| In recent years,with the exploration of deep natural gas and exploration of surrounding basins,the lithology of the main target stratum of exploration has gradually become volcanic rocks and metamorphic rocks.As we all know,the difficulty in identifying volcanic rocks is mainly manifested in various rocks,and the composition and structure of minerals are complex.In the past,the volcanic rock lithology was identified mainly by means of visual observation,thin section identification,etc.,based on structural types of volcanic rocks,type and mineral content of primary and secondary minerals,crystallinity,and distribution.However,the new drilling technology introduced with the demands of quickening drilling speed seriously destroys the structure of the rock,therefore the rock mineral composition,microstructure,and inclusions are difficult to identify and describe even under high magnification microscopes.Under this condition,the establishment of correct lithological section is affected.At present,the volcanic rock reservoir still plays a strategic role in“stabilizing oil production and enhancing gas exploration”in Daqing Oilfield.Especially on the deep natural gas exploration and development field,geologists urgently need to use some new technology and new methods to quickly and accurately identify the complex rocks,so as to correctly divide the stratigraphic horizons.Thereby,they can provide a reliable geological basis for oil field exploration and development department to make completion decisions for single wells.Even more,sometimes the information is indispensable for the exploration deployment departments.Based on oil-gas exploration and development needs and the relevant lithology identification project of the company,this paper applies the “chemical composition +electrical characteristics + structures” three-level comprehensive method to identify and name the volcanic rocks.In the process,the author's long-term geologic logging knowledge about volcanic rocks in Songliao Basin is indispensable.By this means,the accuracy of the complex lithology identification while drilling is improved.Firstly,on the basis of collecting and reviewing previous literature,reports and research results,this paper analyzed and summarized the general laws of various volcanic rock element changes and identified 18 characteristic elements of volcanic rocks and clastic rocks such as Si,Ti,Fe,Y,V and Zr.Then a typical volcanic rock analysis database was established by the X-ray elemental analysis of more than 2,500 representative rock hand specimens accumulated by seniors for a long time.Then the comparison and comprehensive study of the analysis data was conductedby using the crossplot method to establish the lithology identification crossplot plate for volcanic rock and detrital rock.Secondly,through the analysis of predecessors' studies,this paper has obtained the response characteristics of different volcanic rock formations in the natural gamma logging of ??the studied area.Based on the previous method of recognizing volcanic rock lithology by using natural gamma logs,the study has formed the cuttings natural gamma detection method to divide the stratum and identify the major types of volcanic rocks.Finally,when there are doubts about the comprehensive analysis of debris element analysis and cuttings natural gamma detection,rock samples are selected to be identified by polarized light microscopy to correct the lithology at the key horizons.Therefore,a more correct volcanic rock section can be built while drilling.From the actual oid-gas field practice,the method discussed in this paper provides a better solution for the geology personnel at the exploration and development field to identify the volcanic rock lithology while drilling,but it also needs certain field experience and traditional volcanic rock identification basis in the comprehensive judgment.In the future,the program still needs to be further developed and improved intelligently. |
PDF Full Text Request