层序格架下页岩岩相非均质性及其储层品质差异性

页岩岩相作为页岩气勘探开发研究的基础，对于页岩气储层基础地质评价具有至关重要的作用。针对四川盆地南部长宁地区五峰组—龙马溪组一段（龙一段）页岩，在层序划分基础上，基于岩心、钻井、分析测试等资料，研究层序格架下页岩岩相非均质性特征及其储层品质差异。结果表明：①川南长宁地区五峰组—龙一段可划分成2个三级层序SQ1、SQ2，每个三级层序均由海进体系域（TST）和高位体系域（HST）构成，进一步将SQ1和SQ2划分出6个准层序组。②川南长宁地区SQ1—SQ2层序内主要发育混合硅质页岩、含黏土硅质页岩、含灰/硅混合质页岩、混合质页岩、含黏土/硅混合质页岩及含硅灰质页岩6种岩相类型。SQ1—TST时期以含灰/硅混合质页岩为主，SQ1—HST时期灰质含量较高，发育含灰/硅混合质页岩和含灰硅质页岩。SQ2—TST时期，硅质含量增多，稳定发育混合硅质页岩。SQ2—HST早期，由于黏土含量增多，主要发育含黏土硅质页岩为主。SQ2—HST中晚期（准层序组5、准层序组6）灰质含量、黏土含量较高，主要发育含黏土/硅混合质页岩。③平面上，SQ1—TST时期全区主要发育含黏土/硅混合质页岩，在研究区的西部和东部发育混合硅质页岩，北部发育含灰/硅混合质页岩。SQ1—HST时期，全区以混合质页岩为主，研究区东部发育含灰硅质页岩。SQ2—TST时期，全区主要为混合硅质页岩，南部N16井区主要发育含灰/硅混合质页岩，SQ2—HST时期，含黏土硅质页岩广泛分布于研究区。④不同层序内不同岩相储层品质具有明显差异：SQ1—TST时期混合质页岩以高碳为特征，含气性好，孔隙度高，是储层品质较好的岩相类型；SQ1—HST时期，岩相主要以混合质页岩和含灰/硅混合质页岩为主，其有机质含量较低，含气性较差。SQ2—TST时期以混合硅质页岩和混合质页岩储层品质最佳，有机质含量高，孔隙度高，含气性好；SQ2—HST时期所有岩相有机质含量均偏低，孔隙度偏低，含气性较差。

Shale lithofacies heterogeneity and the different of reservoir quality within sequence stratigraphic framework： Case study of Wufeng Formation-lower Longmaxi Formation in Changning area， South Sichuan Basin

Based on well logs， well cores and chemical test data， the authors established a sequence stratigraphic framework for the Late Ordovician Wufeng Formation to the Early Silurian Longmaxi Formation in the Changning area of the Sichuan Basin. The shale lithofacies heterogeneity within sequence stratigraphic framework was studied in detail through core observation and drilling data analysis， the results are as follows： （1） The Wufeng Formation to the Lower Longmaxi Formation was interpreted as two 3^rd sequences （SQ1 and SQ2）， and they are further divided into six parasequence groups. （2） Based on the lithofacies ternary diagram of siliceous minerals-carbonates minerals-clay minerals， six lithofacies in SQ1-SQ2 sequence were identified： mixed siliceous shale， argillaceous-rich siliceous shale， calcareous/siliceous mixed shale， mixed shale， argillaceous/siliceous mixed shale， calcareous-rich siliceous shale. The calcareous/siliceous mixed shale dominated in the SQ1-TST， while the SQ1-HST consisted of the calcareous/siliceous mixed shale and the calcareous-rich siliceous shale because of the high content of calcareous. The mixed siliceous shale dominated in the SQ2-TST due to the high siliceous content. In the early stage of the SQ2-HST， due to the increase of argillaceous content， argillaceous-rich siliceous shale was mainly developed. In the middle and late period of SQ2-HST， argillaceous/siliceous mixed shale is dominated because of the increase of calcareous and the high argillaceous content. （3） In the transgressive system tract of SQ1， the argillaceous -rich siliceous shale dominated in the study area， while mixed siliceous shale develops in the west and east， and the calcareous/siliceous mixed shale develops in the north. The highstand systems tract of SQ1 is characterized by the mixed shale in the study area， while the calcareous-rich siliceous shale develops in the west and east. The transgressive system tract of SQ2 is mainly composed of mixed siliceous shale， while the calcareous/siliceous mixed shale is dominated in the N16 well block in the south area， and the highstand systems tract of SQ2 is characterized by the argillaceous-rich siliceous shale. （4） The shale reservoir quality of different lithofacies is different in different sequence. In the transgressive system tract of SQ1， the mixed shale is characterized by high TOC， high gas content and high porosity， which is the best lithofacies type. The highstand systems tract of SQ1 is characterized by mixed shale and calcareous/siliceous mixed shale， the TOC content and gas content are both low. The mixed siliceous shale and mixed shale are characterized by high organic matter content， high porosity and high gas content in the transgressive system tract of SQ2， which are the best lithofacies types. The highstand systems tract of SQ2， almost all lithofacies have low TOC， low porosity and poor gas content.