Snorre Low-Salinity-Water Injection—Coreflooding Experiments and Single-Well Field Pilot

Skrettingland, Kjetil; Holt, Torleif; Tweheyo, Medad T.; Skjevrak, Ingun

doi:10.2118/129877-pa

Cited by 163 publications

(83 citation statements)

References 30 publications

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“…Several oil companies, such as BP [34], Shell [35], Saudi Aramco [36], and PetroChina [17,18,21,37] have conducted numerous lab experiments, i.e., Log-Inject-Log, Single Well Chemical Tracer Test (SWCTT), and field scale trials. Their results have shown that, while in some cases LSWF has achieved an additional 5-25% oil recovery, in other cases, only minor incremental oil recovery was observed [38].…”

Section: Introductionmentioning

confidence: 98%

Effect of multi-component ions exchange on low salinity EOR: Coupled geochemical simulation study

2016

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The mechanism(s) of Low salinity water flooding (LSWF) has been extensively investigated for 15-20 years, as a cost-effective and environmentally friendly technique for improved oil recovery. However, there is still no consensus on the dominant mechanism(s) behind low salinity effect due to the complexity of interactions in the Crude oil/Brine/Rock (COBR) system. While wettability is most agreed mechanism of low salinity EOR effect. Nevertheless, the mechanism(s) behind the wettability change is debated between multi-component ion exchange (MIE) and double layer expansion (DLE) in sandstone reservoirs. This paper aims to investigate the effectiveness of MIE with a coupled geochemical-reservoir model using published experimental data reported by Nasralla and Nasr-El-We created core-scale numerical models with parameters identical to those used in the experiments. We simulated the low salinity effect using a commercial reservoir simulator, CMG-GEM, by coupling three chemical reactions: (1) aqueous reaction, (2) multi-component ion exchange, and (3) mineral dissolution and precipitation. We modelled the adsorption of divalent cations on the surface of the clay minerals during low salinity water injection. Simulation results were compared with the experimental results.Simulation results show that the fractional adsorption of divalent cations (Ca 2+ ) increased almost 25% by injecting a 2,000 ppm NaCl solution, compared to initial 10,000 ppm NaCl. Injecting a 2,000 ppm of CaCl 2 solution, however, significantly increased the adsorbed Ca 2+ from 0.1 to 1, which implies the complete saturation of mineral surface with divalent cations. Moreover, injecting 50,000 ppm of CaCl 2 solution also demonstrated the same effect as the 2,000 ppm CaCl 2 solution but with a faster rate.Upon combining the simulation and experimental results, we concluded that the multi-component ion exchange is not the sole mechanism behind low salinity effect for two reasons. First, almost 10% additional oil recovery was observed from the experiments by injecting the 2,000 ppm CaCl 2 compared with 50,000 ppm CaCl 2 solutions. Even though in both cases the surface is expected to be fully saturated with Ca 2+ according to the geochemical modelling. Second, 6% incremental oil recovery was achieved from the experiments by injecting 2,000 ppm NaCl solution compared with that of 50,000 ppm NaCl. Although 25% incremental adsorption of divalent cations (Ca 2+ ) were presented during the flooding of the 2,000 ppm NaCl solution. Therefore, it is worth noting that the electrical double layer expansion due to the ion exchange needs to be taken into account to pinpoint the mechanism(s) of low-salinity water effect.

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Section: Introductionmentioning

confidence: 98%

Effect of multi-component ions exchange on low salinity EOR: Coupled geochemical simulation study

2016

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“…Saturating rock with the oil may cause the rock to become more oil-wet through a variety of brine/oil/rock interactions [6]. LSW studies on sandstones conclude that a high oil recovery is observed in rocks that are weakly waterwet [3,7]. LSW alters the wettability of the sandstones from an oil-wet state towards an optimum weakly water-wet state, thereby leading to an improved recovery.…”

Section: Introductionmentioning

confidence: 99%

Thin liquid films in improved oil recovery from low-salinity brine

Myint

Firoozabadi

2015

Current Opinion in Colloid & Interface Science

270

214

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Low-salinity waterflooding is a relatively new method for improved oil recovery that has generated much interest. It is generally believed that low-salinity brine alters the wettability of oil reservoir rocks towards a wetting state that is optimal for recovery. The mechanism(s) by which the wettability alteration occurs is currently an unsettled issue. This paper reviews recent studies on wettability alteration mechanisms that affect the interactions between the brine/oil and brine/rock interfaces of thin brine films that wet the surface of reservoir rocks. Of these mechanisms, we pay particular attention to double-layer expansion, which is closely tied to an increase in the thickness and stability of the thin brine films. Our review examines studies on both sandstones and carbonate rocks. We conclude that the thin-brine-film mechanisms provide a good qualitative, though incomplete, picture of this very complicated problem. We give suggestions for future studies that may help provide a more quantitative and complete understanding of low-salinity waterflooding.

