Research And Application Of Drawing And Changing Out Casing In Shallow Gas Zone Of Side-track Wells

For difficult well-control of operation wells in shallow-gas zones, there is a newisolation technology of shallow-gas zones putted forward, which can effectively preventoil and gas channeling and prevent well kick and blowout. This process, in the lowerbound of shallow-gas layer and near cement cap, uses the upper and lower twoperforation intervals to set up a injecting circulation channel for injecting sealingmaterials, which utilizes temporary plugging materials such as high density mud oreternal sealing materials filling isolation areas such as liquid cement in order to separateshallow gas.By means of adding oil well cement reinforcer of low density developed accordingto grain composition and theory of high packing in drift-bead liquid cement of lowdensity and high strength as sealing material, this process, through the field test, canmeet the requirement of isolation technology of shallow gas zones in Daqing oilfield.Through the compatibility study about washovering hole of side-tracking wells, itcan calculate the optimal placement of the ball bearing centralizer and the maximumcutting length and the construction parameter, can guide design and preventconstruction safety. The determined process about washovering and importing ofside-tracking wells under the condition of different borehole curvature has valid fieldapplication effect and pertinence of the technology and high reliability, and can satisfythe technical requirement of the drawing and changing out casing of side-tracking wells.The success of technical study of drawing and changing out casing of side-trackingwells, thoroughly repaired the directional well casing damage for years, and widenedthe field of oilfield workover, and realized the technological breakthrough.Through developing special tools, the form a complete set of the drawing andchanging out casing of side-tracking wells was realized, which had reasonable structuredesign and the characteristic such as high strength and good cutting protective effect. Inthe process of research, according to the actual production requirement of thedown-hole operation branch sites, the process has been in the application in othercomplex wells and had a good prospect of popularization and application.Out of the total seven characteristics of secondary structures in Daqing oilfield, theshallow gas zone is found to be existed in six oil deposits such as Lamadian, Saertu,Xingshugang, Gaotaizi, Putaohua and Aobaota except for Taipingtun. More and more of these type of casing damaged wells are accumulated as years move on, there is a hugemarket potential for directional workover operations if take into consideration of largeamount of directional wells in Daqing oilfield. Hence, the significance of carrying outresearch on drawing and changing out casing in shallow gas zone can be expected. Thistechnology has a broad application prospect to develop workover businesses andtransactions, to extend related enterprises and create considerable economic and socialbenefits.