四川盆地火成岩发育区地震波传播规律及成像方法

多口钻井证实四川盆地西南部地区发育火成岩,火成岩主要分布在龙潭组内部,火成岩发育区地震资料存在岩下地震同相轴连续性较差、反射能量弱等现象,火成岩下屏蔽效应机理不清、岩下地震反射井震标定能量相位差异大,明确火成岩区地震波传播规律是地震资料采集、处理解释的基础。这里从地震波反射透射基本原理出发,阐述了火成岩地层的反射透射能量及对下伏地层的屏蔽机理,利用波动方程地震模拟及偏移,分析了不同火成岩分布模型对下伏地层地震信号的屏蔽作用,采用低频补偿、逆时偏移等方法改善岩下成像质量。结果表明:火成岩发育会不同程度导致下伏地层地震透射能量的衰减,纵向多套火层岩发育时,下伏地层屏蔽效应明显,发育区地震表现为类似生物礁的外形隆起、内部杂乱反射特征,下部多次反射较多且能量较强。通过低频优势频带保护处理、利用全波场波动方程偏移成像等方式可以改善岩下地震成像质量。     

利用正演模拟技术改善火成岩下目标层成像——以阳信洼陷火成岩下成像研究为例

阳信地区深大断裂控制了阳信凹陷的火成岩时空展布,受断裂网络及其活动影响,阳信火成岩异常发育,沙三段、沙四段盆地断裂的高峰期使火成岩广泛分布。这些火成岩发育区地震资料同相轴连续性差,成像困难,构造不清。通过对阳信洼陷火成岩构造特征分析,建立了3种不同类型的火成岩模型,利用波动方程有限差分进行正演模拟与照明分析,模拟记录和波场能量说明火成岩的存在导致岩下地层界面反射能量弱,形成照明阴影区,出现典型的屏蔽效应。研究了造成火成岩对下伏地层屏蔽作用和火成岩层间产生次生干扰的机理,火成岩非均质特征导致散射会引起下伏地层反射的不连续性,并衰减能量,且低频信号越过不均质体的能力较强,火成岩下地层成像要充分使用低频信息。提出了改善下伏地层能量弱的5项处理措施,加强优势频段以改善地震资料品质,阳1三维地震资料处理结果表明,火成岩成像明显改善,构造得以落实。     

火成岩覆盖区地震有效成像技术探讨及其在辽西金羊盆地油气调查中的应用

辽西金羊盆地是下辽河盆地外围盆地群中面积最大的中生代盆地,盆地浅层火成岩广泛发育、其厚度大、期次较多,受火成岩对地震信号屏蔽以及该地区复杂的地震地质条件的影响,使得地震勘探采集的原始资料信噪比低、火成岩下伏地层反射能量弱,给地震资料的有效成像带来了极大挑战。本文根据原始地震资料特点,采用针对性的采集、处理技术,首先从采集方面以大能量激发、低频检波器接收,并且处理中应用反射能量补偿、静校正、叠前多域去噪等几项技术进一步提高资料的深层反射能量和信噪比,最后通过高精度速度场建模与地震偏移成像技术的多种方法对比,优选叠前时间偏移技术进行最终成像。与以往地震资料比较,采用这套有效成像技术重新处理的地震剖面信噪比、分辨率明显提高,更重要的深层反射能量得以有效恢复,火成岩的下伏地层反射信号清晰、地层接触关系明确,特别是大倾角地层及断层的成像得以明显改善,为后续的构造解释和勘探潜力区评价提供了高质量的地震资料。     

塔中地区奥陶系典型地质体地震识别模式

针对塔中地区奥陶系岩溶缝洞型储层类型多、埋藏深且非均质性强的难点,设计了符合实际地层条件的地震地质模型,对储集体内部结构和参数采用微小管网和孔洞组成的等效储集空间进行精细刻画.应用波动方程交错网格高阶有限差分法进行波场正演模拟,选用常规处理和波动方程叠前深度偏移处理方法,得到偏移剖面,验证储层解释结果.从振幅、相位和频率等信息分析模拟记录地震波场特征,研究储层与围岩接触关系以及储层内部结构的变化对地震波场特征的影响,建立了缝洞储层和火成岩的地震识别模式.该地区存在层状火成岩、火成岩颈、顺层侵入火成岩等地震反射特征,碳酸盐岩储层表现为表层弱振幅、空白反射结构和内幕中强振幅反射结构.     

