Experimental Study On The Effect Of Rich Organic Shale And Oxidation Solution

China’s shale gas resource is rich,but shale block is very compact and there are adsorbed gas in shale.Multi-scale complex flow mechanism of the shale gas led to the shale gas well in general there is no natural capacity or low yield.The main body of the shale reservoir reconstruction technology is horizontal well staged fracturing technology,which generally exist the fracturing fluid flowback rate is low,the transformation validity of short,fast declining production.Organic matter and pyrite can be oxidized.Therefore,this paper carried out the rich organic shale oxidation experiments and analysed the modification of shale transmission capacity by oxidation,which have great significance for the effective development of shale gas reservoirs.This paper chose shale as experimental sample.I designed and carried out the rich organic shale and the liquid oxidation experiment and analyzed the rich organic shale components and physical property change before and after oxidation,preliminary reveals the rich organic shale oxidation mechanism of increased permeability.This paper put forward the idea that rich organic shale transformation can be done by the oxidation of liquid.By adding oxidant in the fracturing fluid,the oxidation corroded organic matter and pyrite in shale,prompted adsorption gas desorption.Corroding the matter near the hydraulic fractures by oxidation is a new way of shale transformation.Shale oxidation fluid is composed of oxidant,distilled water,surface active agent and catalyst.Shale and the liquid oxidation experiments have been designed.By oxidation and acidification corrosion rates test of shale,this paper choose a reasonable oxidation liquid solubility and reaction time.By testing the TOC of shale before and after oxidation,this paper made the oxidation rates of organic matter clear,and selected reasonable shale sample size.In order to make clear the dissolution rate of inorganic minerals,the XRD tests of the shale before and after oxidation have been carried out.Using means such as SEM,mercury injection,nitrogen absorption,permeability tests,stress sensitivity tests and calculating shale temperature and pressure after oxidation change,this paper analyzed the changes of shale physical parameters.The influence of oxidation of organic matter rich shale components have been made clear.We should use 15%concentration of oxide react with less than 1 mm size of sample proceed shale oxidation experiment;Shale oxide dissolution rate(1.5%～3.5%)is less than the acidification corrosion rate(0.6%— 0.8%);Oxidation can corrod 100%of the siderite and pyrite in shale and 86%of dolomite;Shale organic carbon and sulfur oxide dissolution rate can reach 91.7%and 99.8%respectively.The experiment confirmed that oxidation significantly increased the rich organic matter shale permeability.The oxidation of shale formed a large number of dissolution pore and seam;The total pore volume of shale increased to 1.6 times,the average pore size of shale increase to 3.1 times,the surface area of shale decrease 53.2%after oxidation reaction.New cracks were formed in shale after oxidation.Permeability of shale increased 7-60 times.Stress sensitivity of shale has no obvious change.Shale oxidation can increase the temperature and pressure in the shale,thus affecting the shale gas transmission.This paper has cleared about the rich organic shale oxidation mechanism of increased permeability.Liquid oxidation reaction with shale can form high temperature and high pressure environment,organic acid in the reaction product can further dissolution carbonate minerals;Oxidation corrosion pore seam communicated hydraulic fracture and pore throat.Heat and gas produced by reaction can form high temperature environment.The corrosion and changes of temperature and pressure which caused by oxidation promoted the desorption,diffusion and darcy flow of shale gas.In conclusion,the corrosion and changes of temperature and pressure which caused by oxidation increased the rich organic shale gas multi-scale transport capacity.