The effect of rock type on natural water flooding and residual oil saturation below free water level and oil water contact: A case study from the Middle East
Abstract:The presence of residual oil below the present day free water level (FWL) and oil water contact (OWC) is common in many fields of the Middle East. This residual oil is seen in reservoirs prior to the start of production.A rock typing study was carried out to investigate the effect of rock types on the presence and distribution of residual oil below the free water level (FWL) and oil water contact (OWC) and potential recovery from ROZ's following water flooding.The rock typing study was carried out by integrati… Show more
“…The results of coring well data show that the common sedimentary structures in the study area mainly include deformation structure, bedding plane structure, bedding structure and biogenic structure (Fig. 5 ) 22 . Figure 5 Analysis of Sedimentary characteristics of coring Wells.…”
Due to the poor situation of water-flooding mechanism research on Chang 4 + 5 reservoir of Ordos basin, the authors quantitatively studied the influence factors of water-flooding characteristics by sedimentology, casting thin sections, constant-speed mercury injection, scanning electron microscope as well as production records. The size and distribution of pore-throat were also found closely related with the water-flooding seepage law. The results show that the microscopic seepage paths of Chang 4 + 5 reservoir include uniform displacement, finger displacement and peak displacement, and their correspondent oil displacement efficiency reduces in turn under the same conditions. Reservoir heterogeneity, reservoir properties, distribution of pore structure and wettability play a decisive role in water-flooding efficiency. Generally, When the intra-layer range is greater than 4.65, the breakthrough coefficient is greater than 3.54, the coefficient of variation is greater than 0.7, the distribution frequency of inter-layer is greater than 0.5 per meter, and the distribution density is greater than 0.435%, the range between layers is greater than 6.86, the breakthrough coefficient is greater than 2.58, the coefficient of variation is greater than 0.51, and the thickness of inter-layer is greater than 7.54 m. the increasing trend of oil displacement efficiency will be obviously weakened.
“…The results of coring well data show that the common sedimentary structures in the study area mainly include deformation structure, bedding plane structure, bedding structure and biogenic structure (Fig. 5 ) 22 . Figure 5 Analysis of Sedimentary characteristics of coring Wells.…”
Due to the poor situation of water-flooding mechanism research on Chang 4 + 5 reservoir of Ordos basin, the authors quantitatively studied the influence factors of water-flooding characteristics by sedimentology, casting thin sections, constant-speed mercury injection, scanning electron microscope as well as production records. The size and distribution of pore-throat were also found closely related with the water-flooding seepage law. The results show that the microscopic seepage paths of Chang 4 + 5 reservoir include uniform displacement, finger displacement and peak displacement, and their correspondent oil displacement efficiency reduces in turn under the same conditions. Reservoir heterogeneity, reservoir properties, distribution of pore structure and wettability play a decisive role in water-flooding efficiency. Generally, When the intra-layer range is greater than 4.65, the breakthrough coefficient is greater than 3.54, the coefficient of variation is greater than 0.7, the distribution frequency of inter-layer is greater than 0.5 per meter, and the distribution density is greater than 0.435%, the range between layers is greater than 6.86, the breakthrough coefficient is greater than 2.58, the coefficient of variation is greater than 0.51, and the thickness of inter-layer is greater than 7.54 m. the increasing trend of oil displacement efficiency will be obviously weakened.
“…Akai et al [12] used direct numerical simulation to study the mechanism of microscopic displacement during enhanced oil recovery in mixed-wet rocks. Heydari-Farsani et al [13][14][15][16] proposed that the characteristics of reservoirs and structures can affect the location and migration direction of hydrocarbons. Liu et al [17] analyzed the mechanism and effect of nitrogen foam flooding using sand-packing pipe experiments to enhance oil recovery and concluded that high-porosity, highpermeability, and strong edge-water reservoirs entered the high water-cut stage in the middle and late development stages, with the remaining oil mainly distributed at the top and edge of the structure and reservoirs.…”
Oil saturation is a critical parameter when designing oil field development plans. This study focuses on the change of oil saturation during water flooding. Particularly, a meter-level artificial model is used to conduct relevant experiments on the basis of similarity principles and taking into account the layer geological characteristics of the reservoir. The displacement experiment's total recovery rate is 41.35%. The changes in the remaining oil saturation at a millimeter-scale are examined using medical spiral computer tomography principles. In all experimental stages, regions exists where the oil saturation decline is more than 10.0%. The shrinkage percentage is 20.70% in the horizontal well production stage. The oil saturation reduction in other parts is less than 10.0%, and there are regions where the oil saturation increases in the conventional water flooding stage.
“…The trajectory, thermodynamic properties, radial distribution function (RDF), time-related physical quantities, and free energy can be calculated accurately in the process of simulation [6]. The dispersion effect of modified SiO 2 nanoparticles was investigated to improve the practical production owing to the agglomeration of unmodified nanoparticles [7,8].…”
The dispersion characteristic of nanoparticles is of more interest in some engineering applications, including polymer filling, foam stability, chemical catalysis, and materials surface package. In this paper, the surface modification of SiO 2 nanoparticles was carried out based on molecular dynamics simulation. The characteristics of aggregation and diffusion of SiO 2 nanoparticles were explained by the radial distribution function (RDF), concentration profile, length distribution, mean squared displacement (MSD), and microscopic testing (MT). The results showed that the orbital provided by the three types of atoms (H, O, and Si) corresponding to the different bandwidths caused the energy alternation of state density. According to the results of RDF, the H O bond energy mainly provided by the water molecules showed the maximum bond energy with 463 kJ/mol. The results indicated that the bonds breakage and formation were accompanied by changes in total energy, kinetic energy, non-bond energy, and potential energy. After the modification of SiO 2 nanoparticles, the concentration profile of the water molecules decreased first at 1-8.5 Å and then increased at 8.5-17.2 Å, but the length distribution climbed to 15.7 at 0.975 Å.When the temperature reached 398 K, the peak value of the length distribution declined to 13.6 Å and the relative concentration profile of water molecules fluctuated around 1.0. With the increase of salinity, the peak value of length distribution reached 15.7 at 0.975 Å, but the concentration profile of water molecules at 3.1-9 Å decreased quickly and then gradually increased. The results of MSD and MT about water molecules presented the largest diffusion coefficient appeared at 398 K and had the best dispersion effect owing to the average kinetic energy among the molecules. Conversely, the diffusion coefficient decreased with the incremental solution salinity because the inhabitation of sodium for the motion of water molecules resulted in the ion bridging and hydrogen bonding.
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