Development Of New Gel Plugging Agent And Its Application In Workover Fluids

With the deepening of the oil and gas exploration,the frequency of the leakage problem is more and more high.Due to the existence of leakage of workover fluid from the wellbore through leakage channels into the formation,it not only leaded to great loss of time,manpower and financial resources,but also caused great damage to the reservoir,destroyed the balance of the formation,oil production efficiency decreased significantly.In view of this,the paper achieved optimization of a new gel plugging agent formula and gel breaking agent formula and evaluated the new gel plugging agent plugging performance,strength performance,provided a reference for the application of a new type of gel plugging agent in workover fluid.Based on the scientific research on plugging technology and plugging materials at home and abroad,the completion of the research work are as follows:(1)using single factor analysis method,combined with visual qualitative method and quantitative method of micro rheometer,considering initial pumping,gel time,gel strength and stability after the transaction,the new gel plugging agent formulation was optimized;(2)calculating the rate of gel breaking by measuring the residual gum block quality,optimizing breaker concentration by regarding gel breaking rate as the standard;(3)using a suitable instrument to evaluate shear dilution,plugging performance,anti water ability,strength and other properties of new gel plugging agent.The indoor test shows that between 90?-120?,gelling time can be controlled to less than 5h,and with the increase of polymer concentration,crosslinker concentration increase and temperature rise,the gelling time is reduced,the strength increased;at the same time in the system of salt solution has delayed gelling effect,with the increasing of salt concentration,the gelation time increased and gel strength increased first and then decreased.Through the optimization of the concentration of the gel breaker,the gel breaking rate of the new gel plugging agent can reach more than 95%.The new gel plugging agent has the advantages of good shear dilution and water resistance,and the filtration loss is far less than 10% of the gel base liquid,and the blocking ability is high and the temperature resistance is above the temperature of 120?,and the pressure is more than 3.5MPa.The field test of G28-12 well shows that the new gel plugging agent can meet the requirements of "blocking and releasing",and the plugging effect is remarkable,and the gel breaking rate is high.