冀中坳陷杨税务地区奥陶系岩相古地理特征及其对潜山内幕储集层的控制作用

Ordovician lithofacies palaeogeography characteristics and their controlling effect on the reservoirs of buried hills in Yangshuiwu area,Jizhong Depression

近年来,冀中坳陷杨税务地区潜山内幕油气勘探取得了显著成绩,而潜山内幕储集层形成受控因素多、成因较复杂,表现出较强的储集层非均质性。岩相古地理为潜山内幕储集层发育分布的重要影响因素之一,对指导潜山油气藏的勘探具有重要意义,其研究就成为解决问题的关键。根据岩心和薄片观察、结合钻测井及油气生产数据,通过单因素综合分析,认为奥陶系为潮坪沉积,划分为潮下带、潮间带、潮上带3个沉积亚相及8个沉积微相类型,在垂向上沉积微相由于海平面升降变化频繁,空间亦相变快,以潮间—潮下带沉积微相为主。平面上优势沉积微相以潮下带灰坪、潮间带云灰坪、灰云坪及灰坪为主;不同沉积微相环境下的储集层孔隙度差异较大,结合油气生产,认为潮间—潮上带的云坪、灰云坪和云灰坪微相控制了有利储集层的分布。

In recent years,significant progress has been made in the exploration of oil and gas reserves in the buried hills of the Yangshuiwu area in the Jizhong Depression.However,the formation of reservoirs in inner buried hills is influenced by many complex factors,resulting in strong reservoir heterogeneity.Among these factors,lithofacies and palaeogeography obviously control the distribution of reservoirs in buried hills,which is helpful in guiding the exploration of oil and gas reserves.Based on studies of cores and thin sections,combined with drilling,logging,and oil and gas production data,it is believed that the Ordovician deposition in the Yangshuiwu area are tidal flat deposits,which consists of three sedimentary subfacies(subtidal zone,intertidal zone,and supratidal zone)and eight sedimentary microfacies.The frequent changes in sea levels caused the rapid variation in vertical sedimentary microfacies and it was characterized as an intertidal zone-subtidal zone.The dominant sedimentary microfacies in the plane direction are subtidal limestone flats,intertidal dolomitic limestone flats,limy dolomite flats,and limestone flats.The porosity of reservoirs in different sedimentary microfacies environments varied significantly.It is illustrated that some sedimentary microfacies,including the dolomite flat,limy dolomite flat,and dolomitic limestone flat in the intertidal zone-supratidal zone,control the distribution of favorable reservoirs.