Development Of High-Temperature Resistant And Environment-Friendly Polysaccharide Polymer Filtrate Reducer For Drilling Fluid

In oil and gas drilling engineering,as the drilling depth continues to increase,the bottom hole temperature rises accordingly.Under high temperature and harsh environment,the drilling fluid treatment agent is prone to degradation and failure,resulting in performance failure such as filtration loss of the drilling fluid,and it is very easy to induce complicated downhole accidents.Therefore,it is particularly important to control the filtration loss performance of drilling fluid under high temperature.At the same time,with the increasingly stringent requirements of environmental protection laws and regulations,the development of green and environmentally friendly drilling fluid treatment agents is of great significance to the protection of the environment.Sugar polymers have a wide range of sources,are low in cost,and are easily biodegradable.Based on the molecular structure characteristics of carbohydrate polymers and combined with the high-temperature filtration loss performance requirements of drilling fluids,this paper intends to develop a high-temperature resistant and environmentally friendly filtration loss reduction agent to meet the requirements of safe and environmentally friendly drilling engineering under high temperature conditions.Compared with linear polymers,branched polymers have better temperature resistance.For this reason,natural branched polysaccharide SD-HP is preferred as a filtration loss control agent for water-based drilling fluids.Performance evaluation shows that after adding 1%SDHP to the bentonite base slurry,the rheological properties will be stable after 160℃ hot rolling,and the API filtration loss reduction rate can reach 76%,which is significantly better than the traditional modified cellulose and starch filter reduction Lost dose.At the same time,SD-HP has excellent shear thinning,shale hydration inhibition,salt resistance and calcium pollution resistance,showing the characteristics of "one dose and multi-function".SD-HP improves the colloidal stability of the system by adsorbing on the surface of clay particles,and reduces filtration loss by reducing the free water content of the system,physical blocking and viscosity increasing.With SD-HP as the key treatment agent,an environmentally-friendly water-based drilling fluid formula with a temperature resistance of 150°C is constructed,with excellent comprehensive performance,non-toxic and easy to degrade.In order to expand the use temperature range of carbohydrate polymers in drilling fluids,β-cyclodextrin is used as a raw material,preferably a cross-linking agent,and β-cyclodextrin polymer microspheres(β-CDPM)were prepared by inverse emulsion polymerization,with an average particle size of 50.46 μm.Performance evaluation shows that β-CDPM exhibits significantly different performance characteristics from traditional filtration loss additives.When the hot rolling temperature is lower than 160°C,β-CDPM has better filtration loss reduction performance;when the hot rolling temperature is higher than 160°C,the filtration loss reduction performance of β-CDPM does not decrease,but further improves.After adding1%β-CDPM to the bentonite base slurry,the API filtration loss reduction rate after 240℃ ultrahigh temperature action is as high as 61.73%,and the high temperature and high pressure(200℃/3.5 MPa)filtration loss reduction rate reaches 54.26%.β-CDPM also shows excellent filtration loss reduction performance in typical high temperature resistant water-based drilling fluids.Studies have shown that β-CDPM undergoes a hydrothermal carbonization reaction when the temperature exceeds 160°C,and the microspheres are partially degraded and destroyed,forming micro-nano carbon particles,which form a reasonable particle size gradation with clay particles,effectively controlling the ultra-high temperature environment Under the filtrate loss wall-making property.β-CDPM exhibits a unique mechanism of filtration loss reduction,realizing the transformation of ultra-high temperature damage to the treatment agent structure into favorable conditions for improving filtration loss.This idea provides a reference for the future development of new environmentally friendly anti-high temperature filter loss reducer.