复式小型断陷湖盆群洼槽生长演化过程及与油气富集关系研究

For the contradiction between the consumption and the supply and demand of oil and gas resources intensifies, looking for scattered, small but fat oil and gas resources is the most important in the following exploration while monolithic large gas fields were discovered. In recent years, some oil and gas rich troughs have been discovered in a series of complex small rift lacustrine basins group developed around the eastern part of central Asia Mongolia arcuate tectonic belt, such as Hailar-Tamsag basin and Erlian basin, but the success rate of drilling is lower than expection. The reason is that each trough is independent and complex small rift lacustrine basins group has the characteristic of multiple troughs composite structure, which differs it from the traditional rifted basins in the tectonic framework and formation mechanism, such as Songliao basin, Bohai Bay basin, so research of trough growth and evolution mechanism is urgently needed to guide the oil and gas exploration. For this significant weak link, the project taking Hailar-Tamtsag basin as an target area, identifying troughs by using space development regular of transverse anticlines and structural response characteristics such as field geological observation, seismic attribute sections, stratigraphic contact relationships and growth rules of spacial transverse folds, on the basis of 〞three figure-one profile〞technology to restore the distribution of paleo faults and troughs, reappear the formation and evolution history of troughs through drawing the structural balance section and pagoda map and construct sand box physical modeling. Then analyse the center of subsidence and depocencer movement laws and its controlling to effective hydrocarbon source rocks and high-quality reservoir, which can also guide to revealing the effective resource potential and finding the laws of hydrocarbon accumulation.

随着油气资源消耗和供需矛盾的加剧，寻找零散且小而肥的油气资源是继整装大油气田发现之后的重要勘探领域。近年来，在中亚蒙古弧形构造带东段发育的一系列诸如海拉尔-塔木察格盆地、二连盆地等复式小型断陷湖盆群内发现了个别的富油洼槽，但钻探成功率较低，究其原因是洼槽间彼此相对独立，多洼槽复合的构造格局有别于诸如松辽、渤海湾等大型断陷盆地，故亟待开展洼槽生长演化机制方面的研究以指导油气勘探。针对这一薄弱但有重要意义的环节，本项目以海拉尔-塔木察格盆地为靶区，利用野外地质观察、地震属性切片、地层接触关系等构造响应特征以及空间横向褶皱发育规律对洼槽进行识别，在利用“三图一剥”技术恢复古断层和古洼槽分布的基础上，通过编制构造平衡剖面、宝塔图和构造砂箱物理模拟实验等手段再现洼槽的生长演化历史，分析洼槽的沉降-沉积中心迁移规律及其对有效烃源岩和优质储层发育的控制作用。为揭示有效油气资源潜力和油气富集规律予以指导。

本研究结合最新三维地震数据，对海塔盆地内构造演化及主干边界断裂进行了精细解析。利用“三图一剥”技术恢复海塔盆地古断层和古洼槽分布，解剖了盆地内洼槽构造演化过程，确定了南一段上和南二段地层沉积时期为洼槽主要演化时期，同时根据主干边界断裂平面生长机制将洼槽演化模式分为孤立断层控洼演化模式和分段生长断层控洼演化模式。采用平衡剖面技术和砂箱物理模拟实验以及结合不同时期断裂构造特征，自下向上厘定了5个构造演化阶段，并明确了不同时期的应力场特征。从多个角度来分析洼槽构造演化对油气成藏控制作用，得到洼槽对有效烃源岩分布的控制方式分为孤立洼槽控源分布和分段生长洼槽控源分布，其中反向断层控制的下盘掀斜隆起更易于形成优质储层。本研究通过系统分析复式小型断陷湖盆群的洼槽结构及构造演化特征对恢复古洼槽对烃源岩预测、油田提交优质新增探明储量以及加快裂陷盆地油气勘探步伐均具有理论价值和实际意义，同时对完善裂陷盆地“洼槽控油”理论及丰富裂陷盆地“断裂控藏”理论均具有重要的指导作用。