Studies On The Gel Breaking And Modification Of Guar Gum For Fracturing In Oilfield

In this paper,based on investigation and analysis for properties of guar gum,using GMH-1,GMH-2,GMH-3 as modifiers,chemical modified guar gum was obtained.The optimal modification conditions of the three modification reactions were determined by orthogonal and single factor analysis experiment.On this basis,the structure of the optimal modified products was characterized,and relative performance in fracturing fluid was evaluated.Meanwhile,a micro fluidized-bed unit was designed and set up to prepare capsule gel breaker with certain slow-release properties,then the physical and chemical properties were analyzed and performance was evaluated.Summarized as follows:(1)The guar gum of chemical modification was obtained with GMH-1 as a modifier,the apparent viscosity and insoluble substance content in water were regarded as synthetical evaluation index,by orthogonal and the single factor analysis experiment,the optimum synthesis conditions were determined as follows: the temperature is 35.0?,the reaction time is2.0h,the addition amount of Na OH is 2.0%(based on the mass fraction of guar gum),and addition amount of GMH-1 is 0.2%(based on the mass fraction of guar gum).(2)The guar gum of chemical modification was obtained with GMH-2 as a modifier,the apparent viscosity and insoluble substance content in water were regarded as synthetical evaluation index,the optimum synthesis conditions were determined as follows: the temperature is 55.0?,the addition amount of Na OH is 0.9%(based on the mass fraction of guar gum),the addition amount of GMH-2 is 5.7%(based on the mass fraction of guar gum),and the reaction time is 2.0h.(3)The guar gum of chemical modification was obtained with GMH-3 as a modifier,the apparent viscosity and insoluble substance content in water were regarded as synthetical evaluation index,the optimum synthesis conditions were determined as follows: the addition amount of Na OH is 0.1%(based on the mass fraction of guar gum),the temperature is 40.0?,the addition amount of GMH-2 is 0.9%(based on the mass fraction of guar gum),and the reaction time is 2.5h.The apparent viscosity of 0.6% aqueous solution(m/v)of three groups of modifiedproducts are 125.3,127.4,124.6m Pa.s,the water insoluble matter are 5.1,4.4,4.7%,compared with the guar gum(89.3 m Pa.s and 12.4%),which have been enhanced significantly.The performances in fracturing fluid showed that,compared with the guar gum,the effectiency of three modified products all have been improved.(4)The micro fluidized-bed unit has been designed and set up.Its main technical performance parameter are 0.1kg/h(output),DR =8.0cm(diameter of fluidized-bed),10.0cm(height of fluidized-bed),H=56.0cm(height of fluidized-bed reactor).The gel breaker capsule products(H-1,H-2)have been produced,and the evaluation results showed that effective content of the products(H-1,H-2)are 82.0%,79.0%,the embedded rate are 94.9%,93.3%,and the release rate are 57.0%,71.0%(30.0?,60.0min),88.0,86.0%(50.0?,60.0min).Gel-breaking performance evaluation results showed that gel breaker capsule products(H-1,H-2)all have certain slow-release gel breaking properties,and H-1 is better.