摘要
利用裂变径迹分析方法测量了取自花海拗陷的钻井磷灰石样品的裂变径迹年龄和长度。结果表明,随井深增加年龄减小,平均径迹长度亦变短。取自白垩纪地层的磷灰石样品的裂变径迹年龄都比地层年龄年轻得多,表明沉积后曾长时间处于磷灰石裂变径迹退火带中,沉积前的径迹记录已部分消失,古地温高于今地温。利用蒙特卡罗随机取样的热史模拟方法对裂变径迹数据进行了分析,结果表明白垩纪地层沉积后曾经历过超过110 ℃的加热,达到最高古地温的地质时代是早白垩世晚期—晚白垩世末,为主要生烃期。新生代以来盆地变冷,生油岩的成熟度主要受古地温控制。在此基础上对该盆地的油气勘探方向进行了评价。
Apatite fission track analysis was carried out to study the thermal evolution and timing of hydrogen generation in the Huahai Basin. Fission track ages and lengths of apatite samples from the Huashen-1 well both decrease with increasing well depths. Apatite fission track ages of the samples from the Cretaceous system are all much younger than their stratigraphic ages,suggesting that the strata were heated to higher paleotemperature after deposition. Inverse modeling based on Monte Carlo random sampling was used to reconstruct the temperature-time history. The results show that the Cretaceous strata in the basin experienced maximum paleotemperatures of 110～120 ℃, which were attained during the Cretaceous Period; subsquent cooling took place in Mesozoic;the maturity of source rock was mainly controlled by the paleotemperature, and the timing of hydrogen generation was before 80～100 Ma.
关键词
磷灰石
裂变径迹
生烃期
热演化
油气勘探
apatite fission track thermal history modeling paleotemperature timing of hydrocarbon generation
