大港探区上古生界烃源岩热史模拟——以泊古1井为例

Geothermal History Simulation of Upper Paleozonic Source Rocks in Dagang Prospecting Area—A Case Study of Well Bogu 1

摘要: 泊古1井位于渤海湾盆地中部的大港探区，沧县隆起西南侧泊头市附近。运用镜质体反射率(Ro)对大港探区上古生界烃源岩进行了热演化模拟并分析其生烃期次。研究表明，大港探区古生代热流值较低，到三叠纪(225 Ma)受印支运动的影响热流值持续升高，后因地层抬升剥蚀，热流值开始下降，直至渐新世末(25 Ma)，随后热流值趋于平稳。印支、燕山、喜山3大构造运动造成的不整合面上地层剥蚀量分别为3600、1000、300 m。泊古1井上古生界太原组烃源岩在中三叠世末期(239 Ma)进入生烃门限，227 Ma达到生油高峰期，后期地层多次沉降抬升，现今处于成熟早期阶段；山西组烃源岩成熟度演化历程与太原组基本相似，但比太原组的演化程度略低一些。晚三叠世为主要生排烃期。

Abstract: Well Bogu 1 was located in the center of Bohai Bay Basion where Dagang Prospecting Area was si-tuated. It was near the Botou City which was in the southwest of Cangxian Uplift. By taking Ro as palaeotemperature scale, the geothermal history of upper paleozonic source rocks in Dagang Prospecting Area was simulated, and hydrocarbon generation stages were analyzed. The results showed that the heat flow value in Dagang Prospecting Area was lower in paleozonic. Affected by Indo-China movement, the heat flow value in Triassic (225 Ma) was continuously elevated. Because of the strata uplift and erosion, the heat flow value began to decline till the end of Oligocene (25 Ma); then it tended to be steady. The stratigraphic erosion amount on the unconformity surface in Indo-China movement, Yanshan movement and Himalayan movement was 3600, 1000 and 300 m, respectively. The source rock of the Upper Paleozonic Taiyuan Formation in Well Bogu 1 enters the hydrocarbon generation threshold in the late period of Middle Triassic (239 Ma). It reached oil generation peak in 227 Ma. The strata are suffered by several subsidences and uplifts in the late period. Nowadays it is at the early maturation stage. The maturity evolution process of Shanxi Formation source rock is basically similar to Taiyuan Formation, but the evolution degree is slightly lower than that of Taiyuan Formation. Late Triassic is the main period of hydrocarbon generation and expulsion.