下刚果盆地A区块流体势特征及其对油气运聚的影响

Characteristics of fluid potential and its implication to hydrocarbon migration and accumulation in block A, Lower Congo Basin

下刚果盆地A区块因发育盐岩而分为盐上与盐下2套含油气系统,油气运聚方式存在一定差异。结合三维地震和盆地模拟资料,综合考虑温度场和压力场对油气密度的影响,重点查明了下刚果盆地A区块流体势特征及其对油气运聚的影响。盐上含油气系统流体势具有位控和相控特征,油气运移的动力机制为以浮力和毛管压力为主控因素的流体势势差驱动,油气成藏的关键要素为有效发育的张性断裂和海相烃源岩及浊积砂岩间的良好匹配;盐下含油气系统流体势具有位控和压控特征,油气运移的动力机制为以浮力和水动力为主控因素的流体势势差驱动,油气成藏的关键要素为盐构造处下伏地层埋藏深度和盐岩厚度大小间的耦合关系。总体而言,研究区流体势低势区与已发现油气藏匹配较好,油、气及水势低值叠合部为下一阶段油气勘探的重点区带。

Petroleum systems of block A in Lower Congo Basin were divided into two salt layers such as pre-salt and pos-salt, and hydrocarbon of this two systems migrated in different ways. Based on seismic and basin modeling data, temperature and pressure fields were employed to calculate density of oil and gas in order to find out the characteri- stics of fluid potential and its implication to hydrocarbon migration and accumulation in block A of Lower Congo Basin. The fluid potential of post-salt petroleum system was controlled by depth and sedimentary facies. Hydro- carbon migration dynamics exhibited fluid potential driving difference, with the most important controlling factors being buoyancy and capillary pressure. The key factor of hydrocarbon accumulation is the good match between effective tensional fault, marine oil-gas source rock and turbidite stone. The fluid potential of pre-salt petroleum system was characterized by depth-controlled and hydraulic pressure-controlled while buoyancy and overpressure allowed hydrocarbons to migrate. underlying salt layer and study area, and the coinc The key factor of hydrocarbon accumulation is the coupling between burial depth of strata salt thickness. Overall, fluid potential is better matched with hydrocarbon discovery in the iding lower regions of oil, gas and water potential are the major next-term exploration area.