Controlling Factors and Favorable Area Prediction of Cretaceous Qingshuihe Formation in Gaoquan Area of the Southern Junggar Basin

Petroleum resources are abundant in deep formation of the foreland thrust belt, the large-scale oil and gas reservoir exploration field. However, due to the large buried depth, low exploration degree and complex reservoir forming mechanism, it also faces great challenges. It is of great scientific and guiding significance to reveal the reservoir control factors and enrichment rules under complex reservoir forming conditions. Taking the southern margin of Junggar Basin as an example, basing on core observation, thin section identification, logging and single well facies analysis, the sand body sedimentary microfacies and reservoirs type and key factors of Qingshuihe Formation in Gaoquan area were clarified. The comprehensive analysis shows follows: (1) The Cretaceous Qingshuihe Formation sand bodies in Gaoquan structure were superposed by multi-stage underwater distributary channel sand bodies in the fan delta front, with fast lateral changes in sand body reservoir performance and strong heterogeneity. (2) The oil and gas reservoir preservation conditions of the Qingshuihe Formation vary greatly. The Gaoquan anticline structure had been an inherited structure since the Yanshanian Period. Affected by multiple tectonic movements, the anticline structure was severely cut and transformed by faults. In the anticline wing with strong compression deformation, deep and shallow faults were vertically connected, causing the oil and gas in the anticline wing to disperse along the fault adjustment, and only enriched and formed reservoirs at the structural highs. (3) The physical properties of the sand bodies at the bottom of the Qingshuihe Formation were controlled by the paleogeomorphology of the sedimentary period. The sand bodies deposited in areas with relatively high ancient landforms have low shale content, good sorting and excellent reservoir physical properties. The gravels deposited in areas with relatively low ancient landforms are poorly sorted and rounded, with high shale content and poor reservoir physical properties. (4) The oil and gas accumulation of Qingshuihe Formation in Gaoquan structure area are controlled by two key factors: high-quality reservoir and preservation conditions. Focusing on the two major reservoir control factors and based on 3D seismic data, ancient landform restoration and sensitive attribute analysis are carried out to predict the high-quality reservoir development area of Qingshuihe Formation in Gaoquan structure, which is mainly distributed in the southwest of the 3D work area, in NW-SE strip distribution, with a favorable area of about 110 square kilometers, it provides effective support and reference for deep oil and gas exploration in this area.