川东地区茅口组岩溶储层地震预测研究

Research on seismic prediction of karst reservoirs in Maokou formation in eastern Sichuan

针对川东地区茅口组岩溶储层具有岩溶发育规模小、裂缝充填多等特点,提出了一套川东地区茅口组岩溶储层预测方法。首先分析茅口组岩溶储层的地质特征,其次对原始地震数据进行提高分辨率处理,细化分析茅口组内部反射特征,再利用正演模拟,建立茅口组岩溶储层地震响应模式,最后利用地震属性分析、分频相干分析和地震反演等手段,建立了茅口组岩溶储层地震预测模式.已利用檀木场区块实际数据对预测结果进行验证,证明对茅口组岩溶储层综合运用多种手段可以提高预测准确性,其地震预测模式为首先寻找强振幅背景下振幅变弱区及地震融合属性高值区,并在此基础上根据35 Hz高频相干属性值大于0.9、波阻抗值小于16000和孔隙度值大于1.5%等量化指标进一步圈定储层分布范围。已钻井分析结果显示,在钻井较少的情况下,以上模式预测的储层厚度误差在4 m以内.该预测模式可以有效地识别川东地区茅口组岩溶储层发育有利区,为后期井位部署提供依据.

Aiming to the karst reservoir of the Maokou formation in the eastern Sichuan area has the characteristics of small karst development scale and more fracture filling,this paper proposes a set of ideas for the prediction of the karst reservoirs in the Maokou formation in the eastern Sichuan area.Firstly,the geological characteristics of Maokou formation karst reservoir are analyzed,secondly,the original seismic data was processed with improved resolution,and the internal reflection characteristics of the Maokou formation were analyzed in detail,and forward modeling was used to establish the seismic response model of the Maokou formation karst reservoir,finally,the seismic prediction model of the Maokou formation karst reservoir was established using seismic attribute analysis,frequency-division coherence analysis and seismic inversion,and use the actual data of the Tanmuchang block to verify the prediction idea.It has been proved that the karst reservoir of Maokou formation can be accurately predicted by comprehensive application of various means.The seismic prediction model is to find the weak amplitude area in the strong amplitude area and the high value area of seismic fusion attribute firstly,and then further delineate the reservoir distribution according to the quantitative indexes such as the 35 Hz high-frequency coherent attribute value greater than 0.9,the wave impedance value less than 16000 and the porosity value greater than 1.5%.The drilling analysis results show that the reservoir thickness error predicted by the above model is less than 4 m under the condition of few wells.The prediction model can effectively identify the favorable development zone of karst reservoirs in the Maokou formation in the eastern Sichuan area,and provide basis for later well location deployment.