摘要
论文以千米桥潜山凝析气藏为例,在研究潜山形成演化基础上,采用先进技术手段(平衡剖面技术、碳同位素分析、储层流体包裹体测定),讨论了该潜山油气藏研究中三个重要问题:(1)古岩溶发育与奥陶系储层特征;(2)临近凹陷下第三系油气源:(3)油气生成史与运移期次以及成藏历史。论文取得以下成果:
1采用古构造分析和平衡剖面技术,研究了千米桥潜山的形成演化史,指出其下古生界奥陶系潜山的形成主要经历了稳定抬升、褶皱冲断、块断翘倾和热沉降坳陷四个时期。
2首次将千米桥潜山构造划分为三层结构:即潜山内幕逆冲断块、古地貌残山与低地和翘倾地垒块。
3探讨了该区潜山储层形成经历加里东、海西早期、印支和燕山中期运动抬升型岩溶作用,指出印支、燕山中期运动抬升型岩溶是形成良好储集层的关键。两期岩溶相互叠合发育形成了千米桥潜山奥陶系峰峰组和上马家沟组上段溶洞-孔隙型储集层。
4根据烃源岩地球化学特征和油气源对比,指出潜山凝析油气主要来自翘倾地垒块两侧板桥和歧口凹陷的沙三段腐植-偏腐植型有效烃源岩,该凝析油气是“新生古储”型潜山的主要油气源。
5根据烃源岩热演化史,结合奥陶系灰岩中不同类型的有机和盐水溶液包裹体类型、物理特征和均一温度分布,确定了油气的形成时期和运移期次。其中,油气形成有三个时期,其温度主值区间为:第一期,120~125℃,为生油时期,第二期,140~150℃,为凝析油生成时期,第三期,160~190℃,为凝析油和干气生成时期;油气运移期次为三期:即沙一早期—馆陶末期,明化镇早期—明化镇中期和明化镇晚期—现在,而且明化镇晚期以后油气才发生大规模运移。
6烃类产物的特征和气油比比较高,这表明潜山以气相(包括凝析气相)运移为主:早期的运移为凝析气相,晚期为气相。
7根据流体包裹体和油气地球化学特征,研究表明低成熟天然气源于板桥凹陷,而凝析气和高成熟天然气源于板桥和歧口凹陷;并指出千米桥潜山油气成藏分为四期:即沙一段—东营期第一成藏期、馆陶末期—明化镇早期第二期成藏期、明化镇期第三成藏期和明化镇末期以后的第四成藏期。据此作出预测,千米桥潜山的油气勘探,应以寻找临近板桥凹陷一侧的凝析油气藏为主,而临近歧口凹陷一侧则比较可能发现气藏。
8对黄骅坳陷区“新生古储”型潜山成藏条件的类比分析表明,中区凹陷中分布有厚度较大的优质沙三段烃源岩,南区分布有较好的孔二段烃源岩,但中区千米桥地区生储配置比南区好,因此,整体上中区千米桥潜山一带油气藏的勘探前景优于南区。目前,在千米桥潜山的东面和西面与歧口凹陷和板桥凹陷的邻近地区,且缺失石炭-二叠系的潜山,已成为寻找与千米桥类似油气藏比较现实的目标。
The paper takes an example of condensed gas feild in Qianmiqiao buried-hills. Based on the research of formation and development of the buried-hills, three important subjects in the research are discussed with the application of advanced technical and methods (namely, balanced cross sections, analysis of carbon isotope , mensuration of reservoir fluid inclusion): (1) the development of karstification and characters of reservoir in Ordovician ; (2) lower Tertiary (Es3) source in the depression nearby ; (3) the hydrocarbon generation history , migration phase and reservoir formation history. Results obtained in the research are:
l.By the virtue of palaeostructure analysis and method of balanced cross sections, we have studied the formation and development history of Qianmiqiao buried hills ,and indicate that the formation of Ordovician buried hills can be mainly divided into four periods, namely, stable uplift period , fold-thrust period , block-fault tilting period, and thermal subsidence and depression period .
2.It is the first time to divide the structure of Qianmiqiao buried hills into three structural layers : buried hills thrust fault block, paleogeomorphic relict mountain and lowland, tilting horst block.
3.It is discussed that the buried hill reservoir in this zone experienced karstification in Caledonian-early Hercynian , Indosinian and mid Yenshan movement period , and it is indicated that karst formed in late Indosinian and mid Yenshan movement period are the key periods to form fine reservoir. Karst formed in both periods piled up and formed the karst cave- pore reservoir of the Ordovician Fengfeng Formation and Upper Majiagou Formation in Qianmiqiao buried hills.
4.Based on the research of geochemical characters of hydrocarbon source rock and comparison of oil and gas sources , it is indicated that the condensed oil and gas in buried hills mainly came from ES3 effective hydrocarbon source rock of type III kerogen - type II2 kerogen in Banqiao deprssion and Qikou depression beside both sides of the tilting horst ,and which is the main source of buried hill with early reservoir and late oil and gas source .
5.With the help of thermal history of hydrocarbon source rock , and combined with the types , physical characters and homogeneous temperature distribution of organic and salty
solution fluid inclusion with different types in Ordovician limestones , the formation time and migration stages of oil and gas are determined. The formation of oil and gas experienced three periods with different temperature peak zone : first, 120-125 , oil generation period ; second, 140~150 , condensed oil generation period ; third , 160-190 , condensed oil and dry gas generation period .Likewise, the migration of oil and gas are divided into three stages : from early Esi to late Ng ,then from early Nm to mid Nm ,and last from late Nm to now . We can see clearly that oil and gas began to migrate with large scale after Nm .
6.The character of hydrocarbon production and high gas-oil ratio show that the main migration facies in buried hills is gas facies (including condensed gas facies) . The early
migration facies is condensed gas facies , later ,gas facies.
7..Based on fluid inclusion and oil and gas geochemical character, it is concluded that low mature gas came from Banqiao depression and condensed gas and high mature gas came from Banqiao depression and Qikou depression. Futhermore, the formation of reservoir experienced four periods: the first, from Esi to Ed ; the second , from late Ng to early Nm ; the third , Nm ; the fourth , from late Nm to now .So we predict that exploration in Qianmiqiao should be mainly directed to condensed oil and gas reservoir nearby Banqiao depression and gas reservoir is more probably found near Qikou depression.
8.Analogue of the conditions required for reservoir formation in Huanghua buried hills shows that,high quality and thick Es3 hydrocarbon source rock distributed richly in the middle area depression, and moderate quality sandstone distributed in south area, but
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