Experimental Study on Medium Viscosity Oil Displacement Using Viscoelastic Polymer

Abstract

With the growing demand for oil energy and a decrease in the recoverable reserves of conventional oil, the development of viscous oil, bitumen, and shale oil is playing an important role in the oil industry. Bohai Bay in China is an offshore oilfield that was developed through polymer flooding process. This study investigated the pore-scale displacement of medium viscosity oil by hydrophobically associating water-soluble polymers and purely viscous glycerin solutions. The role and contribution of elasticity on medium oil recovery were revealed and determined. Comparing the residual oil distribution after polymer flooding with that after glycerin flooding at a dead end, the results showed that the residual oil interface exhibited an asymmetrical “U” shape owing to the elasticity behavior of the polymer. This phenomenon revealed the key of elasticity enhancing oil recovery. Comparing the results of polymer flooding with that of glycerin flooding at different water flooding sweep efficiency levels, it was shown that the ratio of elastic contribution on the oil displacement efficiency increased as the water flooding sweep efficiency decreased. Additionally, the experiments on polymers, glycerin solutions, and brines displacement medium viscosity oil based on a constant pressure gradient at the core scale were carried out. The results indicated that the elasticity of the polymer can further reduce the saturation of medium viscosity oil with the same number of capillaries. In this study, the elasticity effect on the medium viscosity oil interface and the elasticity contribution on the medium viscosity oil were specified and clarified. The results of this study are promising with regard to the design and optimum polymers applied in an oilfield and to an improvement in the recovery of medium viscosity oil.

Capillary Desaturation Tendency of Hybrid Engineered Water-Based Chemical Enhanced Oil Recovery Methods

“…However, our paper shows that by combining PF with low-salinity ion-tuned water, a considerable reduction in S or is possible for lower N c values. The conventional PF in the studies of Zhong et al [118], Qi et al [117], and Clarke et al [119] lowers the S or by 25-40% for capillary numbers ranging from 1.5 × 10 −4 to 3.1 × 10 −2 . The hybrid EWPF, on the other hand, has reduced the S or by 27% for a relatively lower capillary number range from 4.0 × 10 −6 to 4.5 × 10 −5 .…”

“…Three coreflood tests were performed for hybrid EW-polymer flooding (EWPF) design. The residual oil saturation as a function of capillary number for the three cases is plotted in Figure 4, along with conventional PF CDCs extracted from various studies [117][118][119]. The hybrid EWPF experiments have recovered more residual oil compared to conventional tests.…”

“…For each hybrid EW-CEOR design, the corresponding typical capillary desaturation curves are collected from the literature. The studies consulted for polymer flooding [117][118][119], surfactant flooding [120,121], alkali-surfactant flooding [122], surfactant-polymer flooding [90], and alkali-surfactant-polymer flooding [123,124] are summarized in Table 2. Almost all of the studies were performed on sandstone cores, and we used the sandstone CDC curves to compare our hybrid designs performed on carbonates.…”

“…Basic conditions promote HPAM viscoelastic behavior, causing a reduction in S or . Recently, some researchers have suggested that S or can be reduced by using viscoelastic polymers as they can strip off the trapped oil from pore throats and walls [118,[129][130][131][132][133][134][135][136][137]. However, this discussion is beyond the scope of the current paper.…”

Relationship between the Molecular Coil Dimension and the Energy Storage Modulus of Polymer Solution Configured with Oilfield-Produced Sewage

“…With the gradual expansion of the application scale of polymer flooding and composite system, the water resources used for the preparation of the polymer solution are becoming increasingly tense; at the same time, a large number of produced water bring great pressure on environmental protection [1][2][3][4]. e viscoelastic properties of the polymer solution are the key factors affecting oil recovery and the type of residual oil [5][6][7][8][9]; the test results of the geometrical form of the polymer molecules in the polymer system configured with the treated sewage directly affect the polymer system and the pore adaptability, thereby affecting the microscopic residual oil use effect [10][11][12][13][14]. In this paper, the use of oilfield-produced sewage to prepare the polymer solution has become an inevitable choice for the oilfield production.…”