砂岩侵入体系物理模拟实验

近十年来,从露头、地震、岩心和测井曲线等资料中识别出了越来越多的砂岩侵入体。这些砂岩侵入体对油气勘探和开发既有正面影响,也有负面影响,但由于其发育过程和分布的复杂性,使得对于其成因机制和形成过程探讨较少。笔者建立了一套模拟砂岩侵入体系的实验装置,并设计了完整的实验程序,以模拟砂岩侵入体的形成过程,并探索其形成机理。在此基础上,进行了5组实验,分析了顶层沉积物厚度和进水管结构对砂岩侵入体形成的影响。通过对实验结果进行冷冻、切片和照相,将砂岩侵入体的形成过程分为5个阶段,并借助软件对每次实验的模型进行了三维重构,以期为更好地分析砂岩侵入体系的形成机理提供实验基础。     

北海盆地维京地堑渐新统砂岩侵入体形态特征及成因

砂岩侵入体是由处于浅埋藏阶段、尚未固结的砂质沉积物发生液化并侵入到上覆盖层所形成的一类软沉积物变形,在北海盆地维京地堑渐新统地层中非常发育。为探讨砂岩侵入体的形态特征及诱发机制,通过高分辨率三维地震及测井资料,利用地震反射结构分析、地震相干切片等手段对砂岩侵入现象进行了识别;并结合多边形断层系统、流体充注与砂岩侵入之间的关联性,对砂岩侵入体的成因机制进行了分析。结果表明:在地震剖面上可识别的砂岩侵入体多呈V型或W型强振幅反射特征,其横向展布规模约1~2 km,垂向侵入高度约100~200 m;流体的大规模充注及多边形断层诱发盖层破裂是形成砂体内部超压并诱发其发生液化的关键因素。砂岩侵入体在形成之后可以作为流体运移通道,对强化流体的垂向运移具有重要意义;并且砂岩侵入体本身即可作为油气的有利储集体。因此识别并分析砂岩侵入体的成因机理,对盖层封闭性评价及油气勘探具有重要指导意义。     

地震触发下砂岩侵入体变形模拟实验研究

砂岩侵入体形成的触发机制有差异压实、地震、流体注入、波浪、重力滑动等,但普遍认为地震是最常见的一种触发机制。目前对于地震触发的砂岩侵入体的变形机理研究还相对薄弱,通过建立一套模拟地震触发砂岩侵入体的实验装置,成功地模拟了地震发生不同阶段的砂质变化过程。基于实验结果观察、分析,将地震触发砂岩侵入体的形成过程分为三个演化阶段,即：（1）震前阶段,局部地层因差异压实或地层饱含流体,导致砂质地层微弱起伏变形或无变化;（2）震中阶段,由于地震循环剪切波的影响以及不同介质内地震波波速存在差异,地层异常压力迅速增大并突破上覆盖层破裂强度,产生裂缝,同时砂质发生液化、流化形成一系列的变形构造;（3）震后阶段,伴随余震的产生,液化砂质会继续进行小规模的迁移改动直到地震完全结束,砂岩侵入体整体形态固定。地震作用可以独立触发砂岩侵入,也可以诱发其他地质作用,共同控制砂岩侵入体的形成。     

砂岩侵入体系模拟及形成机理分析

砂岩侵入体系是一种普遍的地质现象,近些年来越来越受到地学界的重视,但对其形成机理探讨较少。作者及研究团队通过设计一套室内模拟实验装置,来简化模拟3层地层结构中砂岩侵入体系的形成和演化过程。在之前模拟实验(实验变量为顶层沉积物的厚度、进水管的结构)结果的基础上,进一步考察了地形坡度对实验结果的影响,并对砂岩侵入体系的形成机理进行了分析。实验过程中,共观察到7种不同形态不同样式的管道,并对实验过程中压力变化进行了测试。对实验结果分析认为:盖层厚度越大,压力下降的速度越慢,越不利于压力的释放;随着实验的继续进行,砂岩侵入体最终会转化为砂岩喷出体并喷出地表;不稳定的地形有利于触发疏松沉积物发生变形。实验表明,超压是砂岩侵入体发生的最重要条件之一, 沉积盆地中的压实不均衡和生烃作用是可独立产生大规模超压的2种主要机制。     

