奥连特盆地北部灰岩增厚成因及储层预测分析

The Reason of Limestone Formation Thickering and Its Effect to Reservoir in the North of Oriente Basin

厄瓜多尔奥连特盆地是南美地区最重要的含油气盆地之一,油气资源丰富,主要含油气层系为白垩系Napo组砂岩储层,为浅海潮坪相沉积,岩性复杂,发育石英砂岩、海绿石砂岩、灰岩和泥岩,其中3套分布发育稳定的灰岩段(由上至下分别为A、B、C灰岩段),可作为全区对比标志层。Napo组A灰岩段在盆地北部发育较稳定(平均厚度约40 ft),但地震资料显示局部区域存在多个强振幅异常体,实钻结果表明,异常体内A灰岩段地层存在不同程度增厚,严重影响下伏砂体预测。针对奥连特盆地北部白垩系Napo组A灰岩段增厚现象,从区域地质、岩石物理、地球物理特征等方面入手,开展增厚原因分析;将测井与地震结合,以正常沉积厚度下优质砂体地震响应特征分析为基础,通过正演模拟,对不同厚度A灰岩段下砂体地震响应特征开展研究;根据地震正演模拟结果,反复比选,采用基于CRP道集的限角叠加和基于调谐厚度的频谱分解预测技术,可以较好地消除上覆A灰岩段增厚的影响,实钻结果证实了该认识和技术的可靠性。

The Oriente Basin is one of the most important basin with hydrocarbon source rocks in South American.The maj or petroleum system is Creatures Napo sandstone.The Napo Formation developed in tide sediment environment with the complex lithology including quartz sandtone,glauconite sandstone,limestone and shale.There are 3 sets of limestone formation in the Napo named as A,B,C limestone from lower to upper which are the marker formation.The A limestone in the north of Oriente Basin develops stably with average thick 40 ft.However several abnormal bodies of A limestone had been found in the northern of Oriente Basin which show the high seismic amplitude.It had been proved that some good sand bodies of A limestone thickened,which makes it difficult to predict the reservoir accurately by seismic data.The regional geology,petrophysics and geophysics data had been used to analysis the reason of A limestone formation thickening.By the seismic forward modeling based on the seismic response character analysis of good sandbody in the normal sedimentation,the seismic response character of sand below the different A limestone had been study.According to the seismic inversion result,many technology had been comparatively analyzed and stack bond seismic data analysis technology based on CRP and spectrum decomposition technology based on tuning body thickness had been used to get off the effect of A limestone thickening.Drilling results have proved the effectiveness of the technologies.