| Puguang Gas field is a carbonate gas reservoir with large reserves,high reservoir abundance and deep burial.At present,the main development layers of Puguang gas field are the first and second member of Feixianguan Formation and changxing Formation.A great deal of research has been done in this area,and six oil-bearing blocks such as Puguang and Dawan have been found,with good exploration prospects.However,with the continuous failure of several exploration Wells,it is urgent to strengthen the reunderstanding of gas reservoir characteristics and accumulation mode in Puguang area.In this paper,the types and main controlling factors of gas reservoirs in Puguang area are analyzed by using logging data,seismic data,core description data and analysis data.The results show that there are four different types of gas reservoirs in Puguang area,including fault-anticlino-lithologic gas reservoirs,fault-lithologic gas reservoirs,fault-anticlinal gas reservoirs and lithologic gas reservoirs.After that,this paper dissected the four types of gas reservoirs from four aspects of trap characteristics,gas composition characteristics,physical properties and gas reservoir pressure characteristics.It was found that they have four high characteristics of high porosity,distribution in high structural position,upper sealing of regional cap layer,gas reservoir pressure higher than hydrostatic pressure,and are far away from source rock.It can be concluded that typical conventional structurelithology gas reservoirs are developed in Puguang area.Further analysis shows that the formation and distribution of gas reservoirs in Puguang area are mainly controlled by six geological factors: source rock,sedimentary facies,cap rock,paleo-uplift,fault zone and relatively low interfacial potential energy.Taking Changxing Formation as the target layer,the probability distribution model of reservoir controlled by six main controlling factors is established respectively.Reuse function elements combination control of oil and gas distribution patterns respectively on the lithology,anticlinal structure and fault structure,quantitative characterization of the accumulation rate of such a gas reservoir and prediction,predict a total of four lithology,five anticlinal structure,four fault structure of such a gas reservoir favorable into Tibetan areas,and then to predict the three types of gas reservoir favorable to Tibetan areas in planar composite,The favorable areas of changxing Formation fault-anticlinal lithology and fault-lithology are pointed out in Puguang area. |
