This article introduces the engineering flow and technical measures for casing side-tracking of complicated accidental wells according to well .

In recent years, the structure and reserves are determined further using sidetrack drilling in old wells by deepened geological knowledge and reservoir engineering research.

Horizontal well drilling technology by slim hole casing window sidetracking in Daqing Oilfield;

It is base upon general casing cutting windows,aiming at bad feasibility stratum,through optimizing desi gn sidetracking technology,changing tool,optimizing measure and choosing bit,we succeed in casing window sidetracking of ultradeep well KS101C.

Cased hole directional window cutting drilling is a special drilling technology.

Tuocan 1 well is the firstφ244 5mm casing window sidetracking horizontal well.

According to the eight casing window sidetracking horizontal wells' conditions in Liaohe Oilfield, the main technical measures are given to improve the milling efficiency, which have important effects on improvements of casing milling technologies.

Duringφ139 7 mm OD casing window sidetracking drilling or deepening drilling, using the smaller size, single cone bit has apparent economic benefit.