准噶尔盆地腹部盆1井西凹陷超压研究

准噶尔盆地腹部盆1井西凹陷存在明显的深部超压系统(4400m以下)。通过对超压段地质、钻井、地球物理特征的研究发现,超压段多为砂、泥岩互层,泥岩段大多几米到十几米厚,孔隙度在8%以下,已经过充分的压实,进入超压段,泥浆密度大幅增加,远大于1.2g/cm~3,砂岩、泥岩段同时具有高声波时差和低电阻率特征,井旁地震速度具有异常低值特征,超压顶面形态不规则,穿层分布,并且宏观上往往在一定的深度范围内。经过分析,欠压实以及煤层不是超压带低速的原因,烃类生成尤其是天然气生成对现今超压贡献最大。

Overpressure in the well Pen-1 West subbasin in the interior of the Junggar basin

A noticeable deep overpressure system occurs below 4,400 m depth in the well Pen-1 West subbasin in the interior of the Junggar basin.Studies of the geological,well log and geophysical data in the area show the following:the overpressure interval consists mostly of alternating beds of sandstone and mudstone;the mudstone interval is mostly a few to more than ten meters thick with a porosity of<8% and has been fully compacted;the slurry density increases greatly,being far higher than 1.2 g/cm~3;both the sandstone and mudstone intervals have higher acoustic transit time and lower resistivity,and the stack seismic velocities near the wells also have abnormally lower values;the top of the overpressure interval is irregular in shape and penetrates the bed and macroscopically usually in a certain depth range.Analysis indicates that the lack of compaction and coal beds are not the cause for the lower velocity in the overpressure interval and that hydrocarbon,especially natural gas, generation makes the greatest contribution to the present overpressure generation.