【作者】 成玮；

【导师】 周瑶琪；

【作者基本信息】 中国石油大学 ， 地质学， 2010， 硕士

【摘要】 随着勘探难度的增加,泥岩裂缝性油气藏等非常规油气藏越来越受到人们的重视(张金功,袁政文, 2002;曾联波,肖淑蓉, 1999;甘秀娥, 2003;丁文龙,张博闻等, 2003;杨涛, 2007;徐福刚,李琦等, 2003)。泥岩裂缝可分为构造裂缝和非构造裂缝,非构造裂缝是指由非构造因素诱发形成的与构造应力无关或间接有关的裂缝类型(郭璇,钟建华等, 2004;赵澄林, 2001;姜在兴, 2003)。现代泥质沉积物非构造裂缝主要包括水下收缩裂缝和干燥裂缝两种,国内外学者已经对其进行了卓有成效的探索和研究,然而多数只针对其中一种裂缝展开讨论,且定量化程度低,尚缺乏综合性、定量化的研究。本文以黄河三角洲古河道为研究工区,分别针对水下收缩裂缝、干燥裂缝和首次提出的混合成因裂缝,进行了定量分级、分形特征、生长特征和形成模式等方面的研究,建立了不同种类现代泥质沉积物非构造裂缝的定量描述和对比标准。另外针对安徽巢湖凤凰山剖面石炭系高骊山组泥岩非构造裂缝,分析了其形态特征及可能的成因类型。黄河口现代泥质沉积物非构造裂缝可分为:水下收缩裂缝、干裂和混合成因的裂缝。本文详述了各个工区不同类型裂缝的形态特征,并且认为在沉积相无明显变化的研究区内能够发育如此多种多样的裂缝类型,其根本原因与原上覆水体体积和深度有关。通过对各个工区发育完全的裂缝最高级基块面积采取统一的标准进行定量分级,得到面积分布情况:水下收缩裂缝的面积分布最集中,干裂缝面积分布最广,而混和成因裂缝介于两者之间。选择覆盖法计算了裂缝分维度,发现裂缝的分形维值从水下收缩裂缝到暴露阶段和干裂随着发育程度有逐渐变大的趋势。观测发现干燥裂缝与水下收缩裂缝有相似的平面生长特征。文章通过选择合适的裂缝阶段,分别针对新开裂的裂缝和方向发生改变的裂缝,测量和统计了裂缝开裂和变化的角度,建立了相应的裂缝生长角度模式。利用收缩圆这种非线性模式解释裂缝的平面生长特征。剖面上可由收缩圆引申为收缩体来解释水下收缩裂缝,但是这与干裂的V字型成因有着本质的不同。通过综合分析,分别探讨了干燥裂缝、水下收缩裂缝及混合成因裂缝的形成模式,建立了某些裂缝间的相互联系、转化的关系。总的规律可以概括为对于不同深度的水体,由深至浅会发育水下收缩裂缝到混合成因裂缝到干裂,随着季节的变化,已有的裂缝类型也会发生一定程度的转化。可以预测在复杂的条件下会有更多不同成因类型的裂缝出现。论文第二部分研究了安徽巢湖凤凰山剖面石炭系高骊山组泥岩非构造裂缝。通过对安徽巢湖凤凰山剖面高骊山组岩性、地层及沉积环境进行了充分的调研总结,并对发育在高骊山组中段上部紫红色泥岩中的泥岩非构造裂缝的成因进行了分析,通过与以往国内外文献中记载的裂缝和黄河三角洲泥岩非构造裂缝考察成果的对比,否定了高骊山组泥岩裂缝的暴露干燥成因、地震成因和重荷构造压裂成因,认为该裂缝形成于表层沉积物。虽然对现代泥质裂缝的空间展布有了较多的认识,但是各种边界条件对于裂缝的发生、发育的控制作用,仍然没有细致可靠的研究。在接下来的研究工作中,如果能够进行裂缝模拟实验,通过控制单因素、多因素变化来分析裂缝发生、发育规律,将会取得更好的成效。更多还原

【Abstract】 Unconventional reservoirs such as fractured mudstone reservoirs are drawing more and more attentions with the increasing difficulty of exploration. Mudstone cracks can be further divided into tectonic cracks and non-tectonic cracks. Non tectonic cracks can be defined as cracks which are induced by non-tectonic factors.Modern cracks of mud sediments contain mainly two types: desiccation cracks and synaeresis cracks. Abundant and effective researches have been done on them, however, most of which concentrated on only one type of cracks and lacked quantitative and comprehensive researches. This essay studied contemporary non-tectonic cracks in mud sediment of delta plain at Yellow River Delta. Subaqueous shrinkage cracks, desiccation cracks and mixed origin cracks are studied in detail at the aspects of quantitative classification, fractal features, planar and sectional growth pattern and development models. This essay has established the quantitative characterization and comparison standards of different non-tectonic cracks in modern mud sediment. Moreover, the formation mechanisms are studied for non-tectonic cracks in Gaolishan Formation of Carboniferous in Fenghuangshan profile in the city of Chaohu, Anhui, China.Non-tectonic cracks at Yellow River Delta can be divided into three types: Subaqueous shrinkage cracks, desiccation cracks and mixed origin cracks. Characteristics of each crack type in each typical work area are described in detail. The occurrence of many different crack types in this study area without significant microfacies changes can be attributed to the various volume and depth of overlying water body.Quantitative classification of first-grade crack unit area is applied to all study areas under the same criteria. The distribution of areas of subaqueous shrinkage cracks is the most centralized; desiccation cracks unit areas have the largest area span; while the mixed origin cracks fall in between the first two. Fractal dimensions are calculated for each crack area by the overlapping method. It is found that the fractal dimension rises from subaqueous shrinkage cracks to desiccation.Similar planar growth patterns of all kinds of cracks are observed: New crack bifurcating and original crack orientation changing angles are measured and angle development modes are established. A theory of shrinkage circle is adopted to demonstrate crack growth pattern. In vertical section, shrinkage sphere is used to illustrate the structure of bottom-up subaqueous shrinkage cracks, whereas there is a distinct difference from the V-shaped top-down desiccation cracks.Development models are established respectively for all types of cracks, in which relationships of mutual transformation of certain crack types are shown. Generally, from deep to shallow areas, subaqueous shrinkage cracks, mixed origin cracks and desiccation cracks develop in sequence, and some of them can transform if affected by weather. It is possible that more types of mixed origin cracks appear under more complicated conditions.The second part of this essay focuses on the non-tectonic cracks in Gaolishan Formation of Carboniferous in Fenghuangshan profile in the city of Chaohu, Anhui, China. Lithology, strata, and sedimentary environment are summarized. Then formation mechanism of Gaolishan Formation cracks is studied by analogy of those in documentation and researched at Yellow River Delta. The causes of desiccation, earthquakes activities and burthen are denied respectively, and finally, it is suggested that the Gaolishan Formation cracks are formed at the sediment-water interface.Although there seem to be numerous studies on spatial distribution of non-tectonic mud shrinkage cracks, convincing theories of factors affecting crack development is still yet to be discovered. It is recommended more studies of crack simulation experiment on certain crack development factor(s) to be done in order to gain a better understanding of non-tectonic shrinkage cracks.更多还原