威远—自贡地区五峰期—龙马溪期古地形及其对页岩储层品质的控制  

PALEOTOPOGRAPHY OF WEIYUAN–ZIGONG AREA IN WUFENGIAN–LUNGMACHIAN STAGES(ORDOVICIAN–SILURIAN TRANSITION) AND ITS EFFECT ON THE QUALITY OF SHALE GAS RESERVOIR

作　　者：施振生[1] 王红岩[1] 林长木 孙莎莎[1] 金惠[1] 郝翠果[1] 陈胜[1] 张蓉 SHI Zhen-sheng;WANG Hong-yan;LIN Chang-mu;SUN Sha-sha;JIN Hui;HAO Cui-guo;CHEN Sheng;ZHANG Rong(PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083;Nuclear Industry No.262 Team of Zhejiang Province,Huzhou 313000;Laboratory of Geological Resources and Engineering,Huzhou 313000;Research Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay 834000)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]浙江省核工业二六二大队,浙江湖州313000 [3]浙江湖州地质资源与地质工程实验室,浙江湖州313000 [4]中国石油新疆油田分公司勘探开发研究院技术服务中心,新疆克拉玛依834000

出　　处：《地层学杂志》2020年第2期163-173,共11页Journal of Stratigraphy

基　　金：国家自然科学基金(41572079);国家科技重大专项(2017ZX05035-001)共同资助。

摘　　要：古地形影响着黑色页岩的累计厚度、储层品质和含气性。综合研究威远—自贡地区582.57km^2三维地震全覆盖、多轮二维、11口井及4根岩芯资料表明,该地区WF1—LM4笔石带发育时期的古地形为"一缓坡、一鼻隆、一台地、一中心"分布格局。缓坡位于自203井—威202井—威201井一线,为川中古隆起的水下自然延伸,地形坡度小,地层厚度相对较薄;鼻隆位于威203井—威205井—内江地区,与川中古隆起相连,地形坡降相对较小,形态上为鼻状;台地分布于邓探1井—富顺地区,隆起幅度相对较小;沉积中心位于威远—自贡—威206井区,水深较大,水体还原性较强。WF1—LM1带发育期,威远小型鼻隆分布于威204井—威206井之间,五峰期分布面积63 km^2,LM1带分布面积45 km^2;LM2—LM4带发育期,鼻隆分布于威202井区,面积仅29 km^2。古地形差异表现在页岩厚度、地震反射特征和笔石带等方面。沉积中心区地层厚度最大,由沉积中心向两侧上超尖灭,笔石带减少或缺失。古地形差异造成页岩储层厚度、品质及含气性等差异,沉积中心区页岩储层最厚、TOC含量、脆性矿物含量、孔隙度及含气量均最高,单井测试产量大于15万方/天。综合地层厚度和储层品质,本研究认为沉积中心区是Ⅰ类有利开发区,斜坡区是Ⅱ类有利开发区,鼻隆区是Ⅲ类页岩气开发区。Paleotopography is among the principal controlling factors for the shale thickness,reservoir quality and gas-bearing properties of the Wufeng–Lungmachi shale.A comprehensive study of the 3D seismic data,2D seismic data,11 wells,and 4 drill-core data for the Weiyuan–Zigong area of 582.57 km^2 shows that the area included landforms of a ramp,a nose-shaped bulge,a platform,and a depocenter in the time interval of WF1–LM4(Dicellograptus complanatus Biozone to Cystograptus vesiculosus Biozone)of Late Ordovician to Early Silurian.The ramp,located along wells of Zi 203–Wei 202–Wei 201,was characterized by its gentle slope and thin shale thickness.The nose-shaped bulge,located in the well Wei 203–Wei 205–Neijiang area and graded into the Central Sichuan Submarine High,was featured by its distinctive shape and gentle slope.The platform is situated in the well Dengtan 1–Fushun area and distinctive in its relatively small elevation and relief.The depocenter,located in the area of Weiyuan–Zigong–well Wei 206,was typified by its large water depth and strong reduction of water column.In the WF1–LM1 time interval,a small-scale,nose-shaped bulge was developed in the area between well Wei 204 and Wei 206,ca.63 km^2 in the Wufengian Stage and 45 km^2 in the LM1 age.In the LM2–LM4 time interval,the nose-shaped bulge shrank significantly to be around the well Wei 202,with an area of only 29 km^2.These paleotopographic differentiations accounted for the differences of shale thickness,seismic reflection characteristics,and graptolite zones.The gas shale was the thickest in the depocenter and was thinner in the other areas.The paleotopographic differentiations are also the causes to the variations of shale reservoir thicknesses,TOC content,brittle minerals content,porosity,and gas content.In the depocenter,the shale thickness,TOC content,brittle mineral content,porosity,and gas content are all the highest and a single well production of gas may exceed 150000 m^3/d.Based on the shale thickness and reservoir quali

关 键 词：四川盆地 威远—自贡地区 古地形 五峰组—龙马溪组 页岩气 地层划分 

分 类 号：P534.42[天文地球—古生物学与地层学] P534.43[天文地球—地质学]