Damage Evaluation Of Fractured Tight Sandstone Reservoirs In Kuqa Piedmont Of Tarim Oilfield

Fractured tight sandstone reservoirs is characteristic of developed natural factures which lead to lost circulation of working fluid and induce formation damage.In order to study the damage rule and mechanism of working fluids on fractured tight gas reservoirs,based on Kuqa piedmont of Tarim oilfield which is a fractured tight sandstone reservoir,we carried out dynamic damage evaluation experiments of drilling fluid and fracturing fluid.The results show that the dynamic damage degree of drilling fluid is range from 27.99% to 82.43%.It is affected by crack width,surface roughness and solid particle size.The main causes of damage to the fractured reservoir include solid-phase particle plugging,emulsion plugging,wettability inversion and liquid phase trap.For the conventional fracturing fluid,its gel breaking time is short and content of residue is low and gel breaking liquid damage degree is range from 28.69% to 28.69%.For the KCl weighting fracturing fluid,it is difficult to break and gel breaking time is long.The residue content of KCl weighting fracturing fluid is higher,and gel breaking liquid damage degree is range from 40.54% to 46.22%.Using shielding temporary plugging technology can effectively reduce the volume of drilling fluid losing into the fractured reservoir.The experiment proved that adding 4% compound temporary plugging material into the current oil-base drilling fluid doesn't impact the performance of drilling fluid.The optimizing temporary plugging materials can improve the core permeability recovery value to a certain extent.