Research Of Sedimentary Characteristics And Reservoir Prediction Of The Permian Lower Urho Formation In The Eastern Slope Area Of The Mahu Sag

The Mahu sag is one of the most important hydrocarbon-producing sag in Junggar Basin and many substantial achievements has been made,including submitting accumulative total over one billion prognostic reserves through oil-bearing series.However,the Permian Lower Urho Formation in the Eastern Slope Area of the Mahu sag hasn't been explored deeply and capacity is very limited at present.It is found that the Lower Urho Formation was formed in Fan delta system,but the research about sedimentary characteristics of the formation isn't accurate enough,which means the advantageous sedimentary microfacies distribution in fan delta front area can't be studied clearly.Although the main pore types of the glutenite reservoir in Lower Urho Formation has been researched,the effective reservoir controlling factors especially the total influence from laumontite towards the reservoir is not clear yet.The physical property of glutenite containing laumontite in research area used to be good and such a type of reservior is the main oil layers recently,which has great significance for exploration.However,there are still some difficulties on well logging evaluation and prediction by seismic inversion of the glutenite reservoir containing laumontite.Some scrutiny of sedimentary characteristics has been made to solve above problems about restricting oil production and finding new exploration targets.The transportation direction of sediments in research area can be assured by recovering paleogeomorphology and analyzing diplog,etc.The types of sedimentary microfacies are divided by analyzing facies marker,such as core facies,sedimentary structure,well logging,etc.The evolution rule of sedimentary microfacies are researched by analyzing single well facies and well-tie section.The lithology,petrophysical properties and types of reservoir space of glutenite reservoir in the Lower Urho Formation are summarized according to cores,cast slice and poroperm relation statistics.The main controlling factors of reservior are analyzed and a comprehensive evaluation chart is established.The well logging evaluation indexes of glutenite reservoir containing laumontite are determined and the classification chart of such reservoir is also established.The prediction is available about the thickness distribution of glutenite reservoir on advantageous structural region in the Eastern Slope Area of the Mahu sag by seismic inversion combined with the well logging indexes.Finally,summarizing the plane distribution rule of effective glutenite reservoir containing laumontite can provide scientific basis on prospecting of Lower Urho Formation in the Eastern Slope Area of the Mahu sag and guide prospecting practices.It's found that the sediments in Madong-2 block are from Madong Fan Delta and transported in a nearly east-west direction.The sediments in Yantan-1 block in south part of the Eastern Slope Area are from Xiayan Fan Delta and transported in a NW-SE direction.The Lower Urho Formation develops sand-shale interbed in vertical direction,which belongs to Fan delta sedimentary system that is close to the provenance and mainly develops fan delta plain subface and fan delta front subface.It is mainly developed fan delta plain subface and fan delta front subface during the period of three oil layers'?P₂w₃¹,P₂w₄⁴ and P₂w₄³?deposition and the former's area is bigger than the latter.The sedimentary source recharge became less gradually and lacustrine level kept rising during the period generated retrograding sequences.Shaliness is considered the main controlling factor of reservoir quality and laumontite's dissolution caused by acidic fluids has particular and important impact on reservoirs in Madong-2 block.The glutenite reservoir containing laumontite can be distinguished with well logging evaluation indexes of RT and DEN.The prediction of thickness and depth reservoir of this type in P₂w₃has been done with the help of well logging evaluation and seismic inversion,located in the south area of Ma-11 well and area from Da-13 well to Yanbei-2 well.The distribution range in plane of glutenite reservoir containing laumontite in Madong-2 well area is also predicted.