叠前各向异性强度属性在乍得Bongor盆地P潜山裂缝性储层预测中的应用

Application of prestack anisotropic intensity attribute in prediction of P Buried hill fractured reservoir in Bongor Basin, Chad

裂缝性储层是乍得Bongor盆地潜山油藏主要储集类型,研究区地震资料较差,基底成像不清,利用地震资料进行裂缝预测符合率不高.近几年,在乍得多个潜山实施了"宽频、宽方位、高密度"(以下称"两宽一高")三维地震勘探,基底成像效果有了明显改善.由于"两宽一高"地震勘探近几年刚刚兴起,目前利用"两宽一高"OVT处理资料预测裂缝的方法较少,主要是基于振幅随偏移距及方位角的变化的原理(AVAZ),目前主要的方法为基于椭圆拟合的各向异性强度预测法,本文首先应用椭圆拟合法预测了Bongor盆地P潜山的各向异性强度,对结果进行了分析,指出了椭圆拟合法的局限性,进而首次在Bongor盆地研发并应用了基于统计法的各向异性强度预测技术,即首先通过道集规则化将不规则的道集处理成螺旋道集,然后在道集中统计振幅或双程走时的方差进行裂缝预测,在乍得P潜山取得了较好的效果,预测符合率达到80%以上,平面规律性明显.

Fractured reservoir is the major reservoir type of buried hill oil pool in Bongor Basin,Chad.Due to the poor quality of the old seismic data in the study area,the basement imaging is unclear,which leads to the low coincidence rate of the previous fracture prediction.In recent years,3D seismic data acquisition of“wide bandwidth,wide azimuth and high density”(hereafter referred to as“two-wides and one-high”)has been implemented in several buried hills in Chad.As a result,the effect of basement imaging has been improved remarkably.As“two-wides and one-high”seismic survey has just become popular in recent years,there are fewer methods to predict fractures by using“two-wides and one-high”OVT processing data,and most of them are based on amplitude versus offset and azimuth theory(AVAZ).In this study,ellipse fitting method was firstly used to predict anisotropic intensity of P Buried hill in the Bongor Basin,then based on the results analysis,the limitation of ellipse fitting was pointed out.Furthermore,the anisotropic intensity prediction technology based on statistics was firstly applied in the Bongor Basin,in which the irregular gathers were first processed into helical gathers through gather regularization,and then variance of amplitude or TWT in gathers were counted to predict fractures.With this method,good results have been achieved in fractures predicting in P Buried hill in Chad,with more than 80%coincidence rate and a clear planar regularity of fracture distribution.