfield is 10-100 times lower than that in Jiyang Depression in Shengli oilfield due to smaller pore throat,complex mineral composition and the existence of pore-filling anhydrite.