页岩气工业建产区选区地质评价指标及其下限标准--以蜀南地区X区块为例

Geological evaluation indexes and lowest limit standards for selection of shale gas industrial construction areas:Case study of X block in southern Sichuan Basin

蜀南地区作为我国页岩气商业开发示范区,勘探开发前景良好。为了解决页岩气单井产能差异大、部分产井低能低效的问题,从X区块实际产气效果出发,结合页岩测井解释数据、X?射线衍射、岩石有机碳分析和储层物性等资料,对页岩气产能的影响因素进行分析,确定页岩气工业建产区地质选区评价指标;根据研究区目前开采深度,以8.0×104 m^(3)/d作为页岩气工业油气流下限,探究相应地质评价指标的下限标准。研究表明:①优质储层钻遇率、TOC、有效孔隙度、脆性指数对页岩气产能的影响作用比较显著,可以作为页岩气工业建产区选区地质评价的关键指标;②页岩气产能与页岩总含气量没有十分必然的联系,而与游离气含量及游离气占比呈现十分明显的正相关关系,因此页岩游离气含量和占比可作为页岩工业建产区的选区评价指标;③相比于BImer和BRMC4指数,BIbm指数能够更好地指示页岩脆性;④要达到工业油气流下限标准,建议优质储层钻遇率至少要达到65%、TOC含量要达到3.3%、孔隙度要达到3.5%、含气量要达到3.0 m^(3)/t,其中游离气占比要达到60%以上,即游离气含量要达到2.0 m^(3)/t、BIbm指数要达到0.5。

As a demonstration zone for commercial shale gas development in my country,the areas in southern Sichuan Basin have a good prospect for exploration and development.In order to solve the problem of large different single well productivity in shale gas and low energy and low efficiency of some production wells,starting from the actual gas production effect of the X block,combined with shale logging interpretation data,X-ray diffraction,rock organic carbon analysis and reservoir physical properties,the factors which influence shale gas production were analyzed to determine the evaluation index of the geological selection of the shale gas industrial production area,also using 8.0×104 m^(3)/d as shale gas industrial flow lowest limit,exploring the lowest limit standard of corresponding evaluation index.The study shows that:(1)The drilling rate of high-quality reservoir,TOC content,porosity,and brittleness index have a significant effect on shale gas production capacity,and these can be used as a key indicator for the selection of shale gas industrial production areas.(2)Shale gas production capacity is not necessarily related to the total gas content of shale,but it has a very obvious positive correlation with the relationship between free gas content and free gas proportion.Therefore,free gas content and proportion of shale can be used as one of the evaluation indicators for the selection of production areas.(3)Compared with BImer and BRMC4,BIbm can better indicate the shale brittleness.(4)To reach the lowest limit of industrial oil and gas flow,it is recommended that the drilling rate of high-quality reservoirs should reach at least 65%,TOC content should reach 3.3%,porosity should reach 3.5%,gas content should reach 3.0 m^(3)/t,and the ratio of free gas accounts should reach more than 60%,that is,the free gas content should reach 2.0 m^(3)/t,and the BIbm should reach 0.5.