【作者】 刘朋波；

【导师】 蒲仁海；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2010， 博士

【摘要】 延长探区位于鄂尔多斯盆地的中东部,在上古生界山西组的天然气勘探中屡获高产气井,显示了该区良好的勘探前景。与此同时,储层砂岩的展布和油气富集规律不明确制约着下一步勘探。针对目前勘探中的难点问题,本文在前人研究的基础上,根据现有的勘探资料,以寻找有利勘探目标为最终目的,综合运用层序地层学、储层沉积学、地震沉积学、石油地质学等原理和方法,对延长探区山西组进行了系统的层序划分、沉积相分析、地震储层识别及有利勘探目标分析等研究,为后期勘探布井提供科学依据。本次研究的创新点主要体现在：①在沉积相分析的基础上,以各种地震正演模拟技术为手段,分析和解释地震属性。②在沉积相分析与地震储层识别过程中地质与地球物理方法相互反馈,沉积模式指导地震储层识别,地震储层识别结果又进一步完善沉积相认识。研究过程中取得的主要成果和认识有：(1)以Cross的基准面旋回法为主要指导思想,同时利用地层厚度法、井震循环标定法加以辅助,将研究区山西组划分为2个长期旋回和6个中期旋回。2个长期旋回分别对应于山一段和山二段。6个中期旋回与山西组内部的山23～山11的6个砂层组对应较好。(2)山西组沉积为典型的缓坡型浅水三角洲,主要发育三角洲前缘。山西组沉积期水体浅,地形平坦,湖泊波浪改造作用较弱,三角洲前缘以水下分流河道和水下分流间湾微相为主,三角洲的典型沉积微相类型河口坝发育较差。水下分流河道能量较强,底冲刷构造非常发育,且河道砂岩中通常夹泥砾。砂岩以中-细粒石英砂岩为主,分选、磨圆较好,单层厚度一般小于6m,大套厚层砂岩为多期河道相互切割叠置而成。剖面中砂岩横向连续性差,呈透镜状分布；平面上砂体呈朵叶状展布,同时受河控影响,展布具有一定的方向性。山西组沉积过程中,水体整体逐渐加深,滨浅湖体系北迁,沉降中心也向北移,研究区北部三角洲体系后缩,南部三角洲体系北进。(3)正演模型研究表明地震振幅、相位及多道统计相干、波形分类等属性均不能表征砂岩,主要是由于含气砂岩具有AVO效应、煤层和灰岩的屏蔽及泥质粉砂岩(粉砂质泥岩)与砂岩速度相近等因素综合影响而致。实际井含气层段孔隙中不同性质流体(原始状态、含气饱和及含水饱和状态)的AVO正演模拟表明：含水饱和、含气饱和模型及原始模型的AVO截距P均为正值,AVO斜率G都为负值。含气饱和度越大,AVO斜率的绝对值|G|越大。一维正演模型研究表明,煤层厚度变化能引起振幅的明显变化；而砂岩厚度增大或减小时,振幅变化不明显。低速煤层对地震振幅的贡献几乎完全淹没了砂岩对振幅的贡献。(4)根据地震、测井资料的分析,结合各种地震反演方法的原理和适用性,三维区选择以测井为主体的地震特征参数反演方法来反演自然伽玛、波阻抗、速度、孔隙度等参数体,用自然伽玛和波阻抗参数相结合来识别砂岩；二维区选择约束稀疏脉冲反演波阻抗体,用波阻抗来表征砂岩。三维区内基于反演结果所计算出的砂岩厚度横向变化明显,与井点统计砂厚吻合较好,同时其自北向南的朵叶状展布特征反映了三角洲前缘水下分流河道的沉积特征及三维区的物源方向。二维区的波阻抗反演结果未能准确的揭示储层砂岩的横向变化,但能粗略的区分砂泥岩,砂岩厚度大的井均位于高阻抗异常带内。(5)地震含气性检测尝试表明,含气砂岩对高频的吸收效应显著,高级频F3的平面分布较好的指示了地层含气性。(6)基准面旋回对储集体发育特征控制明显,连通性好、厚度大的砂层均发育于基准面旋回早期。同时,砂体厚度越大,沉积期水动力条件越强,颗粒越粗,成岩作用后期抗压实能力越强,有利于形成相对高孔高渗储层。(7)区域盖层和局部盖层与山西组烃源岩夹持的河道砂岩构成自生自储的成藏组合。延长探区构造平缓,断层不发育,烃源岩以上下相邻和侧向连接的方式为储层提供了气源,属于典型的岩性气藏。在“广覆式”生烃模式下,储层条件为成藏的主控因素,勘探布井应首选多期河道叠置的富砂区。更多还原

