Detection method for porosity distribution of upper formation of fire district of coal field

Abstract

Disclosed is a detection method for porosity distribution of an upper formation of a fire district of a coal field. A plurality of measuring lines are arranged on the ground surface of the upper portion of the fire district of the coal field, a plurality of measuring points are disposed on each measuring line at intervals, holes are constructed and drilled on the measuring points on each measuring line one by one, then a transmitting antenna and a receiving antenna are respectively disposed in each two adjacent drilled holes on the same measuring line one by one, drilled hole radar multi-offset-distance cross-hole transmission detection is sequentially carried out for all the drilled holes on each measuring line, and the time span of electromagnetic waves propagating from the transmittingantennas to the receiving antennas under conditions that offset distances are different are acquired; and data of the acquired propagation time span of the electromagnetic waves are processed by the aid of a computer, mosaic and combination of porosity data on a two-dimensional section between each two adjacent drilled holes on each measuring line is realized, and a contour map of porosity distribution of the formation on the section of each measuring line is drawn. Accordingly, porosity distribution of the upper formation of the fire district of the coal field is obtained, and the condition of the porosity distribution of the loose and broken formation in an upper space of the fire district of the coal field is quickly and effectively detected in an in-situ state.

Description

technical field [0001] The invention relates to a detection method, in particular to a detection method suitable for the porosity distribution of strata above coal field fire areas. Background technique [0002] The porosity distribution of the strata above the coalfield fire zone is the basis for studying the air supply and outlet channels of the combustion system in the coalfield fire zone and the migration law of fire extinguishing medium in the loose strata above the fire zone. However, there is no method that can detect the porosity distribution of unconsolidated formations in situ. The measurement of formation porosity is widely used in oil and gas geology, mainly including logging methods (such as acoustic logging, density logging and nuclear magnetic resonance logging) and seismic inversion methods. However, the detection range of acoustic logging, density logging and nuclear magnetic resonance logging is very limited, and the development of formation pores can only...

AI Technical Summary

Problems solved by technology

However, since it is difficult to directly establish a definite relationship between the extracted seismic attributes and porosity, the calculation error of formation porosity is relatively large

From the above analysis, it can be seen that neither the logging method nor the seismic inversion method can be used to detect the porosity distribution of loose and broken formations with large spatial variations.