Transcripción del resumen del autor: Few previous studies have focused on solid bitumen distribution and its effect on gas reservoir quality during oil cracking. Solid bitumen is commonly found in both gas and nongas reservoirs of the Triassic Feixianguan Formation BLTN14018eq1 in the Jiannan gas field. The BLTN14018eq2 natural gases are mainly secondary cracking gases of oil generated from source rock of the Permian Wujiaping Formation BLTN14018eq3, and the reservoir experienced temperatures above 150°C (302°F) for about 35 m.y. A relatively narrow range of BLTN14018eq4 values and a wide range of BLTN14018eq5 values and widespread solid bitumen indicate that oil cracking took place in the gas field. Low concentrations of BLTN14018eq6 (commonly <0.81%) suggest that high-reflectance (2.57%&#x96;3.07%) solid bitumens are pyrobitumens, which would have been mainly derived from oil cracking. Gases preferentially occupy larger pore spaces, and oil is displaced into small pores and throats by overpressure during oil cracking. In this way, pyrobitumens can reduce the magnitude of porosity in relatively tight reservoirs. Moderate-quality oil reservoirs (paleoporosity 2.2%&#x96;8.0%) are between or adjacent to high-quality oil reservoirs and are probably poor-quality or nongas reservoirs after oil cracking. Carbonate reservoirs (paleoporosity >8.0%) can be high-quality gas reservoirs after oil cracking and should be favorable targets for future gas exploration in the northeastern Sichuan Basin and adjacent areas.

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