Investigation of synergistic inhibition effect of hydrate inhibitors and paraffin inhibitors on hydrate formation

•The evaluation method of the synergistic inhibition effect of hydrate inhibitors and paraffin inhibitors was established.•The compatibility experiments of hydrate inhibitors and wax inhibitors were systematically conducted.•The combination of 0.2 wt% PI and 1 wt% PVCap has the best synergistic effect on reducing hydrate nucleation and growth rate.•The combination of 0.2 wt% PIvb and 0.2 wt% DDBAB has the best synergistic effect on reducing hydrate adhesion and aggregation strength. The flow obstacles caused by hydrate and wax deposition with the development of oil and gas, the co-injection technique of hydrate inhibitors and paraffin inhibitors have attracted much attention. However, the compatibility studies between the two inhibitors are lacking. This work established the test technique to evaluate the synergistic inhibition effect of hydrate inhibitors and paraffin inhibitors on hydrate formation. The screening and evaluation experiments of eleven hydrate inhibitors and two paraffin inhibitors were conducted respectively. The results illustrate that the PVCap, PVP and PEG of KHIs have better inhibition performance in prolonging hydrate induction time, the DDBAB, CEDA and PKOC of AAs have better inhibition performance in decreasing hydrate aggregation, the PI and PIvb have better inhibiting performance on paraffin and hydrate prevention. The combinations of paraffin inhibitors and KHIs significantly prolong induction time and inhibit hydrate growth, the induction time increased by 96.3% when PI coexists with PVCap, and the growth rate decreased by 79.3% when PEG coexists with PI. The combinations of paraffin inhibitors and AAs show the synergistic inhibition effect on hydrate growth and aggregation, the growth decreased by 83.2% and the bulk hydrate form into smoothies when PIvb coexists with DDBAB. The combination of paraffin inhibitors and hydrate inhibitors also enhances the paraffin inhibitory. On this basis, we propose two co-injection schemes of hydrate inhibitor and paraffin inhibitor for flow assurance. The first scheme is the combination of 0.2 wt% PI and 1 wt% PVCap, and the second scheme is the combination of 0.2 wt% PIvb and 0.2 wt% DDBAB. This work provides references for the optimization of inhibitor dosage design in natural gas safety production.