高密度地震采集弱反射信号的变化规律

地震信号在传播过程中受到近地表和深地层吸收衰减的影响,能量变弱,高频成分衰减比低频成分更为严重,接收与识别反射系数较小或高频的弱反射信号是高密度地震勘探的瓶颈问题。笔者通过建立典型的粘弹性地质模型,分析了弱反射信号与近地表、震源主频、炮检距以及与深地层的关系,得出以下认识:在近地表吸收衰减严重的低噪比地区,由于截止频率的存在,高密度采集的宽频优势难以体现;良好的激发条件对提高弱反射信号能量、拓宽频带作用较大;中小炮检距是弱反射信号有效反射系数较好的区域,是提取弱反射信号的最佳区域。     

波场延拓反Q 滤波的正则化方法

基于波场向下延拓的反Q 滤波是补偿大地衰减效应的一种常用方法,但其振幅补偿的不稳定性限制了该方法在中、深层地震资料处理中的应用。针对于此,提出波场延拓反Q 滤波的正则化方法,该方法不仅较好地解决了地震波能量补偿的不稳定问题,同时对经过品质因子较低地层的深层地震波有着较好的能量补偿效果。模型试验和实例应用均表明: 与常规稳定的反Q 滤波方法相比,基于正则化法的反Q 滤波不仅具有较强的抗干扰能力和较好的振幅补偿能力,而且有效地提高了中、深层地震资料的分辨能力。     

一种简易快速的时域地震波衰减补偿算法

针对地震波的能量随着传播时间的增加而递减,提出了一种时间补偿方法。通过调试与传播时间有关的两个可调参数进行地震波振幅补偿。模型试验证实了该方法可以有效地补偿能量的损失,而且在地层中地震波振幅衰减与品质因子Q值有关时,其中的一个可调参数可以用另一个可调参数和Q值来表示。也就是说,本文方法同样是一种反Q滤波方法。     

多子波分解在地震反射系数研究中的应用

反射系数反演是高分辨率地震解释的常用技术之一,广泛使用的是基于奇偶分解的谱反演技术。本文采用基于匹配追踪(Matching Pursuit,MP)的多子波分解技术,将地震信号分解成一系列包含时间、频率、振幅的子波集,然后进行井震能量标定,选定研究层段内最强能量处,将分解的振幅比例到对应的反射系数。楔形正演模型表明,该思路可以得到准确的反射系数,实际资料表明对反射系数求取相对阻抗,能准确识别气层边界,拓展了多子波分解技术的应用领域。     

含透射衰减的地震反射信号褶积模型在波阻抗反演中的应用

研究了地震波在层状地质模型内透射衰减对地震反射信号振幅的影响,给出了含透射衰减的褶积模型,为基于模型的波阻抗反演提供了一种新的正演方法。采用含透射衰减的褶积模型做正演运算,能够校正地层透射对波阻抗反演结果的影响,尤其能够消除地层的屏蔽现象。实际的资料处理表明含透射衰减的褶积模型有较好的应用价值。     

基于振幅谱能量误差最小原则的品质因子提取方法研究与应用

品质因子Q是衡量地震波传播过程中能量衰减的重要参数,对含油气储层识别和地震波衰减补偿具有重要意义。谱比法是实际资料处理中最常用的方法之一,但容易受到时窗、频带范围选取等人为因素的影响,使品质因子反演结果存在不稳定性。这里提出基于振幅谱能量误差最小原则的品质因子提取方法,该方法充分利用整个频带范围内振幅谱的信息,通过构建衰减前、后振幅谱能量随Q变化的目标函数估算品质因子,有效地解决了频谱直接相除和频带拟合区间选取等引起的影响。零偏VSP模型测试表明,基于振幅谱能量误差最小原则的品质因子提取方法比谱比法具有更高的精度,并在实际资料应用中取得了较好的效果。     

Study on Distribution Characteristics of Mining Stress and Elastic Energy Under Hard and Thick Igneous Rocks

