Abstract: Laojunmiao oilfield is the first field exploited by water flooding process. For 51 years since its waterflooding, it has been characterized by highly dispersed remaining oils, complicated oil-water relations, regional high pressure, shale swelling and squirming, greater difficnlty for drilling and low rermaining oil potentials. In 2003, according to composite geologic analyses and horizontal drilling study, Well LH-1, the first horizontal well in Yumen field, was designed and drilled successfully. The good effect could be as a brand-new way for late-period regulation and finding out potential recoverable reserves in the old oilfield.

Key words: Laojunmiao oilfield, high pressure area, horizontal well, study, implementatiou