Study and Application of Pre Crosslinking Gel Particle- Polymer Compound Deep Profile Control and Flooding Technology in Offshore Heterogeneous Reservoirs

Abstract

Aiming at the problems of enhanced reservoir homogeneity, severe injection water breakthrough and low oil production after polymer flooding in Bohai B oilfield, through laboratory research and evaluation, two heterogeneous composite systems: FJX-1 and FJX-2 were optimized, and the profile control and profile control performance evaluation, and displacement efficiency analysis of heterogeneous combination flooding in high water cut stage after polymer flooding in offshore oilfield have been studied. The results show that the plugging efficiency of polymer, FJX-1 and FJX-2 compound profile control and flooding systems are 61.42%, 83.45% and 93.17% respectively. The composite viscosity and elastic modulus of FJX-2 profile control and flooding system are better than those of polymer and FJX-1 profile control and flooding system, indicating that its plugging performance and viscoelastic performance are the best. Compared with the fluid flow diversion ability, after injection of polymer with FJX-1 and FJX-2 composite system, the liquid production fraction ratio of high and low permeability layers decreased from 87:23, 89:21, 88:12 to the lowest 61:39, 48:52 and 35:65, respectively. In the subsequent water flooding process, after FJX-2 composite profile control, the liquid yield ratio of high and low permeability layers in core can still reach 66:34, which indicates that the plugging effect of FJX-2 composite profile control and flooding system for high permeability layers is obvious. From the oil displacement experiment, it can be seen that the lowest water cut of the three systems in the process of water flooding is 54.58, 52.97 and 44.39, respectively. After polymer flooding, the oil recovery can be increased by 6.32% and 11.84% respectively to continue FJX-1 and FJX-2 composite profile control flooding. The case comparison shows that the best combination of profile control and profile control slug is profile control (1500 mg/L PL + 1500 mg/L JLJ) + profile control (1500 mg/L RY + 300 mg/L PPG). The profile control and displacement performance of heterogeneous composite system can not only make use of crude oil in medium and low permeability reservoirs, but also exert displacement effect on some crude oil remaining in reservoirs through effective plugging of high permeability reservoirs. At the same time, field tests also show that heterogeneous composite flooding has broad prospects for development in offshore oilfields. The profile control and displacement performance of heterogeneous composite system can not only put crude oil in medium and low permeability reservoirs to be used, but also some crude oil remaining in the reservoir can be displaced through effective plugging of high permeability reservoirs. At the same time, field tests also show that heterogeneous composite flooding has broad prospects for development in offshore oilfields.