In the coal measure strata, igneous rocks are often invaded, and their occurrence, size, and distribution form play an important role in mining safety. The breakage of hard and thick igneous rocks easily induces dynamic disasters, such as rock burst, mine seismicity, gas outburst, and surface subsidence, which seriously threaten mine safety production. In view of the working face with overlying hard and thick igneous rocks, the evolution characteristics of mining stress and energy distribution under hard and thick igneous rocks were investigated. Furthermore, the influence law of different horizons and thicknesses of igneous rock on overlying strata movement law, stress distribution, and energy distribution was analyzed based on FLAC3D numerical simulation. Results show that no evident subsidence of the overlying strata exists before the igneous rock is broken. Additionally, the subsidence amount of the overburden is suddenly increased after the igneous rock is broken, thereby showing significant mutability. Before the igneous rock breaks, a high stress area is formed around the goaf, and the stress concentration gradually increases with the increase of the mining scope. After the igneous rock breaks, the coal under high stress is prone to induce dynamic disasters under the action of strong dynamic load. However, the advanced abutment pressure and stored energy rapidly decreased. The accuracy of the numerical simulation is verified by field monitoring. Results of the study are of considerable significance for safe mining of working face under similar geological conditions.     

Characteristics of Meso-Cenozoic Igneous Complexes in the South Yellow Sea Basin, Lower Yangtze Craton of Eastern China and the Tectonic Setting

The South Yellow Sea Basin is partially surrounded by the East Asian continental Meso-Cenozoic widespread igneous rocks belt. Magnetic anomaly and multi-channel seismic data both reveal the prevalent occurrence of igneous rocks. We preliminarily defined the coupling relation between magnetic anomalies and igneous rock bodies. Some igneous complexes were also recognized by using multi-channel seismic and drilling data. We identified various intrusive and extrusive igneous rock bodies, such as stocks, sills, dikes, laccoliths and volcanic edifice relics through seismic facies analysis. We also forecasted the distribution characteristics of igneous complexes. More than fifty hypabyssal intrusions and volcanic relics were delineated based on the interpretation of magnetic anomaly and dense intersecting multi-channel seismic data. It is an important supplement to regional geology and basin evolution research. Spatial matching relations between igneous rock belts and fractures document that extensional N–E and N–NE-trending deep fractures may be effective pathways for magma intrusion. These fractures formed under the influence of regional extension during the Meso-Cenozoic after the Indosinian movement. Isotopic ages and crosscutting relations between igneous rock bodies and the surrounding bedded sedimentary strata both indicate that igneous activities might have initiated during the Late Jurassic, peaked in the Early Cretaceous, gradually weakened in the Late Cretaceous, and continued until the Miocene. Combined with previous studies, it is considered that the Meso-Cenozoic igneous activities, especially the intensive igneous activity of the Early Cretaceous, are closely associated with the subduction of the Paleo-Pacific Plate.     

Assessment of rigid overlying strata failure in face mining

The method of overlying strata failure assessment of extracted seams is based upon the simultaneous assessment of surface subsidence and seismic activity, considering the spatiatemporal progress of mining, depending on the character of the rock mass. The rigid overlying strata failure assessment results in finding whether a failure of the firm overlying rocks occurred or whether a strutting arch was formed over the mined-out area. The practical importance of the overlying strata failure assessment consists in determining the size of the mined-out area at which the com-plete failure of the rigid overlying strata occurred and in the assessment of the current stress condition of the overlying strata failure. The assessment method is applicable in deep mine workings where thick coal seams are being mined by means of the method of longwall mining with controlled caving. The results of this method are used to amend contemporary known methods of rock-burst protection, namely (regarding the use of surface measurements for the evaluation) in overlying strata areas.     

