鄂尔多斯盆地镇泾地区延长组低孔低渗砂岩物性与石油临界注入压力关系实验研究

岩性油藏的形成受到石油流体动力及储层物性等因素的控制。岩性油藏理论分析和勘探实践表明,成藏期当砂岩体孔隙度和渗透率过低或石油充注动力不足时,石油往往无法充注其中。本文采用砂岩样品石油充注临界条件实验测量了不同围压条件下石油进入砂岩样品的最小注入压差,定量研究了已知不同物性砂岩样品的临界石油注入压差与埋深的关系,并建立了镇泾地区延长组低孔低渗砂岩体成藏解释图版。石油充注临界条件实验表明:镇泾地区延长组低孔低渗砂岩体石油充注临界孔隙度约为10.5%,小于该临界值时,石油难以注入砂岩样品; 该地区低孔低渗砂岩体临界注入压差受储层埋深和物性的双重控制:相同物性不同埋深的砂岩样品临界注入压差随深度增加而迅速增大,表明随深度增加石油需要更大的充注动力才能成藏; 而相同深度时不同物性的砂岩样品临界注入压差随物性条件变好迅速降低,即同一深度不同物性时较好物性的砂体更容易发生石油充注。应用成藏图版解释研究区长8低孔低渗砂岩体成藏条件,发现成藏期石油充注压差大于临界压差者为高产油井,充注压差等于或者小于临界压差多为低产油井或者水井,解释结果与油田实际试油结果有一定吻合。

Experiment analysis of relationship between property and oil injection critical pression of low porosity and permeability sandstone within Chang-8 Member,Zhenjing area of Ordos Basin

The formation of lithological reservoir is controlled by dominant petroleum migration pathways,fluid dynamic,reservoir property and sealing condition of lithological trap.It is proved that the more excessive porosity than critical porosity is not the deciding factor for hydrocarbon accumulation process in the exploration practise of lithological reservoir.The hydrocarbon injection into the trap is essentially dominated by the fluid dynamic in the accumulation period.In this paper,the oil injection experiment is used to mensurate the oil immission critical press on different confining pressure.On the base of the data,the relationship between the oil immission critical press and depth has been studied.Last the reservoir interpretation chart of low-permeability sandstone is established base on the relationship above.The oil injection experiment indicates the minimum injection porosity is 10.5%.The oil can not been injected into the sample when the property and permeability are lower than 10.5% no matter what press applied.The hydrocarbons charging critical press is controlled by the depth and property of the reservoir.If the porosity is the same,the injection critical press is more greater when the sandbody is imbeded more deeper.When the depth is the same,the press is negative correlation with the property of sandbody,expressing the trap of better property is more easier for oil accumulation.Applying the reservoir interpretation chart to the low-permeability lithological reservoir of study area,the oil charging press of oil wells are more greater than the hydrocarbons charging critical press., which of low producing oil well or water well is lightly greater or less than the critical charging press.Those results are all accord with the test of Chang-8 reservior,and the interpretation chart of low-permeability sandstone make a good effect in lithological reservoir exploration practice of Chang-8 Member,Zhenjing area.