Reservoir Protection Technology For Fractured Tight Sandstone Of Sulige Gasfield

Fractured tight sandstone gas reservoir with low porosity,low permeability,small pore throat,and natural fracture development.In addition,the clay mineral is rich.There are different formation damage of sensitivity damage,water-locking damage,leakage of drilling fluid filtrate and solid invasion.It seriously hindered the tight gas economic and effective development.The eastern of Sulige gasfield in ordos basin is rich in tight gas production,which is a typical fractured tight sandstone reservoir with serious formation damage.In this paper,the damage mechanism of fractured tight sandstone reservoir is revealed,and the drilling fluid production technology of fractured tight sandstone reservoir is carried out.Reservoir physical property,pore permeability structure and fracture characteristics were researched.Low solid polymer drilling fluid system,core sensitivity and water locking damage mechanism and damage mechanism of solid phased particles was evaluated.Revealing the fractured reservoir damage mechanism.Based on the damage mechanism of reservoir,the countermeasures of reservoir protection drilling fluid are proposed.Based on the countermeasures of the reservoir protection drilling fluid of the fractured tight sandstone,the strong inhibition of amido-cyanogen silanol inhibitor is selected.High acid soluble asphalt,lignite resin were selected as anti-collapse agents to reduce the high temperature and high pressure filtration loss.FCSA-1 anti-waterlock agent is selected,which is belong to fluorocarbon surfactant.It is extremely low surface tension and hydrophobic and oleophobic properties.The high-acid soluble shielding temporary plugging agent,high-acid soluble whisker material and deformation particles were selected and developed.In view of fracture loss,the materials such as rigid particle,high-acid soluble fiber and high-acid soluble asphalt,DF-1 and walnut shell were selected and developed.Low solid and high-performance temporary plugging reservoir protection drilling fluid system was developed,and it has moderate viscosity and shear force.High temperature and high pressure filtration volume(120?/3.5MPa)is small,and good lubrication performance,high acid soluble rate of mud cake,system inhibition performance is good,good performance of water lock preventing property.The permeability recovery value is over 80% after pollutes the core of tight sandstone,and the invasion depth is less than 1cm.For micro-cracks with the opening less than 200?m,the optimized drilling fluid system is high temporary plugging rate,and high core permeability recovery value after pickling.The formulas for lost circulation control of fractures with different opening of 1-3mm were optimized,with high pressure capacity and small loss voleum,also high acid dissolution rate.The application of field test well shows that the drilling complexity is reduced by 8 days,the reservoir wall collapse and well leakage are solved well,the reservoir protection effect is good and the output is improved.Compared with the adjacent Wells,the initial gas production increased by 40.4%,and the gas production increased by 29.8% after fracturing.The reservoir protection effect was significant.