Permeability Gas Reservoir To Reservoir Damage Mechanism In The Production Process And Study The Dynamic Rule Of The Gas Well

When exploitation a low or a extra-low permeability gas reservoir, the mechanism study of the formation damage around the hole bottom and its influence on the dynamic performance of the gas well is always an important and hot scientific problem, which related to how to exploit these gas reservoir effectively and reasonably.This paper has carried out following researches and gotten corresponding conclusions.1. Combining the experiment study and the theory analysis, we performed the phase behavior research for the condensate gas-water fluids system, and presented condensate gas-water phase behavior simulation theory and method.2. Aimed at the potential damage of the formation for low permeability reservoir or extra-low permeability reservoir, we conducted a series of experiments by using the samples of oil, gas, water and core to research the influence of liquid property, liquid absorption and imbibitions, dynamical characteristic and water sensitivity of the rock on the formation damage mechanics. We measured the threshold pressure and the conditions to relieve the liquid lock. Furthermore, We evaluated the feasibility to relieve the condensate liquid damage in the hole bottom with CO₂. The experiment results showed that when the irreducible water does not exit or when the irreducible water saturation is lower than 40% or the effective permeability of gas is bigger than 0.3md, there is no threshold pressure gradient, while when the permeability of the core is less than 0.63md and the water saturation is more than 40%, the quantified expression of threshold pressure gradient is A=0.0002Sw-0.0071. The imbibitions of the liquid in the hole bottom has serious effect on the gas effective permeability but will not lock the gas well, and CO₂ can effectively relieve the condensate liquid damage in the formation near the bore-hole bottom.3.Basised on the experimental study result, the fluids flow theory and modern mathematics, considering the effect of gas slippage and the initial flowing pressure gradient(water-saturation ≥ 40%), we can define a proper pseudo-pressure to solve the influence of gas slippage effect on gas flowing theory by which it can be transferred into general Darcy flowing problem, and we can also solve threshold pressure effect on gas flowing theory by introducing a new variable factor. Furthermore, the unsteady gas flowing theory, well test theory and the dynamic performance analysis method which can describe several kinds of formation damage in hole bottom of low permeability gas reservoir have been presented in this paper.4. Making use of the gas well performance analysis theory, this paper has developed the analysis method research for gas well. Meanwhile, according to the practical data about three gas wells which possess typical formation damage and adopting the modern computer techniques, this paper has conducted the interpretative method study for gas well performance datawhich has contained the typical formation damage. The interpretation results verified the correctness and the applicability of the theory and method for gas well performance analysis which is presented in this paper.