准噶尔盆地南缘下组合储层异常高压成因机制及演化特征

准噶尔盆地南缘喜马拉雅晚期构造挤压强烈，导致其下组合储层超压的形成和演化过程复杂。综合地层压力和实际地质资料，探讨了准噶尔盆地南缘下组合超压的测井响应特征和砂岩、泥岩的综合压实特征；结合改进的超压识别图版和声发射测定的古应力等，确认了研究区下组合储层超压的主要形成机制；结合构造应力和垂向载荷双重压实作用的数值模拟，定量分析了各超压形成机制的演化特征和对现今超压形成的贡献。结果表明，构造挤压作用是研究区下组合储层超压形成的最主要成因，其次为垂向上的不均衡压实作用及沿断裂的垂向和沿砂体的侧向超压传递作用。古近纪以来到塔西河期，垂向上的不均衡压实作用在研究区部分地区开始形成，该增压作用对四棵树凹陷东部和第三排构造带东部深层下组合齐古组强超压形成的贡献分别为1.4%和33.3%；塔西河末期以来，持续的强烈构造挤压作用引起了研究区下组合储层压力快速增加，该增压作用对四棵树凹陷东部和第三排构造带东部下组合齐古组强超压形成的贡献分别为65.8%和50.8%；独山子末期以来特别是第四纪，背斜的形成和断裂的开启引起下组合深层储层形成了快速的超压传递增压，该增压作用对四棵树凹陷东部和第三排构造带东部下组合齐古组强超压形成的贡献分别为32.8%和15.9%。

Genetic mechanism and evolution characteristics of overpressure in the lower play at the southern margin of the Junggar Basin,northwestern China

Intensive tectonic compression during the late Himalayan resulted in overpressure of complex evolution history in the lower play at the southern margin of the Junggar Basin.Based on an integration of formation pressure with geological data, this study discusses the features of log responses and comprehensive compaction of sandstone and mudstone in the lower play of the study area.The genetic mechanisms of the overpressure in the play are identified in combination with modified overpressure recognition diagrams and paleo-tectonic stress measured by Kaiser effect.The evolution characteristics of these mechanisms and their contribution to the current overpressure are also quantitatively evaluated based on the numerical simulation of both tectonic stress and overburden on compaction.The results show that horizontal tectonic compression is the main cause of the over-pressurized Qigu Formation in the lower play of the study area, followed by vertical disequilibrium compaction and overpressure transmission vertically along the faults and laterally in sandstone.The vertical disequilibrium compaction began to develop in certain parts of the study area since the Paleogene to the deposition of the Taxihe Formation.Its contribution to the presently over-pressurized Qigu Formation in the eastern Sikeshu Sag and the east part of the third row of structural belt in the play are 1.4% and 33.3%, respectively.The continuous tectonic compression in high intensity led to a rapid increase of overpressure in the lower play since the end of the Taxihe depositional period, with contributions of 65.8% and 50.8% respectively to the overpressure in the formation of the two locations.The overpressure transmission mechanism was initiated and accelerated in the deep reservoirs of the play since the end of the Dushanzi depositional period, especially the Quaternary, when anticlines and faults were formed.Its contributions to the overpressure of the formation in the two locations are 32.8% and 15.9%, respectively.