| Visual inspection technology utilizes downhole cameras to obtain video images of wellbore,allowing oil and gas well engineering technicians to grasp the most realistic underground conditions in the most intuitive way.Currently,the array side-view visual logging tool is a commonly used technical means in oil and gas well visualization inspection,and has achieved good application effects in monitoring and maintenance.In practical engineering applications,due to the inherent properties of cameras and limitations of special application environments,the obtained video images are deformed and distorted,resulting in deviations in logging data.Therefore,this paper uses image correction technology to process video images,obtain complete and undistorted panoramic images of the wellbore inner wall,and provide more accurate logging information for oil and gas well inspection.The main research contents are as follows:(1)In view of the imaging of the array side-view camera in the wellbore,the main factors causing image distortion are summarized,and the imaging distortion mechanism of the camera is analyzed in combination with the optical system.In order to further analyze the imaging of the wellbore,a three-dimensional column is established to form a digital model,and the linear projection method of the three-dimensional column is derived based on the linear imaging principle to obtain the linear projection function of the column.Then,based on the inverse mapping principle,a linear projection-based inverse mapping distortion correction model is established.Simulations are conducted on a wellbore with a fixed-scale checkerboard pattern using the linear projection method,and the change rules of the projection radius and projection grid of the wellbore are analyzed to verify the accuracy of the model.(2)A linear projection-based image correction algorithm is proposed.This algorithm establishes a three-dimensional grid reference model of the array side-view camera through linear projection,matches the model with the distorted image,and specifies the effective unfolding area by determining the grid interval.Then,using the spatial coordinate mapping method,the pixel points in the effective area are re-laid into a blank rectangular image to achieve area unfolding and eliminate distortion.For the unfolded four rectangular images,the SIFT feature extraction algorithm is used to fuse them into a wellbore inner wall panoramic unfolding image containing all the information of the target column,and a three-dimensional surface image of the wellbore is drawn to provide visual reference for visual evaluation.(3)Based on the above research,with the wellbore imaging distortion mechanism and image correction method as the core,an array side-view wellbore image correction software is designed,and the design ideas of the software modules are elaborated in detail,and the operation results of the software are given.The software realizes functions such as video playback,model matching,image correction,and image stitching,and can quickly process logging video images,which has certain application value. |
