砂泥岩地层断层岩压实成岩埋藏深度预测方法及其应用

Prediction method and its application for burial depth of fault rock compaction diagenesis in sandstone and shale strata

为了更加准确地评价砂泥岩地层中断层的封闭性,文中在研究断层岩压实成岩埋藏深度影响因素的基础上,将与断层岩具有相同泥质体积分数的围岩孔隙度随压实成岩埋深变化关系曲线,从围岩停止沉积时间平移至断层岩开始压实成岩处的沉积时间,将平移后的曲线看作断层岩孔隙度随压实成岩埋深变化关系,断层岩现今压实埋深对应的孔隙度看作断层岩现今的孔隙度。据此,由围岩孔隙度与压实成岩埋深和泥质体积分数的关系,建立了一套砂泥岩地层中断层岩压实成岩埋深的预测方法,并以南堡凹陷南堡5号构造F3断裂为例,验证了该方法的可行性。研究结果表明:F3断裂在东营组三段、二段和一段内断层岩压实成岩埋深分别为2486.13,1031.55,847.90 m,压实成岩埋深相对较大,具有一定的封闭能力,有利于油气在东三段、东二段和东一段内聚集和保存,与目前F3断裂附近东三段至东一段储层已发现的油气分布相符,表明该方法用于预测砂泥岩地层中断层岩压实成岩埋深是可行的。

In order to evaluate fault sealing in sandstone and shale strata more accurately,based on the study of influencing factors of burial depth of fault rocks compaction diagenesis,the curve of host rock porosity with compaction diagenesis burial depth is shifted from the time of host rocks stopping sedimentation to the time of fault rocks starting diagenesis,in which the host rocks have the same shale volume fraction as the fault rocks.The shifted curve is regarded as the relationship between porosity fault rocks and compaction diagenesis burial depth,and the porosity corresponding to current compacted burial depth of fault rocks is regarded as current porosity of fault rocks.On this basis,a set of prediction methods for burial depth of fault rocks compaction diagenesis of sandstone and shale strata are established according to the relationship of host rocks porosity vs.compaction diagenesis burial depth and shale volume fraction.The F3 fault of Nanpu 5 structure in Nanpu Sag is taken as an example to verify the feasibility of this method.The research shows that the compaction diagenesis burial depths of fault rocks in Ed_(3),Ed_(2) and Ed_(1) of F3 fault are 2,486.13 m,1,031.55 m and 847.90 m respectively,with relatively large compaction diagenesis burial depth and certain sealing capacity,which is conducive to oil and gas accumulation and preservation in Ed_(3),Ed_(2) and Ed_(1).It is consistent with the distribution of oil and gas discovered from Ed_(3) to Ed_(1) reservoirs near F3 fault,suggesting that this method is feasible for predicting compaction diagenesis burial depth of fault rocks in sandstone and shale strata.