库车前陆盆地白垩纪巴什基奇克组沉积层序与储层研究

DEPOSITIONAL SEQUENCE AND RESERVOIR OF CRETACEOUS BASHIJIQIKE FORMATION IN KUQA FORELAND BASIN

文中紧密结合生产勘探实践 ,充分运用陆相前陆盆地的观点对库车前陆盆地陆相沉积层序控制下的白垩纪巴什基奇克组储层进行了重点研究。库车前陆盆地白垩纪地层具有北厚南薄分布的特点 ,在纵向上可以划分出两个层序 :层序 1为亚格列木组、舒善河组和巴西盖组 ;层序 2为巴什基奇克组。每个层序分别由低位体系域、湖侵体系域和高位体系域组成 ,其中层序 2巴什基奇克组为克拉 2气田主要储层。巴什基奇克组低位体系域为冲积扇—扇三角洲沉积体系 ,湖侵体系域为辫状河三角洲前缘沉积体系 ,高位体系域为辫状河冲积平原沉积体系。储集砂体类型主要为扇三角洲前缘和辫状河三角洲前缘水下分流河道砂体、河口坝砂体和辫状河冲积平原砂质辫状河道砂体 ,空间上由互相切割的多个辫状河道砂体叠置而成 ,具有厚度大、分布广、连续性好、物性好和隔夹层少的特点。巴什基奇克组储集岩以褐色中、细粒岩屑砂岩为主。储层孔隙类型以剩余原生粒间孔为主 ,具有排驱压力低和中小孔—中细喉的孔隙结构特点。巴什基奇克组为偏碱性成岩环境 ,压实和胶结作用中等偏弱 ,溶蚀作用改善了孔隙结构 。

Based on the theory of continental foreland basin combining with petroleum exploration practices,Basijiqike formation reservoir of Cretaceous in Kuqa foreland basin controled by continental depositional sequence has been studied. Cretaceous stratigraphy in Kuqa foreland basin is thicker in the north than in the south,and is composed of two sequences.Sq1 is equivalent to Yageliemu formation,Shushanhe formation and Baxigai formation.Sq2 is equivalent to Bashijiqike Formation.Each sequence is composed of lowstand system tract,transgressive system tract and highstand system tract. Important reservoir of Kela2 gas field is in the Bashijiqike Formation. Lowstand system tract of the Bashijiqike Formation is alluvial fan delta depositional system. Transgressive system tract is braided delta front depositional system. Highstand system tract is braided delta plain depositional system. The important reservoir rocks are brown medium to fine litharenite.The major sandbody types are distributary channel sand and channel-mouth bar of the braided delta front, and sandy braided channel sandbody of the braided delta plain. The reservoir is characterized by a lot of braid channel arising one erosion after another, great thickness,extensive distribution, more continuous,high porosity and permeability, and only a few barrier beds.Primary intergranular pores are the main reservoir space.The association of clay minerals shows that the diagenetic environment is alkaline one.The sandstone of Cretaceous experienced a middle weaker compaction and cementation.Dissolution of feldspar and lithic fragment make the pores linking. Diagenesis has reached the late diagenesis the stage A.