子波相位与振幅属性关系研究——以DF气田为例

Relationship between wavelet phase and amplitude attributes of DF gas field

DF气田经过近10年的投产发现,储层含气后在地震剖面上含气砂体顶面表现为波谷特征,利用最小振幅属性寻找有利油气聚集区取得了一定的成果,相继发现了DF1-1、DF13-1以及DF13-2等大中型气田.但是经过42口井的钻探,逐步认识到并非所有强振幅区域均为有利储层,即振幅属性并非只受储层单一因素影响.通过提取各井井旁道地震子波,分析发现振幅强的区域钻探井的井旁道地震子波相位较振幅弱的区域大.针对这一问题,从一阶速度-应力方程出发,利用紧致交错网格有限差分对不同相位子波进行正演模拟.结果表明储层厚度小于相位拐点厚度时,零相位子波的最小振幅属性最小,相位角越大其振幅属性值越大;而当储层厚度大于相位拐点厚度时,零相位子波振幅属性最大,相位角越大振幅属性越小.利用振幅属性寻找油气聚集区时,应充分考虑子波相位的影响,消除由于地震子波相位不同引起的振幅能量变化.

DF gas field after nearly 10 years of production,the gas reservoir in the seismic profile of gas bearing sand on top for trough characteristics, using the minimum amplitude attribute find favorable oil and gas accumulation achieved certain results,have been found lots of large and medium gas fields,such as DF13-1 DF13-2 and DF1-1 gas fields. However,after drilled 42 wells,it is recognized that not all strong amplitude zones are favorable reservoirs. Through the extraction of the wells in the seismic wavelet analysis found the wavelet phase in amplitude strong regional is bigger than amplitude weak regional. In order to solve this problem,a new method based on the first order velocity stress equation is used to simulate the different phase wavelets with the compact staggered grid finite difference method. The results show that the thickness of reservoir is less than the thickness of the inflection point phase,zero phase wavelet minimum amplitude attribute minimum,the bigger phase with stronger amplitude attribute, but when the reservoir thickness is greater than the thickness of the inflection point phase,zero phase wavelet amplitude attribute maximum,the smaller phase with stronger amplitude attribute. When the amplitude attributes are used to locate the oil and gas accumulation area,the influence of wavelet phase should be taken into full consideration to eliminate the amplitude energy variation caused by the phase difference of seismic wavelet.