Southwest Petroleum University Master's Thesis The Productivity Study Of Carbonate Matrix Acidification Considering Wormhole

Matrix acidizing is one of the important means of reservoir stimulation in the development of carbonate reservoirs.During the process of injecting active acids into reservoir under appropriate flow rate,wormholes will be propagated as the result of convection and diffusion effect of acid together with the effect of acid rock reaction.The initial formation area will be communicated by the generation of wormholes with high permeability.Meanwhile,the skin factor of near wellbore will be reduced.Then the production will be improved.In matrix acidizing,the prediction of polluted area and wormholes propagation mechanism together with productivity calculation are all the key points.According to the current research status,the prediction of oil well pollution is mostly based on the oil-water two-phase flow equation.Besides,among the existing wormhole propagation model,the two-scale model is a relatively more reasonable model.However,most of the domestic and foreign scholars have been able to calculate the production capacity by deducing the analytic solution.As the permeability of wormhole is simplified by the average permeability,the heterogeneity of the formation and the irregular growth of the wormhole can not be accurately reflected.Therefore,the numerical simulation method based on wormhole propagation model becomes particularly important.This paper has applied theories of petroleum engineering and reservoir numerical simulation and other related knowledge to study wormhole propagation and productivity calculation in carbonate reservoir.Main achievements of the study are summarized as following:(1)The 2-D radial coordinate model of filtration damage of drilling mud was established,which provides the data in the calculation of wormhole propagation.(2)The propagation rules of the wormhole under different phase angle and perforation position were simulated by using the two-scale propagation model of dimensionless wormhole.At the same time,a new method for calculating the productivity of wormhole was established.Besides,this model was combined with the oil-water two-phase flow model to calculate the capacity.(3)According to the new method of productivity calculation,this paper has analyzed the influence of wormhole density,wormhole length and completion method on the acidizing productivity of straight well and obtained the result that the main factor to the acidizing productivity is whether the wormhole has broken through the polluted area.When it comes to open hole completion,the smaller the wormhole density is,the more economical it will be.When it comes to perforating completion,the increment of wormhole density can achieve considerable yield increase in a certain range.The wormhole propagation simulations of reservoirs with different perameability have found that the lower the reservoir permeability is,the more obvious the effect of wormhole on reservoir stimulation is and the length of the principal wormhole is the main factor on production-increasing ratio.