Shale gas well wellhead pressure control method and control system thereof

Abstract

The invention discloses a shale gas well wellhead pressure control method and a control system thereof. The control method comprises the steps that S1, the ratio A of pipeline return pressure to wellhead oil pressure and the current critical flow pressure ratio of a gas well wellhead are calculated; S2, whether the ratio A is smaller than a critical flow pressure ratio or not is judged, if yes, the step S3 is entered, and if not, the step S5 is entered; S3, the wellhead pressure of the shale gas well is collected according to the set frequency, and the pressure difference between the wellheadpressure and the initial wellhead pressure is calculated; S4, the opening degree of an oil nozzle valve is adjusted according to the relation between the pressure difference and the pressure drop boundary, and then the step S1 is executed again; S5, wellhead oil pressure and pipeline back pressure are collected according to a set frequency within a set time, and an oil pressure average value and aback pressure average value of the wellhead oil pressure and the pipeline back pressure within the set time are calculated; and S6, a ratio B between the oil pressure average value and the return pressure average value is calculated, the opening degree of the oil nozzle valve is adjusted according to the relation between the ratio B and the boundary of the critical flow pressure ratio, and then the step S1 is executed again.

Description

technical field [0001] The invention relates to gas exploitation technology, in particular to a method for controlling the wellhead pressure of a shale gas well and a control system thereof. Background technique [0002] For high-pressure gas wells, especially shale gas wells, the initial production pressure is high, and under the production mode of casing blowout, the initial gas production is large, and a large amount of liquid and sand are carried out, resulting in the closure of fractures near the well end and secondary sand production in the formation. At the same time, due to the closure of the fractures near the well end, the oil and gas at the far end lose their seepage channels, so the pressure and production decline rapidly, which greatly reduces the recoverable volume EUR estimated by a single well. [0003] At present, the domestic shale gas market is concentrated in the Sichuan-Chongqing region, where shale gas is deeply buried and the formation pressure coeffic...

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Problems solved by technology

[0004] In view of the above-mentioned deficiencies in the prior art, the shale gas well wellhead pressure control method and its control system provided by the present i

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