苏北盆地海安凹陷曲塘—李堡地区新生代演化和油气响应评价

THE CENOZOIC EVOLUTION AND PETROLEUM RESPONSE ESTIMATION IN THE QUTANG-LIBAO REGION OF THE HAIAN DEPRESSION, THE NORTH JIANGSU BASIN

曲塘—李堡地区位于苏北盆地海安凹陷南部,是受NE向和EW向大断裂控制的新生代盆地。总体表现为北断南超的箕状断陷盆地,期次性断裂活动分别控制北部曲塘次凹和南部海北次凹的沉降幅度和沉积厚度,形成3套生储盖组合。在新生代断陷-坳陷盆地原型叠加的构造-热体制边界条件控制下,5套烃源岩中的泰州组、阜一段和阜三段主力生油层在三垛组沉积末前后均已进入生油门限,盐二段沉积以来(11.3 Ma—今)进入生烃高峰。我们运用TSM盆地模拟评价方法计算出曲塘次凹总生烃量约为230.54×106 t,海北次凹总生烃量约为149.21×106 t;排烃期以坳陷发育期为主,总排烃量为88.837×106 t,坳陷期排烃占总量的95%以上。各次凹水势和油汇模拟分析表明,不同时期发育的不同级别的断裂影响着油气规模,邻近断陷深凹多期断裂复合构组的断块带是主要勘探区带,部分外斜坡带的鼻状隆起和断阶带也有可能是较有利的聚集带。

The Qutang-Libao region lies in the south of Haian depression, the north Jiangsu.It is a Neozoic depression controlled by NE- and EW-oriented big faults. Periodic fault activities controlled deposition and sediment in the Qutang subdepression in the north and the Haibei subdepression in the south, resulting in 3 combinations of hydrocarbon generation, reservation and capping. Primary hydrocarbon terrane including the Taizhou Fm. and the Member 1 and 3 of Funing Fm. came into threshold of oil yielding after the Sanduo Fm.subsided and then entered peak era when the Member 2 of Yanchen Fm.subsided. It is estimated applying the TSM basin modelling that, Votal hydrocarbon yielding of the Qutang subdepression is about 230.54×10~6 t,and that of the Haibei subdepression is about 149.21×10~6 t.The hydrocarbon expelling period took place during depression development, accounting for 95% of the total discharging amout (88.837×10~6 t).Fractures of different level generated in different period affect hydrocarbon scale.Fault belt of multiple faults near deep depression is the main target for exploration.Nose uplift in exterior slope and fault step belt may be favorable accumulation zone.