Mahu sag is an important hydrocarbon-generating sag in Junggar Basin. The whole well section in Fengcheng Formation of Well-MY1

which is located in the north of the sag

has been continuously coring. Therefore

the coexisting characteristics of conventional and unconventional reservoirs in Fengcheng Formation are revealed by the combination of the systematic description and analysis of core characteristics with the analysis of high-density sampling and electrical/nuclear magnetic resonance. The main conventional reservoirs are volcanic rocks

glutenite and sandstone

which is developed in the low stage freshwater or low salinity water body. The main unconventional reservoirs are mud-stone

dolomite and siltstone

which is developed in the weak hydrodynamic conditions and strong evaporation environment. On this basis

with the comprehensive analysis of lithology

electrical properties

physical properties

oil content and other characteristics

it is further confirmed that there is one conventional “sweet spot” and three unconventional “sweet spot” in Fengcheng Formation of Well-MY1

and the conventional “sweet spot” is developed in the middle and lower part of 1st member of Fengcheng Formation

the unconventional “sweet spot” is developed in the lower part of 3rd member and the 2nd member of Fengcheng Formation. The core analysis and features of Fengcheng Formation in Well-MY1 further confirms the hydrocarbon resource potential of alkali lake deposit

and lays a foundation for the establishment of “Standard Lithology Profile” of Fengcheng Formation in Mahu sag.