【Abstract】 The yanchang exploration area locates in the mid-eastern of Ordos Basin, which is found high gas rate wells at the Shanxi formation of the upper paleozoic, showing a good exploration prospect in this area. Meanwhile, the indefinite distribution of reservoir sandstones and oil-gas abundance law restrict the following exploration.Aiming at the recent problems in the exploration, on the basis of previous studies and according to the available exploration data to find favorable exploration targets for the ultimate goal, this paper comprehensively used the principle and method of sequence stratigraphy, reservoir sedimentary, seismic sedimentology and petroleum geology etc. to do research in the stratigraphic classification, sedimentary facies analysis, seismic reservoir recognition and analysis of favorable exploration target, which provided scientific basis for later exploration and well spacing.The innovative points mainly embodies in:firstly, taking various seismic forward modeling techniques for means to analyze and explain seismic attributes; secondly, using geological and geophysical methods mutual feedback in sedimentary facies analysis and seismic reservoir identification, sedimentary model can guides seismic reservoir identification, the results of seismic reservoir identification can perfect sedimentary face understanding furtherly.The main results and understandings from the research are as follows:(1) In the base-level cyclic sequences method of Cross for major guiding ideology, using the method of stratum thickness, well-seismic cycling calibration method to assist, this paper divided shanxi formation of study area into two long-term, six middle-term datum plane cycles. The two long-term cycles correspond to the first and the second member of Shanxi Formation respectively; the six middle-term cycles grossly correspond to six sand sets of Shan23～Shan11.(2) Shanxi formation is a typical shallow slope delta depositional model, which mainly develop delta front.The features during Shanxi formation depositional period were shallow water, flat terrain, relatively weak reformation of lake waves. Underwater distributary channel and bay are the main sedimentary microfacies types of the delta front in which the typical mouth bar developed poorly. The energy of underwater distributary channel was strong, the bottom washout structures are very developed, and the river sandstone usually clip mud bricks. Sandstone sorts are mid-fine grained sandstone of quartz sandstone with good sorting and grinding which is less than 6m in thickness, big thick layer of sandstone is overlaied by multi-stages channels cutting. Sandstone had a poor horizontal continuity and lens shaped distribution in the section, and shaped distribution in lobes in the plane, which exhibited in certain direction effected by the river.The water gradually deepened during Shanxi formation depositional process, the shore-lacuatrine system and subsidence center both moved toward north, the northern delta system moved backward and southern delta system northward.(3) The forward modeling study shows that seismic amplitude, phase, multi-traces statistical coherent and waveform classification attributes cannot reflect the sandstone, which mainly due to the comprehensive effect of gas sandstone with AVO effect, coal and limestone shielding and shale silty sandstone (silty mudstones) have the similar speed with sandstone.The AVO forward modeling of actual containing gas wells with different pore fluid (original state, gas and water saturated state) illustrated:water saturation, gas saturation model and the original model AVO intercept are positive, the AVO gradient are negative. The higher the gas saturation was, the bigger the absolute value |G| of AVO was with offset increases.1D forward modeling study shows that, thickness variation of the coal can cause to significantly change of amplitude, but the sand can not. The thin-low velocity coal seam was the mainly contribution to seismic amplitude, almost completely submerged sandstone contribution.(4) According to the analysis of the seismic data, with all kinds of seismic inversion method, the principle and the applicability, in the 3D area author selected seismic character parameters inversion method subject with log data to invert GR, IMP, VEL and POR parameters etc., use the combination of GR and IMP to identify sandstone; sandstone reflection using IMP which were inverted by constrained sparse spike inversion were selected in the 2D area.The sandstone thickness calculated by the inversion results in 3D area changed significantly horizontally, which had a fine match with well statistical sand thickness. Meanwhile, north to south exhibition features reflect the delta front distributary channel of sedimentary characteristics and the source direction in 3D area.The impedance inversion in 2D area can not accurately reveal horizontal changes of sandstone reservoir, but can distinguish mudstone from sandstone roughly, wells had thick sandstone are located within the high impedance anomalous zone.(5) Seismic gas-bearing properties detection shows that gas bearing sandstone can effect the absorption of high frequency, the distribution of high frequency F3 can indicate strata gas bearing properties well.(6) Base-level cycle obviously controlled reservoir development characteristics, good connectivity, thick sandstone developed in early base-level cycle. At the same time, the thicker the sandstone were, the stronger the hydrodynamic conditions in depositional period were; the coarser the grain were, the stronger the anti-compaction in late diagenesis period were, which were better for forming the relatively high porosity and permeability reservoirs.(7) Local and regional seal bed and the channel sandstone clamped by source rock in Shanxi formation formed a reservoir combination of self generation and self preservation. Yanchang exploration area had a gentle structure and undeveloped fault, source rock provided gas source to reservoir neighboring, which belongs to typical lithologic reservoir. Reservoirs conditions were the main controlling factors of reservoir forming in the "wide covered type" hydrocarbon generation model, exploration well spacing should be preferred to the thick sandstone overlaied by multi-stages channels.更多还原