Study on the Profile Control and Oil Displacement Mechanism of a Polymer Nano-microsphere for Oilfield

Abstract

In this study, the mechanism of migration/plugging and the main performance of polymer nano-microspheres (HQ) were investigated using environmental scanning electron microscopy (ESEM), swelling hydration experiments, sand-filling pipe flooding experiments, and microscopic displacement experiments. Results show that the swelling ratio of HQ in salt solution first increases and then reaches equilibrium with the increase in swelling time. The expansion ratio of HQ increases rapidly at the initial stage of swelling and reaches its maximum value after swelling for 7 days. The maximum value of the expansion ratio was 15. In addition, the higher the salinity, the smaller the particle size of the studied microspheres. The particle size of the microspheres increases with increasing temperature. According to the visualized microscopic experiments, the migration and blocking mechanism of microspheres in the pore throat were discovered. When the particle size is 1/3–1/7 times the pore throat diameter, the microsphere particles can enter the interior of the pores. The microspheres aggregate together, and bridge plugging occurs due to the mechanical trapping of pore throats. In this case, the pore throats are blocked by the produced inner filter cake. The pressure at each point fluctuates up and down in a zigzag pattern during the displacement experiment, revealing the “migrated-plugged-breakthrough-replugged” mechanism for HQ. It can be seen from the oil displacement experiment that the final cumulative recovery and the enhanced oil recovery were 65.71 and 17.31%, respectively. Thus, the studied nano-microspheres have excellent oil displacement performance.

Pore-Scale Transport Dynamic Behavior of Microspheres and Their Mechanisms for Enhanced Oil Recovery

“…Channeling of the injected fluid due to reservoir heterogeneity will reduce the swept fluid volume and reduce oil recovery. , No matter whether conventional or unconventional reservoirs − or gas − or water injection, plugging the dominant channels and expanding the swept volume of the injected fluid are the developmental ideas throughout the whole process of oil and gas field development . Additionally, due to the influence of reservoir wettability, the injected fluid tends to invade the pore throats with the least flow resistance under the action of a capillary force, which will also lead to the formation of dominant channels. , Therefore, the optimal selection of profile control agents and the revelation of their transport and plugging mechanisms in porous media are the focus of research. − …”

Evaluation of Profile Control and Oil Displacement Effect of Starch Gel and Nano-MoS2 Combination System in High-Temperature Heterogeneous Reservoir

“…Gel systems block formations by swelling upon water absorption, but the gelation time is influenced by many factors, and the plugging measures become ineffective once water breaks through the gel layer, reducing the profile modification effect [16,17]. Polymer/nanomicrosphere systems need to be selected based on the actual pore sizes of the reservoir, and their plugging effectiveness in high-permeability channels is limited [18][19][20].…”

Effects Evaluation on Multiround Injection of a N2 Foam & Viscosity Reducer to Improve the Recovery of Fault-Block Heavy Oil Reservoir with Edge-Bottom Water: A Two-Dimensional Visualization Experimental Study

“…In fault-block reservoirs with bottom water and heavy oil, the bottom water is usually very active. During the oilfield development, there is a common issue of a rapid increase in water cut, which results in severe water channeling in production wells. , The development of such reservoirs is mainly limited by two factors: the effect of edge and bottom water and the influence of fault blocks. During the early stage of water flooding, edge and bottom water can effectively provide the driving force for reservoir development.…”