杭锦旗探区储层致密化与天然气成藏的关系

Relationship between the densification of reservoir and the accumulation of natural gas in Hangjinqi area of Ordos Baisn

杭锦旗地区储层主要为低孔低渗的致密砂岩储层.通过对储层特征的描述及致密化原因的分析认为,硅质胶结物、钙质胶结物和黏土矿物的生成是影响储层致密化的主要因素,最后一期胶结物——方解石是导致储层最终致密化的主要原因.根据方解石形成时的包裹体测温和氧同位素计算出的温度判断,早白垩世晚期是储层最终致密化的时间.结合生烃模拟研究及成藏期次的分析认为,研究区天然气藏分为2种类型,即常规圈闭气藏和根缘气藏,分别在中侏罗世晚期之前和早白垩世晚期之后成藏,主体上分别分布在以三眼井—泊尔江海子断裂为界的北部地区和南部地区.

The reservoir in Hangjinqi area is mainly the tight sandstone with low porosity and low permeability.According to the description of the reservoir characteristics and the analysis the cause of the reservoir densification,it is held that the formation of siliceous cement,calcareous cement and clay minerals is the main cause of the reservoir densification,and it is also held that the formation of calcite cement in last period leads to the ultimate densification of the reservoir.According to the fluid inclusion thermometry when calcite is formed and the temperature calculated from oxygen isotope,it is held that the final densification of the reservoir is in the late period of Early Cretaceous.By combining the simulation study of hydrocarbon generation with the analysis of the periods of hydrocarbon accumulation,it is indicated that natural gas reservoirs in the studied area can be divided into two types:conventional trap gas reservoir and source-contacting gas reservoir.They are formed before the late period of middle Jurassic and after the late period of early Cretaceous respectively,and they are distributed mainly in the northern and southern regions of Sanyanjing--Boerjianghaizi fault respectively.