渤海湾盆地渤南洼陷沙四段岩相的岩石力学性质差异

Difference of lithofacies mechanical properties of the fourth member of Shahejie Formation in the Bonan Subsag, Bohai Bay Basin

根据渤海湾盆地渤南洼陷沙四段低渗透油藏取心井资料,研究了其岩相类型,利用不同岩相常规三轴压缩实验分析资料,建立了静态岩石力学参数油藏围压条件的恢复图版,分析了不同岩相静态力学参数及应力—应变关系的差异性。渤南洼陷沙四段低渗透油藏可划分为粗粒砂岩相、细砂岩相、粉砂岩相、泥质砂岩相及碳酸盐质砂岩相5种岩相;同一岩相随着围压的不断增加杨氏模量变大,泊松比增加;随着岩相粒度变粗,存在杨氏模量增加、泊松比减小的整体趋势;粗粒砂岩相的泊松比不遵循整体趋势,较细粒砂岩相大,比粉砂岩相小;岩相粒度变粗,应力—应变关系越趋近线弹性,初始颗粒重排列塑性段变小,高应力塑性段变短。

Based on the data of well cores in low permeability reservoirs in the fourth member of Shahejie Formation in the Bonan Oilfield,the rock facies types were studied.Using conventional three axis compression test data of different lithofacies,restored static rock mechanical parameters were established under reservoir confining pressure conditions.The differences of static mechanical parameters and stress-strain relation between lithofacies were analyzed.The low permeability reservoirs in the Bonan Oilfield can be divided into 5 types:coarse grained sandstones,fine sandstones,siltstones,mudstones and carbonate sandstones.In the same rock,with the increasing confining pressure,the Young's modulus becomes larger,and the Poisson's ratio increases slightly.With the increase of rock gain size,the Young's modulus increases and the Poisson's ratio decreases.However,the Poisson's ratio of coarse grained sandstones does not follow the overall trend,and is larger than that of fine sandstones and smaller than that of siltstones.As the grain size of rock becomes coarser,the stress-strain relation becomes more linear.And the initial grain rearrangement plastic section and the high stress plastic section become smaller.