On Oil Recovery Mechanisms and Potential of DME–Brine Injection in the North Sea Chalk Oil Reservoirs

Abstract

North Sea tight chalk oil reservoirs are well-known for their submicron pore throat sizes and heterogeneous porosity pattern that includes fractures and microfractures. The host rock of these reservoirs is extremely sensitive and can easily react with the injected fluid, which in turn adversely affects the permeability and thus injectivity. The combined effect of these parameters makes oil production in chalk reservoirs extremely difficult. A novel solvent-based enhanced oil recovery (EOR) method that can address these issues is investigated for the first time in the chalk reservoirs. We thouroughly investigate the oil recovery potential and dominant oil recovery mechanisms by dimethyl ether (DME)−brine injection under conditions pertinent to the North Sea tight chalk oil reservoirs. A series of systematically designed high-pressure and high-temperature flooding experiments were carried out using reservoir core and crude oil. The experimental results revealed the strong oil recovery potential of tertiary DME−brine injection with two different DME contents. Furthermore, both secondary and tertiary DME−brine injection scenarios significantly improved the oil recovery with the better performance in the secondary scenario. The results show that the dominant oil recovery mechanism is rapid and strong oil swelling is caused by the preferential partitioning of DME into the oil phase. During DME−brine injection, no indications of rock mineral dissolution and adverse effects on rock permeability were observed. This is one of the advantages of this method over CO 2 , CO 2 −water alternating gas (WAG), and alkaline injections in which the EOR agent causes calcite dissolution, wormhole formation, and scaling issues in fragile chalk reservoirs.

Investigating the Effectiveness of Phosphonate Additives in Hindering the Calcium Sulfate Dihydrate Scale Formation

“…Mineral scale formation is a major problem in many industrial processes such as crude oil production, reverse osmosis desalination, cooling systems, papermaking, etc. [1][2][3][4] These unfavourable minerals that usually deposit in pipes, membranes, heat exchangers, and mixing tanks cause a considerable reduction in fluid flow and blockage of the pipelines, and other equipment, together with other consequences like corrosion. [5][6][7][8] There are various types of minerals that form scales.…”

Numerical modeling of water-soluble solvents for enhancing oil recovery in heterogeneous chalk reservoirs

“…Moreover, the presence of DME reduces the water-oil interfacial tension, which can cause the formation of a stable water-oil emulsion. We could not observe this behavior (i.e., a constant large pressure drop) in our own DEW flooding experiments (for this range of DME concentration in the injected water), conducted on the chalk cores from the Danish sector of the North Sea (Javanmard et al, 2018).…”

“…DME is miscible with oil and due to its slight polarity, it also can be dissolved in water, which makes it an attractive candidate for tertiary recovery as an additive to the injected water. DME enhanced water-flooding (DEW) is a novel EOR technique, first introduced by Shell (M. Chernetsky et al, 2015;Parsons et al, 2017), that can significantly increase the oil recovery (Chahardowli et al, 2013;Mohammad Chahardowli et al, 2016;Javanmard et al, 2018;Riele et al, 2016). Initially, water flooding is performed to produce oil from a virgin reservoir (Figure 1, Step 2).…”

“…DEW flooding can be applied to both Carbonate (M. Javanmard et al, 2018) and Clastic reservoirs (M. regardless of rock permeability (Groot et al, 2016a). It can also be implemented as tertiary or part of secondary recovery processes (Chernetsky et al, 2015).…”

Compositional Modeling of Dimethyl Ether–CO2 Mixed Solvent for Enhanced Oil Recovery

“…Additionally, DME can be extracted from the produced fluid and reused through distillation and adsorption processes [14]. DME was first introduced as a solvent for EOR by Shell [15][16][17][18], and this method has proven effectiveness in improving oil recovery [14][15][16][19][20][21]. Recent research on DME in the field of EOR has focused on modeling and experiments of the DME-water-oil phase behavior or studies modeling the core scale [15,16,[21][22][23][24][25].…”