断盖配置封闭油气时期预测方法及其应用

Prediction method and its application for oil and gas sealing period in fault‑caprock configuration

为了准确地反映含油气盆地断盖配置之下油气富集规律,从断盖配置封闭油气机理出发,由断盖配置古断接厚度与断盖配置泥岩封闭油气所需的最小断接厚度,确定了断盖配置封闭油气部位;由泥岩盖层、断层岩和下伏储层岩石排替压力随时间变化关系,确定了断盖配置封闭油气时期,二者结合建立了一套断盖配置不同部位封闭油气时期的预测方法。应用结果表明:大张坨断裂与沙一中亚段区域性泥岩盖层配置泥岩封闭油气时期(东营组沉积中期至现今)主要在其中西部,少量在其东部的中部,且时期相对较长,有利于油气在沙一下亚段内聚集与保存;断层岩封闭油气时期(明化镇组沉积末期至现今)主要在东部泥岩封闭油气时期的两侧,且时期相对较短,不利于油气在沙一下亚段内聚集与保存,这与大张坨断裂处沙一下亚段目前已发现油气分布相吻合,表明该方法用于预测断盖配置封闭油气时期是可行的。研究成果可为断盖配置之下油气勘探提供依据。

In order to accurately reflect hydrocarbon enrichment law under fault-caprock configuration in petroliferous basins,based on sealing mechanism of fault-caprock configuration,oil and gas sealing location is determined by paleofaults juxtaposition thickness and minimum faults juxtaposition thickness required for mudstone-sealing oil and gas in fault-caprock configuration.Oil and gas sealing period in fault-caprock configuration is determined by variation of mudstone caprock,fault rock and underlying reservoir rock discharge pressure with time.Combining above-mentioned 2 aspects,a set of prediction method for oil and gas sealing period in different location of faultcaprock configuration is established.Case application shows that:oil and gas sealing period(middle period of Dongying Formation deposition to present)in configuration of Dazhangtuo Fault and regional mudstone caprock in middle sub-member of Es1 is mainly distributed in midwest,with small part distributed in the middle of the eastern part,and with long period favorable for hydrocarbon accumulation and preservation in lower sub-member of Es1.Fault rock sealing oil and gas period(late period of Minghuazhen Formation deposition to present)is mainly distributed on 2 sides of the distribution of eastern mudstone sealing oil and gas period,being short and unfavorable for hydrocarbon accumulation and preservation in lower sub-member of Es1.The results are coincident with the distribution of oil and gas discovered in lower sub-member of Es1 in Dazhangtuo Fault,indicating the feasibility of this method for predicting the distribution of oil and gas sealing period in fault-caprock configuration.The research results can provide basis for oil and gas exploration under fault-caprock configuration.