鄂尔多斯盆地西峰地区长7段泥岩古压力恢复

Pa!eo-pressure restoration of Chang 7 shale in Xifeng area，Ordos Basin

关键词:  欠压实泥岩  古孔隙度  古压力  长7段  西峰地冈

Key words:  undercompacted shale  paleo-porosity  paleo-pressure  Ghang 7 formation  Xifeng area

摘要:

依据钻、测并资料，运用统计分析、埋藏史模拟以及地层压力恢复等方法对西峰地K长7段欠压实泥岩古压力 进行恢复。结果表明:地层孔隙度问时受埋藏深度和埋藏时间的双重影响,埋藏时间对孔隙度的影响具有持续效 应,地层抬升会导致深度效应的停止;欠压实泥岩总孔隙度可以认为是正常压实孔隙度和欠压孔隙度实增量之和，正常压实孔隙度演化是埋藏深度和埋藏时间的双元函数,而欠压实增讀只受控于埋藏深度;长7段欠压实泥岩孔隙 度增量与其埋深之间存在良好的指数关系,利用该指数关系冉结合埋藏史可以恢复欠压实泥岩在成藏期的古孔隙 度;西峰地区长7段烃源岩在成藏期普遍存在异常高压，压力系数为1.3?1.65，说明其在成藏期具有很强的排烃动 力.同时可以很好地解释西峰地区现今的油气分布特征。

Abstract:

Based on the data of drilling and logging, paleo-pressure of Chang 7 undercompacted shale in Xifeng area was restored by u&ing statistic analysis, buried history simulation and formation pressure calculation. The results show that the formation porosity is always influenced by buried depth and geological time. The influence of geological time on porosity is working all the time in the whole buried process，but depth effect would cease during uplift. The total porosity of undercompacted shale can be considered to be a sum of normal compacted porosity and undercompacted porosity increment. The nonnal compacted part is influenced by buried depth and geological time, but the undercompacted porosity increment is controlled only by buried depth. There is a good exponential relationship between undercompacted porosity increment and buried depth of Chang 7 shale. Porosity of Chang 7 undercompacted shale during accumulation period could be easily figured out by employing this function in combination with formation buried history. Significant overpressure develops in Chang 7 undercompacted shaie during accumulation period. The pressure coefficient mainly ranges from 1.3 to 1.651 which reflects a strong hydrocarbon expulsion power in the source rock during that time, meanwhilet it could well explain today's reservoir distribution in Xifeng area.