Synthesis and Evaluation of a High Strength Curable Resin LCM PMMM

Severe loss of borehole working fluids into fractured formations is one of the major technical problems encountered in oil and gas drilling engineering. Curable resin and downhole crosslinking polymers are common lost circulation materials (LCMs) used for controlling this kind of loss. However, these LCMs are difficult to control in downhole crosslinking reaction and the cured LCMs have low strengths. This paper describes PMMM, an amino resin modified through partial etherification. Using Raman spectroscopy, the molecular structure of PMMM was analyzed and the mechanism of curing of the resin revealed. The time for PMMM to cure is shortened with increase in the concentration of curing agent or time, and can be controlled in a range of 1-10 h at temperatures between 80 ℃ and 130 ℃. PMMM will not shrink after curing, and is resistant to the contamination by maximum 10% water based mud. The compressive strength of PMMM which is treated with nano CaSO₄ whickers, first increases and then decreases with increase in the concentration of the CaSO₄ whiskers. PMMM treated with 0.5% nano CaSO₄ whiskers has a maximum compressive strength of 56 MPa after aging at 80 ℃ for 24 hours, which is higher than the same compressive strength of conventional cement LCMs. Using viscosity data gathered at temperatures between 100 ℃ and 130 ℃ and the revised Arrhenius viscosity equation, a viscosity-temperature-time equation was obtained through data fitting. Change of viscosity at 90 ℃ predicted with this equation coincides with the data measured, indicating that the fitted equation can basically be used to predict the viscosity change of PMMM when heated. All in all, the curable PMMM resin LCM has many advantages such as easy to formulate, curing condition controllable and high compressive strength after curing etc. PMMM LCMs can be a good choice in dealing with severe lost circulation.