Evaluation Method and Evaluation Device for Water Breakthrough Risk of Production Wells in Aquifer Drive Gas Reservoirs

Abstract

The present invention provides an evaluation method and an evaluation device for water breakthrough risk of gas wells in gas reservoirs with aquifers, the method comprising the following steps: building evaluation factors that influence water breakthrough risk of gas wells in gas reservoirs with aquifers; acquiring weight vectors of the evaluation factors based on an analytic hierarchy process; building a fuzzy relationship matrix between the water breakthrough risk of gas wells in gas reservoirs with aquifers and its evaluation factors; and synthesizing the fuzzy relationship matrix and the weight vectors according to a weighted average fuzzy synthesis operator, to acquire a comprehensive evaluation result of water breakthrough risk of gas wells in gas reservoirs with aquifers. The present invention improves the accuracy of the evaluation result of water breakthrough risk of the gas wells, and is able to obtain an evaluation result that is more consistent with the case of actual water breakthrough of gas wells in gas reservoirs with aquifers.

Description

[0001]This application claims the benefit of co-pending Chinese patent application 201410670301.5, filed 20 Nov. 2014, which is hereby incorporated herein as though fully set forth.TECHNICAL FIELD[0002]The present invention relates to the technical field of natural gas development, in particular to an evaluation method and an evaluation device for water breakthrough risk of production wells in gas reservoirs with aquifer.DESCRIPTION OF THE RELATED ART[0003]As for development of gas reservoirs with strong edge-bottom aquifer drive, once water breakthrough occurs in gas wells, a lot of trouble may be brought to gas field surface engineering, and meanwhile productivity of the gas wells may be decreased greatly, causing the gas wells to be shut down due to too low production rate in early period, thereby greatly influencing gas reservoirs recovery and development performance. Therefore, how to identify aquifer influx of gas wells are urgent in order to guide the well production rate opt...

AI Technical Summary

Benefits of technology

The present invention is a combination of two methods: the analytic hierarchy process and the fuzzy synthetic evaluation method. These methods are used to evaluate water breakthrough risk in gas wells. The analytic hierarchy process is a systematic research method that uses decomposition, comparison, judgment, and comprehensive thinking to determine the weight coefficients of evaluation factors. This method is more adaptable to the objective fact and easy to calculate quantitatively, improving the accuracy of the result. Overall, this method helps to obtain an evaluation result that is more consistent with the actual water breakthrough situation of gas wells in gas reservoirs with aquifers.

Problems solved by technology

As for development of gas reservoirs with strong edge-bottom aquifer drive, once water breakthrough occurs in gas wells, a lot of trouble may be brought to gas field surface engineering, and meanwhile productivity of the gas wells may be decreased greatly, causing the gas wells to be shut down due to too low production rate in early period, thereby greatly influencing gas reservoirs recovery and development performance.

Wherein, water breakthrough time prediction method adopts a water coning breakthrough time calculation formula to predict specific water breakthrough time of a gas well, but because actual gas reservoir has high heterogeneity and the production plan is continuously adjusted, use of these methods to perform evaluation of water invasion of the gas reservoirs may result in great difference with the actual situation.

There are also literatures involved the material balance method and the water invasion indication curve method, but application of these methods is also limited, because these methods need too much static pressure data and good prediction can be gotten only when a certain degree of recovery is achieved, but actually, there are few testing points of static pressure and the degree of recovery of many wells when water breakthrough occurs is very low as a result, at present it is difficult to quantitatively evaluate the water breakthrough risk, which can objectively reflect the actual situation, by using existing technology.

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