砂岩侵入体的形成机制分析*

砂岩侵入体是指深水沉积砂体受到外界的触发,并在一定条件下形成超压,致使上覆弱渗透性沉积物等围岩发生破裂,砂体以流化和液化的形式向周围沉积物产生侵入。砂岩侵入体的形成过程为形成超压、盖层破裂、产生液化和流化、发生侵入。差异压实、地震引发的液化、流体的加入和压力传递等多种因素都可以使砂岩中形成超压,当地层压力达到并超过破裂压力时,发生水力破裂,或地震引起上覆地层破裂,超压砂岩发生流化,侵入到低渗透围岩中。大量未固结的深水沉积砂岩、低-非渗透层的快速覆盖、形成超压的机制和触发事件是砂岩发生侵入的必备条件。     

砂岩侵入复合体的建筑结构要素及其特征

砂岩侵入复合体是指沉积砂质母岩,在未固结时由于某种机制而积累了异常高压,产生液化、流化、再活动,向上覆细粒沉积物侵入的各种砂体的总和。目前已经在全球50多个深水盆地中(Braccinietal,2008)及所有的年代地层中都发现了从毫米到千米级别的砂岩侵入体。砂岩侵入复合体包含母岩、侵入体系和喷出体系三部分,通过对目前报道的一些砂岩侵入复合体实例分析,对其各建筑要素的外部几何形体和边界特征、内部沉积构造和显微结构进行了总结。不规则的几何形态,突变的边界特征,与液化作用相关的无构造砂岩、碟状构造、管状构造以及独特的泥岩碎屑表现出来的粒序性、条带等沉积构造,形状各异的矿物颗粒以及泥岩碎屑中砂岩裂缝切割等显微结构都可以作为识别砂岩侵入复合体的标准。加强砂岩侵入复合体的研究,为侵入圈闭的勘探和开发提供理论基础。     

储层建模在复杂断块油气藏中的应用——以留西油田为例

复杂断块油藏是我国油气田开发中重要的油藏类型之一,其构造复杂,隐蔽性强,描述比较困难。对留西油田属于复杂断块油田,根据其断层发育,构造复杂,非均质性强等特点,采用Petrel软件,以三维地震解释为基础,充分利用钻井、测井、地层对比等数据,分析断层在空间的相互切割关系,建立了三维构造模型,并利用断点数据对模型进行质量校正,更加精确地反应了研究区的构造特征。同时,应用＂相控克里金储层参数建模软件＂,建立在沉积相和流体相约束下的储层参数模型。由于采用相控～克里金建模技术,通过合理添加虚拟井点,弥补了因实际井点不足,造成的预测井间储层参数时出现的误差,提高了储层模型的精度和准确性,反映了油藏非均质性特点和油水分布规律,为精细油藏数值模拟等后续油藏研究奠定了基础。     

论地洼构造对砂岩铜矿床的控制作用

本文以四川会理地洼盆地为例，论述了地洼构造对砂岩铜矿床成矿的控制作用。即地洼盆地沉积前基盘构造控制了盆地的形态及矿源层的展布方向和物质来源；沉积期构造任制了矿源层的岩相和厚度；沉积后的构造决定了储矿砂体的空间位置、铜质来源和矿体的形成；成矿后的构造对砂岩铜矿床成矿的控制有二重性：一方面可以形成新的矿体；另一方面可破坏原来已形成的矿体。     

