Process for developing deep coal seam by using underground coal gasification technology

Abstract

The invention provides a process for developing a deep coal seam by using an underground coal gasification technology. The process comprises the following steps of: drilling a horizontal production well in parallel above the bottom of the coal seam, and drilling two rows of vertical injection wells on two sides of the horizontal production well; perforating the vertical injection wells on the coalseam, performing CO2 fracturing in turn to form cracks, keeping stratum hydrostatic pressure in the cracks, and filling quartz sand; putting a coiled tubing into the horizontal production well, and putting a packer according to the distribution position of large-size slotted screen pipes; continuously injecting air or oxygen-enriched air into each large-size slotted screen pipe well completion section corresponding to the vertical injection wells from the vertical injection wells until the coal seam fracture pressure is reached, closing the horizontal production well, quickly injecting high-temperature steam from the vertical injection wells, and continuously supplementing the oxygen-enriched air to keep the pressure in the vertical injection wells above the hydrostatic pressure; and monitoring the temperature change condition near the vertical injection wells, and opening the horizontal production well for production when the temperature and pressure of the vertical injection wells are suddenly increased.

Description

technical field [0001] The invention relates to a technique for developing deep coal seams by using underground coal gasification technology, and belongs to the technical field of coal seam development. Background technique [0002] Underground coal gasification technology (Underground Coal Gasification, UCG) is also called in-situ coal gasification. Separation, fixed carbon, etc.) are transformed into combustible gases through physical and chemical transformations such as pyrolysis, combustion, and gasification. UCG combines the three major processes of well construction, coal mining and gasification into one, which has the advantages of low gas production cost, high safety and good environmental benefits. The cost of coal gas produced by UCG is only 25-50% of the gasification of the surface gasifier. The gas can be used as raw material gas for gas-fired power generation, boiler fuel, and synthetic chemical products, which can significantly reduce the cost of power generat...

AI Technical Summary

Problems solved by technology

The disadvantages of this gasification furnace construction process are that the penetration speed is slow, the penetration direction is poor, and the penetration is difficult or impossible when the vertical well spacing is large; Without a gas injection device, the gasification agent diffuses and burns throughout the gasifier, resulting in ineffective control of the combustion range and boundary, resulting in low gas quality; the expanded combustion range leads to large-scale collapse of the overlying rock, and poor stability control of the surrounding rock

Since the 1970s and 1980s, European and American countries represented by the United States have mainly developed the wellless CRIP process. In terms of gas injection control, this process uses a tube-type mobile gas injection point device, which periodically retreats to pull the gas injection Each time the gas injection point is moved back a certain distance, but this process needs to build a large gas injection elbow spiral pulling device on the ground, the equipment investment is high, the process operation is complicated, and it is difficult to seal the gas injection elbow at the ground end. When the coal seam When the buried depth is large, the operational reliability of the mobile gas injection device is reduced due to the influence of geological stress and borehole deformation

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