Coal bed gas sand flushing pipe string and its sand flushing method

Abstract

The invention discloses a coal-bed gas sand flushing pipe string and a sand flushing method thereof. The coal-bed gas sand flushing pipe string comprises downward-put isolating pipe columns which are hung at a well opening in a sitting mode, a sand flushing pipe column downwards put from the well opening, a sand flushing head mounted at the front end of the sand flushing pipe column and close to the sand flushing face and a self-packing sand prevention circulation sealing device mounted in the middle of the sand flushing pipe column; the upper end of the sand flushing pipe column extends out of the well opening; the sand flushing pipe column and the well opening are sealed through a sealing device; and a sand flushing medium is injected into annular spaces between the sand flushing pipe column and the isolation pipe columns through an inlet. In sand flushing, the sand flushing medium is injected into the annular spaces between the sand flushing oil pipe and the isolation pipe columns through the inlet, due to the packing effects of the well opening sealing device, a self-packing sand prevention circulation short section self-packing valve and a sealing short section sealing piece, the medium can enter the sand flushing pipe column only through a self-packing sand prevention circulation short section circulation hole and is sprayed out form the sand flushing head to achieve sand flushing. When the sand flushing medium is upwards returned, due to the annular spaces between the sealing short section packing sand flushing pipe column and the isolating pipe columns, the sand flushing medium is returned out of the well opening from an annular space between an isolating sleeve pipe and a well completion pipe column. Thus, the process of continuous sand flushing is achieved in the mode that sand flushing is conducted as well as the pipe columns are lowered.

Description

technical field [0001] The invention relates to a coal bed gas well sand washing technology, in particular to a coal bed gas sand washing pipe string and a sand washing method thereof. Background technique [0002] At present, domestic coalbed methane wells are mostly completed with casing or screen pipes. During the mining process, coal ash enters the wellbore along with the coalbed methane and gradually accumulates, affecting gas production. Regular sand washing is required. The existing domestic sand washing technologies mainly include coiled tubing sand washing technology and conventional tubing sand washing technology. [0003] Coiled tubing is used for sand washing, the cost of equipment is high, and good economic benefits cannot be achieved, while for conventional oil tubing for sand washing, the sand washing medium is injected through the wellhead tubing, and the pump needs to be stopped for single connection, and the sand washing process is discontinuous. At this ti...

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Problems solved by technology

[0003] Coiled tubing is used for sand washing, the cost of equipment is high, and good economic benefits cannot be achieved, while for conventional oil tubing for sand washing, the sand washing medium is injected through the wellhead tubing, and the pump needs to be stopped for single connection, and the sand washing process is discontinuous. At this time, the pulverized coal Falling back, prone to the risk of sand jams

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