Jurassic Stratigraphic Comparison And Sedimentary Analysis In The North Nuraly Area Of The South Turgay Basin

The North Nuraly area is located in the southeast of the South Turgay Basin in Kazakhstan.More than 30 wells have been drilled.The oil and gas resources are rich.,Leading to unclear understanding of sequence stratigraphic correlation and sedimentary evolution laws,which severely restricted the subsequent exploration and development of oil and gas resources.Therefore,this topic is aimed at the Middle and Lower Jurassic in the North Nuraly area of the South Turgay Basin.Based on previous studies,the core identification,logging facies identification,structural evolution analysis and exploration results The research serves as a clue for the establishment of isochronous stratigraphic framework,detailed interpretation of the stratum,and analysis of sedimentary facies,and finally the favorable facies zone is divided into the study area.Applying the principle of high-resolution sequence stratigraphy to identify the sequence interface,a comparison plan for the Jurassic in the North Nuraly area was established,the key horizons were re-divided,and the Jurassic was divided into 4 tertiary sequences.This scheme can make a reasonable comparison among well location profiles in the whole area.Through detailed interpretation of the structure and faults of the 3D work area of North Nuraly in the South Turgay Basin,a total of nearly 70 faults have been identified and discovered.The nature of the faults is mainly normal faults.The oil source faults control the structure and sedimentary development of the work area.Deposit faults.By drawing the structural maps of the Middle and Lower Jurassic and the basement,it can be seen that the structural form of the work area is a monoclinic uplifting in the northeast direction.According to the characteristics of regional structural evolution,it can be roughly divided into three stages in the longitudinal direction: the rift,Faultdepression transition period and depression period.A typical sedimentary facies sequence was established through comprehensive analysis of core observations and logging curves.The main development was the deposition of the fan delta front controlled by the Aksabrak boundary strike-slip fault zone,which was further identified on the basis of this study.The development of various sedimentary microfacies such as underwater distributary channels,estuary dams,mat-shaped sand,and front fan delta.Combined with the detailed structural interpretation of the work area,a total of 105 traps in 4 floors were identified.Through this study and previous work,it is known that the main oil layer in the North Nuraly area is the Jurassic Duoshang Formation.With comprehensive consideration of structural lithology and existing reservoir conditions,the nasal uplift zone in the NN8 well area can be considered as the next step Exploration potential area.