Inversion calculation method of coal-bed gas parameters of fast test while-drilling

Patent metadata

Field	Value
Publication number	US-2021262341-A1
Application number	US-201917043728-A
Country	US
Kind code	A1
Filing date	Oct 12, 2019
Priority date	Jun 24, 2019
Publication date	Aug 26, 2021
Grant date	—

Abstract

The present invention provides an inversion calculation method of coal-bed gas parameters of fast test while-drilling. The technical solution is that an inversion calculation method of coal-bed gas parameters of fast test while-drilling includes: during drilling in a coal bed, testing a gas flow and a gas concentration of an orifice in real time while-drilling, calculating drilling gas discharge amounts of the orifice, inversely calculating a coal-bed gas pressure at a drill bit based on borehole and coal-bed permeability parameters, and calculating a coal-bed gas content according to a gas content and gas pressure relational expression. The present invention has the beneficial effects that the present invention does not occupy the drilling and drill rod replacement time, is accurate, convenient, real-time and fast, and can test and calculate the coal-bed gas parameters of each section along the whole borehole length.

First claim

1 . An inversion calculation method of coal-bed gas parameters of fast test while-drilling, comprising: during drilling in a coal bed, testing a gas flow and a gas concentration of an orifice in real time while-drilling, calculating a real-time drilling gas discharge amount and an average drilling gas discharge amount of the orifice, inversely calculating a coal-bed gas pressure at a drill bit based on borehole and coal-bed permeability parameters, and calculating a coal-bed gas content according to a gas content and gas pressure relational expression.

2 . The inversion calculation method of coal-bed gas parameters of fast test while-drilling according to claim 1 , wherein the inversion calculation method specifically comprises the following steps:
a. during drilling of a coal-bed borehole or a coal-passing borehole, mounting a blowout prevention device or an orifice quick sealing device at an orifice section, and connecting a comprehensive gas parameter tester and a drainage pipeline connected with a drainage system to an extraction opening of the blowout prevention device or the orifice quick sealing device; b. connecting the drill bit to a drill rod, and starting to drill after the drill bit passes through the blowout prevention device or the orifice quick sealing device; c. during drilling of the coal bed, recording a coal appearing time and position, automatically recording the gas flow and the gas concentration by the comprehensive gas parameter tester, and calculating the real-time drilling gas discharge amount and the average drilling gas discharge amount; d. during drilling of the boreholes, automatically calculating a coal-bed gas pressure of a test section by formulated ground monitoring and analysis software according to input drilling parameters, the coal-bed permeability, and an average drilling gas flow, and calculating the coal-bed gas content according to a coal adsorption constant and environmental parameters; e. during drilling of a main borehole and branch boreholes by a directional drilling machine, automatically calculating the coal-bed gas pressure of the test section by the formulated ground monitoring and analysis software according to the input drilling parameters, an exposure time of each coal section, the coal-bed permeability, and the average drilling gas discharge amount, and calculating the coal-bed gas content according to the coal adsorption constant and the environmental parameters; f. predicting an outburst risk of each section of the coal bed according to parameters of the coal-bed gas pressure and the coal-bed gas content of each section; and g. in the process of drilling the coal-bed borehole or after the drilling ends, stopping drilling, closing a slag outlet, automatically recording a gas flow and a gas concentration within each time period by the comprehensive gas parameter tester, and calculating a natural gas discharge velocity of the borehole by the formulated ground monitoring and analysis software, automatically calculating a penetrability coefficient and a permeability of the coal bed at the section, and correcting the calculated coal-bed gas content or pressure parameter.

3 . The inversion calculation method of coal-bed gas parameters of fast test while-drilling according to claim 2 , wherein the inversion calculation method of the coal-bed gas pressure specifically comprises: in a drilling process of the drilling machine, recording in real time the gas flow and the gas concentration of the orifice and the real-time drilling gas discharge amount in the drilling process by the comprehensive gas parameter tester at the orifice, calculating the average drilling gas discharge amount, and inverting gas feature parameters of different positions of the coal bed according to the average drilling gas discharge amount, wherein a total amount of gas drained by the gas drainage system at the orifice is composed of three portions, comprising a gas amount released from a borehole wall newly formed in the coal-bed drilling process of the drilling machine, a gas amount released by drilling cuttings peeled off from the borehole wall, and a gas amount released from the borehole wall before a new borehole wall is formed; and the coal-bed gas pressure at the drill bit in the drilling process is:

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Assignees

• Univ China Mining
• Xuzhou Fuan Tech Co Ltd

Inventors

• Wang Enyuan
• Wang Hao
• Ou Jianchun
• Shen Rongxi
• Wang Xiyuan
• Li Baolin
• Li Zhonghui
• Liu Xiaofei

Classifications

• E21B47/00

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• E21B47/06 Primary

  Measuring temperature or pressure · CPC title

• E21F7/00

  Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose · CPC title

• G06Q50/02 Primary

  Agriculture; Fishing; Forestry; Mining · CPC title

• E21B47/01

  Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like · CPC title