含强屏蔽滩坝砂储层正演模拟分析及描述

Forward modeling analysis and description of beach-bar sand reservoir with strong shielding

滩坝砂储层在国内各大盆地均有发育,是一种较为常见的油气储集层,虽有较好的油气开发潜力,但描述也相对困难.本文针对含强屏蔽滩坝砂进行声波方程有限差分正演模拟,通过对不同主频、不同地层速度以及多套砂体组合等不同条件下含强屏蔽滩坝砂储层地震响应正演分析可知:在一定范围内主频越高,地层速度越小,强屏蔽对薄层的影响范围越小;对于多组砂体,地震响应往往不能直接指示砂体特征,其弱反射信号是多组砂体的叠合结果.在此基础上,针对苏北盆地三河北工区“盖层复杂,储层信号弱”双复杂滩坝砂储层特点,采用“拓频+去屏蔽+90°相移”的研究思路与对策,先有效分离上覆盖层,再通过去强屏蔽处理消除强反射对下伏储层的影响,最后通过90°相移技术对滩坝砂体进行描述,获得满意的效果,为此类复杂油气藏勘探提供一种切实可行的方法.

Beach-bar sand reservoir is a common oil and gas reservoir developed in various basins in China.Although it has good potential for oil and gas development,it is difficult to describe.There are relatively few studies on seismic insider reflection characteristics of beach bar sand with strong shielding.In this paper,the finite difference forward modeling of acoustic equation is carried out for the beach bar sand with strong shielding.Through the forward modeling analysis of the seismic response of the beach bar sand reservoir with strong shielding under different conditions such as different main frequency,different formation velocity and multiple sets of sand bodies,we can see that the higher the main frequency is in a certain range,the smaller the formation velocity is,and the smaller the influence range of strong shielding on the thin layer is.For multiple groups of sand bodies,the seismic response often can not directly indicate the characteristics of sand bodies,and the weak reflection signal is the result of the superposition of multiple groups of sand bodies.Combined with Sanhebei industrial area in northern Jiangsu Basin,The research ideas and countermeasures of first lifting frequency and then shielding the last 90°phase shift can effectively separate the overburden cap layer in view of the double-compound beach bar sand reservoir with complex cap layer and weak reservoir signal.Then,the influence of strong reflection on the underlying reservoir is eliminated by the de-strong shielding process.Finally,the 90°phase shift technique is used to describe the beach bar sand body,and satisfactory results are obtained,which provides a feasible method for the exploration of such complex oil and gas reservoirs.