松辽盆地古龙凹陷上白垩统浊积岩沉积与成藏特征

SEDIMENTARY AND ACCUMULATION CHARACTERISTICS FOR UPPER CRETACEOUS TURBIDITE IN GULONG SAG OF SONGLIAO BASIN

应用钻井和测井资料区分地层及沉积环境,通过岩心观察和粒度分析判断沉积类型,用三维地震属性分析技术识别和刻画地质体,研究发现松辽盆地古龙凹陷上白垩统青山口组湖相区发育水道型浊积岩、带状浊积岩和湖底扇等3种类型浊积岩。水道型浊积岩发育在青山口组一段,以粉砂岩及细砂岩为主,沿古龙凹陷呈南北向线状展布,末端形成喇叭口状湖底扇,水道型浊积岩以形成低渗透岩性油藏为主,自然产能低,局部发育"甜点",需要储层改造才能获得较高产能;带状浊积岩发育在青山口组二段,岩性为粉砂—泥质粉砂岩,沿三角洲前缘向湖相区延伸,平面上呈宽带状,末端形成规模不等的湖底扇,带状浊积岩和湖底扇属于非常规储层,空间上相互叠置,形成连续型油藏,一般无自然产能,依赖水平井分段体积压裂才能获得工业产能。

The stratigraphic and sedimentary environments are classified by the drilling and well logging data,and the sedimentary types are judged through the core observation and particle size analyses,with the help of 3D seismic attribute analyzing technique,the geological bodies are identified and characterized,three types of the well-developed turbidite including channel-type turbidite,banded turbidite and sublacustrine fan are studied and discovered in Upper Cretaceous Qingshankou-Formation lacustrine-facies zones of Gulong Sag of Songliao Basin. The former is developed in Member 1 of the formation,taking the siltstone and fine sandstone as the main forms,and moreover they are linearly distributed along the NS direction of Gulong Sag,and the flared-form sublacustrine fan is found at the end of the turbidite where the low-permeability lithologic oil reservoirs are mainly enriched and charac-terized by lower natural productivity and partial'desserts',thus the reservoir stimulation is needed to achieve higher productivity; the middle is developed in Member 2 of the formation with wide-banded planar distribution,its lithology is composed mainly of siltstone-argillaceous siltstone,extended to the lacustrine-facies zones along the delta front,the turbidite is formed at the end of the rocks with unequal sizes of the sublacustrine fan. Both of the latter belong to unconventional reservoirs,and in detail,the continuous oil reservoirs are vertically overlaid and unfortunately with rather lower natural productivity,so the horizontal-well segregated volume fracturing is needed to achieve the industrial productivity.