The Study Of Reservoir Identification In Shahejie Formation Of Zhangdong Structure In Chenghai Area

On the basis of well loggging,well testing and laboratory analysis data, the lithology, physical properties, electrical properties and oil-bearing relation in different layers of Zhangdong structure reservoir in Chenghai area have been systematically analyzed.Then the dominant factors which result to the confusion of distinguishing oil,gas and water layers have been displayed. The standards of oil-gas-water recognition for different layers of the reservoir have been summered by means of cross plot method and multianalysis method. Then the method of reservoir identification of Zhangdong structure in Chenghai area has been improved and finally formed.The carbonate reservoirs in 1st member of Shahejie formation of Zhangdong structure are stable which can be identified by well logging and GR curve while other sandstone and fine sandstone layers often exhibit low GR and abnormal of SP.In the same time,porosity logging curve exhibit fine physical properties. Because of its high irreducible water, oil layers in the straticulate fine sandstone and siltstone of 2nd member of Shahejie formation of Zhangdong structure exhibit low resistance which is different from the nomal reservoirs's high resistance response.The salty mud invasion may be the reason of the oil layer's resistance reduction in the plane. Acquifers offen show low resistance while tight layers show higher .The excavation effect of condensate gas layers between CNL and DEN is clear.According to the complexity of lithology of each bed,the multi-mineral components analysis interpretation of lithology and physical properties for each well has been given by using the FORWARD software.For each bed,the dominant mineral types are determined by the log data and core analysis data, then their logging interpretating parameters are determined by the mineral handbook. The representative mudstone points are determined by the GR distribution.Then,the shale parameters have been given. The optimized well logging interpretation of each well in this area is used the method of repeated optimization computing methods,and it has gotten porosity, permeability and oil saturation of single well.According to the analysis of well testing datas and logging of oil-water bed, oil-water bed distinguishing plates for each part and each layer have been developed and multivariate method (composite variable obtained) is used for quantitative analysis of oil-water bed.And its correct return discriminant ratio is very high.Then, it has emphasized particularly on the well testing that proves confused to interpretating either by quantity or by quality.Multiwell layers comparison analysis demonstrates:the three carbonate reservoirs of 1st member of Shahejie formation with mini-depth of individual layer are stabilized. Hydrocarbon reservoirs are commonly distributed in high parts of each fault block while the low parts with poor properties are usually contributing water which can be of high productivity by acid fracturing.The porosity frequently rings from 8%-15% by logging interpretating and hydrocarbon is clear in well log and gas surveying.2nd member of Shahejie formation is the main oil-bearing formation of Zhangdong area.Sand body developing is discontinuous with great variation and has poor comparison in the plane.It gradually overlapped from the east to the west ,which could be seen through the deeper in the north versus the thinner in the south and the deeper in the east versus the thinner in the west.Hydrocarbon reservoirs of 2nd member of Shahejie formation are commonly distributed in the up of 2nd member of Shahejie formation and Zhanghai 5 well area and Zhanghai 501 well in the bottom of 2nd member of Shahejie formation while the oil-water lateral distribution is governed by the structure. Lithology of 3rd member of Shahejie formation became rough from up to down vertically and became fine from east to west laterally with the depth decresing.Fine reserviors offen distribute in the verge while distribute little in the west of the center.Es33 is the main oil-bearing formation of 3rd member of Shahejie formation.Hydrocarbon reservoirs are commonly distributed in the high parts of Zhang 27X1 disconnecting nose structure and in partly sand body areas which are governed by Zhanghai15 well and Zhanghai503 well.Physical property in downthrow block is worse than upthrown block on the whole.