Evaluation On Reservoir Characteristics In Xihu Depression Central Uplift Belt

In recent years,along with the increasing maturity of marine oil and gas exploration,the oil and gas exploration in the east China sea of Xihu depression began to the deep stratum,also there revealed good reservoirs in the deeply stratum,many wells had found secondary porosity in the deep zones.These data not only break the characteristics and physical properties of previous understanding about the deep reservoir,but also greatly enhance the confidence to prospect the deep stratum,in order to expand oil and gas exploration in new areas of marine.The central uplift belt with dense sandstone reservoir characteristics and low degree of prospecting,the reservoir characteristics and distribution of central uplift belt still need further research.In the studied area,first summarizing predecessors' research results,make full use of original materials such as mud logging,core,well logging,physical properties and test data.Second we have deep research about reservoir lithology,reservoir space,physical property,relationship between the four properties and diagenesis characteristics.Third establish the classification criteria of reservoir.Fourth have a further understanding of reservoir characteristics and high quality reservoir distribution.The depositional system of study area is a fluvial delta reservoir sedimentary system.The composition of sandstone reservoir is relatively complex,which has many types,low compositional maturity and many types of interstitial materials.The lithology mainly develop feldspar lithic sandstone and lithic feldspar sandstone,fine grained.Many kind of pore types,which mainly develop residual intergranular pore and intergranular dissolved pore,these constitute four pore combination types and pore structure type.The physical property in study area belongs to mid-low porosity mid-low permeability reservoir.The physical property in upper Huagang Formation is better than the lower section,the south is better than the north.The physical property became worse due to the particle size is fine.Study on the relationship between the four properties known the greater lithology granularity,the lower shale content,the higher porosity and permeability,the better reservoir property.Otherwise,the property and permeability is worse.With the increasing of the reservoir porosity,there has different changes in well logging,such as the numerical value of GR,DEN and SP is reduced,the numerical value of AC and CNL is increased.With better reservoir physical property,oil and gas saturation is obvious showing an increasing trend.The oil-gas possibility of reservoir is controlled by property and permeability.Vertical distribution of reservoir has certain regularity,in the upper section of Huagang Formation mainly developed class ? and class ?reservoir,in the lower section of Huagang Formation mainly developed class ? and class ?reservoir.In southern central uplift belt developed class ? and class ? high quality reservoir.Other areas developed class ? and class ? reservoir.