Marine Carbonate Rocks Of Subtle Reservoir Exploration

The petroleum resource of the carbonate stratum is very pelentful. At present, the whole probe petroleum resource of the world is about 346.068 billion ton(2005,Oil and Gas Journal.United-States), and more than 50 percent of these resource is accumulated in the carbonate stratum, moreover, the main productive formation of lots of the large-middle oilfields is the marine carbonate stratum. Sichuan Basin is a large scale area of enrichment in oil and gas, At the present time, main prospected aim is the structural trap, but as the petroleum industry development, fewer structural trap can be found, so , the drilling success rate of structural trap is becoming more and more lower. In order to deal with this problem , the explorating ideal, technological and methods of the subtle reservoir in the marine carbonate stratum is put up, and are carried out in the north-east of the Sichuan province.When prospected for the subtle reservoir in the marine carbonate stratum, the object is the marine carbonate stratum, and aims is to look for the suble lithological trap and the structural trap. Based on the regional structural studying, applied the sequence stratigraphy theory and reservoir sedimentary concepts, utilized the drill data and regional investigation results of studying area as well as the neighboring areas, the distribution law of the sequence stratigraphy ,lithofacies palaeogeography and the ooliticfacies is studied in the main aimed formation, that is the Changxin-Feixianguan formation. By setting up the sedimentary modle ,this paper point out the sedimentary modle and facies distribution of the north-easte in the Sichuan province is controlled by the regional structural background ,evolutional phase , climate and others factors. From late Permian to early Triassic, there formed lots of facies distribution modle and its sedimentary modle can be compared well with the Wilson carbonate sedimentary model. By studying, there are six kinds of sedimentary modle in this areas. They are basin sedimentary, shelf sedimentary, oolitic faciecs of the platform edge , slop sedimentary ,platform sedimentary and evaporative platform sedimentary. Though the analysis of reservoir type and its main controlled factors, this paper point out that because of the low buried water and powerful energy easily to form oolitic reservoir, oolitic facies of the platform edge and platform sedimentary facies is a good area of looking for the gain gas fields.Especially in the oolitic facies of the platform edge, organic reef and oolitic facies of dolostone reservoir is very plentiful. Besides that, these areas is closing to the deep buried shelf and basin areas and the gauge of the reservoir is very good quantity, so these areas is the Exploration-favoring Areas to look for large-scale or oversize oil and gas field .At last, under the guidance of the geology model, combined the seismic analysis with the specially process explain, based on the geology , drilling, logging and seismic theory, the lateral predication of reservoir, the distribution areas of favourable reservoir is identified and point out that the main reservoir is oolitic facies of Dukouhe , Teishanpo, Maoba and Jiannan in the Feixianguan formation as as well as the oolitic and organic reef facies of dolostone of Fei xianguan and Changxin formation in the Puguang areas. Through the drilling, the most largest gas fields is found in Sichuan basin-Puguan gas field.