| Wang Guantun area in Huanghua Depression is one of the typical objectives of oil and gas exploration and development in Eastern China.Reservoir heterogeneity is very serious,reservoir quality is great different and the contradictions between injection and production are strong because of the factors,such as the fragmentation of fault blocks and intersection of multiple provenances.It restricts the further development of the oilfield and tapping the potential of remaining oil.In this paper,fault activity,provenance,and diagenetic characteristics are studied using seismic,logging data and experimental data.Petrological characteristics,physical properties and pore structure are studied using Petrology,Mineralogy and Geochemistry.We classify and evaluate reservoir quality based on Analytic Hierarchy Process?AHP?and Fuzzy Mathematics and summarize the basic characteristics of each type of reservoir.On this basis,we further study the control of sedimentary conditions,diagenesis and the synsedimentary fault activity on reservoir quality.Then,we summarize the genesis of high-quality reservoirs,and establish the formation model of high-quality reservoirs,and study the distribution law of high-quality reservoirs.We classify the reservoir of Ek1 Formation in Wang Guantun area into three categories based on Analytic hierarchy process and Fuzzy Mathematics.Class I and II reservoirs are mainly distributed in the middle part of channel bar,braided channel and underwater distributary channel.Class I and II reservoirs are characterized by large grain size,and its reservoir space is mainly intergranular pores and intergranular dissolution pores,its throat type is mainly neck-shortening throat.The porosity of class I reservoirs is generally larger than 22%,and the permeability is generally larger than 230×10-3?m2.The porosity of class II reservoirs ranges from 13%to 22%,and permeability ranges from100×10-3?m2 to 230×10-3?m2.The overall pore size of reservoir of Ek1 Formation is obtained by combining pressure-controlled mercury injection with rate-controlled mercury injection,the pores with radius greater than 100?m control the reservoir performance,and the pores and throats with radius ranging from 0.6?m to 20?m control the reservoir permeability.Ek1 Formation in Wang Guantun area is controlled by two provenances of Cangxian uplift in Northwest and Xuhei uplift in Southeast.The difference of plastic debris content has little effect on physical properties,while Quartz and Feldspar content have great influence on reservoir physical properties,reservoir porosity increases with the increase of quartz and feldspar content.Ek1 Formation in Wang Guantun area experienced medium-strong compaction,and compaction is not the main factor of reservoir pore reduction when the compaction rate is less than 60%.The main cementation of Ek1Formation in Wang Guantun area is carbonate cementation,especially near the interface of sand and mudstone.The weak ion exchange ability of kaolinite makes the clastic particles show oil-affinity and easy to accumulate oil and gas,which inhibite late compaction and cementation.The dissolution pores in the downthrown block of Kongdong fault is more developed.When the plane porosity of dissolution pores is more than 3.5%,the dissolution pores have obvious pore-increasing effect on reservoir,but have no obvious improvement on permeability.The activity of Kongdong fault was strong during the sedimentary period of the Zao II and III,which produces strong suction of seismic pumps.The acidic fluids are easy to migrate to the downthrown block of Kongdong fault,so more dissolution pores were formed in the downthrown block of Kongdong fault.On the plane,the activity of Kongdong fault is strongest near Guan 3 well area,so the dissolution pores are also more developed.The stronger the activity of Kongdong fault is,the greater the difference of sandstone thickness between the two blocks.Where the activity of Kongdong fault is strong,the particle size is larger in the downthrown block of Kongdong fault.In the downthrown block of Kongdong fault,sedimentary microfacies,grain size and cementite content are the main controlling factors for the formation of high-quality reservoirs,while in the upthrown block of Kongdong fault,sedimentary microfacies and carbonate cements are the main controlling factors for the formation of high-quality reservoirs.We studied the influnence of water flooding on reservoir quality by combining CT scanning and water flooding.The primary pore structure,clay mineral content and type of reservoir are the main controlling factors of reservoir quality change in the process of water flooding.For reservoirs with better original physical properties and larger pore throat size,and clay mineral swelling reaction is the dominant factor,reducing the size of the pore throat in the early stage of water injection.Microparticle migration plays a leading role,increasing the size of the pore throat and porosity in the later stage of water injection.For the samples with poor original physical propertiess and smaller pore throat size,microparticle migration plays a leading role,increasing the size of the pore throat and porosity in the early stage of water injection.As water injection volume increases,clay mineral swelling reaction become to be the dominant factor,reducing the size of pore throat and porosity. |
PDF Full Text Request