基于电成像资料的应力方向自动确定方法研究

Study on automatic determination method of stress direction based on electric image logging

钻井过程中,当地层被钻开时地层应力会重新分配,原始地层应力得到释放从而分产生应力释放缝。为确定地层水平地应力方向,采用图像处理技术对电成像图进行阈值分割,把裂缝信息与地层以及图像噪点分开,再通过图像细化技术以及自动拟合技术,将评价电成像图中的裂缝转化为提取形态相似的正弦曲线,用Hough变换将正弦曲线自动拾取出来。研究表明,应力释放缝的形态由最大水平应力的方向决定,在电成像测井资料图中可以直观地观察到应力释放缝的形态,即显示了裂缝发生处地层的水平应力方向信息。该方法提高了电成像应力释放缝形态评价的准确性与效率,为地层水平地应力方向确定带来了极大便利。

In the process of drilling,the in-situ stress will be reallocated when the local layer is drilled,the original formation stress is released to generate the stress free crack. To determine the horizontal direction in-situ stress,image processing techniques was used to make segmentation on image logging with different thresholds, the information of fracture and strata and the noises of images can be dis-tinguished ;the application of the image processing and automatic fitting technique, will evaluate the crack image into electrical sine curve similar to the extracted form, and through Hough transform method, the sine curve can be obtained automatically. Study shows that,the form of stress free crack is decided by the maximum horizontal stress,the shape of stress release slot can be observed directly in the electrical imaging logging data,which shows the information of horizontal stress direction while crack occurs. The method has im-proved the accuracy and efficiency of the electric imaging stress free crack morphology evaluation, and has bought great convenience for the determination of direction of horizontal stress.