东濮凹陷及邻区凹陷上古生界热演化史与二次生烃史研究

【作者】 刘丽；

【导师】 任战利；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2007， 博士

【摘要】 沉积盆地热演化史在油气勘探和油气成藏研究中占重要的地位。东濮凹陷及邻区受印支、燕山、喜山多次构造运动的改造和影响，中生代、新生代盆地类型明显不同，导致烃源岩热演化程度及热演化史复杂。对于研究区热演化史的恢复，以活动论及地质发展阶段论思想为指导，将盆地热历史与整个区域构造演化史的结合起来进行研究。将采用今、古地温并重；测试分析古温标样品，将地震、钻井与露头资料相结合，充分考虑不同期次盆地的叠加、改造对盆地地温场影响，建立热演化史的概念模型，分演化阶段恢复了不同构造单元的热演化史和生烃史，指出了东濮凹陷及邻区凹陷上古生界有利生烃区。主要取得了以下的认识：1、分析连续测温资料，认为研究区现今地温场格架主要受地壳深部结构、构造背景的控制。东濮凹陷地壳薄，临清坳陷中部区次之，开封坳陷最厚且受北北东向和北西西向两组断裂相互牵制和影响，导致地温梯度依次减小，分别为34℃/km、27-32℃/km、23.3-29.1℃/km之间。现今地温场平面分布受研究区构造格局的控制，相同层位埋藏厚度大的部位，地温高；埋藏浅的隆起部位温度低。2、在区域构造特征分析的基础上，有针对性的重新测试包裹体、磷灰石裂变径迹样品。综合分析，认为不同的构造单元古地温差别较大，将其划分为古今地温接近型、古地温高于今地温型两种类型。以兰聊断裂带、汤阴地堑、临清中部隆起区以及济源凹陷中央隆起带为例，分别确定了研究区中生代三叠纪的古地温梯度为31.7℃/km，早、中侏罗世古地温梯度为27.8℃/km，早白垩世末的古地温梯度分别为40-50℃/km；古近纪地温梯度为30-37℃/km。3、综合构造演化特征及多种古温标方法，划分了四个热演化阶段，确定了关键时期(中生代晚期)的古地温梯度为35-45℃/km，热流值可达90mW/m~2以上，热演化程度在此时期迅速升高，确定研究区中生代晚期(130-140Ma)发生了一期构造热事件。这次构造热事件对油气的生成运移和聚集起着十分重要的作用，在隆起和凹陷边缘使烃源岩达到最大演化程度，现今仍然处于生烃阶段。4、应用多种古地温研究方法与盆地模拟方法相结合，恢复了不同构造单元的古地温演化史，共划分了5种不同构造单元的热演化史类型。即中生代以来持续沉降增温型、中生代—古近纪持续增温新近纪以来降温型、中生代早期增温—中生代晚期降温—新生代增温型、中生代增温—降温交替变化新生代以来持续沉降增温型、抬升降温型。从热演化史的角度来看，前四类热演化史类型是古生界烃源岩找气的较为有利类型。5、东濮凹陷及其邻区古生界烃源岩二次生烃具明显的迟滞性，各构造单元生烃史有明显差异。结合构造演化特点和后期保存条件分析，确定东濮凹陷东、西部次凹、中央隆起带和中牟凹陷为明显二次生烃的有利区。更多还原

【Abstract】 The thermal history of sedimentary basins plays an important role on studies of petroleum exploration and hydrocarbon accumulation. The tectogenesis of Indosinian movement Yanshan movement and Himalayan orogenic movement reconstruct Dongpu sag and surrounding regions. Different basin types of Palaeozoic Mesozoic and Cenozoic lead to the complication of thermal evolution degree and paleogeothermal gradient of the source rocks. Using mobilistic theory and geoevolutionism as the governing principle restored thermal history of region of interest by the combination thermal history and the region structural evolution. The present-day temperature and palaeogeothermal are same important. By combination the seismic, drilling and outcropping data, according to the prototype basin of different time and thinking fully the influence of the superimpose and reformation by multiphase and multistage tectonic movements to geothermal, upbuilded conceptual model of thermal history, simulated the thermal evolution of the source rocks of Paleozoic in different tectonic units in accordance with the evolutionary phase, estimated the favorable hydrocarbon generation areas.1 Based on volumes of temperature data, the distribution of temperature is affected by deep-crustal structure and tectonic setting. Crust thinkening from Dong sag to middle part of Lingqing depression, Kaifeng depression has a more thickness Crust than Lingqing depression, and it is joint controled by the NNE and NWW faulting, which lead to the decrease of temperature gradient, the corresponding gradient is 34℃/km, 27-32℃/km and 23.3-29.1℃/km respectively. The distribution of temperature is affected by structural framework, tectonic position of buried deeply has higher temperature and the upwelling area has lower temperature at the same horizon.2 On the basis of analysis structural feature, inclusion and apatite fission track sample was retested oriented. The type of palaeogeothermal in Dongpu sag and surround regions was divided into two types by multidisciplinary analysis multiple data, (1)present-day temperature is close to palaeogeothermal,(2)palaeogeothermal is higher than present-day temperature. On the studies of Lanliao faulted zone, Tangyin graben, uplift of Linqing depression and central uplift belt of Jiyuan depression, temperature gradient of Triassic, Early-Middle Jurassic, Early Crataceous, Early Teriary is 31.7℃/km,27.8℃/km,40-50℃/km, 30-37℃/km, respectively.3, Using feature of structural evolution and multiple geothermometer, four thermal evolution phase were divided .The paleogeothermal gradient of critical time (late Mesozic) is 35-45℃/km and heat flow is higher than 90mW/m~2, and the degree of thermal evolution rising rapidly. A tectonic heat event happened in Late Mesozoic era in 130-140Ma.It is very important to hydrocarbon generation, migration and accumulations. Oil source rock of mole track and depression marginal zone are in largest degree of thermal evolution and still in the phase of hydrocarbon generation nowadays. To the oil source rock in depression, Cenozoic is the time of thermal evolution increasing and secondary hydrocarbon generation for the great subsidence.4 Combination geothermometer and basin modeling, reconstructed thermal history of different tectonic unit, five type of history of thermal was divided, i.e. (1)sustained elevating temperature after Mesozoic, (2)sustained elevating temperature after Mesozoic-Early and temperature drop after Neogene, (3)elevating-decreasing temperature alternately in early and late phase of Mesozoic and Cenozoic, (4) elevating-decreasing temperature alternately in Mesozoic and sustained elevating temperature after Cenozoic,(5)decreasing temperature for uplift. Viewed at thermal history, the first four types is beneficial to find gas.5 The secondary hydrocarbon of Dongpu sag and surrounding regions’s has the lag effect obviously. The different tectonic unit has different history of hydrocarbon generation. Combination characteristic of structural evolution and condition of conservation, the beneficial secondary hydrocarbon generation district of Upper Paleozoic were ascertained, i.e. Eastern and Western depression of Dongpu sag, central uplift belt of Dongpu sag and Zhongmou sag.更多还原