Causes and control measures for sand production in volcanic gas reservoirs,Jianyang-Santai area,Sichuan Basin
There exists sand production during the drainage of volcanic gas reservoirs in Jianyang-Santai area,Sichuan Basin,causing testing-string blockage.It is necessary to probe some appropriate measures against this sand production.Thus,not only reservoir char-acteristics but single-well sand production were analyzed to find out sand-production causes.And then,borrowed the method to predict this production in unconsolidated sandstone formations,the possibility of sand production was discussed for volcanic gas wells.Final-ly,a technical parameter of oil-pressure control during this drainage was optimized and tested on site to evaluate measure availability.Results show that(i)there is rich clay mineral in rocks with weak cementation,low intensity,and underdeveloped fractures.And the bottomhole flowing-pressure difference during the drainage is too high or higher than the critical production-pressure difference of sand production,which may induce formation collapse and thus sand production;(ii)two methods of both log-based interval travel-time and combined modulus can qualitatively predict the probability of sand production in Jianyang-Santai volcanic gas reservoirs,and the other drag and empirical model formulas can also easily calculate the critical difference in various formation-testing intervals;and(iii)in-situ practice demonstrates that,being a main measure against sand production during oil testing of exploratory wells in Jianyang-Santai volcanic gas reservoirs,the approach of step-by-step constant-pressure-difference managed bleeding can mitigate sand-production risks with effect.
Sichuan BasinVolcanic gas reservoirs in Jianyang-Santai areaPyroclastic lavaSand productionOil-pressure controlMiddle-late Permian
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