Geophysical Research And Application On The Sequence Division Mothod Of Carbonate Sedimenditary

With the increasing complexity of the oil-gas exploratory development object and the maturation of seismic interpretation technology , seismic oil-gas forecasting technology become more and more delicate and practical. In order to improve the accuracy of the oil-gas forecasting, the division of the seismic facies is especially important. The method of seismic exploration has many strong points as the lower cost and widely applicability. .But in the exploration of carbonate rocks, because of the different mineralize degree, the carbonate physical characteristic has the huge differences, the reservoir analysis accurately is disturbed. Therefore, It is necessary to study and summarize the method of sequence partition of carbonate rock.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 fieldThis text guided by carbonate sedimentology and sequence stratigraphy and other related theories. And examines the sedimentary system,sequence stratigraphy of Changxing formation and Feixianguan formation in northeastern Sichuan.basin by using logging,seismic and geologic methods.In Northeastern Sichuan, we took the organic reef-bank reservoir as the main study object. The reef reservoir possesses unique pore space, with a generally high porosity and permeability, it is an excellent reservoir of carbonate rock, blessed with a great potential for hydrocarbon. The reef hydrocarbon reservoir, however, ranks among one of the subtle reservoirs that are difficult to explore. Considering the status of the work area– not sufficient wells and being underdeveloped, the author fully utilizes the unique characteristics of geophysical response of the reef so as to identify the characteristic of seismic response over the three-dimensional seismic section.Firstly we based on the full comprehension of the geological background and the available information, We focused on the mutual relations between layers. We studied the characteristic of seismic response with the synthetically analytic method. On the basis of accurate level calibration of the target level,we contrast and divide the sequences.Secondly,numerically simulated all the possible mutual relations, and got rid of the false impression in the seismic cross section. With the method of seismic section analysis and the waveform classification technology, we analyzed and simulated the stratum of Permian Changxin formation and the Triassic Feixianguan formation in Northeastern Sichuan and presumed the sedimentary facies.Finally,we divide the Changxing formation and Feixianguan formation as three squences.