夹层型页岩油突破及其油气地质意义——以四川盆地中部G119H井为例

Exploration breakthrough of sandwiched shale oil in Sichuan Basin and its gas-oil geological implications:Taking Well G119H in the central Sichuan Basin as an example

近期,中国石油西南油气田公司在四川盆地中部(以下简称川中)公山庙西地区部署实施的侏罗系凉高山组夹层型页岩油重点评价井——G119H井,测试获产油20 t/d、产气0.6×10^(4) m^(3)/d,取得了该盆地湖相夹层型页岩油的新突破。为了进一步明确四川盆地凉高山组湖相页岩油的资源潜力及勘探前景,基于G119H井所在区域的地质、地震资料,开展了凉高山组沉积地质背景、河道刻画、优质储层特征、富集模式等研究。研究结果表明:(1)凉高山组在多期湖盆迁移背景下,纵向发育多期叠置湖相页岩、三角洲前缘砂体;(2)公山庙西地区凉二段底部发育浅水三角洲前缘砂体,砂体由西南向北东推进入湖;(3)凉二段分流河道为最有利微相,岩性主要为细—中粒岩屑砂岩,平均孔隙度达6.3%,孔喉结构为小孔—微喉连通模式,可动油占比较高;(4)凉高山组夹层型页岩油分布广,具备烃源岩厚度大(超过10 m)、储层物性好、源储组合相邻匹配等有利条件;(5)该盆地内凉高山组夹层型页岩油有利地区面积约1.38×10^(4) km^(2),利用四川盆地现有三维地震资料刻画凉二段分流河道分布面积为2 336 km^(2),估算石油资源量约15×10^(8) t。结论认为,G119H井的突破揭示了川中地区凉二段夹层型页岩油具有规模开发潜力,进一步展现了盆地侏罗系页岩油良好的资源基础,明确了川中地区凉二段夹层型页岩油是“十四五”及中长期增储上产重点层段。

The PetroChina Southwest Oil&Gasfield Company deployed a key appraisal well G119H to explore the sandwiched shale oil in the Lianggaoshan Formation in the western Gongshanmiao area,central Sichuan Basin.Recently,the well achieved a production rate of 20 t/d oil and 0.6×10^(4) m^(3)/d gas in test,recording a new breakthrough of lacustrine sandwiched shale oil in the basin.In order to further clarify the potential resources and exploration prospects of such shale oil in the Sichuan Basin,this paper investigates the Lianggaoshan Formation in terms of sedimentary geological setting,channel characteristics,high-quality reservoirs,and accumulation models,based on the geological and seismic data collected in the area where Well G119H is located.The results suggest that the Lianggaoshan Formation vertically develops multiple periods of lacustrine shales and delta front sand bodies overlapped under the setting of multi-phase lake basin migration.In western Gongshanmiao,the second member of Lianggaoshan Formation (Liang-2 Member) is characterized by shallow-water delta front sand body at the bottom.The sand body advances into the lake from southwest to northeast.In this member,distributary channel is the most favorable microfacies,and the dominant lithology is fine to medium-sized lithic sandstone,with an average porosity of 6.3%and a pore structure consisting of connected small pores-microthroats,where a high proportion of movable oil takes.The sandwiched shale oil in the Lianggaoshan Formation is widely distributed,with several positive factors such as thick source rocks (>10 m),good physical properties of sandstone reservoirs,and favorable source-reservoir assemblage.According to preliminary evaluation,the favorable area for sandwiched shale oil in the basin is 1.38×10^(4) km^(2).Based on the existing 3D seismic data,the channel area of the Liang-2 Member is depicted to be 2 336 km^(2),and the sandwiched shale oil resources are estimated to be about 15×10^(8) t.It is concluded that the exploration breakthrough by Well G119H suggests a large potential of sandwiched shale oil in the Liang-2 Member in central Sichuan Basin and further proves the solid endowment of shale oil in the Jurassic of the basin.The sandwiched shale oil in the Liang-2 Member in central Sichuan Basin is determined as a key interval of the 14~(th) Five-Year Plan and the medium and long term incremental reserves/production.