有限元数值模拟技术在潜山裂缝定量预测中的应用——以珠江口盆地惠州凹陷惠州26构造为例

潜山储层的裂缝发育预测是勘探开发领域一个技术难题。目前多采用地震刻画、地震属性提取、周边钻井资料揭示以及岩芯观察等方法对地下裂缝的分布情况进行预测,但存在不少问题。笔者等通过有限元数值模拟方法对珠江口盆地惠州26构造裂缝发育情况进行预测,并提出预测流程。该方法首先采用断层生长连接分析结合演化史分析建立合适的几何模型和数理模型,通过给定力学参数和边界条件,模拟裂缝主要形成期文昌期、恩平期的古构造应力场,最终通过对张应力和剪应力大小及分布的分析来预测储层构造裂缝的发育程度。模拟结果显示,文昌期裂缝强烈发育区位于F2断层西段和F1断层西段,在惠州26构造处,构造的高部位裂缝发育强度较强,在4井位置裂缝发育较弱,在7井位置发育较好的裂缝。恩平期受应力方向和大小的改变影响,主要的裂缝发育区集中在F2断层下盘惠州26构造高部位。将预测结果与钻井结果进行比较,预测结果和钻探结果较一致,印证了该方法在古潜山裂缝预测中的实用性。有限元数值模拟方法不仅能够恢复构造裂缝形成期构造应力场的分布情况,也可以对储层构造裂缝的分布及发育程度进行预测,为裂缝型潜山油气藏勘探开发提供技术支持。     

冀中坳陷束鹿凹陷潜山分类与成藏模式

冀中坳陷束鹿凹陷发育于太古宙变质岩结晶基底上,其经历了中晚元古代裂陷槽阶段、古生代克拉通盆地阶段、中生代构造转换调整阶段和新生代断陷型盆地等4个阶段,为一典型地台-断陷-坳陷多层结构的复合盆地。盆地历经多次构造运动改造,潜山较发育,类型多样。在总结前人对潜山研究的基础上,结合束鹿凹陷三维连片地震资料,对该地区潜山类型进行系统划分,并对典型潜山的构造特征及生储盖匹配关系进行了描述。研究区潜山根据成因可划分为剥蚀型潜山和拉张型潜山两大类,根据形态可划分为剥蚀残丘型潜山、不整合潜山、断阶型潜山、断槽冲蚀沟型潜山、断垒型潜山和断块型潜山等类型。束鹿凹陷潜山的发育具有分带性,按潜山的构造位置,分为凸起潜山带、缓坡潜山带、洼槽潜山带和陡坡潜山带,不同构造带发育不同类型的潜山。研究结果表明束鹿凹陷中新元古界、古生界潜山数量众多,规模较大,是束鹿凹陷实现油气突破的一种重要油气藏类型。     

Low-velocity zone and topography as a source of site amplification effect on Tarzana hill,California

Tarzana station is located in the foothills of the Santa Monica Mountains in California near the crest of a low (<20 m) natural hill with gentle slopes. The hill is about 500 m in length by 130 m in width and is formed of extremely weathered shale at the surface to fresh at depth. Average S-wave is about 250 m/s in the top 17–18 m, and S- and P-wave velocities significantly increase below this depth. According to the NEHRP classification based on V_S30∼300 m/s it is a site class D. Strong-motion instrumentation at Tarzana consisted of an accelerograph at the top of the hill, a downhole instrument at 60 m depth, and an accelerograph at the base of the hill. More than 20 earthquakes were recorded by at least three instruments at Tarzana from 1998 till 2003. Comparisons of recordings and Fourier spectra indicate strong directional resonance in a direction perpendicular to the strike of the hill. The dominant peaks in ground motion amplification on the top of the hill relative to the base are at frequencies ∼3.6 and 8–9 Hz for the horizontal components. Our hypothesis is that the hill acts like a wave trap. This results in an amplification at predominant frequencies f=V/4 h (h is layer's thickness) at f∼3.6 Hz for S-waves (using average V_S17=246 m/s and h=17 m) and f∼7.9 Hz for P-waves (using average V_P17=535 m/s and h=17 m). As was shown by Bouchon and Barker [Seismic response of a hill: the example of Tarzana, California. Bull Seism Soc Am 1996;86(1A):66–72], topography of this hill amplifies and polarizes ground motion in the frequency range of 3–5 Hz. Hill acts as a magnifying polarizing glass: It polarizes ground motion in the direction perpendicular to the strike of the hill and also amplifies ground motions that had been also amplified by a low-velocity layer.     

古潜山油气藏研究综述

文章介绍了古潜山油气藏的勘探历史、研究现状、分类及特征, 并指出开展“残留盆地”的研究对古潜山油气藏的勘探具有指导意义.作者按照简单易行的原则,将古潜山油气藏分为两大类共六种.随后作者阐述了形成大型古潜山油气藏的条件,包括构造背景、沉积环境以及成藏配置等等,最后文章介绍了古潜山油气藏勘探的重要技术,主要有叠前深度偏移处理、综合地球物理方法以及古潜山内幕裂缝预测技术等等.     

