Research On Light Oil Reservoir Recognition And Evaluating Method With Mud Logging Of Jurassic In Block 4 Of Central Junggar Basin

Block 4 of central Junggar basin is the main zone for ShengLi oil field to raise reserves and output in western region of China.Analysis shows that crude oil of Jurassic formation in block 4 of central Junggar basin has many distinct features.For example,the oiliness is light,the oil can easily volatilize and has high gas content and etc..So the oli and gas show has great difference of on-site well logging field.At the same time,there is a big difference between comprehensive interpretation conclusion and oil testing conclusion.What is worse,the reservoir identification criteria are uncertain.Considering these features s of the crude oil of Jurassic in block 4 of central Junggar basin and the phenomenon that slurry density be greater than formation equivalent mud weight when drilling the target layer,research on mud logging characteristics and comprehensive evaluating method with mud logging is carried out from the aspects of lithological characteristics,microscopic features and physical properties respectively.Jurassic light oil reservoir has low mineral composition maturity,medium overall structure maturity and poor pore development with mainly intergranular pore and micropore.Reservoir in east area has better property than the west,with the Qigu and Tou tunhe has the best.By means of basic experiment,the mud logging characteristics of light oil reservoir are studied,a standard crude oil atlas is established,interim provisions on data collection of light oil reservoirs are formed.According to the analysis of oil testing data,the lower layer limit of the Jurassic stratum in the work area is determined as porosity greater than 7%and permeability greater than 0.5×10^-3?m².In accordance with geochemical parameters of pyrolysis,the evaluation chart of Jurassic crude oil property was established.On the basis of research on response characteristics of mudlogging and well logging,we preliminarily summarize the reference standards for oil-bearing evaluation of Jurassic reservoirs,and complete old wells'hydrocarbon reservoir review and comprehensive interpretation of hydrocarbon reservoir in new well.Establishment of oil and gas identification system and evaluation criteria in block 4 of central Junggar basin is of great significance for the formulation of exploration and development measures.It is beneficial for mudlogging to play a better role in oil and gas exploration in western region of China,which provides basis for block and layer selection.