Research On Rruse Technology Of Horizontal Well Water-based Drilling Fluid In Weiyuan Area

As the drilling field tends to expand and the depth of drilling tends to deepen,the amount of abandoned drilling fluids increases rapidly.Improper disposal of abandoned drilling fluids not only results in extreme abandoned of water resources,but also causes pollution to groundwater and soil,which causes serious damage to the natural environment.This paper focuses on the reuse of abandoned water-based drilling fluids.The performance parameters of the drilling fluid were measured using instruments such as ambient temperature and pressure dilatometer,solid content analyzer,and extr eme pressure lubricator.The research method such as XRD,atomic absorption spectro metry,and laser particle size distribution were used to analysis the shale gas well wat er-based drilling fluid system(calcium-containing)used in the Sichuan Weiyuan area.The reason account for the failure of the water-based drilling fluid was revealed throu gh the physicochemical characteristics and microscopic chemical analysis.The technical procedure that colloidal destruction-flocculation-centrifugation was used to carry out th e solid-liquid separation of the drilling fluid.Then,take the separated liquid and solid phases for the preparing of drilling fluids.Therefore,the reuses of the drilling fluids were obtained.The instruments such as ultraviolet spectrophotometers were used to determine the colloidal destruction performance of the colloidal breaker such as sodium hypochlorite and sodium persulfate.In addition,the flocculation performance of the flocculant such as polyaluminum chloride and polyethylenimine were obtained.The results showed that the best colloidal breaker for drilling fluid is aluminum sulfate and the optional addition amount is 1.00%.In order to achieve the colloidal destruction of the drilling fluid in effective,the pH is supposed to between 7.0 and 7.5.The preferred flocculant for drilling fluid is a combination of 0.10%polyaluminum chloride and 0.02%polyethylenimine.The corresponding oil removal rate is 90.3%,and the removal rate of the suspended material content is 96.0%.The mechanism of aluminum sulfate collapsing is the action of compressive double layer and the role of sediment volume sweeping and trapping.The flocculation mechanism of flocculant polyaluminum chloride and polyethylenimine includes the neutralization of adsorption,the action of precipitation sweeping,and the adsorption and bridging.The method of ion composition analysis was used to study the rationality of the liquid phase of the abandoned drilling fluid used for new drilling fluids.The liquid phase separated from the water-based drilling fluid was used to preparing the base drilling fluid,polymer drilling fluid,polysulfonic acid drilling fluid,and shale gas horizontal well water based drilling fluid.The performance of the drilling fluid is close to that of the corresponding drilling fluid configured with clean water,indicating that the liquid phase after the separation of the water-based drilling fluid could be reused to preparing the drilling fluid.After treatment,the solid phase of the failure drilling fluid has a barite content of 93.16%,a quartz content of 6.07%and very small amount clay of 0.77%.Therefore,it can be concluded that the solid phase of the water-based drilling fluid after treatment can be used as a weighting material to produce drilling fluid.