渤钻低密度固井水泥浆降低煤层气储层伤害的实验

Experimental research on decreasing coalbed methane formation damage by using low density cement slurry

针对煤层气井传统的固井水泥密度较大,在固井过程中产生较大压差,影响半径较大,且滤液成分矿化度较高,持续对储层产生伤害的问题,通过对比渤海钻探所使用的低密度固井水泥浆(统称渤钻浆)和常规固井水泥浆的失水量、滤液性能和稠化时间,并通过分析其滤液成分、电导率、渗透率回复率和计算污染半径,评价了渤钻浆降低煤层气储层伤害的能力。结果表明:渤钻浆失水量比常规固井水泥浆小一半,并且滤液黏度高、矿化度低和电导率低,使渤钻浆污染的煤样渗透率降低为28.97%(常规水泥浆污染的煤样渗透率降低为65.87%),渗透率恢复率为89.81%(常规水泥浆渗透率恢复率为61.18%)。综合来看渤钻浆不仅密度低,形成压差小,保证煤层稳定,还减小污染半径,降低了对煤层气储层的伤害。

By comparing the loss of water, the filtrate performance and thickening time of low density cement slurry used in Bohai Drilling (hereafter called as Bohai drilling slurry) and conventional cement slurry, through analyzing their composition, conductivity, permeability response rate, the paper calculates the pollution radius, evaluates the ability of Bohai drilling slurry to reduce the damage of CBM reservoir. The results showed that water loss of the Bohai drilling slurry was 50% less than that of the conventional cement slurry .And filtrate viscosity is high, salinity is low and conductivity is low. So the permeability of coal contaminated by Bohai drilling slurry was reduced to 28.97%, the recovery rate of permeability was 89.81%, while the permeability of coal contaminated by conventional slurry was reduced to 65.87%, permeability recovery rate was 61.18%. With the integrative consid-eration, Bohai drilling slurry is not only low-density, which forms small pressure and ensures stable coal, but also reduce pollution radius and the coal reservoir damage.