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“…Thus, we really have one phase flow (in absence of water). The wettability of rock formation from the Snorre field is classified as neutral-wet to weakly water-wet (Skrettingland et al, 2011).…”

Section: Snorre Field Descriptionmentioning

confidence: 99%

“…The main sand interval porosity is 0.30 and the initial water saturation (S w ) is in the range of 0.1 -0.2. Three single well chemical tracer (SWCT) tests have been carried out in Well P-07 which in each test, three tracers (Ethyl acetate (EtAc) as a primary and reactive tracer which produces Ethanol (EtOH) as a fourth tracer, n-propanol (NPA) as a backup tracer for EtAc if the amount of remained EtAc be negligible after hydrolysis reaction, and isopropanol (IPA) tracer for material balance proposes) were injected in order to evaluate the effect of injection of seawater, drill water, and low salinity (Skrettingland et al, 2011).…”

Section: Snorre Field Descriptionmentioning

confidence: 99%

“…Three SWCT test have done in Snore oil field to assess the effect of injection of high, drill, and lowsal waterflooding (Skrettingland et al, 2011). The results of the tests proved that the amount of oil recovery after lowsal waterflooding in the Snorre oil field is insignificant and it can be because of the wetting conditions in this sandstone reservoir that are in optimum condition (water-wet) which seawater flooding is efficient.…”

Section: Introductionmentioning

confidence: 98%

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Numerical Interpretation of Single Well Chemical Tracer (SWCT) Tests to Determine Residual Oil Saturation in Snorre Reservoir

2015

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Determination of residual oil saturation (S or ) is heavily required for evaluating the effect of EOR methods. While there are some methods to determine S or such as coring, logging, and tracer methods, it is generally accepted that tracer methods are more efficient mainly due to the measurement of large reservoir volume and non-dependency on porosity. Among all proposed tracer methods to determine S or of EOR methods, only Single Well Chemical Tracer (SWCT) method is widely implemented in the industry.Several SWCT tests have been carried out in Snorre reservoir to evaluate the effect of injection of high, drill, and lowsal waterflooding. Since characteristics of each SWCT test is unique and often is different even on the same well in various tests, simulation procedure for finding multiple history matches to the measured tracer production from the field is a challenging process. In this paper, the numerical interpretation of first SWCT test after high salinity waterflooding is done. The necessary parameters to model the field test and the value of numerical interpretation of SWCT tests is also introduced. UTCHEM is used as the numerical simulation tool to get an acceptable history match to the measured field data.The procedure of interpretation is started with a single-layer (ideal) model. The unknown parameters that affect tracer production are grid size, hydrolysis reaction rate, and average S or are obtained. The S or is determined 0.24 in the present test in the original reservoir temperature of 194°F. While ideal model shows a worthy fit, there is still some deviation between measured and modelled profiles at the tail of the curves because of non-ideality effects. Flow irreversibility in layered test zones is considered for departing ideal model from the real test in this sandstone reservoir. The three new unknown parameters of non-ideal model are the number of layers in the test zone, the fraction of total fluid injected and produced from each layer, and the S or for each layer. In the interpretation of the present test, two other layers are added to determine the effect of flow irreversibility in test zone. The main layer, the early layer, and the late layer accepted and produced 52%, 17%, and 31% of the total injected tracer, respectively. The average S or of 0.22, 0.24, and 0.26 is resulted to the main layer, the early layer, and the late layer, respectively. The best history match without any deviation between modelled and measured profiles is obtained using non-ideal model.According to the reservoir cooling and heating from shale layers above and below the flooded sand interval, the temperature of the fluids near-wellbore will change. Since the tracer bank is injected with lower temperature than reservoir temperature, the effect of reservoir cooling on the ester partitioning coefficient is investigated in order to determine S or more precisely. Using this numerical SWCT interpretation, it is achievable to examine other EOR methods to reach more oil recovery in this sandstone reservoir via obtained unk...

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Snorre Low-Salinity-Water Injection—Coreflooding Experiments and Single-Well Field Pilot

Cited by 163 publications

References 30 publications

Effect of multi-component ions exchange on low salinity EOR: Coupled geochemical simulation study

Effect of multi-component ions exchange on low salinity EOR: Coupled geochemical simulation study

Thin liquid films in improved oil recovery from low-salinity brine

Numerical Interpretation of Single Well Chemical Tracer (SWCT) Tests to Determine Residual Oil Saturation in Snorre Reservoir

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