大港探区油气形成过程的古地温特征及其演化

THE CHARACTERISTICS AND EVOLUTION OF THE PALEO-TEMPERATURE DURING FORMATION PROCESS OF OIL- GAS IN DAGANG EXPLORATION AREA

大港探区包括黄骅凹陷及其周缘地区。依据流体包裹体测温学研究,本区的油气形成过程主要经历了三期古地温变化,并与油气运移和成藏期次相一致。各区古地温变化略有差异,主要是由于热液活动、岩浆侵位和断裂构造所造成。第一期古地温变化在区域上表现为北高南低和东高西低的特点;第二期则表现为西高东低和北高南低的特点;第三期古地温变化不明显,趋于平缓。总的古地温变化随时间演化呈现出由强到弱,逐渐趋于平缓的态势。表现出古高今低,晚期具有继承早期而发育的特点。古地温变化与大地构造环境具有密切关系和成因联系,是控制油气运移和成藏的重要动力学因素。

Dagang exploration area is located in the hinterland of Bohai basin, including Huanghua depression and its surrounding areas. According to the features of tectonics, this exploration area can be classified into three sectionsnorth, middle and south regions. The research results on the temperatures determined from the fluid inclusions showed that the paleo-temperature experienced three periods change, which was corresponding to that of the migration and accumulation of oil-gas. The paleo-temperature of the individual section had a slight difference, which was caused by the activities of volcanoes and hydrothermal fluids, as well the emplacement of magmas and tectonic process. The studies on the paleo-temperature characteristics revealed that the change of the paleo-temperature was very different. The paleo-temperature of the first period in south area is generally higher than that in north area, and the paleo-temperature in west area is lower than that in east area.The paleo-temperature of the second period in west area was higher than that in east area and north area is generally higher than south area. The change of the paleo-temperature was not very obviously in the third period and tended to be stabilized. Generally speaking, the paleo-temperature varied with time and had a the tendency from intensive to weak. The change of the paleo-temperature was closely related to the tectonic background of the area. It was an important dynamic factor controlling the migration and accumulation of oil-gas.