Organic-rich shale deposits in the anoxic reductive environment

and is rich in pyrite

chlorite

organic matter and other reductive components. In the process of oil and gas development

a large amount of oxidizing working fluids enter the reservoir

which is incompatible with rock and fluids in reservoir

thus breaking the physical and chemical equilibrium between shale reservoir and formation fluids such as oil

gas and water. The organic-rich shale of Silurian Longmaxi Formation in Pengshui area of southeast Sichuan Basin was selected to conduct the experiment on the interaction between oxidizing fluid and organic-rich sh

ale

so that to analyze the effect of oxidizing working fluid on shale reservoir permeability. The results show that the after the contact of organic shale and oxidizing working fluid

the permeability will change with the fluid oxidation-reduction potential（

Eh

）

which is called oxygen sensitivity. When the fluid oxidation-reduction potential is less than 450 mV

the generated chemical precipitation solid particles and solid particles of shale debris

such as Fe

2

O

3

Fe（OH）

3

siderite（FeCO

3

）

calcium sulphate dihydrate（CaSO

4

·2H

2

O）

MgSO

4

and BaSO

4

lead to the reduction of shale permeability. Regulating

Eh

of working fluid

inhibiting oxygen sensitivity damage

and playing the role of oxidation and permeability enhancement are the development direction of completion fluid of oil and gas reservoirs under reductive environment.