川中地区上三叠统须家河组二、四段地震相特征及其地质意义
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摘要
四川盆地中部地区上三叠统须家河组气藏为构造背景下的岩性圈闭气藏,利用地震资料研究不同岩性组合、划分出不同的地震相带,将有助于预测无井区储层的沉积特征及其展布。考虑到研究区范围广、地震测网间距大的实际情况,选用了"相面法"来进行地震相分析,即主要从反射结构、反射波组的振幅、频率、相位、连续性、时差和反射外形等属性来研究须家河组的地震响应特征及其平面分布情况。研究结果表明:①须二段上部,一种表现为弱振幅、平行、亚平行反射地震相,主要代表的是三角洲前缘亚相的叠置分流河道及河口坝;另一种地震反射特征则表现为较强振幅、断续反射,为三角洲平原亚相的水上分支河道及河道间湾;须二段下部平行、亚平行、强振幅、较连续反射上超地震相主要为一套楔状体。②须四段地震相一种为平行、强振幅、断续至连续反射地震相,为三角洲平原亚相的水上分支河道及分流间湾;另一种为弱振幅、平行、亚平行反射地震相,为三角洲前缘亚相的水下分流河道。③区域地震大剖面资料显示须六段厚度呈南厚北薄之势。
Gas reservoirs in the upper Triassic Xujiahe Formation in the central Sichuan Basin are lithologic gas reservoirs formed in structural settings.Identification of lithologic combinations and division of seismic facies zones according to seismic data are helpful to understand the sedimentary features and distribution of reservoirs in the areas without wells.In view of the large study area and sparse line spacing,various seismic attributes,such as reflection structures,reflected waveforms,and amplitudes,frequencies,phase positions,continuity and interval transit time of reflected wave groups,are used to study the characteristics and distribution of seismic response.(1) In the upper 2 nd member of the Xujiahe Formation,seismic facies featured by parallel to sub-parallel reflection with a low amplitude are represented by superimposed distributary channels and mouth bars of delta plain subfacies;while another seismic facies featured by discrete reflection with a relatively high amplitude are represented by above-water distributary channel and inter-channel bay of delta-plain subfacies.And there a set of wedges are the onlapping seismic facies characterized by relatively continuous parallel to sub-parallel reflection with a high amplitude.(2) In the 4 th member of the Xujiahe Formation,seismic facies characterized by discrete to continuous parallel reflection with a high amplitude are represented by above-water distributary channel and inter-channel bay of delta-plain subfacies,while another seismic facies characterized by parallel to sub-parallel reflection with a low amplitude are represented by the underwater distributary channel of delta-front subfacies.(3) Regional large seismic profile reveals that the thickness of the 6 th member of the Xujiahe Formation is large in the south and small in the north.
Gas reservoirs in the upper Triassic Xujiahe Formation in the central Sichuan Basin are lithologic gas reservoirs formed in structural settings.Identification of lithologic combinations and division of seismic facies zones according to seismic data are helpful to understand the sedimentary features and distribution of reservoirs in the areas without wells.In view of the large study area and sparse line spacing,various seismic attributes,such as reflection structures,reflected waveforms,and amplitudes,frequencies,phase positions,continuity and interval transit time of reflected wave groups,are used to study the characteristics and distribution of seismic response.(1) In the upper 2 nd member of the Xujiahe Formation,seismic facies featured by parallel to sub-parallel reflection with a low amplitude are represented by superimposed distributary channels and mouth bars of delta plain subfacies;while another seismic facies featured by discrete reflection with a relatively high amplitude are represented by above-water distributary channel and inter-channel bay of delta-plain subfacies.And there a set of wedges are the onlapping seismic facies characterized by relatively continuous parallel to sub-parallel reflection with a high amplitude.(2) In the 4 th member of the Xujiahe Formation,seismic facies characterized by discrete to continuous parallel reflection with a high amplitude are represented by above-water distributary channel and inter-channel bay of delta-plain subfacies,while another seismic facies characterized by parallel to sub-parallel reflection with a low amplitude are represented by the underwater distributary channel of delta-front subfacies.(3) Regional large seismic profile reveals that the thickness of the 6 th member of the Xujiahe Formation is large in the south and small in the north.
引文
[1]杨家静.四川盆地合川地区须二段气藏新增天然气控制、预测储量报告[R].成都:中国石油西南油气田公司勘探开发研究院,2007.
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[2]黄平,安辉.川中—川南过渡带上三叠统储层预测及烃类检测研究[R].成都:中国石油西南油气田公司勘探开发研究院,2009.
[3]李国辉,谢继容.四川盆地川中—川西地区上三叠统层序地层与沉积相研究[R].成都:中国石油西南油气田公司勘探开发研究院,2009.
[4]中国石油勘探与生产分公司.岩性地层油气藏勘探理论与实践[M].北京:石油工业出版社,2005.
[5]张奇,屠智慧.川中长兴组—飞仙关组沉积相及含气条件研究[R].成都:中国石油西南油气田公司勘探开发研究院,2009.
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