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Collaborating Authors
Waterflooding
Abstract Low salinity has been studied extensively, but still the mechanisms for improved oil recovery by lowering brine salinity are unsolved. The target of this paper was to address this problem and make systematic studies that can give insight to the key mechanisms. Given the variety of conditions under which increased recovery by low salinity brine injection may or may not be observed, it is likely that more than one mechanism is contributing to the observed oil recovery. The mechanisms most claimed to be the reason for improved oil recovery are shift in wettability, multi-component ion exchange, and dissolution/fines migration. In this paper, we have studied low salinity waterflood by systematic changing the rock wettability. The wettability is changed by varying aging with crude oil at elevated temperature. We are investigating how aging time effect affects core analysis properties like; spontaneous imbibition, Amott-Harvey and USBM wettability oil and water indices. The wetting properties were also cross-checked by NMR. The detailed core analysis is the background for study of oil recovery by seawater injection and subsequent lowering of salinity. In addition to detecting trends of initial wetting and the potential for low salinity, all mechanisms for low salinity recovery are discussed. It is expected from the literature that the clay content in Berea cores favors oil recovery by low salinity waterflooding, however the more oil wet character of the Bentheimer cores in this study, seems more important for improved oil recovery by low salinity waterflood.
- Europe (1.00)
- Asia (1.00)
- North America > United States > Texas (0.28)
- North America > United States > California (0.28)
Experimental Studies of Low Salinity Water Flooding in Carbonate Reservoirs: A New Promising Approach
Zahid, Adeel (Center for Energy Resources Engineering, Department of Chemical and Biochemical Engineering Technical University of Denmark) | Shapiro, Alexander (Center for Energy Resources Engineering, Department of Chemical and Biochemical Engineering Technical University of Denmark) | Skauge, Arne (CIPR (Centre for Integrated Petroleum Research), Uni Research and University of Bergen)
Abstract Low salinity water flooding is well studied for sandstone reservoirs, both laboratory and field tests have showed improvement in the oil recovery in many cases. Up to very recently, the low salinity effect has been indeterminated for carbonates. Most recently, Saudi Aramco reported that substantial additional oil recovery can be achieved when successively flooding composite carbonate core plugs with various diluted versions of seawater. The experimental data on carbonates is very limited, so more data and better understanding of the mechanisms involved is needed to utilize this method for carbonate reservoirs. In this paper, we have experimentally investigated the oil recovery potential of low salinity water flooding for carbonate rocks. We used both reservoir carbonate and outcrop chalk core plugs. The flooding experiments were carried out initially with the seawater, and afterwards additional oil recovery was evaluated by sequential injection of various diluted seawater. The experiments applied stepwise increase in flow rate to eliminate the influence of possible capillary end effect. The total oil recovery, interaction of the different ions with the rock, and the wettability changes were studied both at ambient and high temperature. No low salinity effect was observed for the reservoir carbonate core plug at the ambient temperature, but increase of the pressure drop over the core plug was detected. On the contrary, a significant increase in oil recovery was observed under low salinity flooding of the reservoir carbonate core plugs at 90 ยฐC. An increase in pressure drop was also observed in this case, possibly related to migration of fines or dissolution reactions. The outcrop Aalborg chalk core plugs did not show any low salinity effect, both at the room and at a high temperature. In the light of experimental results, discussions are made about possible mechanisms for improving oil recovery in carbonate reservoir as a function of change in brine salinity.
