一种基于岩性补偿系数的沉积相约束反演方法及应用研究——以渤海湾盆地埕岛南部东营组为例

Facies constrained inversion method and application based on lithology compensated coefficient:a case study of the southern part of Chengdao Oilfield in Bohai Bay Basin

为了降低研究区薄储层反演多解性,提高反演预测准确度,本文提出一种基于岩性补偿系数的沉积相约束反演储层预测方法.首先在确定研究区目的层沉积相展布特征前提下,建立目的层3D沉积相模型;将测井GR曲线投影映射为岩性补偿系数,通过补偿地震波阻抗数据区分薄层砂泥岩,并在沉积相和补偿后波阻抗数据共同约束下进行相控反演研究.本研究方法加入了沉积相以及测井、地震数据等约束信息,最终的反演结果提高了纵向薄砂体识别能力,同时预测的砂体平面展布特征与实际地质沉积规律吻合,在渤海湾盆地埕岛南部地区取得了较明显的实际应用效果.

In this paper,a sedimentary facies constrained inversion method based on lithology compensated coefficient is proposed in order to improve the accuracy of inversion results and reduce the inversion non-uniqueness of thin sandstone reservoirs in the study area.Firstly,building the 3D sedimentary facies model of Dongying formation under the condition of the sedimentary distribution characteristics in the study area.Then mapping the GR curve as lithology coefficient and applying the lithology coefficient to compensate the wave impedance curve.Under the compensated wave impedance,we can better distinguish thin sandstone.And then implementing post stack wave impedance inversion under the joint constraints of the built sedimentary facies model and the compensated wave impedance,and finally we can obtain the facies constrained wave impedance data.The method proposed in this paper contains multiple constraint information,such as sedimentary facies,logging data and seismic data.The facies constrained inversion result can obviously identify thin sandstone with thickness about 3 m in the vertical direction and this method can significantly improving the vertical resolution.In addition,compared to conventional methods,the predicted characteristics of sandstone plane distribution using the facies constrained inversion result are more consistent with the actual geological sedimentary characteristics.The facies constrained inversion is more stable and reliable with the constraints of sedimentary facies and compensated wave impedance.This proposed method has achieved obvious application results in the southern part of Chengdao Oilfield in Bohai Bay Basin,and the predicted characteristics of sandstone plane distribution are consistent with the sedimentary characteristics of the nearshore subaqueous fan in the study area.The method is suitable for complex sedimentary areas with thin sandstone and strong heterogeneity.