Abstract: Technical countermea sures for well Kun-2 are drawn up to solve the key difficulties in deep exploration well in the northern marginal zone of Qaidam Basin. A suite of optimal a nd fast drilling techniques suitable to the northern marginal zone of the basin are dev eloped on the basis of the optimization of drilling equipment, wellbore structure, drilling bits and tools assembly, a s well a s drilling parameters and properties of drilling fluid, and the resea rch a nd application of oil-gas reservoir protection techniques. As a result, the completion drilling depth of wellKun-2 rea ches 5,950 meters.As the well depth increases by 888 meters and the big-sized well hole gets longer, the cycles of drilling and well completion of well Kun-2 are reduced by 98.75 days and 124.2 days respectively, with the speed of each drilling rig increasing by 317 meters monthly a nd the a verage drilling rate increasing by 0.82m per hour. An optima l composite and temporarily blocked plan is established to protect the oil-gas reservoir. By applying this plan, a new kind of drilling fluid is made up, with its restorable permea bility rea ching more than 87.5 percent and having better fluidity and lower filtration loss, obviously improving mud-ca ke qua lity a nd enhancing sidewall stability.

Key words: optimal and fast drilling, drilling bit, wellbore structure, oil-gas reservoir protection, wellKun-2, Qa idam Basin