A method for exploiting coalbed methane from structural coal reservoirs

Abstract

The invention discloses a method for exploiting coalbed methane from structural coal reservoirs. The coalbed methane is exploited by using vertical production wells and horizontal wells, wherein the vertical production wells are connected to the horizontal wells, and the horizontal wells increase the contact between the borehole and the structural coal reservoirs. area; after the horizontal well drilling is completed, the horizontal well should be cleaned once to reduce the pollution of the drilling fluid to the original formation; the coal seam should be treated with anti-permeability treatment, which is to increase the leakage rate of the coal seam at the microscopic level. The damage to the coal seam is reduced to a certain extent; the horizontal well is cleaned again after the anti-reflection treatment, which effectively removes the reservoir pollution; after the second well cleaning, the screen pipe is run in the horizontal well to ensure the long-term communication between the wellbore and the coal seam. Improve the mining efficiency of coalbed methane. The method for mining coalbed methane from structural coal reservoirs provided by this program not only reduces the pollution of drilling fluid to the original formation, but also reduces the damage to coal seams, and increases the seepage channels of structural coal reservoirs in an environmentally friendly manner, improving the coalbed methane. mining effect.

Description

technical field [0001] The invention relates to the technical field of coal bed gas exploitation, in particular to a method for mining coal bed gas from structured coal reservoirs. Background technique [0002] In recent years, the target of coalbed methane development has shifted from primary structural coal to structural coal such as fragmented coal and crushed coal. Structural coal has the following characteristics: the first coal structure is poor, the firmness coefficient is low, and it is easy to collapse during the drilling process; the second structural coal has low original permeability, poor connectivity of coal reservoirs, and the range of pressure drop funnel is limited. Without transformation, the output of coalbed methane is low. [0003] For tectonic coal, the existing CBM development technology is mainly casing fracturing to complete a single horizontal well. The casing fracturing completion of single horizontal well is to use the drilling fluid to form mud...

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Problems solved by technology

[0004] However, the horizontal well fracturing technology of single horizontal well completed by casing fracturing is restricted by the following factors: first, the type and magnitude of in-situ stress need to be considered, for example, horizontal fractures are easy to form in the shallow part, and it is difficult to realize the formation of reservoirs. Effective reformation; after the second fire attack perforation fracturing or hydraulic sandblasting perforation, the communication channel between the wellbore and the reservoir is limited; the third fracturing is easy to communicate with the upper and lower aquifers, resulting in high water production of horizontal wells and difficult to be effective reduce reservoir pressure

[0005] From the above, it can be seen that the effect of casing fracturing and completion of a single horizontal well is affected by many factors during the drilling process, resulting in a certain risk in the production of coalbed methane, and the fracturing fluid system will also cause pollution to the original formation

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