Reservoir Characteristics And Favorable Area Selection Of Feixianguan Formation In Huanglongchang Structure In Northeastern Sichuan

The oolitic beach reservoir of Feixianguan Formation in Northeast Sichuan shows good drilling and has good potential for oil and gas exploration.At present,the understanding of the relationship between beach body distribution and reservoir development is not incomplete,it restricts the selection of the next exploration direction.On the basis of drilling,seismic and logging data,combined with rock thin section observation,analysis of laboratory test,this paper studies the comprehensive geological characteristics of Feixianguan Formation,such as stratigraphic division and correlation,sedimentary facies characteristics,reservoir characteristics and distribution rules by stratigraphic sequence,facies control and well-seismic combination.The Feixianguan Formation in the study area is divided into 5 shallow upwards four-rank sequences by means of 18 Wells and 2 well tie profiles by stratigraphic isochronal correlation method.The first-rank sequence is the thickest,about 200-300m,and gradually thins up;the fourth-rank sequence is the thinest,about 30-60m.the stratum and sequence thickness of Feixianguan Formation increase significantly in the direction of the trough.On the plane,the thickness of the strata and stratigraphic sequence of Feixianguan Formation increases obviously in the direction of the ocean trough.Based on the two seismic interpretation profiles and the well-seismic combination method,it is believed that the Feixianguan Formation of Huanglongchang structure developed four types of sedimentary microfacies,including platform margin oolitic dam,oolitic beach,beach interact sea,tidal flat and lagoon.Through core description and rock thin section observation of 5 Wells,based on the description method of migrating oolitic beach reservoir considers there are two types of reservoirs in Feixianguan Formation of Huanglongchang structure,which are fissure-pore platform margin oolitic beach facies and fissure slope-trough facies.Among them,the lithology of oolitic beach facies reservoir rocks at platform margin is mainly composed of oolitic dolomite,silty dolomite and a few oolitic limestone,its reservoir classification is given priority to with ? and ? reservoir,locally developed ? reservoir,and the pore space is mainly composed of intergranular dissolved pore,intragranular dissolved pore,and a few intergranular pore;slope-trough facies reservoir rock lithology is mainly composed of micrite,only development ? reservoir and its quality is relatively poor,the fissure is the main reservoir space.The development of reservoir is mainly influenced by oolitic beach distribution and diagenesis,the formation of high-quality reservoir is mainly transformed by dolomitization and dissolution,and structural fractures can improve the reservoir to some extent.The results of reservoir correlation by means of sequence and facies control show that there are "two longitudinal stages" in Feixianguan Formation shoal facies reservoir,the HL6 well area of Feixianguan beach facies reservoir development in the main ?-? sequence,and HL9,009-H1 well group of Feixianguan beach facies reservoir development in the main? sequence;"Plane divided into three zones" shows that "Early oolitic beach reservoir" is developed in well HL6,which is controlled by sedimentary facies and distributed in a long and narrow shape;"Late oolitic beach reservoir" is developed in well HL009-H1,and"limestone reservoir" is sporadically developed in well HL8.According to different seismic response characteristics of reservoir,four seismic response modes are established.Among them,the model I is the most advantageous reservoir response model,the reservoir response is characterized by continuous strong wave peak reflection,and the reservoir rocks are mainly oolitic dolomite rocks with a reservoir thickness of more than 40 m.The reservoir type is fissure-pore type,which is mainly distributed in well HL6 and well HL009-H1.Through stratigraphic sequence division,oolitic shoal stage and spatial distribution,reservoir vertical migration characteristics and plane distribution rules,and seismic response model,the optimized evaluation index of favorable area was defined.Based on the evaluation of exploration potential of gas reservoir,one favorable area and one sub-favorable area are divided according to the factors of structure and production data.