Blockage Types of Gas Well and Technical Countermeasures for De-Plugging in Low-Permeability Tight Gas Reservoirs

The Changqing gas field is a typical low-permeability tight lithological gas reservoir with strong heterogeneity and poor physical properties. With its development deepening, the gas well production rate gradually decreases, which gives birth to the rising number of low-yield and low-efficiency gas wells year by year. Due to the corrosion and scaling, sand production and deposition, water lock damage and other reasons, wellbore and reservoir blockage is formed in the production process. It will seriously affect the gas well productivity, even cause gas well effusion and water flooding, affect the development benefits of gas fields. In view of this problem, the study and analysis of blockage types are starting with the research on the mechanism of blockages, and the causes of gas well blockage are clarified from the two aspects of wellbore and reservoir. On this basis, the main technical countermeasures with wellbore coiled tubing sand flushing, reservoir hydrolysis lock of the near wells in the Upper Paleozoic gas reservoir, wellbore chemical descaling and reservoir depth unblocking of the near wells in the Lower Paleozoic gas reservoir were gradually established, which achieved differentiated de-blocking and recovery. Though the field scale application of the technology being carried out, more than 750 gas wells with an average daily gas increase of 9,000 m3 were revived. Until now, the total gas production has been obtained more than 1.5 billion m3, equivalent to 1.2 million tons of oil. The input-output ratio is as high as 1:9.0. The outstanding effect and economic benefits effectively solve the problem of low production or production stoppage caused by plugging. It can provide some technical support and guarantee for the improvement of de-plugging technology in Changqing gas field and other similar gas reservoirs.