火山岩覆盖区三维地震勘探方法探究

宣化——下花园煤田位于燕山山脉的西段,区内地形复杂,成孔形式不一,采集难度大;火山岩覆盖范围广,浅层地震地质条件较差,地震记录信噪比低,静校正问题突出。为了查清宣东矿井深部煤炭资源状况,除了克服地表影响因素外,还需攻克该区火山岩对地震信号的屏蔽难题。通过对岩石出露区及黄土覆盖区进行试验分析,采取了高叠加次数等措施,有效地压制了干扰,提高了信噪比,在此基础上对地震记录进行一些有针对性资料处理技术,如绿山静较正技术等,使目的层有效波反应明显。本次勘探圈定了上覆火成岩范围及火成岩破坏区,控制了区内主要可采煤层Ⅲ3、Ⅴ2煤层的埋藏深度及构造形态,解释断层20条及Ⅲ3煤层火成岩破坏区3处,勘探成果表明,本次勘探所采用的野外采集措施和资料处理方法是行之有效的。     

基于重磁异常的新生代丽水—椒江凹陷基底分布特征研究

丽水—椒江凹陷位于东海陆架盆地西南部,是在中生代残留盆地基础上发育起来的新生代具有典型东断西超特点的断陷,是油气勘探的新区域。区域地质条件复杂、构造叠加、沉积厚度大,地震勘探无法获得较好的反射数据,因此采用面积广、深度大的重磁数据结合地震数据来描述基底构造和火成岩岩性特征,通过重磁数据的阶跃边界识别技术划分区域断裂。丽水—椒江凹陷内断裂呈北东向分布,控制凹陷的形状,且断裂作用使凹陷形成多个小型次凹,断陷特征明显。中—新生代火成岩具有较高的重磁异常,结合质量较好的地震剖面来获得地层、火成岩及岩性分布特征,并建立了多联通域地层的计算公式。区域内中—古生界较为发育,但凹陷内中—新生代火成岩侵入较少,不会对于油气构造造成大的破坏,因此该凹陷具有良好的油气前景。     

白云凹陷浅成岩浆侵入体发育特征、成因及油气地质意义

珠江口盆地白云凹陷内发育大量早中新世(约15.5 Ma)浅成岩浆侵入体(侵入深度<3 km).目前对其形态特征、相互关系以及岩浆侵入诱发的强制褶皱等尚缺乏系统研究.通过利用高精度三维地震资料,细致刻画了侵入体的形态、岩浆运移通道以及岩床复合体内各岩床的空间关系,定量分析了强制褶皱与侵入体的几何关系.白云凹陷内岩浆侵入体...     

The controlling effect of thick-hard igneous rock on pressure relief gas drainage and dynamic disasters in outburst coal seams

Intrusive igneous rock is usually found in the overlying strata above mining stopes, and its occurrence, lithology, and distribution play important roles in coal mining safety. Of the numerous coal mine disasters in China, a large number have been caused by magma intrusion. Magmatic activity is intense and widely distributed in the Haizi Coal Mine which has suffered eleven coal and gas outburst accidents and one water inrush accident under a thick-hard igneous rock with 120-m-thick. Based on theoretical analysis, laboratory testing and field observations, we found that under the effect of thermal evolution and entrapment of the igneous rock, the coal pore structure developed, the gas adsorption capacity was enhanced, and the risk of gas outburst increased. The igneous rock, as the main key stratum, will not subside or break for a long time after mining. The closing time of fractures and separations is also prolonged and provides good conditions for gas drainage. The distant penetration borehole for draining pressure relief gas is proposed which can ensure effective gas drainage and reduce the number of rock laneways. However, with the continuous mining of a large area, the igneous rock could suddenly break, instantly releasing a tremendous amount of elastic strain energy, which will easily induce the occurrence of complex dynamic disasters, such as rock bursts, water inrush, gas outbursts, and surface subsidence. Based on the cause analysis of dynamic disasters, a reasonable goaf filling height is proposed for fully eliminating mine disasters under the special geological condition.     

重力-地震联合反演解释技术在拉布达林盆地油气资源评价中的应用

内蒙古拉布达林盆地面积大、油气勘探程度很低.由于浅层广泛分布的火山岩的强反射屏蔽作用造成地震勘探对深层成像差,难以评价盆地油气勘探潜力.为了解决盆地主要目的层上库力组底界深度及沉积岩分布不清的问题,对盆地南部二维地震资料开展重力-地震联合反演解释.通过在GM-SYS重磁剖面解释软件中加载地震剖面,建立重力模型,利用地震浅层可靠解释成果做约束条件,消除上覆火山岩的重力干扰,减少了重力反演深层构造界面的多解性,成功地反演了盆地上库力组底界深度、沉积岩厚度,指出巴彦哈达断陷为有利勘探区,在此基础上估算出油气资源量.