The Relationship Between Source-reservoir Combination And Oil-gas Distribution Of The Fengcheng Formation In The Southern Part Of The Mahu Sag

The Fengcheng Formation of the Mahu Sag is the main source rock formation of the Junggar Basin,with abundant oil and gas resources and great exploration potential.The existing research is mainly concentrated in the northern part of the Mahu Sag,and there are few studies on the source-reservoir combination type and oil-gas distribution in the southern part of the Mahu Sag.This paper systematically analyzes the source rock characteristics,reservoir characteristics,oil-gas distribution and source-reservoir combination type of the Fengcheng Formation through logging wells,core observation,oil test data,source rock geochemical parameters and reservoir test analysis,and clarifies the relationship between source-reservoir combination and oil-gas distribution,which plays an important role in further oil and gas exploration in the study area.The study shows that the source rocks of the Fengcheng Formation in the southern part of the Mahu Sag are mainly gray-black mudstone and black tuff mudstone,mainly distributed in the P₁f₂ and the P₁f₃ of the sag.The organic matter abundance is medium,and the types are mainly mixed organic matter,the source rocks are generally in the mature stage.The hydrocarbon generation potential of the P₁f₂ is better.The reservoir lithology is complex and changeable of mainly glutenite,sandstone and volcanic rocks.It is basically in the dense and extremely low porosity and low permeability range with more fractures in local area and its pore structure is poor-medium.Sand bodies have a regular distribution in the plane,volcanic rocks are stably developed at the top of the P₁f₂,and the oil and gas storage capacity of reservoirs of different lithology has obvious differences.From the high part of the sag to the inside of the sag,the aquifer,the oil-water layer,the oily water layer and the pure oil layer are in order.The source-reservoir combination in the study area is mainly divided into four types:Ⅰ,Ⅱ,Ⅲ and Ⅳ,and its distribution characteristics have a good correspondence with the oil-gas distribution.From the edge of the sag to the center of the sag,there is a source-reservoir combination transition from type Ⅰ to type Ⅳ.The type Ⅰ source-reservoir combination is mainly the aquifer;the type Ⅱ source-reservoir combination is mainly the oil-water layer or the oily water layer;the distribution of type Ⅲ and Ⅳ source-reservoir combinations correspond to the pure oil area,they have higher oil test yields and are favorable exploration plays in the study area.