摘要
西湖凹陷平北斜坡带平湖组含油气地层普遍发育薄煤层,煤层导致含油气砂岩地震振幅、相位、频率发生变化,为剔除薄煤层影响和识别含油气砂岩,开展了储层预测研究工作。首先,利用地震、测井、岩心资料,开展含煤系地层沉积特征分析;然后,利用岩石物理分析技术优选出能识别平湖组煤岩、泥岩、含水砂岩、含油气砂岩的敏感特征参数;最后,综合利用地震波形指示反演及模拟技术剔除储层中薄煤层干扰,完成含油气储层预测。结果表明:平湖组煤层多发育于受潮汐影响的三角洲泥炭坪、河控三角洲泥炭沼泽沉积环境中,厚度约为1m,煤层间隔约为5m,具有厚度薄、层数多的分布特征。煤层纵波阻抗多低于9000g/cm^(3)·m/s,密度多低于2.2g/cm^(3),含油气砂岩vP/vS门槛值基本处于1.65~1.70,含气砂岩表现为弱波谷或中弱波峰地震反射特征。地震波形指示反演可有效识别优势储层,预测斜坡东部近洼陷带含烃概率较大,是下一步寻找构造岩性油气藏的勘探方向。
Thin coal seams have developed widely in the Pinghu Formation in the Pingbei slope of the Xihu Depression.The presence of such coal seams elicits changes in the seismic amplitude,phase,and frequency of the oil-bearing sandstone.To eliminate the effect of the thin coal seams and effectively identify the oil-bearing sandstone,reservoir predictions were carried out in this study.First,the sedimentary characteristics of the coal-bearing strata were analyzed using seismic,logging,and core data.Subsequently,the sensitive parameters that can be used to identify coal rock,mudstone,water-bearing sandstone,and oil-bearing sandstone in the Pinghu Formation were optimized using petrophysical analysis.Finally,the interference from the coal seams was eliminated via seismic waveform indication inversion;thus,the oil-gas reservoir could be predicted.The results of the analysis pointed out that the coal seams in the study area are mostly developed in the sedimentary environments of the tidal-affected delta peat flat and the river-controlled delta peat swamp.The seams are~1m thick and are spaced by~5m—that is,they are thin but frequent in occurrence.The coal seams feature P-wave impedance<9000g·cm^(-3)·m·s^(-1),a density<2.2g·cm^(-3),and a vP/vS threshold with the gas bearing sandstone of 1.65~1.70.The latter is characterized by a weak trough or a medium-weak wave peak reflection.Seismic waveform indication inversion can distinguish coal-bearing mudstone,oil-bearing sandstone,water-bearing sandstone,and mudstone,thereby aiding identification of the dominant reservoir.Overall,the results of this study indicated the area near the depression zone in the eastern part of the slope to be the one most likely to contain hydrocarbons.This area will represent the next direction of investigation in terms of exploration of tectonic-lithologic reservoirs.
作者
王红岩
周祥林
胡伟
蔡坤
杨敏
汤睿
WANG Hongyan;ZHOU Xianglin;HU Wei;CAI Kun;YANG Min;TANG Rui(Shanghai Branch,CNOOC,Shanghai 200335,China)
出处
《石油物探》
CSCD
北大核心
2021年第4期595-603,共9页
Geophysical Prospecting For Petroleum
基金
国家科技重大专项(2016ZX05027-001)资助。
关键词
西湖凹陷
含煤层系
沉积特征
地震波形指示反演
Xihu depression
coal-bearing strata
sedimentary characteristics
seismic waveform indication inversion
