Abstract: In view of the increasing proportion of subtle reservoirs, using examples of successful domestic and overseas exploration, this paper introduces a new idea of "non-restricted exploration". Study shows that oil and gas resources assessment is a process of deepening understanding, and innovative thinking could bring new exploration results. For example, Chunguang Oilfield, a shallow high-quality reservoir, was discovered by creating the oil and gas accumulation model of western margin of the Junggar Basin; Puguang gas field was found in the old basin by innovating geological knowledge and transforming exploration strategy. Innovation of geological theory could reveal the real features of reservoir formation. For example, new reserves potential was shown in the old exploration area of Shengli Oilfield through the creation of continental rift basin subtle reservoir exploration theory; a bar and shoal reservoir was found by constructing large-scale continental rift basin shoal reservoir exploration theory. Through the innovation of engineering technology, new reserves were discovered and new progress was made in the exploration of Nanpu Oilfield, Changqing Oilfield, and Shengli Offshore Oilfield. With hard work and perseverance, new breakthroughs were achieved in the northeast slope of Shengli Oilfield and in Sangequan reservoir of Xinjiang Oilfield. The exploration practice in the deep formations of Songliao Basin and the volcanic rocks of Carboniferous in Junggar Basin is a classic instance of "nonrestricted exploration". Oil and gas exploration needs to emancipate mind, change thinking and innovate recognition. Oil and gas exploration workers are required to have the philosophers' dialectical thinking, artists' imagination, scientists' rigorous attitude, and explorers?spirit of adventure

Key words: non-restricted exploration, exploration potential, subtle reservoir, lithostratigraphic oil and gas reservoir