基于模糊变异熵权法的页岩气藏多参数评价——以四川盆地武隆地区F-2井为例

Multiple parameter evaluation of shale gas reservoirs based on a fuzzy entropy weight and coefficient variation method:A case of well F-2 in Wulong Area,Sichuan Basin

受地质条件、经济成本和开采工艺等影响,页岩气开发前需对页岩储层质量进行评价。目的为明确影响页岩储层质量的关键参数,方法以黏土矿物、脆性指数、TOC、孔隙度和含气量为评价指标,采用熵权法-变异系数法求组合权重,并利用模糊理论联合TOPSIS法和RSR法评价F-2井五峰组-龙一1段(龙111段、龙112段、龙113段、龙114段)储层品质。结果结果表明:(1)武隆地区F-2井五峰组-龙一1段页岩矿物组分以石英和黏土矿物为主,物质组分与物性垂向非均质性显著。(2)五峰组-龙111段石英平均含量最高、TOC平均含量大于4%、孔隙度大于4%,向上各指标均出现降低趋势,至龙114段降至最低;五峰组-龙111段含气量相对较高,龙114段含气量降至2%以下。(3)龙111段沉积期水体相对较深、较低能,形成了最佳的物质组分比例与最高的有机质含量,层理发育,富含生物源硅质,有机孔隙发育,储层质量最优;龙112段和龙113段沉积环境相对较浅,陆源碎屑输入增多,储层品质次优;五峰组沉积期储层发育于滞留海盆环境,部分层段受陆源输入影响,非均质性相对更强,整体品质相对下降;龙114段储层品质最差。结论因此,建议优先开采龙111段,次选龙112段、龙113段和五峰组其他部分层段。

Due to the complex geological conditions,insufficient economic costs and mining technology and other factors,it is necessary to evaluate the quality of shale reservoir before exploiting the shale gas.Objec⁃tives In order to explore the key parameters that affect the shale reservoir quality,Methods taking clay minerals,brittleness index,TOC,porosity and gas content as evaluation indexes,the entropy weight method and variation coefficient method were used to calculate the combination weight,and the fuzzy theory combined with TOPSIS method and RSR method was used to evaluate the reservoir quality of Wufeng Formation-Long11 subsection(Long 111,Long 112,Long 113,Long 114)of well F-2.Results The results showed the shale mineral components of Wufeng Formation-Long 11 subsection of well F-2 in Wulong Area were mainly quartz and clay minerals,and the vertical heterogeneity of material components and physical properties was significant.The average content of quartz in Wufeng Formation-Long 111 subsection was the highest.Its average content of TOC was more than 4%,and its porosity was greater than 4%.A relatively downward trend of these elements had been shown in the upward direction,and they dropped to the lowest in Long114 subsection.The gas content was relatively high in Wufeng Formation-Long 111 subsection,and also showed a downward trend in the upward direction,and in Long 114 subsection the gas content decreased to less than 2%.The Long 111 subsection with relatively deep water body and high static degree formed the best material composition ratio and the highest organic matter content during the sedimentation period.Its bedding was well developed and rich in biogenic silica,and its organic pores were developed to a high degree.Therefore,its reservoir quality was optimal.The sedimentary environment of Long 112 subsection and Long 113 subsection was relatively shallow.The input of terrigenous detritus to these two sections was increased,and the reservoir quality was inferior.In the sedimentary period of Wufeng Formation,the reservoir was developed in a detention basin environment,and the heterogeneity of some intervals was relatively stronger due to the influence of terrigenous input,and the overall quality was relatively lower.The reservoir quality of Long 114 subsection was the worst.Conclusions Therefore,it was recommended to give priority to the exploitation of Long 111 subsection,and the exploitation of Long 112 subsection,Long 113 subsection and other parts of the Wufeng Formation was the second choice.