| Fracture-cave carbonate reservoir of Cambrian Longwangmiao Formation in Moxi area is one of the major discoveries of natural gas exploration in Sichuan Basin in recent years.As the key exploration strata in Sichuan,Longwangmiao Formation gas reservoir has the characteristics of well-developed fractures and caves,strong heterogeneity and difficult gas and water identification.The above characteristics of reservoir bring many difficulties to the calculation of reservoir parameters,the identification of fluid properties and the evaluation of reservoir validity,which make the interpretation and evaluation of reservoir logging difficult in this area.In this paper,based on the above difficulties and the domestic and foreign research methods of this type of reservoir currently,the principle of well-logging,logging geology,mineral petrology,petrophysics,reservoir geology and related disciplines are considered,the experimental results of rock physics and actual data are taken as accordance,with the combination of theory and practice,various geological data(core,NMR,physical analysis,mercury injection,casting thin section and other special experimental data)and development data(drilling,mud logging,production performance,gas testing,etc.)are applied,logging evaluation is carried out from four aspects:logging data standardization,identification of lithology,fractures and caves,reservoir fluid property discrimination and reservoir parameter modeling.It is concluded that:?The abnormality of natural gamma curve exists in the study area.The main reason for the abnormality is the high content of radioactive heavy metal elements in mud.Some natural gamma anomalies of wells have correlation with borehole diameter enlargement.Frequency histogram method and formula method are used to correct the abnormality,the effect of which is acceptable.The interpretation results of standardized data are consistent with the actual situation.?The lithology of the study area is complex,and there are local enrichment of special mineral asphalt and pyrite.In this paper,a correction model is established based on conventional logging and special logging data(ECS,NMR logging),which eliminates the influence of special minerals on interpretation accuracy.For fracture and hole identification,based on the idea of core calibration imaging and imaging calibration conventional logging,the identification model of dissolution hole and fracture is established.At the same time,it is found that the three-porosity model can be used to identify fractures,and good results can be obtained.On this basis,the reservoir is divided into karst cave type,karst pore type and matrix porosity,and the corresponding identification chart is established.The Forward.NET platform is used to carry the corresponding module of automatic identification and output of reservoir types.?Combining with oil testing and logging data,seven kinds of fluid property discrimination methods are used for fluid identification in the study area,good recognition results have been achieved.?Based on"core calibration logging",a fine interpretation model of mineral content,porosity,permeability and saturation is established,and the model has good correlation.A processing module of logging interpretation software is compiled,and the final interpretation results are verified,and its accuracy meets the actual needs.The purpose of this study is to carry out standardized processing and fine logging evaluation of Longwangmiao gas reservoir in Moxi Block,to solve the technical problems of lithology identification,fluid property discrimination and reservoir parameter calculation,and to further deepen the logging evaluation method of fractured-vuggy carbonate gas reservoirs.Therefore,the development of this study has important guiding significance for the detailed description,exploitation and exploration of carbonate gas reservoirs under similar geological conditions in China. |
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