Multi-parameter quantitative assessment of 3D geological models for complex fault-block oil reservoirs

Xuequn TAN,Yunyan LIU,Xiaozhou ZHOU,Jiandang LIU,Rongchen ZHENG,Chao JIA

Table 1 Quantitative Assessment Standard of 3-D Geological Models for Complex Fault-block Oil Reservoirs and a Case.

Category Characteristic parameter Weight assignment Assessment standard Case score Low Medium High Data verifi- cation (60 points) Static data Structural model Contact relationship of complex faults 10 Unreasonable or over- simplification. 1 point Basically reasonable, or fault surfaces are constructed without seismic constraint. 5 points Reasonable in space or arbitrary section. Surfaces are guided by fault sticks from seismic interpretation. 10 points 10 Layer depth of target zone 10 Mean absolute error >2 m. 1 point Mean absolute error is 1-2 m. 5 points Mean absolute error <1 m. 10 points 10 Facies model Lithofacies or depositional facies 10 Mean relative error >20%. 1 point Mean relative error is 10%-20%. 5 points Mean relative error <10%. 10 points 10 Property model Net pay 10 Mean relative error >30%, 1 point Mean relative error 10%-30%, 5 points Mean relative error <10%, 10 points 10 Permeability 10 Mean relative error >80%. 1 point Mean relative error is 40%-80%. 5 points Mean relative error <40%. 10 points 10 Dynamic data Reservoir numerical model Initial water- cut fitting error 10 The number of wells with a relative error of less than 5% <60%. 1 point The number of wells with a relative error of less than 5% accounts for 60%-90%. 5 points The number of wells with a relative error of less than 5% >90%. 10 points 5 Geological understanding (20 points) Variogram parameter selection 5 When sample points are few and disorder, analog data are not used. 1 point Analog data are used when sample points are sparse. 3 points Due to sufficient sample points, the automatic fitting rate is higher and the law is clear. 5 points 5 Final static model selection 15 The relative error of OOIP >10%. 1 point The relative error of OOIP is 5%-10%, or not performing dynamic test. 8 points The relative error of OOIP <5%, honoring production performance. 15 points 15 Process check (20 points) Structural model Grid design 5 Many irregular grids around faults, or intersection between layers, or negative grid cell volume, etc. 1 point Few irregular grids around faults, no intersection between layers, and no negative grid cell volume, etc. 3 points Reasonable grid design and no abnormal case in arbitrary section across faults. 5 points 5 Facies model Facies modeling method selection 7 Just apply a deterministic method. 1 point Arbitrarily use a stochastic approach without any analysis. 4 points Investigate several modeling techniques and select the most suitable one. 7 points 7 Property model Seismic constrain 4 For area with limited well data, seismic constraint is not integrated without interpreting reasons. 1 point Seismic data are not available or poor link between seismic attributes and well data. 2 points Owing to relatively high correlation, seismic constraint is incorporated. 4 points 4 Saturation calculation method 2 Kriging interpolation according to well data. 0 point Derived from porosity log without allowing for transition zone. 1 point Considering transition zone, capillary pressure method or saturation-height function method is thus used. 2 points 1 Uncertainty analysis of the model Sensitivity Analysis on reserves 2 No any analysis. 0 point Qualitative analysis. 1 point Quantitative uncertainty analysis in form of probability distribution, and rank by weights. 2 points 0 Cumulative score 100 11-59 60-79 80-100 92