The Tectonic Evolution Of The Ulungur Area And Its Impact On Hydrocarbon Accumulation

Ulungur area was confimed the conditions of hydrocarbon source rocks by borehole. Many wells had oil & gas shows and some had the industrial oil or gas flow. It shows the exploration potential of this area with no substantial exploration breakthrough. The Ulungur depression were squeezed under the QingGeLiDi mountain and KeLa MeiLi mountain. So it has the complicated tectonic deformation and tectonic evolution which is one of the key factors restricted the exploration understanding. This article based on the analysis of structural characteristics, through the interpretation of seismic data and tectonic evolution research, had clarified that, the study area formed the structural style of thrust nappe tectonics dominated and mainly developed four structural styles including ramp-flat, opposite, imbricated and stepladder thrusts. There are almost NW and EW fault systems. And the study area experienced three evolution stages including the regional uplift stage, the whole subsidence stage and the again uplift stage. By means of the controlling on hydrocarbon accumulation by tectonic activity, it indicated that: the tectonic evolution controlled the migration of subsiding center and the evolution of source rock. Deep faults formed in the earlier stage of tectonic activity could communicate carboniferous hydrocarbon source rock. And its forming time matched with the the main stages of hydrocarbon generation and expulsion of hydrocarbon source rock. So they can be the main hydrocarbon migration channel. The secondary faults formed in later time could adjust or damage the earlier reservoir. The structural traps of Ulungur depression were firstly formed at the Triassic period. They were developed continuously till the Jurassic period, and finally deformed during later Jurassic or earlier Cretaceous, stopped thereafter. The traps forming time were so earlier that they could store oil and gas effectively. Traps formed along the Karasay fault zone and Red Rock step-fault zone are effective. The most unconformities formed by multi-stage tectonic movement can provide advantage channels for oil&gas transverse migration. From the comprehensive analysis about controlling on hydrocarbon accumulations by the tectonic evolution, it can be deemed that, the Karasay fault zone and Red Rock step-fault zone are the most favorable exploration region.