渤海湾盆地构造圈闭类型与勘探方向——以济阳坳陷为例

提出了渤海湾盆地初期挤压、早期张压交替、中后期持续张裂的新的成盆模式,并在该模式指导下,以济阳坳陷为例总结了盆内深层压性、张性、张压复合作用等多种成因的构造圈闭类型及其石油地质意义,最后指出盆内勘探的有利方向.     

SH波入射时半圆形凸起与凹陷地形的地震动

研究了弹性半空间中半圆形凸起与凹陷相连地形对SH波的散射问题。将整个求解区域分割为2部分,在其中分别构造满足边界条件的位移解,通过移动坐标使之满足“公共边界”以及半圆形凹陷表面上的边界条件,从而建立起求解该问题的无穷代数方程组。最后,给出了地表位移幅值的数值结果以及凸起地形顶点和凹陷地形最低点处位移幅值的反应谱并进行了讨论。     

英买力地区复合潜山的地层分布及意义

英买力地区复合潜山构造非常复杂,采用地震相与地震多属性聚类分析技术时潜山不同岩性进行了识别和有效区分,明确了白垩系下伏地层的分布范围和意义,特别是侏罗系的分布直接导致潜山油气的漏失.同时利用地震多属性聚类方法对复合潜山储层发育进行预测,有利储层主要分布在上寒武统白云岩潜山、英买7以北下奥陶统灰质云岩潜山以及志留系柯坪塔格组沥青砂岩段.     

潜山裂缝型油气藏绕射波属性预测方法

潜山裂缝型油气藏的勘探重点之一是裂缝发育区域的预测,本文发展了应用绕射波属性数据进行裂缝分布描述的方法,并提出利用主成分分析方法,结合绕射信息及敏感属性提取,给出裂缝预测的工作流程。模型试算表明绕射波场能够较好地反映构造裂缝的分布规律。将该方法应用于裂缝型油藏精细描述中,绕射波分析方法能够更为精细、全面地描述潜山裂缝型油气藏中裂缝的分布规律。      

High resolution lake sediment record reveals self‐organized criticality in erosion processes regulated by internal feedbacks

Reconstruction of high‐frequency erosion variability beyond the instrumental record requires well‐dated, high‐resolution proxies from sediment archives. We used computed tomography (CT) scans of finely laminated silt layers from a lake‐sediment record in southwest Oregon to quantify the magnitude of natural landscape erosion events over the last 2000 years in order to compare with palaeorecords of climate, forest fire, and seismic triggers. Sedimentation rates were modeled from an age–depth relationship fit through five ¹⁴C dates and the 1964 AD ¹³⁷Cs peak in which deposition time (yr mm^‐1) varied inversely with the proportion of silt sediment measured by the CT profile. This model resulted in pseudo‐annual estimates of silt deposition for the last 2000 years. Silt accumulation during the past 80 years was strongly correlated with river‐discharge at annual and decadal scales, revealing that erosion was highly responsive to precipitation during the logging era (1930–present). Before logging the frequency–magnitude relationship displayed a power‐law distribution that is characteristic of complex feedbacks and self‐regulating mechanisms. The 100‐year and 10‐year erosion magnitude estimated in a 99‐year moving window varied by 1.7 and 1.0 orders of magnitude, respectively. Decadal erosion magnitude was only moderately positively correlated with a summer temperature reconstruction over the period 900–1900 AD. Magnitude of the seven largest events was similar to the cumulative silt accumulation anomaly, suggesting these events ‘returned the system’ to the long‐term mean rate. Instead, the occurrence of most erosion events was related to fire (silt layers preceded by high charcoal concentration) and earthquakes (the seven thickest layers often match paleo‐earthquake dates). Our data show how internal (i.e. sediment production) and external processes (natural fires or more stochastic events such as earthquakes) co‐determine erosion regimes at millennial time scales, and the extent to which such processes can be offset by recent large‐scale deforestation by logging. Copyright © 2018 John Wiley & Sons, Ltd.     

叠前各向异性强度属性在乍得Bongor盆地P潜山裂缝性储层预测中的应用

裂缝性储层是乍得Bongor盆地潜山油藏主要储集类型,研究区地震资料较差,基底成像不清,利用地震资料进行裂缝预测符合率不高.近几年,在乍得多个潜山实施了"宽频、宽方位、高密度"（以下称"两宽一高"）三维地震勘探,基底成像效果有了明显改善.由于"两宽一高"地震勘探近几年刚刚兴起,目前利用"两宽一高"OVT处理资料预测裂缝的方法较少,主要是基于振幅随偏移距及方位角的变化的原理（AVAZ）,目前主要的方法为基于椭圆拟合的各向异性强度预测法,本文首先应用椭圆拟合法预测了Bongor盆地P潜山的各向异性强度,对结果进行了分析,指出了椭圆拟合法的局限性,进而首次在Bongor盆地研发并应用了基于统计法的各向异性强度预测技术,即首先通过道集规则化将不规则的道集处理成螺旋道集,然后在道集中统计振幅或双程走时的方差进行裂缝预测,在乍得P潜山取得了较好的效果,预测符合率达到80%以上,平面规律性明显.