The realization of informatization in the whole process of geological survey is the main direction of the develop-ment of geological survey.In the land quality geochemical survey,the arrangement of soil sampling points is much work,and how to efficiently and reasonably complete the arrangement of sampling points is the premise and key to the orderly develop-ment of field investigation.According to the relevant land quality geochemical survey specifications and based on the MapGIS platform,this paper realizes the automatic and intelligent arrangement of soil points under different work scales in the land quality geochemical survey,which mainly includes:①The preliminary layout and automatic numbering of soil double-layer sampling points in 1∶250 000 land quality geochemical survey;②The automatic layout of soil sampling points for 1∶50 000 land quality geochemical survey was realized under different average density requirements,and the layout results took into ac-count spatial uniformity and rationality;③Based on the K-means algorithm,the automatic point layout of differentiated sam-pling density of different land use types in the land parcel scale geochemical survey was realized,and the distribution of points within a single irregular block was uniform.Through comparison and verification,the automatic point layout method adopted in this paper can better meet the requirements of the relevant specifications and significantly reduce the work burden of technical personnel.
The ultra-deep marine carbonate formation of The Great Desert,Tarim Basin Area,NW China,hosting great potential reservoirs,is a prospective target for petroleum exploration.However,there are several challenges remain in ultra-deep desert seismic data processing:①Loose structures of near-surface in desert regions can bring severe seismic energy ab-sorption,showing distinct low-frequency characteristics,which will eventually affect the reconstruction of signals;②The differences between interlayer multiple wave and primary wave in travel time and velocity are relatively small in desert area.Therefore,it is much more challenging to identify and suppress interlayer multiple waves;③The relatively low-resolution seismic data in ultra-deep area(depth>7500 m)due to energy absorption and wavelet deformation cannot meet the require-ment of high-precision imaging;④The drastically varying velocity medium under the influence of lithology,primarily consis-ted of Permian igneous rocks and Calcareous limestone,causes excellent difficulties in velocity model building.We attempt to a-chieve high-precision exploration progress in Tarim basin:①We use microlog data to constrain the near-surface model build-ing;②The multiple suppression technology we are applying this paper can provide more accurate pre-stack data;③We adopt near-surface Q filtering and migration for high-frequency compensation to improve the seismic resolution;④We build the in-itial velocity model based on VSP data,update the initial velocity model with tomography,finally obtain high-precision ima-ging of ultra-deep carbonate.
Microtremor survey technology has the characteristics of high efficiency,non-destructive,environmental pro-tection,and good economic benefits.In order to overcome the shortcomings of traditional microtremor technology,a new engi-neering geological microtremor survey system has been developed by developing software,continuously optimizing iterative in-terpretation algorithm,field workflow,and other measures,so as to improve the application range and interpretation accuracy of microtremor technology.This technology is based on the extended spatial autocorrelation(ESPAC)theoretical algorithm and the H/V spectral ratio method.It uses a linear array to obtain core parameters such as phase velocity,H/V spectral ratio,peak frequency,etc.Through comprehensive analysis,it can quickly and intuitively obtain the geospatial distribution informa-tion of abnormal bodies,cooperate with geological mapping and drilling to find out the engineering geological conditions of sites along the tunnel project,and provide necessary engineering geological data for line design and construction.Taking a tunnel survey as an example,this paper interprets and infers the abnormal body of the tunnel by using the microtremor survey technol-ogy by linear array,high-density electrical method,and other comprehensive geophysical methods,combined with the geolog-ical conditions,and divides several abnormal zones and lithologic contact zones.The conclusion is consistent with the drilling and field geological mapping.Theory and practice show that the engineering geological microtremor survey technology has a-chieved good results in tunnel investigation and can be popularized and applied.
Channel sands are developed in the Jurassic in the Fudong slope area of Junggar Basin,characterized by faults and sand bodies jointly controlling reservoirs.However,sandstone and mudstone are affected by factors such as borehole col-lapse,and the logging curves are seriously distorted.So,the conventional curve correction methods are challenging to realize the accurate regression of sand and mudstone,which directly affect the accuracy of sand body and oil-gas detection.Through comprehensive comparative analysis in the work area,based on clarifying the characteristics of the low impedance of sandstone and high impedance of mudstone,two steps are adopted:Firstly,the effect of borehole expansion rate on density is used to cor-rect the overall background trend of sand and mudstone;secondly,the NMR porosity which corresponding to the sandstone is selected to constrain sandstone trend,in order to ensure the reasonable relative relationship between sand and mudstone.By su-perimposing the details of density amplitude change,the accurate correction of the logging curve is finally realized.An im-proved method of dichotomous logging environment correction is formed,effectively improving the quality of logging curves and provides reliable data for reservoir prediction and oil-gas detection in the study area.Compared with the conventional tech-nique,this method can precisely correct the area with poor data quality and significant area collapse without selecting marker layer and standard curve and realize accurate regression of sandstone and mudstone.The application of this method solves the geological problem of inaccurate prediction of channel sand body in the Fudong area for many years and guides the later well lo-cation deployment.
The traditional Hilbert-Huang transform(HHT)is a time-frequency analysis method with poor recognition accuracy and suffers from endpoint effects and modal aliasing.The improved Complete Empirical Mode Decomposition(ICEEMD)can decompose complex seismic signals into a series of single-component signals,which can better solve the prob-lem of modal aliasing.However,the instantaneous amplitude and instantaneous frequency extracted by the combined Hilbert transform still have serious endpoint effects on the processing of real seismic data.FWEO(Frequency-weighted Energy Oper-ator)is a non-negative frequency-weighted operator that combines TK energy difference algorithm and the Hilbert transform complex analysis idea,and has higher time resolution than the Hilbert transform.However,due to the algorithm itself,the FWEO energy can only be applied to single-component signals and not directly to complex seismic data.Therefore,this paper combines the advantages of the improved complete empirical mode decomposition method and FWEO energy separation algo-rithm to extract the instantaneous amplitude and frequency information of the actual seismic records in a work zone in the South China Sea and compares the prediction results with the logging data with good prediction agreement and high recognition accu-racy,which proves that the method can accurately reflect the reservoir characteristics.
