Reservoir Evaluation and Development ›› 2020, Vol. 10 ›› Issue (1): 56-63.doi: 10.13809/j.cnki.cn32-1825/te.2020.01.009

• Engineering Process • Previous Articles     Next Articles

Effect of oxidizing working fluid on permeability of organic-rich shale

YOU Lijun,ZHOU Yang,KANG Yili,DOU Liandong,CHENG Qiuyang   

  1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China
  • Received:2019-07-09 Online:2020-02-04 Published:2020-02-26

Abstract:

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 shale, 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 Fe2O3, Fe(OH)3, siderite(FeCO3), calcium sulphate dihydrate(CaSO4·2H2O), MgSO4 and BaSO4, 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.

Key words: shale, oxygen sensitivity, formation damage, reductive minerals, particle migration, oxidation-reduction potential

CLC Number: 

  • TE37