大城凸起煤层地震频率域含气性预测

大城凸起煤层含气性横向变化较大,各向异性强,部分新井钻遇水层,需要进行煤层含气性精细预测。在多井多频正演和地震频谱分析中发现频率对煤层含气性敏感,故采用小波分解和傅里叶变换方法,计算高低频调谐能量比进行煤层含气性预测。通过多井井旁地震高低频调谐能量比与钻采结果统计分析,建立高低频调谐能量比划分煤层含气性的标准,将研究区太原组Ⅵ煤层组划分为3类含气有利区,预测结果与钻探结果符合率达88.9%,取得较好效果。该方法突破了二维地震传统的定性预测,对煤层气井生产部署有较好的指导意义,在类似地区具有推广应用价值。

Prediction of Gas Bearing Property in Seismic Frequency Domain for Coal Beds in Dacheng Swell

The coal bed in Dacheng swell is characterized by large lateral variation of gas-bearing property and strong anisotropy. Aquifer has been penetrated in partial newly-drilled wells so that detailed prediction of gas-bearing property needs to be performed for the coal bed. During multi-well multi-frequency forward modeling and seismic spectrum analysis, it is found that frequency is sensitive to coalbed methane, so wavelet decomposition and Fourier transform are used to calculate high/ow frequency tuning energy ratio for gas bearing prediction. Based on the statistical analysis of the tuning energy ratio of multi-well near-well seismic, drilling and production data, the standards for gas-bearing property division with tuning energy ratio are established. According to which the VI coal bed of Taiyuan formation in the study area is divided into three types of favorable gas-bearing areas, and the coincidence rate of the predicted results with the actual drilling data reaches 88.9%, showing a good effect. This method breaks through the traditional qualitative prediction in 2D work area, which can be a guidance for production deployment in coalbed gas wells and is worth promoting and applying in similar areas.