Logging Evaluation Method Of Ordovician Carbonate Fracture-cavity Reservoirs In Tahe Oilfield

Compared with other conventional pore reservoirs,the Ordovician carbonate fractured reservoir in Tahe oilfield is obviously different from that of other conventional pore reservoirs.It widely develops "holes"," fractures" and " caverns".It has the characteristics of porous space combination,reservoir lateral heterogeneity,complex reservoir space and complex,filling characteristics,and the technique of logging evaluation is very difficult.At present,the method of logging evaluation of carbonate fractured hole type reservoir is not pertinent,the classification recognition and evaluation precision of reservoir type is not enough,and the evaluation precision of reservoir needs to be further improved.In order to predict the seam hole type reservoir more accurately,the classification identification and indication for the fractured hole type reservoir in the study area is carried out,the logging comprehensive characterization of the large scale cave and the well logging interpretation model and evaluation technology of the small scale seam hole are of great significance and application value.In this paper,the reservoir of the Ordovician carbonate fracture-cavity reservoir in Tahe oilfield is the research object.Based on the geological characteristics of the carbonate fracture-cavity reservoir and the logging response mechanism,the logging evaluation method of the seam hole type reservoir is carried out.First,the logging recognition and comprehensive characterization of different seam and hole reservoirs are carried out,and the logging response mechanism of different reservoir spaces is studied.4 types of reservoir space are established and established: fracture,hole,fracture-hole and cavern.Classification,identification and comprehensive indication of collective storage space.Then,the evaluation of the cavern reservoirs can be divided into large scale cavern reservoirs and small scale holes(cracks,holes,cracks-holes)to expand the log interpretation.Secondly,the logging response mechanism of different filling material types and different filling lithologic types is studied in large scale cavern reservoirs,and the logging identification indication and quantitative characterization of large scale cavern reservoirs are realized.Finally,the three porosity logging interpretation model and log interpretation theory are established for the small scale seams.Based on the cementation index,the saturation model is improved and optimized,and the calculation of the porosity and saturation parameters of the small scale fracture-cavity is realized.The results show that the fracture and hole type reservoirs are most developed in the study area,and the classification recognition and indication results of the fractured hole type reservoirs are more in line with the actual situation by using the neural network algorithm,and the classification and recognition of the cave filling by lithologic characteristics is more accurate for the large scale cave type reservoir,and the filling is mainly sand and mud.Most of the caves are not fully filled and have the property of reservoir.In view of the small scale slit and hole reservoirs,the effect of matrix pore,connected pore and non connected pore on the cementation index of the compound pore system in the three porosity model is studied.It is known that the improved three porosity model explains the high precision of the small scale seams and holes,and is more consistent with the actual situation.