重力方法在伊和凹陷油气评价与勘探中的应用

发布时间：2018-05-17 00:04

本文选题：二连盆地 + 伊和凹陷　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：重力勘探是根据岩矿石之间存在的密度差异,进行地质问题研究及寻找矿产资源的一种传统的地球物理勘探方法。重力正演拟合是通过建立和修改场源初始模型来拟合实测重力异常,求取场源物性参数和几何参数,通过正演技术达到反演的目的。重力资料在盆地“探边摸底”、“定凹选带”等方面发挥着重要作用。重力归一化总梯度法是一种利用重力场的特征点或者解析函数中的奇点,探测并估计重力异常场源体的位置的方法。本文通过水平圆柱体及组合模型、三度体背斜构造来研究归一化总梯度法,通过铅垂断面图中归一化总梯度场“两高夹一低”的特征来探测背斜构造顶部的油气藏(或低密度体)。二连盆地由众多小凹陷组成,伊和凹陷是其中之一。在凹陷形成过程中,砂岩和泥岩会产生分离,而砂、泥岩分离程度决定了凹陷(找油角度)优劣程度,凹陷的分离程度越好,找油前景越好。其中,搬运距离和水动力活跃程度是决定砂、泥分离程度的两个决定性因素。伊和凹陷主要勘探目的层系为下白垩统巴彦花群,其中主要的生油层系为古生界、阿尔善组以及腾格尔组一段。本文结合理论模型深入分析了重力归一化总梯度法的基本原理,并将其应用于伊和凹陷,结果表明该凹陷评级较好。利用2.5D建模正反演技术对其中横跨主洼槽的两条测线进行可视化正演拟合。其中,以二维地震解释结果为初始模型的几何参数;以测井声波波速资料为初始模型的物性参数。参考盆地沉积特征,通过人机交互试错调整来实现密度横向变化。通过正演拟合揭示了主洼槽沉积层横向和纵向均存在较大的密度不均匀性,主洼槽有利于油气生成。与地震解释结果对比,二者在赛汉组-第四纪、腾格尔组深度相差不大,但在凹陷底部拟合结果与地震解释结果有明显差异。通过钻井结果验证,正演拟合各沉积层深度与钻井揭示的各层深度结果一致,并且从空间几何和物性(密度)角度证实钻井在阿尔善组底部发现的粗-细-粗沉积旋回(伊和组)存在的合理性。二维地震解释结果偏浅,其可能原因是时深转换选取的速度值偏小或者早期地震解释有错层现象。
[Abstract]:Gravity exploration is a traditional geophysical exploration method to study geological problems and find mineral resources according to the density difference between rock and ore. Gravity forward modeling is to establish and modify the initial model of the field source to fit the measured gravity anomaly, to obtain the physical and geometric parameters of the field source, and to achieve the purpose of inversion by the forward modeling technique. Gravity data play an important role in the exploration of the edge of the basin and the determination of the concave separation zone. The gravity normalized general gradient method is a method to detect and estimate the position of gravity anomaly field source body by using the characteristic points of gravity field or the singularity of analytic function. In this paper, the normalized total gradient method is studied by the horizontal cylinder and its combination model, and the three-dimensional body anticline structure. Based on the characteristic of normalized total gradient field in vertical fault diagram, the oil and gas reservoirs (or low density bodies) at the top of anticline structure are explored. Erlian basin is composed of many small sag, Yi-he sag is one of them. In the process of formation of sag, sandstone and mudstone will be separated, and the degree of separation of sand and mudstone will determine the good or bad degree of sag. The better the degree of separation of sag, the better the prospect of looking for oil. Among them, transport distance and hydrodynamic activity are two decisive factors to determine the degree of sand and mud separation. The main exploration target series in the Yi-he depression is the Bayanhua Group of the Lower Cretaceous, in which the main source systems are the Paleozoic, the Alshan formation and the first member of the Tengger formation. In this paper, the basic principle of gravity normalized total gradient method is deeply analyzed with theoretical model, and applied to Yihe sag. The results show that the sag has a good rating. The 2.5D modeling forward and inverse modeling technique is used to visualize forward modeling of two surveying lines across the main depression. The results of 2-D seismic interpretation are taken as the geometric parameters of the initial model and the logging acoustic wave velocity data are taken as the physical parameters of the initial model. According to the sedimentary characteristics of the basin, the lateral variation of density is realized by the adjustment of error-machine interaction. Through forward modeling, it is revealed that there are large density inhomogeneity in both transverse and longitudinal direction of the sedimentary layer of the main depression, and the main trough is favorable to the generation of oil and gas. Compared with the seismic interpretation results, the depth of the Seihan formation and the Quaternary and the Tengger formation have little difference, but the fitting results at the bottom of the sag are obviously different from the seismic interpretation results. The results of drilling show that the depth of each sediment layer fitted forward is consistent with that revealed by drilling. The rationality of the existence of coarse-fine-coarse sedimentary cycle (Yihe formation) found in the bottom of the Alshan formation is confirmed from the point of view of spatial geometry and physical properties (density). The results of 2-D seismic interpretation are shallow, which may be due to the low velocity value selected by time-depth conversion or the phenomenon of staggered layers in early seismic interpretation.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P631.1

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