Study On Regional Effectiveness Difference Of Source Rocks Of Taodonggou Group In Tuha Basin

A great deal of crude oil generated from coal-bearing formation has been found in Mesozoic and Cenozoic in Turpan-Hami Basin.However,with the continuous exploration and development,it is increasingly important to study the accumulation regularity of deep non-coal-bearing crude oil and the validity of deep source rocks in Turpan-Hami Basin.According to the difference of crude oil physical properties and composition characteristics of biomarkers,crude oil samples can be divided into four categories:A,B,C and D.A crude oil is distributed in the Triassic of Tuokexun Depression;B crude oil is heavy oil,mainly distributed in the Permian and Triassic of Huoyanshan structural belt;C crude oil is distributed in the Triassic of Shanle structural belt;D crude oil is distributed in the Jurassic of Tainan and Taibei sags.Based on oil-source correlation results,all kinds of crude oil are related to the source rocks of the Permian Taodonggou Group in their respective areas,showing that the characteristics of the source rocks of the Taodonggou Group in different areas are different.According to the fine correlation of biomarker characteristics,B crude oil is divided into three sub-categories:B₁,B₂ and B₃.All of B₁ crude oil comed from the source rock of Taodonggou Group in Taipei Depression;B₂ crude oil was produced by Taodonggou Group and mixed with Qiketai crude oil filled later;B₃ crude oil is similar to B₂ crude oil,but the Shuixigou Group source rock had some contribution to it.Based on the comparison of hydrocarbon composition characteristics between Taibei Sag and Jimusar Sag,it is considered that the source rocks of the upper and lower members of the Permian Taodonggou Group in the deep part of Taibei sag are comparable with those of the Lucaogou Formation in Jimusar Sag.B and C crude oil accumulations are closely related to the transport of the unconformities above and under the Taodonggou Group respectively.In the Huoyanshan structural belt,the unconformity surface was developed above the source rocks of the Taodonggou Group,crude oil was mainly the contribution of the the lower Taodonggou Group source rock,whereas in Shanshan area,the unconformity surface was developed under the Taodonggou Group source rock,the crude oil mainly comed from the upper Taodonggou Group source rock.Geochemical analysis shows that the best quality source rock was distributed in Taibei sag.The quality of source rocks in Western Taipei area is better than that in eastern Taipei area,and the evolution degree in eastern Taipei sag is higher than that in Western Taipei area.Deep Permian source rock in Taibei Depression has a high thermal evolution degree and rich hydrocarbon resource.Comparing the biomarker characteristics of source rocks of the Middle and Lower Permian in Taipei Sag,it was found that the organic matter development of source rocks is inherited,which is similar to that of the Fengcheng and Lucaogou Formations of the Middle and Lower Permian in Junggar Basin.At the same time,it is found that there is little difference in biomarker characteristics between the East and west of Taipei Sag,suggesting that the lake basins with developed source rocks have good continuity and scale.The source rocks are continuously distributed in large areas.