Structural evolution and pool-forming in Junggar Basin

The study of tectonic characters, strata distribution and strata unconformity analyses showed that Junggar Basin underwent four evolution periods of aulacogen basin, collision foreland basin, inland depression basin and inland subduction foreland basin. The aulacogen basin controlled the Carboniferous source rock distributed along rift valley. The collision foreland basin controlled the Permian source rock limited in Mahu, Changji and Kelameili piedmont depressions. The term of inland depression was continuous from the Triassic to the end of the lower Tertiary. During this term, mudstone and coal rock were widespread in Junggar Basin. The inland subduction basin was developed in the west of southern basin. The Tertiary source rock was mainly distributed in the Anjihai and Hutubi areas. The correlation of source rock evolution and oil origin showed that there were three times of pool-forming, namely Indosinian epoch (T_3), Yanshan epoch(J_3) and Xishan epoch(E_2). During this term, four composite petroleum systems, including Carboniferous, Permian, Jurassic and the lower Tertiary composite petroleum systems, were developed. According to the difference of tectonic characters and pool-forming condition, oil and gas accumulation area can be divided into five zones of north-west, west, south, east and central areas in Junggar Basin, there are six types of pool-forming models including subduction fault terrace-unconformity single charge, compressive wrench anticline double charge, fault-uplift zone double charge, drape anticline single charge, thrust anticline zone single charge and slope zone single charge.