阿尔泰可可托海伟晶岩中弧形石英白云母层的成因及意义

石英白云母层时常紧贴伟晶岩侵入体的边界出现且平行边界延伸。但是在新疆阿尔泰可可托海伟晶岩型稀有金属矿区伟晶岩体中石英白云母层出现了三种不同类型的弧形起伏,这些弧形形态仅用矿物的定向生长是难以解释的。弧形石英白云母层具有统一的"背地性"指向(弧形凸起顶端一律朝上)并且越靠近伟晶岩侵入体的顶部弧形凸起越明显,在侵入体侧部边界的石英白云母层不存在弧形凸起形态。这些形态特点与浮力作用下形成的形态具有可比性,暗示浮力与弧形石英白云母层间存在密切的成因联系。石英白云母层与石英钠长石层的间隔出现指示伟晶岩浆中挥发分含量的周期性增加。挥发分含量的周期性增加导致了挥发分不断加入未固结的剩余岩浆中并向伟晶岩体顶部上升,逐步在伟晶岩侵入体的顶部形成了弧形石英白云母层。弧形石英白云母层的大量出现不仅说明伟晶岩侵入体规模较大,也暗示存在有利的挥发分保存环境,对伟晶岩型稀有金属矿产的形成和稀有金属找矿预测起到非常重要的作用。     

不同构造环境下形成的花岗岩侵入体和内生矿化的特征

侵入体的形成过程,与产生侵入体的介质的动力学有很大关系.围岩的动力学,不仅影响到侵入体的形态及各种脉岩的侵入和分布特征,而且在很大程度上决定着伟晶岩的存在和特点以及各种热液矿脉的赋存规律,同时它对侵入体的围岩中各种新生地质体的发育也有影响.     

Physical modelling of sand injectites

Sand injectites are structures that result from intrusion of fluidized sand into fractures. We have studied them in the Tampen Spur area of the North Sea, and have reproduced them experimentally, by driving compressed air through layers of sand, glass microspheres, and silica powder. The silica powder was cohesive and capable of hydraulic fracturing, whereas the sand and glass microspheres were almost non-cohesive and therefore able to fluidize. The models were dynamically similar to their natural counterparts, for as long as equilibrium was static. When the processes became dynamic, so that inertial forces were significant, the scaling was approximate and the corresponding Reynolds numbers differed. The experimental apparatus was a square box, 1 m × 1 m wide, resting on a grid of fluid diffusers. During the experiments, the fluid pressure increased, until it attained and surpassed the weight of overburden. Flat-lying hydraulic fractures, containing air, formed within cohesive and least permeable layers. Heterogeneities in material properties and layer thicknesses were responsible for localizing fracture networks. When any one network broke through to the surface, rapid flow of air through the fractures fluidized the underlying mobile materials and even depleted some of the layers. Some of the fluidized material extruded at the surface through vents, forming volcanoes and sheets. The remainder lodged at depth, forming sand injectites or laccoliths. Conical sand injectites formed preferentially, where layers had high resistance to bending. Laccoliths formed nearer the surface, where overlying layers had low resistance to bending. The experimental sand injectites were broadly similar to those in the Tampen Spur area of the North Sea, as well as other areas.     

空间内插方法比较

空间内插可以分为几何方法、统计方法、空间统计方法、函数方法、随机模拟方法、物理模型模拟方法和综合方法。介绍了每一种方法的适用范围、算法和优缺点。指出没有绝对最优的空间内插方法,必须对数据进行空间探索分析,根据数据的特点,选择最优方法;同时,应对内插结果做严格的检验。开发通用空间内插软件、智能化内插以及加强相关基础研究将是空间内插研究的重点。     

Sedimentary facies analysis and seismic interpretation of deep-water reservoirs, “PAC” field,offshore depobelt,Niger Delta basin

A high-resolution study involving the integration of cores, wireline logs and reflection seismic dataset was used to unravel the facies assemblages, reservoir quality and hydrocarbon potential of E1 and H9 reservoirs in the “PAC” field, Offshore Niger Delta. Facies analysis of the cored PAC-14 well shows six lithofacies: massive mudstone, parallel-laminated mudstones with sideritic bands, fine-grained parallel-laminated sandstone, medium-grained parallel-laminated sandstone, fine-grained ripple laminated sandstone, and coarse massive sandstone. These lithofacies were grouped into five facies associations: channel story axis (CSA), channel story margin (CSM), inter-channel thin beds (ICTB), mud-rich thin beds (MRTB) and injectites (INJ). These facies associations are typical of a confined channel and basin floor fan deposit of a deep-water turbidite depositional environment. Reservoir unit E1 was dominated by the facies association CSA while the H9 reservoir consists mainly of the facies associations MRTB and INJ. The observed sand injectites are suggested to have formed due to overloading of compacted sands leading to upward remobilization of sand into the overlying shale. Seismic horizons and faults were mapped to understand the structures, trend and reflections within the study area. Results from petrophysical volumetrics estimated the net hydrocarbon pore volume for the E1 and H9 reservoirs as 456 MMBBL and 378 MMBBL, respectively. Exploration for deep-water reservoir mainly targets high amplitude and bright seismic reflectors and ignores the low amplitude reflectors (dim loops) which are typically interpreted as non-reservoir units. However, this study shows a low-amplitude reflector containing medium-grained sand injectite unit, which has high porosity (31.7%) and permeability (4472 mD) values, and contains recoverable hydrocarbon.     

