Sedimentary microtopography in sequence stratigraphic framework of Upper Ordovician and its control over penecontemporaneous karstification,No.I slope break,Tazhong,Tarim block

In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.

塔中Ⅰ号断裂坡折带上奥陶统碳酸盐岩储层微观孔隙成因

塔中Ⅰ号断裂坡折带上奥陶统良里塔格组碳酸盐岩储集空间类型主要有孔、洞、缝三大类,微观储集空间主要有粒内溶孔、铸模孔、粒间溶孔、晶间溶孔和微裂缝。通过对台地边缘16口井的良里塔格组灰岩进行岩石薄片鉴定、胶结物地球化学分析以及成岩演化序列研究,指出微观孔隙主要形成于埋藏成岩环境中,并列出4项具有指示意义的证据,包括:方解石胶结物中高温包裹体普遍存在;方解石胶结物稳定氧碳同位素丰度分异特征;灰岩中丰富与优质储层伴生的指示埋藏成岩作用的白云石;广泛分布的H2S气体。此外,分析了溶蚀性流体的主要组分和不同区域埋藏溶蚀作用强度的差异性。

塔里木板块塔中83井—16井区上奥陶统礁滩复合体储层结构

塔里木板块塔中I号坡折带的塔中83井—塔中16井区上奥陶统良里塔格组碳酸盐岩地层钻遇厚度170～300m,这套镶边台地型沉积相一般展示为4～5个礁滩复合体叠加旋回,岩相以及之后的岩溶、构造作用是控制圈闭单元形成的决定因素。根据岩芯、薄片及测井的各类指标分析,储集空间类型可划分为溶洞、孔洞、粒内溶孔、铸模孔、粒间溶孔、晶间溶孔、生物格架孔、裂缝等类型;据孔隙结构特征及结合方式可确认孔洞型、裂缝-孔洞型、裂缝型3种比例相当的构建方式。孔隙度、渗透率相对较高的有利储层平面上主要分布在靠近塔中I号坡折带的台缘区,与礁滩体建造密集带相吻合。台地边缘外带具有良好的原始岩相基础,经历多期溶蚀改造且充填程度低,储层类型以裂缝-孔洞型和孔洞型为主,属于I,Ⅱ类厚度大的优质储层。而台地边缘内带沿塔中12井—塔中16井区储层类型以裂缝型为主,但后期充填程度较高,多属Ⅱ,Ⅲ类储层。

塔中Ⅰ号坡折带上奥陶统礁滩相特征及其对储层的控制

研究区上奥陶统良里塔格组沉积时期发育生物礁、灰泥丘、粒屑滩等亚相,这些亚微相组合成的礁(丘)滩复合体已发育。礁滩体的横向变化特征总体上表现为沿Ⅰ号坡折带发育礁滩复合体,内侧主要形成丘滩复合体。储层发育受礁型微地貌影响明显,高能相带的礁滩体有利于储层的发育。礁型微地貌控制着储层发育的层位性与区域差异性。