Summary
Widespread thick-bedded tight dolomite has been developed in Fengcheng Formation with fine source-rock in the west slope of Mahu Sag, Junggar Basin of China. The main controlling factors of favorable reservoir is lithology, porosity and oilbearing possibility, furthermore, porosity is restricted by lithology, and oil-bearing possibility is restricted by porosity. Tight dolomitic reservoir characterization can be, in other words, characterization of lithology, porosity and oil-bearing possibility, they can be predicted in order, based on core analysis data, well logs, seismic and test data. We propose to use impedance inversion to predict the distribution of dolomitic rocks, since dolomitic rock is characterized by high impedance. We also propose to use stochastic simulation inversion to predict the porosity, since fine dolomitic reservoir is characterized by low impedance in the background of high impedance, based on the negative correlation between porosity and impedance. We use seismic spectral decomposition to detect hydrocarbon, since oil-bearing reservoir is characterized by high-frequency attenuation. Finally, we summarize the prediction of lithology, porosity and oil-bearing possibility, the favorable areas of tight dolomitic reservoir are the places where the oil-bearing possibility is high and the reservoir with lager porosity is thick, inside the distribution of dolomitic rocks.
Introduction
The depth of Permian Fengcheng Formation ranges from 3500m to 4500m, the thickness ranges from 500m to 1000m. Dolomitic rocks of Fengcheng Formation contain oil in different degrees. FN7 got industrial oil run in Fengcheng Formation in 2011, located in the slope area, making tight dolomitic oil exploration possible. The key factor of success of tight dolomite oil exploration is the favorable reservoir that we need to find in widespread thick-bedded dolomitic rocks. According to previous study (Popov et al,2000; Yang et al, 2012; Kuang et al, 2012), the favorable reservoirs are the high quality reservoirs under the background of tight reservoir that can provide higher oil and gas industrial production. The favorable reservoir of study area must be dolomitic rocks, with high porosity and well oil-bearing, and have a certain level of thickness and distribution. Compared to conventional reservoir, tight dolomitic reservoir is more complicated.
