Research And Application Of Low Permeability Sandstone Reservoir Protection

The sandstone reservoirs with low permeability have special geological features,usually,they have following conditions:tight rock layers,narrow channels,low porosity,low permeability and water saturation,strong hydrophilicity,strong heterogeneity,high capillary pressure,abnormal pressure and cracks?micro fracture exist,rock hydrophilic,water intrusion caused by the water trap,reservoir heterogeneity,deep burial,high temperature,high pressure and abnormal high pressure wells exist widely.This type of reservoir is highly vulnerable to infringement of drilling fluid and difficult to recover.The damage of low permeability sandstone reservoirs include : incompatibility between external fluids and reservoir rock minerals,incompatibility between external fluids and reservoir fluids,damage caused by solid particle plugging,blockage caused by capillary phenomenon.The damage caused by liquid invasion is more serious than solid plugging.At present,a temporary plugging type polymer drilling fluid technology,strong inhibition and low solid drilling fluid system and gas drilling fluid technology have been applied both at home and abroad for low permeability reservoir protection measures of sandstone reservoir.these reservoir protection drilling fluid technologies have achieved excellent results in practical application.Low permeability sandstone gas reservoir is very sensitive in the process of drilling operation,which results in reducing the productivity of oil and gas well.In view of these complex conditions,We take the Shenmu area as the research object and conduct a series of researching work,including the reservoir protection investigation and evaluation of drilling completion fluid which has been used in Shenmu block,study reservoir damage mechanism and develop a shielding plugging agent appling to potassium polysulfonate drilling fluid,optimization of the low damage drilling fluidsystem and the evaluation of reservoir protection effect on the drilling and completion fluids using on site.We develope a suitable potassium polysulfonate drilling fluid shielding temporary plugging agent,put forward the method to evaluate the protective effect by the reservoir permeability recovery experiment,relative permeability experiment combining with numerical simulation.After these works,an effective drilling completion fluid technology for reservoir protectionthe comes out,which has important guiding significance for the design scheme and efficient development of Shenmu block.