Method Research Of Automatic Stratum Attitude Extraction Based On Electrical Image Logging

Geophysical well logging is an effective method to determine attitude of stratum, mainly using the dipmeter log. It can not only provide sedimentary structure information and geological structure, but also study the bedding structure of strata, thus identify sedimentary moving direction and estimate sedimentary environment, which has important practical significance for oilfield exploration and development. Conventional dipmeter method can obtain satisfactory result for bedding formation, but it is difficult to obtain good result for the geological characteristics of complex or high resistivity layers, especially can not precison detect bedding plane and extract occurrence. Bedding plane has higher resolution than macro structural plane, it can carry on the fine geological interpretation. Image well logging is an advanced logging technology which provide borehole image, not only qualitatively identify formation boundary, fracture and structural form, but also make quantitative processing and analysis of logging image by image processing method, extract formation boundary and occurrence.The paper first maked a brief introduction of electrical imaging logging, such as measurement principle, instrument structure, technical paramenters and suitable conditions, then discussed the corresponding preprocessing of electrical image logging data, mainly including acceleration correction, electric button depth alignment, transmitting voltage correction, bad electrode correction, equalization and so on. Using the imaging module of LEAD software to complete electrical image logging data preprocessing and image generation. We focus on eccentricity correction of electrical image logging when the instrument were eccentric. An algorithm of least square was used for fitting ellipse wellbore based on diameter curves of electrical image logging and the ellipse parameters were derived, and then to judge whether instrument are eccentric. On the basis stated above, the locations of all pads of instrument in the ellipse well were calculated, and the real micro borehole electric image was obtained. Using histogram equalization method to improve the quality and display of image, median filtering was applied to remove noise points that affect the imaging results.Through the research of tests, we obtained the implementation of lamination plane detection method based on statistics. Local orientation estimation for sinusoid curve fitting, the final fitting out of the curve on the small window to estimate the orientation again and fine-tuning based on the depth of contrast, the most accurate lamination plane. We geted attitude of lamination according to the sinusoidal parameters. For the case of tilted borehole, deviation correction for the attitude values should be executed. In order to recover the formation to original deposition and eliminate the influence of structural dip, the dips of mudstone were used to determine structural dips.At the same time, the related methods were realized by vc++programming language and the algorithm were attached to LEAD software. Compared with calculations by AutoDip module of Halliburton, the results proved that the method is effective.