engleski

Geostatistics in Petroleum Industry - Theory and Practice Applied in Reservoir Development in INA Naftaplin

Geostatistics is very powerful and standard tool in geological modelling of hydrocarbon reservoirs in the last 2 decades. It could be used in interpolation or simulation improving as well as mathematical tool for linking of two dependant variables, e.g. porosity and seismic. In practice of INA-Naftaplin (Development Department) several Kriging methods are tested as methods for better porosity mapping, and compared with other interpolation techniques like Inverse Distance Weighting or regression formulas. The Ordinary Kriging is found as the most appropriate interpolation method for porosity estimation on fields/reservoirs with minimum 10-15 inputs. In two cases Ordinary Cokriging is successfully applied with seismic attribute (reflection strength) as secondary variable and such maps were characterised with lower MSE (cross-validation) values than same Kriging maps. Seismic could be valuable secondary source of petrophysical (not only structural) information, when link between well and seismic data was proved with statistical tests. Stochastical simulations (Sequential Gaussian Simulations - SGS) are applied in obtaining 100 equally-probable realizations and calculations of total reservoir pore volume. Consequently, it was possible to make several OGIP calculations. Also new porosity histograms, based on plenty of simulated values, represented benefit of stochastical simulations, especially in cases with less than 30 inputs and variogram model reliable. Geostatistics is accepted as standard tool in INA-Naftaplin practice, supported in several standard software packages. Geostatistical methods are proved as porosity estimation improvements in each type of lithofacies, with better results obtained in coarse-grained clastites and different metamorphites, and poorer in carbonate with mostly secondary porostiy.

geostatistics; Kriging; Cokriging; stochastic simulations; porosity

Interna recenzija organizatora skupa.