【作者】 李斌；

【导师】 陈学华； 翁斌；

【作者基本信息】 成都理工大学 ， 地质工程， 2015， 硕士

【摘要】 随着石油和天然气的勘探步伐的不断深入,油气地球物理勘探的目标变得越来越复杂,已经由原来普遍的构造油气藏转变为岩性油气藏和隐蔽性油气藏。一方面,由于勘探目标变得更深、更小,对储层预测的高精度要求也越来越严格,使得勘探难度成倍上升;另一方面,储层预测的根本目的不仅要能判别储层的存在与否,预测储层发育的好坏程度,同时也要定量化判定储层中所含流体的性质,流体对储层波场特征的影响。而定量化判定主要依靠地震岩石物理学来架设地震数据(属性参数)与油藏特性(储集参数)的关系“桥梁”。地震岩石物理学主要利用储层岩石及其所含流体性质与地震属性参数之间的内在关系,基于岩石弹性、粘弹性和各向异性等物理特性的系统理论和介质模型,建立地震属性参数与储层、油藏特性参数之间的经验关系,通过流体替换模拟等技术手段,为岩性油气藏、隐蔽油气藏勘探提供基础依据。而流体替换的核心是Gassmann等效介质理论,因此,利用Gassmann方程对弹性参数进行数值模拟研究是有意义的。本文在确定了基于Gassmann等效介质理论为研究核心内容后,介绍了岩石物理学中重要的理论模型,包括Hashin‐Shtrikman界限、V‐R‐H平均模量模型、Wood流体模量公式、Kuster‐Toks?z理论、多孔介质的流体机制模型(Gassmann方程、Biot理论和BISQ模型)的假设前提与应用条件,并对一些经典的速度等效经验公式进行了总结。由于毛细管压力作用,不同岩性具有不同的流体压力,使得流体饱和度存在差异。在毛细管压力平衡状态下,本文依据三相饱和流体的Brooks‐Corey模型、Gassmann理论以及边界理论,探讨了非均匀饱和岩石声学性质与含水饱和度定量关系,计算了非均匀饱和多孔岩石的地震响应,并揭示了在不同流体饱和状态下纵、横波速度随含水饱和度的变化规律。若想从测得的地震波速度来推断储层性质,验证岩石物理模型是必不可少的,比如孔隙空间变形、裂缝密度、流体饱和度、构造应力、岩性和温度等因素,都有可能导致地震速度空间的形变。通过分析模拟储层条件下岩石样品的核心属性,对描述温度对地震波速衰减的影响是非常有用的。本文根据不同的温度环境下,对Gassmann表达式进行了适应温度的修正,在不同岩性介质上,验证改进Gassmann方程进行流体替换的结果与实际测量值的一致性,并计算了其Q值变化。对于不同温度下地震响应的差异,一种解释是Gassmann方程假定的剪切模量是不受流体存在的影响,由于流体引起的化学机械减弱,特别是高压和高温下微裂缝产生时,孔隙流体对饱和岩石的剪切模量有着显著的影响;另一种解释是温度不同时,流体的物理属性发生了变化,包括密度、粘度、速度和模量等,从而导致饱含流体岩石的地震响应存在差异性。在饱含水岩石速度随温度变化的基础上,本文还讨论了多相非均匀饱和岩石依赖温度的Gassmann流体替换,展示了饱含多相流体在不同温度下地震速度之间的差异,为油气的识别提供了可靠的岩石物理依据。更多还原

【Abstract】 With the deepening of oil and gas exploration and development, the goal of oil and gas geophysics exploration become more complex, having transferred from the universal structural reservoir to lithology reservoirs and subtle reservoirs. On the one hand, the exploration targets gradually become deeper smaller, more difficult exploration, the prediction accuracy requirements are also increasing. On the other hand, the key goal of reservoir prediction in addition to determine the existence of the reservoir, forecast level of reservoir development is good or bad, also need to determine the quantitative nature of the fluid contained in reservoir, fluid reservoir characteristics of the wave field. The quantitative determination mainly rely on seismic rock physics to set up the "bridge" between the relationship of seismic data(properties parameter) and oil reservoir characteristics(elastic parameters). Seismic rock Physics main use the intrinsic relations of reservoir rock and its pore fluid versus the seismic property parameter. Based on the systematic theory and media models of rock physics property such as elastic, viscoelasticity and anisotropy in rocks, the empirical relations between seismic attribute versus reservoir property parameter are established. Using the techniques such as fluid substitution and so on, provides the reference fundamentals for lithology reservoirs and subtle reservoir exploration. The core of fluid substitution is the Gassmann effective medium theory, Based on this, using Gassmann equation to numerically simulate elastic parameters is meaningful. After determining the Gassmann effective medium theory is the core content, I introduce some important theoretical models of petro physics, such as the assumptions and application conditions of HashinShtrikman bounds, V-R-H average model, Wood fluid modulus formula, Kuster-Toks?z theory and the fluid mechanism model of porous media(Gassmann equation, Biot theory and BISQ model). And some of the classic speed equivalent empirical formulas are summarized.Since the capillary pressure, each lithology has different fluid pressure, so that the fluid saturation is different. When the capillary pressure keep equilibrium,according to three phase saturation fluid Brooks-Corey model, Gassmann theory and bound theory, we build the quantitative relationship between inhomogeneous saturated rock acoustic properties and water saturation. We calculate the seismic response of inhomogeneous saturated porous rocks and reveal the variation between seismic velocity and water saturation in different saturated fluid.If we want to predict the reservoir properties from measured seismic velocity, it is essential to verify the rock physics model. Because certain factors such as pore space deformation, fracture density, fluid saturation, tectonic stress, lithology and temperature et al. may probably lead to the deformation of seismic velocity space. It is very important to describe the influence of temperature on seismic wave velocity attenuation by analyzing and simulating the key attributes of rock sample saturated with hydrocarbon. According to different temperature environment, this paper modifies Gassmann’s equation to reaction temperature. As to different lithology, this paper verifies consistency of modified Gassmann’s equation when there is fluid substitution and actual measurements. Also, we calculates the change of the Q value. For the seismic response at different temperatures, one explanation is that Gassmann equation assumed that shear modulus is not affected by the presence of fluid, due to the weakness of chemical machinery caused by fluid. The shear modulus of the pore fluid saturated rock has a significant impact, especially when micro cracks appear under high pressure and high temperature. Another explanation is that physical properties of the fluid change when the temperature is not the same, including density, viscosity, speed and modulus and so on, which leading to the differences of seismic response of the fluids saturated rock.Based on the velocity of rock saturated with water varied with temperature, this paper discusses temperature-dependent fluid substitution by Gassmann of multiphase inhomogeneous saturated rocks. It shows the difference between seismic velocity of rocks saturated with different fluid, providing reliable rock physics basis for identification of oil and gas reservoirs.更多还原