Study of cross-linking modification for SP tree gum and its application as mud additives

To improve the water solubility and viscosity of tree gum (SP) solution, a new material (SP-1) was developed with SP tree gum as main agent and epichlorohydrin as crosslinker. It was analyzed by the means of DSC curves which showed the phase transformation temperature of SP and SP-1 appeared at 159 ℃ and 156.17 ℃ respectively, indicating the decrease of the hydroxyl amount of SP-1 from that of SP. The optimum reaction conditions were determined by the orthogonally designed experiment and the error analysis. The optimal conditions were found as follows, the mass ratio of the crosslinking agent to SP as 56.40 g/100 g, the pH as 10 and the temperature as 50 ℃. The experiment results showed that comparing to SP, SP-1 have better water solubility, with the viscosity enhancing ratio as 116.7% and the filtration reduction ratio as 30%. While in drilling fluids, the viscosity enhancing ratio of SP-1 was 160% and the filtration reduction ratio was 53.2%. When the aging temperature range between 30 ℃ and 120 ℃, the temperature had a slight effect on rheological properties of SP-1 based drilling fluids, and the API reduction kept below 15 mL. The mud ball immersing experiment results show that SP-1 has an excellent inhibitive to hydration and swell of the mud and shale.