Academic Research On Plugging Micro-clearance For Gas Blocking Of Gas Well

The key point for gas well developing successfully is whether the well cementing is good or not. And to solve the problem of anti-gas channeling after cementing is the key technique for improving cement job quality and gas reservoirs protection. Micro-clearance is developed between casing and cement mantle when casing shrinks by pressure suppressing and fracturing, which is the main cause for gas channeling. Then the topic is pulled out that gas channeling can be prevented by micro-clearance plugging, which is the technique to inject plugging fluid into some section above annual gas zone, as gas channeling, the plugging fluid be invaded into micro-clearance, then serious blocking produced which radically lows plugged zone permeability, at last plugging successfully.A calculation model of micro-clearance size is built up according to elasticity theory in this paper. The micro-clearance size is calculated in the case of high pressure and fracturing in Qingshen gas field. Gas flowing characteristic is studied in micro-clearance. And the gas migration theory is enriched.Plugging mechanism is researched. It is the bridging effect of plugging grain. The mathematical model is built between single grain and double grains. The relationship between pressure of micro-clearance double-end and the coarseness and shape of plugging grain is obtained.In this paper, fractal theory is used to optimize plugging material, which is to get the optimum material formulation from matching the fractal dimensions of size distribution between plugging grain and gap width. The theoretic model of micro-clearance is set up according to the principle of interstitial flow and gas/liquid two-phase flow. From the model the plugging parameters of plugging fluid can be calculated, which contain the height of the plugging fluid and the leakage of the gas. The calculation model provides solid theoretical support for field application of plugging fluid.