叠置薄储层的沉积微相解释研究

Interpretation research into continentalmicrofacies of superposed thin reservoirs

CNPC东方地球物理公司凌云研究组, 河北涿州 072751

Ling Yun Group, BGP, CNPC, Zhuozhou 072751, China

中国陆相沉积盆地腹部油气勘探所面临的问题是:盆地面积小,断裂发育,沉积相变化快,储层薄,当地震勘探分辨率小于1/4波长时,在地震剖面上难以分辨出这些薄储层。针对这一问题,开展了探索和研究,建立了一套针对薄储层的地震勘探技术思路。提出对于叠置薄储层(单层厚度小于3m,埋深2100m,5～7层)的勘探,最终目标是求解叠置薄储层沉积微相的思想。讨论了相对保持振幅和波形的提高分辨率处理的基本原理,即在有效消除近地表影响的条件下,获得相对保持振幅和波形的提高分辨率成像数据;给出了基于层序地层学的储层演化解释方法,即沿参考标准层提取等时地震属性切片,通过动态演化解释方法研究在一个沉积旋回中的薄储层的形成过程和空间展布特征。利用该方法对松辽盆地腹部下白垩系一套叠置砂体进行了沉积微相解释,划分了油气有利运移区和有利储集区,进行了油气富集区的预测。经多口开发控制井验证,预测的准确率在60％以上,说明地震对于薄储层勘探仍是行之有效的方法。

The petroleum exploration difficulties in the hinterland of a continental deposit basin in China lie in the small basin area, developed fractures, rapidly changing sedimentary facies and thin reservoirs. It is by nomeans easy to distinguish the thin reservoirs on seismic sections if the reservoir thickness is less than 1/4 of a wavelength. This paper presents a set of new seismicmethods to deal with the above-mentioned difficulties, which includes themethods to identify the superposed thin reservoirs with the single layer less than 3meters, buried depth 2,100meters, and 5 to 7 layers composed by computing their sedimentarymicrofacies. Themigrated data with high-resolution and preserved relative amplitude and waveform is obtained by effectively eliminating the near-surface impact. A reservoir evolution interpretationmethod based on sequence stratigraphy is proposed, seismic attribute slices are extracted along the reference layer, dynamic evolution interpretationmethod is applied to research thin reservoir development process and its spatial exhibition features in a cycle of sedimentation. We conduct a sedimentarymicro facies interpretation on a group of superposed sand bodies of the Lower Cretaceous in the hinterland of Songliao Basin using this ofmethods; favorable petroleummigration and reservoir areas are differentiated and predicted. Several development wells indicate that the prediction accuracy is over 60% , these new seismicmethods are proved to be effective and efficient in predicting thin reservoirs.