基于三次插值的大地电磁自适应有限元二维正演模拟

大地电磁(MT)数值模拟中通常使用有限单元法,通过伽辽金(Galerkin)法将微分方程转化为与其等价的泛函形式,对泛函求取极值并在单元上定义插值基函数,得到节点上电磁场值的线性方程组,最终形成大型复对称稀疏矩阵。要达到较高的有限元计算精度,一般采用密集的网格或高次插值的方法,这样做大大的减慢了正演的速度。结合两者的优点利用三次插值和h-型自适应相结合的有限元法来实现MT的正演算法。首先从一个粗网格出发并利用三次插值,通过后验误差估计方法局部加密网格,在计算量较小的情况获得较高的计算精度。这种方法可以针对目标区域和介质分界面发生突变处进行网格加密,不需要全局加密网格。最后通过对国际标准模型COMMEMI-2D1的模拟,分别比较二次插值与三次插值的自适应网格数量和数值模拟结果,证明了三次插值自适应有限元算法的可行性。     

A statistical adjustment of Haldorsen's conditioned Boolean simulation algorithm

This paper presents a new simulation algorithm for generating realizations of a Boolean model for sandstone reservoirs conditional on sandstone body intersections in wells. It is a statistically corrected version of the conditional simulation algorithm originally proposed by Haldorsen. In previous work it was shown that the conventional algorithm does not reproduce the correct statistics for sandstone body size at the well locations. The simulation of a Boolean model, given grain intersections on line transects, must be in accordance with the conditional distribution of the model, which implies that sandstone bodies intersected by wells and sandstone bodies in the interwell area should be simulated independently. Based on the conditional distribution a simulation algorithm is developed, which is compared to Haldorsen's algorithm by simulating an outcrop section of fluvial sandstone deposits. Simulations are conditioned on data of two fictitious wells. It turns out that the adjusted algorithm gives better results for the sand fraction that is connected to a set of wells, and also for the sand fraction that would be connected to an infill well.     

自然邻点插值算法及其在二维不规则数据网格化中的应用

由于观测数据的不足,对不规则散点数据的二维插值在地球物理中应用非常广泛。这里研究并实现了自然邻点二维插值算法,并以一个大地电磁测深反演数据为例,验证了该方法的可行性与效果。实际资料试算与成图结果表明,该方法具有精度高、插值效果好、速度快以及便于模拟地形数据等优点。     

硝基苯在傍河地下水源地迁移转化的数值模拟研究

通过开展室内模拟实验研究,探讨硝基苯在傍河水源地的迁移规律、转化机理及其影响因素。在实验的基础上,构建描述硝基苯在傍河地下水源地迁移转化的数学模型。数值模拟结果表明：淤泥介质对硝基苯的吸附能力相对较高,硝基苯在淤泥中的线性吸附系数为0.526 cm³/g,在砂砾中的线性吸附系数为0.123 cm³/g;硝基苯在淤泥介质中的生物降解作用也明显大于在砂砾介质中,其在淤泥介质中的生物降解速率常数可达0.043 h^-1,而在砂砾介质中仅为0.002 h^-1。本次对室内硝基苯迁移转化实验的数值模拟效果较为理想,模拟结果对硝基苯在含水层中的迁移过程和转化规律进行了科学合理的量化描述,可将该模型进一步用于野外硝基苯迁移转化的模拟预测中。