Reducing Formation Damage to Low-Porosity and Low-Permeability CBM Reservoirs Using Calcium Carbonate Nanoparticles
Abstract：It’s difficult to block a mass of nanoscale pores in the low-porosity and low-permeability coalbed methane (CBM)res-ervoirs using traditional temporary plugging additives.The performances of reducing formation damage to low-porosity and low-permeability CBM reservoirs using calcium carbonate nanoparticles (nCaCO3 )are evaluated in this study through micro-scope investigation of coal rocks,the basic performance tests of drilling fluid,mud cake removal tests,pore size distribution tests and gas permeability tests of coal rocks.It is found that only when nCaCO3 are dispersed to nano-scaled state in water solution could it temporally plug the low permeability coal rocks.However,nCaCO3 based degradable drilling fluid not only blocks the microscale pores in low-porosity and low-permeability coal rock,but also blocks the nanoscale pores.With the double unplugging technology of biological enzyme plus low concentration hydrochloric acid on the nCaCO3 based drilling fluid,the permeability recovery rate of coal rocks ranges from 77.17% to 97.98%.The reservoir protective effect on reservoir proves good.It is shown that the pore size distribution test could be used in the investigation on temporally plugging performance of nanoparticles to low-porosity and low-permeability reservoirs on nanoscale.This study may offer a technical support to facilitate future applications of nCaCO3 in drilling and completion process of low porosity and low permeability coal seams and shale formation.
Keywords：calcium carbonate nanoparticles (nCaCO3 )low-porosity and low-permeability CBM reservoirstemporally plug-gingreservoir protectiongas permeabilitypore size distribution
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 1093-1100 )