苏北盆地高邮凹陷热史恢复与成藏期判识

在镜质体反射率、磷灰石裂变径迹和包裹体均一温度系统测试分析的基础上,对高邮凹陷主要构造带进行古地温梯度计算和热史恢复。确定了高邮凹陷主要构造单元古地温梯度:镜质体反射率计算出深凹带古地温梯度为35.6℃/km,北斜坡西为43.9℃/km,北斜坡东为33.2℃/km;磷灰石裂变径迹计算出深凹带古地温梯度为31.4℃/km,北斜坡西为39.3℃/km,北斜坡东为50℃/km;包裹体均一温度计算出深凹带古地温梯度为29℃/km,北斜坡西为42.5℃/km,北斜坡东为32.3℃/km。对比分析现今地温梯度得出:深凹带古地温梯度高于现今0～7℃/km;北斜坡西古地温梯度高于现今10～15℃/km;北斜坡东古地温梯度高于现今4～21℃/km,今古地温梯度变化规律为深凹带变化小,斜坡带变化大。将典型单井埋藏史-热史与包裹体均一温度综合分析,判识高邮凹陷深凹带成藏期介于46～37Ma,北斜坡成藏期介于40.9～37.5Ma,具有深凹带早于北斜坡的规律,判定出三垛期为苏北盆地高邮凹陷主要成藏时期。

The thermal history reconstruction and hydrocarbon accumulation period discrimination of Gaoyou Depression in Subei Basin

Based on the analysis of the vitrinite reflectance,apatite fission track and homogenization temperature of fluid inclusions,we carried out the paleo-temperature gradient calculation and thermal history reconstruction,and then identified the paleo-temperature gradient of main tectonic units of Gaoyou Depression. The calculations of the paleo-temperature gradient gave the following results:(1) from the vitrinite reflectance:35.6 ℃/km in the deep concave zone,43.9 ℃/km in the west part of the north slope and 33.2 ℃/km in the east part of the north slope; (2) from the apatite fission track:31.4 ℃/km in the deep concave zone,39.3 ℃/km in the west part of the north slope and 50 ℃/km in the east part of the north slope; (3) from the homogenization temperature of fluid inclusions:29 ℃/km in the deep concave zone,42.5 ℃/km in the west part of the north slope and 32.3 ℃/km in the east part of the north slope. Compared to the present-day geothermal gradient values,the paleo-geothermal gradient was 0-7 ℃/km higher in the deep concave zone,10-15 ℃/km higher in the west part of the north slope and 4-21 ℃/km higher in the east part of the north slope. The comparative analysis showed that the difference of the ancient value and the present value of geothermal gradient is small in the deep concave zone and significant high in the slope zone. Through the comprehensive analysis of the buried history-thermal history of typical single-well and the homogenization temperature of fluid inclusions,we inferred that the accumulation period of the deep concave zone of Gaoyou Depression was between 46-37 Ma and the accumulation period of the north slope was between 40.9-37.5 Ma; the infill injection of the deep concave zone occurred earlier than that of the north slope. Then,it can be judged that the Sanduo period(E2s)was the main hydrocarbon accumulation period in Gaoyou Depression of the Subei Basin.