- North America > United States (1.00)
- Asia > Middle East > Saudi Arabia (0.54)
- Europe > Denmark > North Jutland > Aalborg (0.25)
- Research Report > New Finding (0.64)
- Research Report > Experimental Study (0.50)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.55)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government > Middle East Government > Saudi Arabia Government (0.54)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
2-D Visualisation of Unstable Waterflood and Polymer Flood for Displacement of Heavy Oil
Skauge, Arne (CIPR, Uni Research and Univ. of Bergen, Norway) | Ormehaug, Per Arne (CIPR, Uni CIPR, Norway) | Gurholt, Tiril (Uni CIPR and Univ. of Bergen, Norway) | Vik, Bartek (CIPR, Uni CIPR, Norway) | Bondino, Igor (Total E&P, France) | Hamon, Gerald (Total E&P, France)
Abstract Waterflooding and polymer assisted waterflood in heavy oil reservoirs has currently gaining great attention. Enhanced water injection schemes represent an alternative in cases where thermal methods are either impractical or uneconomic. This study describes and analyses the oil mobilization by imaging the oil displacement at adverse mobility by injection of brine and polymer. The objectives were to improve description of viscous instabilities, mechanisms for finger growth, water channeling at adverse mobility ratio, and oil mobilization by polymers. Experiments have been made on 2D (30cmx30cm Bentheimer slabs) studying waterflooding and tertiary polymer injection in extra heavy oils (2000cp and 7000cp). The sandstone represents a relatively homogeneous and high permeability porous medium. The experiments utilize gamma and X-ray source for porosity and saturation measurements, and an X-ray imaging system to visualize displacements and thereby quantify the underlying flow mechanisms and oil recovery. At water wet condition capillary smears the front and prevents viscous fingers even at high adverse viscosity ratio. Changes in wettability (aging the rock material) dampen the capillarity and fingers then become more pronounced. High microscopic recovery to waterfloods (up to 30% after 5 PV injected) were achieved, and most importantly a rather impressive further gain in oil recovery after polymer flooding reaching final recoveries of more than 60%. The waterflood creates multiple thin sharp fractal-like fingers that propagate in the Bentheimer sandstone material. The 2D X-ray imaging describes the finger formation, growth, and also the later water channels formed. Polymer injection gives a fast increase in oil production, and analysis from the imaging proves that the oil is mainly produced through the established water channels. The 2-D experiments demonstrate the mechanisms of how heavy oil is mobilized by polymer injection. Saturation maps were accurately measured by means of X-ray scans and this enabled the visualization of flow instability, establishment of water channels and oil mobilization with high resolution.
- Europe (0.69)
- North America > United States (0.68)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.45)
Abstract A new generation EOR methods comes from combining techniques to make the overall process more efficient and minimize the retention or loss of chemicals. One of the hybrid EOR methods we are investigating combines low salinity brine and reduced capillarity by surfactants, which has potential to increase EOR oil and cost efficiency. It is well documented that low salinity waterflooding give improved recovery. Judging from published data, it is likely that more than one mechanism is contributing to the observed oil recovery. We have summarized that two of the main effects are destabilization and mobilization of oil layers, and fines migration due to destabilization of clays. The latter is believed to contribute to increased oil recovery by pore blocking and microscopic diversion. If capillary forces are high, the oil mobilized by either of these two mechanisms is easily re-trapped. However if the capillary forces are lowered by adding surfactant, re-trapping may be avoided. The effect of decreasing interfacial tension was investigated in a series of constant rate, low salinity floods performed on crude oil aged Berea sandstone cores. The purpose is to explore the added benefit of the low salinity surfactant process over low salinity brine injection, and to investigate to which extent the capillary forces needs to be reduced to take advantage of the incremental recovery that may be obtained by combining the two processes. The results show that reduction of interfacial tension in low salinity waterfloods gives an increase in oil recovery which exceeds the expected performance of injecting a solution with the same reduction in interfacial tension but without the low salinity contribution. The combined effect of low salinity brine and surfactant injection may have the potential to improve the economy of EOR operations. The desalination cost and logistic involved may in some cases limit the possibility for low salinity waterflood, but enhanced oil recovery by simultaneous lowering of interfacial tension giving a much higher additional oil recovery may improve the overall economy.
- North America > United States > West Virginia (0.25)
- North America > United States > Pennsylvania (0.25)
- North America > United States > Ohio (0.25)
- North America > United States > Kentucky (0.25)