P波方位AVO在煤层裂缝探测中的应用

探测煤层中的裂缝对于煤田的安全生产具有重要的意义。由于地层上覆载荷的压实作用,水平和低角度裂缝近乎消失,保留下来的是高角度和近于垂直的裂缝,而正是这类裂缝引起了地震P波方位各向异性的传播特征。所以地震P波的方位各向异性反映了地下介质裂缝的发育情况,尤其是P波方位AVO属性,对裂缝的发育程度具有较好的敏感性。通过对P波方位AVO属性的分析,能得到地下介质裂缝的发育情况。基于利用P波方位AVO属性探测裂缝的理论和实用方法,对淮南煤田某矿区的纵波地震资料进行对比和分析,得到了本矿区某煤层的裂缝发育分布情况,其预测结果符合实际井孔实测资料,表明此方法有效。

P-WAVE AZIMUTHAL AVO ANALYSIS OF FRACTURE DETECTION IN COALBED AND ITS APPLICATION TO ENGINEERING

Fractures will exert great menace to the safe production of coal fields. The fracture detection of coalbed is an important problem in the development of many coalfields. Due to the overlying strata pressure, horizontal fractures and low-angle fractures of the stratum almost disappear. The characters of P-wave azimuthal anisotropy are mainly caused by high-angle fracture and vertical fracture of the stratum;and the azimuthal anisotropy of P-wave reflects the situation of fracture of underground medium. Especially,P-wave azimuthal amplitude variation with offset (AVO) is sensitive to fracture. Therefore, the analysis of P-wave azimuthal AVO can be used to delineate fracture patterns and investigate their properties. The theory and method based on P-wave azimuthal AVO analysis are applied to the P-wave seismic data in some mining area of Huainan coalfield. The fracture distributions of some coa beds in this area are achieved. The results of predicted fracture agree well with the in-situ data;and the proposed method is proven to be successful.