(Aerogeophysical Remote Sensing Center, Ministry of Geology and Mineral Resources)
This paper discusses the technical research of digital image processing by using potassium spectrum logging data, TM remote sensing information, earthquake, gravity, aeromagnetism and other comprehensive teaching materials, and applies it to the exploration of potassium salt in Kunteyi Salt Lake in the northwest of Qaidam Basin, Qinghai Province. It is the first time for energy spectrum logging image processing in China. In this work, the technical problems such as digitalization of logging data, vertical registration, principal component analysis, projection histogram and stratigraphic correlation map are studied. Through the statistical analysis of multi-parameter data sets and multi-band brightness characteristics. The abnormal sign of solid potassium chloride is established, the structural situation of the working area, the source of salt materials and the prediction of potash mineralization are discussed by various image processing methods, and a new understanding of the three-time migration of the sedimentary activity center in Kunteyi Basin is put forward.
1. Overview
Kunteyi Salt Lake is located in the northwest of Qaidam Basin in Qinghai Province, with a research area of about 7000km2, with the coordinates of 92 40 ′ ~ 93,040 ′ east longitude and 3815 ′ ~ 39 20 ′ north latitude. Kunteyi is a rhombic modern salt basin, which is the most favorable area for the formation of potassium salt.
This paper makes full use of various geological data accumulated in this area in the past 40 years: logging-ground geophysical exploration-aerial geophysical exploration-space remote sensing, and carries out comprehensive image processing. The following table details the parameters used.
Zhang Yujun on new methods of geological exploration.
The comprehensive image processing not only uses the rich software resources of S600 system, but also uses the airborne geophysical image processing software package (AGIPSP) developed by R Center Institute of Airborne Geophysical Exploration. In addition, several functional softwares specially used for logging image processing have been developed.
2. Image processing technology of energy spectrum logging data.
Firstly, the energy spectrum logging curves (total trace, differential peak, left integral and right integral) of 22 boreholes are digitized, and the interval of data acquisition is 1mm, which corresponds to the actual borehole depth of 20cm. After format conversion, vertical registration and various image processing, an image processing histogram is formed for each borehole, and finally a projection histogram, a stratigraphic correlation diagram and an ancient basin perspective view are formed. See figure 1 for the processing flow.
3. Remote sensing and geophysical comprehensive data image processing technology.
The comprehensive data set for digital image processing is mainly composed of seven bands of space remote sensing TM, such as earthquake, gravity and aeromagnetism. Fig. 2 is the processing flow of integrated data images.
We analyzed the brightness of 7 TM bands in more than 20 kinds of land in detail, which laid the foundation for further research.
Through effective image processing and comprehensive analysis such as KL transform, LAHE processing and solid shadow, the structural information map, pseudo-lithologic classification map and solid potassium salt anomaly map are extracted.
Figure 1 image processing flow of energy spectrum logging data
Figure 2 Integrated data image processing flow
4. Geological interpretation results and discussion
4. The center of sedimentary activity in1Kunteyi basin moved three times.
Comparing the magnetic, gravity, seismic, logging and remote sensing images reflecting different depths, it can be clearly seen that the sedimentary activity center of Kunteyi Basin has experienced three changes from north to south and from south to north. The earliest center of sedimentary activity is located in the northwest and moves to the southwest through the trajectory in the southeast. The southwest is the sedimentary center of Quaternary salt, and the modern sedimentary center moves northward. During the migration process. The uplift and subsidence of the structure formed the dynamic environment of crustal tension, compression and distortion, which led to a series of faults in the Tertiary fold belt on both sides and in the middle of the basin. These faults are good channels for oil and gas migration and also control the evolution and development of salt lakes.
4.2 Dry-wet alternate deposition environment
Kunteyi Salt Lake is a salt lake with alternating deposition of continental debris and rock salt. Remote sensing and logging images show that debris mainly comes from Altun Mountain in the north. The logging image shows its sedimentary rhythm and cycle in the vertical direction, and the horizontal direction is correct. Sudden floods are dominant in the deep part and siltation is dominant in the upper part. The development trend of salt deposition is from thin to thick, from low to high, reflecting the sedimentary environment from wet to dry.
4.3 Prediction of Potassium Salt Deposition Area
Select the best TM 1, 4 and 7 bands to make synthetic images, and display different colors for water bodies with different salinities, so as to distinguish the high-salinity brine that is depositing potassium salt. Using principal component synthesis image and density segmentation image, it shows that the solid potassium salt deposition in the whole region is clear at a glance, and many of them are known potassium salt deposition areas.
4.4 Tracing the source of potassium salt.
Research shows that potassium salt mainly comes from oil, natural gas, water and deep water. Remote sensing images play the role of macroscopic generalization and traceability, showing that potassium has the following sources:
(1) mud volcano;
(2) The leakage of tertiary fold fault zone and its trajectory provide direct evidence for geological interpretation;
(3) Hidden dome or mud volcano structure, which is the new structural information revealed by the image.
Thanks to Zhu Yuee, Shi, Yang, Feng, Wang Yang, Xu Qide, Gao and Jin Fengyun for their assistance in their work.
refer to
Qinghai province first geological hydrogeology brigade. Geological survey report of Kunteyi potassium ore field in Qaidam basin, Qinghai Province. 38388.88686886686
Cai Keqin, Zhao Dejun. Study on material composition, sedimentary characteristics and formation conditions of Kunteyi Salt Lake in Qaidam Basin, Qinghai Province. Research Report of China Geo University, 1989.
Yang Qian. Evolution of Kunteyi Salt Lake and Analysis of Potassium Formation Conditions. Golmud geological society. 1987
Zhang Yujun. Study on comprehensive image processing method and application of multi-source geological information in central Qaidam basin. Research Report of Aerogeophysical Remote Sensing Center of Ministry of Geology and Mineral Resources. 1989
Originally published in "Summary of the Symposium on Computer Application in Geoscience", 199 1.