Objectives/scope: The tight gas reservoir in the southern part of the Songliao Basin is buried at a depth of 4900–5000 m. The wellbore is unstable and prone to falling and collapsing because the basalt in the upper Yingcheng Formation has weak bonding strength. The technical casing is needed to be inserted to seal the formation. If horizontal wells are used for oil and gas reservoir development which the well depth is over 6000 m. The conventional wellbore structures which use 5-inch drilling pipe require the ZJ80 drilling rig or higher models of drilling rig. This not only increases drilling costs, but also difficult to implements efficient development due to the higher models of drilling rig. Methods, Procedures, Process: A technical approach of unconventional wellbore structures optimizing was proposed, followed by optimizing wellbore size and casing selection, and designing unconventional three opening horizontal wellbore structures. On this basis, key drilling matching technologies were studied, including wellbore trajectory optimization, personalized drill bits and matching speed-up tools selection, and performance optimization of high-temperature resistant water-based polymer drilling fluids. Result, Observations, Conclusions: This technology has been applied in the Changshen 47 well, the completed drilling depth is 5950 m, the vertical depth is 4906 m, the horizontal section is 982 m, solving the problem that 70 drilling rigs is unable to meet the requirements of conventional wellbore structure, significantly shortening the drilling cycle, and saving drilling costs of 9.15 million yuan. Novel/Additive Information: The research results indicate that the unconventional three opening wellbore structure design is reasonable, and the drilling matching technology has a significant speed increasing effect. It can be promoted and applied in ultra deep horizontal well drilling, significantly reducing drilling costs.