薄互层火成岩地震响应特征及厚度预测

Seismic response characteristics and thickness prediction of thin interbedded igneous rocks

渤海地区B油田在古近系目的层段内广泛发育多种岩相的火成岩,这种喷发型为主的火成岩多以薄互层形式存在,但其厚度具有不均匀性,横向变化较大,准确描述火成岩厚度分布对后续井位部署和储量评价均具有至关重要的作用。对油田范围内已钻井火成岩厚度及组合规律进行分析,认为对油田勘探开发影响较大的是薄互层形式的溢流相火成岩,系统研究薄互层形式下的组合结构、毛厚度、及净毛比3种因素对火成岩地震响应特征的影响,并通过实际数据建立了不同的分析模型,认为净毛比是振幅响应的主控因素,利用实际子波正演建立净毛比和响应振幅的关系,并采用约束稀疏脉冲反演方法对区域范围内的火成岩厚度进行预测,结果显示,预测厚度与实钻厚度吻合较好,有利于定量化研究火成岩对下伏构造的影响程度。该研究成果对后续勘探及储量评价具有较好的指导意义。

Igneous rocks are widely developed in Paleogene in B oilfield of Bohai Sea area.The igneous rocks dominated by eruption mainly exist in the form of thin interbeds,and their lateral thickness varies largely.It is very important to accurately describe the thickness distribution of igneous rocks for well location deployment and reserves evaluation.Based on the known thickness distribution and combination law of igneous rocks in drilled wells,it is considered that overflow igneous rocks in the form of thin interbeds have a great influence on oil field exploration and development.The influencing factors such as combination,total thickness and igneous rock ratio were systematically studied,which lead to different seismic response characteristics of thin interbedded igneous rocks.Based on real data,different analysis models were established to demonstrate the influences of the three factors.It is considered that igneous rock ratio is the main controlling factor affecting the amplitude of seismic response.Relationship between igneous rock ratios and amplitude was established by using actual wavelet forward modeling,and the thickness of thin-interbed igneous rocks was predicted using constrained sparse pulse inversion.The result shows that the predicted thickness is in good agreement with actual drilling thickness,so this method is helpful to quantitatively study the influence of igneous rocks on underlying structures.The research results have good guiding significance for further exploration and reserves evaluation.