Experiment Research On Acidification Reconstruction For Low Permeability Coal Reservoir

Coal-bed fracturing is a key link in coal-bed gas production.Physics traditional way such as hydraulic fracturing,can improve the ability of the coal reservoir diversion.However,it have little effect on minerals which filling in coal pore and fissure.These minerals greatly reduce conductivity of the coal reservoir.If select a kind of acid formulation,dissolution the minerals fill in coal reservoir hole fracture through chemical reaction with it,increase the flow capacity of filled hole fracture and to improve coal reservoir permeability,that has important significance for development of China's low permeability coal bed methane.This thesis collected coal representative samples of Gaohe No.3 coal seam and Daning No.3 coal seam of Qinshui basin,Shanxi.First,take test on the coal samples of two mines,Gaohe coal mine is meager-lean coal,minerals are mainly clay and carbonate,Daning coal mine is anthracite coal,minerals are mainly clay and less carbonate;Then carrry out reservoir sensitivity experiment,select optimum clay stabilizer are 2% KCl by the water sensitivity experiment,study acid sensitivity characteristics of the two mining area which both have no acid sensitivity by the acid sensitivity experiment.Next the pulverized coal are processed with different acids,select the best acid system of the two coal mine accord the dissolution rate of pulverized coal after acidification.the best acid system of Gaohe coal mine is 3% HCl+3% HF+3%CH₃COOH+2% KCl or 5% HCl+2% HF+2% CH₃COOH+2% KCl,the best acid system of Daning coal mine is 3% HCl+3% HF+3% CH₃COOH+2%KCl or 5% HF+2%HCl+2% CH₃COOH+2% KCl.Then coal cores are processed with best acid system,test the change of permeability?porosity and diffusion amount of the before and after acidification.The results showed coal porosity and permeability increase before and after acidification,and pore connectivity became better,acidfication reconstruction increase the permeability mainly by increase the pore connectivity.Through the reservoir acidification reconstruction experiment study,provides a theoretical guidance for the application of acidfication reconstruction in coalbed methane development.