New understandings and potential of Sinian–Lower Paleozoic natural gas exploration in the central Sichuan paleo-uplift, Sichuan Basin

摘要

Since the Anyue Gasfield, located in the central Sichuan paleo-uplift of the Sichuan Basin, was discovered, great efforts have been made to work on natural gas exploration and discovery in the Sinian–Lower Paleozoic in the north slope of present paleo-uplift which has similar depositional settings. It is verified by the breakthrough of natural gas exploration in the second Member of Upper Sinian Dengying Formation in the north slope of central Sichuan paleo-uplift by wildcat well PT1 and the new sign of natural gas exploration in the Canglangpu Formation of Lower Cambrian and the fourth Member of Dengying Formation by Well JT1 that there are also favorable conditions for the formation of large-scale gas province in the north slope. In order to determine the natural gas exploration potential of Sinian–Lower Paleozoic in the central Sichuan paleo-uplift and provide the guidance for the following exploration deployment, this paper analyzed the petroleum geological conditions of Sinian–Lower Paleozoic in the north slope. And the following research results were obtained. First, the marginal platform belts in the second and the fourth Member of Sinian Dengying Formation in the north slope are basically separated areally, and they are superior to the Gaoshiti–Moxi area in terms of marginal platform width and sedimentary thickness and are intrinsically advantageous in sedimentation. Second, compared with the Gaoshiti–Moxi area, the reservoirs of Sinian Dengying Formation in the north slope are better in reservoir conditions, and many sets of quality reservoirs are developed vertically in Sinian–Cambrian. Third, hydrocarbon accumulation elements of Sinian Dengying Formation are better allocated in the north slope. Lithological traps are developed with a larger cumulative area. Wells JT1 and PT1 verify that there is gas in the lithological trap of the fourth and the second Member of Dengying Formation and large-scale lithological gas reservoirs are developed in the slope setting. In conclusion, compared with the Gaoshiti–Moxi area, the Sinian–Lower Paleozoic in the north slope is superior in petroleum geological conditions and has the advantage of multi-layer stereoscopic exploration vertically, presenting a great natural gas exploration potential and promising exploration prospects, so it is a new important strategic zone of conventional natural gas exploration in the Sichuan Basin.