CEMENTING PRACTICES IN COALBED GAS WELLS IN JINCHENG AREA OF QINSHUI BASIN

Cementing quality in the coalbed gas wells in south Qinshui Basin is very poor. This paper investigates the causes that influence the cementing quality in this area, e.g., inefficient mud displacement caused by high fluid column pressure in annular and "U" tube effect; excessive fluid loss of cement slurry because of high differential; changes of slurry density, and improper field cementing operation, etc. Based on the analysis and in combination with the characteristics of coalbed gas reservoir, some measures are taken in the following cementing jobs. Such as use lightweight cement slurry, control fluid loss, raise viscosity and shear force, displace with low flow rate in slow return velocity, and maintain even density distribution. Cementing quality is highly improved in this area.