塔北地区寒武系白云岩特征与成因研究

Characteristics and origin of Cambrian dolomite, northern Tarim Basin

邢秀娟 焦存礼 王毅 张涛 刘士林

Xing Xiujuan Jiao Cunli Wang Yi Zhang Tao Liu Shilini

中国石油化工股份有限公司, 石油勘探开发研究院, 北京, 100083 2. 中国石油大学(北京), 北京, 102249 3. 中国石油长庆油田分公司勘探部, 西安, 710021

SINOPEC Petroleum Exploration & Production Research Institute, Beijing 100083, China 2. China University of Petroleum, Beijing 102249, China 3. Exploration Department, Changqing Oilfield Company, PetroChina, Xi'an, Shaanxi 710021, China

塔北地区横跨塔北隆起和库车坳陷南缘,是塔里木盆地最大油气富集区之一。该区寒武系台地相沉积厚达1 000 m,是重要的勘探目的层,其中白云岩厚度大、类型多、分布广,发育优质储层,是主要勘探对象。通过塔北地区寒武系钻井岩心和柯坪露头区寒武系白云岩岩石学及同位素、稀土元素地球化学对比分析,结合流体包裹体测温学研究,认为塔北地区寒武系白云岩具有泥微晶到细—中晶和粗晶等多种结构类型,其形成除准同生白云岩化和埋藏白云岩化作用外,还存在构造—热液白云岩化作用,后者受断裂—裂隙、不整合及热流体作用控制,常形成鞍形白云石和多种热液矿物共生组合,是优质白云岩储层形成的重要成岩作用。塔北地区受多旋回构造演化、成岩演化的控制,古隆起遭受多期剥蚀,寒武系白云岩与中生界形成角度不整合,发育强烈的风化壳岩溶作用;同时深大断裂形成通道,使得深部流体对白云岩进行溶蚀改造,形成不同成因类型叠加的复合型的优质白云岩储层。

From the Northern Tarim Uplift to the southern margin of the Kuche Depression,the northern Tarim region is one of the largest hydrocarbon enrichment regions in the Tarim Basin.The Cambrian platform sediment is 1 000 m thick,and is an important exploration layer.Due to big thickness,various types and wide distribution,dolomite in the region is favorable for reservoir generation and is the main exploration target.Based on lithologic,isotopic and REE analyses of well cores and outcrops of Cambrian dolomites in the northern Tarim region,combined with temperature studies of fluid inclusions,it has been concluded that the Cambrian dolomites in the northern Tarim region have various structural types,including mud microcrystal,fine-medium crystal and coarse crystal.Besides penecontemporaneous and burial dolomitization effects,they were also influenced by tectonic and hydrothermal dolomitization effects,which were controlled by fault-fracture,unconformity and thermal flow,usually resulting in the coexistence of saddle dolomite and multiple hydrothermal minerals.The tectonic and hydrothermal dolomitization effects were important for favorable dolomite reservoir generation.Controlled by cycles of tectonic and diagenesis evolutions,ancient uplifts in the northern Tarim region were eroded for several times.Angular unconformity took place between Cambrian dolomite and Meso-zoic,and strong weathering crust karst effect generated.Deep and big faults worked as pathways for deep fluid to flow into dolomite.The dolomite was transformed into complex high-quality reservoir of different origin.

国家重大专项(2008ZX05005-002);国土资源部全国油气资源战略选区调查与评价项目(2009GYXQ02)

https://doi.org/10.11781/sysydz201102130