Core-flood experiments

Tables 5-1 to 5-3 summarize some biocides proposed for bacteria control. Core flood experiments were used to evaluate the efficacy of periodic formaldehyde injection for the control of in situ biogenic reservoir souring. Formaldehyde treatments were demonstrated to control souring in both...

Several surfactants were studied in ambient-pressure foam tests, including alcohol ethoxylates, alcohol ethoxysulfates, alcohol ethoxyethylsulfonates, and alcohol ethoxyglycerylsuUbnates [210]. Surfactants that performed well in the 1-atm foaming experiment were also good foaming agents in site cell and core flood experiments performed in the presence of CO2 and reservoir fluids under realistic reservoir temperature and pressure conditions. 

Most suitable for the examination of the surface is x-ray photoelectron spectroscopy, whereas the wettability determination can be established by a detailed interpretation of core flooding experiments and wettability index measurements. The results of such studies show that the organic carbon content in the surface is well correlated with the wetting behavior of the material characterized by petrophysical measurements [1467,1468]. 

As part of the studies undertaken in our laboratory it was necessary to be able to determine quantitatively the surfactant present in large numbers of samples (> 100 per week) arising, for example, from core flooding experiments. The chosen method needed to be rapid to reduce analysis time, and to require little manipulation of the sample to reduce errors. In this paper we report the development of a method for the determination of anionic surfactants based upon autotitration and comment on the physico-chemical basis of the technique. 

We gratefully acknowledge fruitful discussions with Professor E. L. Claridge. Tschiedel and Larry Bielamowicz performed the CO2 core flood experiments. 

There are large differences between the level of static adsorption of HPAM and dynamically retained level in a core or pack (Lakatos et al., 1979). These differences are the result of changes in the specific surface area of consolidated and unconsolidated packs and also the accessibility of certain portions of the pore space. These differences also depend on the extent of mechaifical retention that is present in the dynamic core flood experiment. Polymer retention in consolidated porous media cannot be determined with static bulk adsorption (batch adsorption techniques) because the process of disaggregation to obtain... 

A 0.1% selected surfactant was then added to the injection water. The core flood experiments showed that injection pressure was reduced by 26.6%, and that the oil recovery was increased by 6.7%. This effect was a result of wettability alteration to more water-wet, reduced immobile water and oil saturations, and increased oil and water relative permeabilities. The data are shown in Table 7.11. 

The optimnm phase type needs to be determined from core floods using reservoir cores. The phase type with the highest oil recovery factor is the optimnm salinity type. It is not necessarily type III. Meanwhile, the optimum salinity is determined. It is not necessarily the middle salinity of type III or a salinity in type III. Core flood experiments take into account all parameters snch as interfacial tension, relative permeability, phase trapping, and so on, becanse these experiments are essentially a replication of the flooding process that wonld occnr dnring the FOR process in the field. Practically, we cannot afford to rnn many core floods to identify the optimum type, but we can run simulations to preselect the type. 

A UTCHEM chemical flood model was built based on history-matching core flood experiments. The chemical parameters were calibrated through matching experiments. The calibrated parameters were used to build a field sector model to simulate the ASP pilot test. In the model, detailed alkaline reactions were considered. It was probably the hrst time such an ASP model was applied in a real held scale. The model was used to optimize injection schemes. For example, the model showed that when the post-flush slug volume was in the range of 0.15 to 0.35 PV, the pilot performance was insensitive to the slug size. Therefore, 0.15 PV of post-flush slug was selected for the injection scheme. 

The mechanisms for foam sensitivity to oils can also be compared to the results from core-flood experiments in which foams were made to flow through porous rock in the presence of residual oil. Holt and Kristiansen (26, 27, 56) studied foams flowing in cores under North Sea reservoir conditions and found that the presence of residual oil could reduce the effectiveness of flowing foams. They compared their results with the spreading and entering coefficients and found foam sensitivity to be correlated with the (oil) spreading coefficient. 

The same conclusions have been reached on the basis of core-flood experiments. Suffridge et al. (35) studied foam effectiveness in Berea sandstone cores, both untreated (water-wetted) and treated with the Quilon C chrome complex described previously. The treated cores became intermediate to oil-wetted at waterflood residual oil saturation. They found that the foams were more effective (stable) in the water-wet cores than in the oil-wet cores. Holt and Kristiansen (27, 56) studied foams flowing in cores under North Sea reservoir conditions that were either partially or completely oil-wetted. They found that foam effectiveness was favored by water-wet conditions any degree of oil-wet character reduced the effectiveness of the flowing foam. 

The most important conclusion from the core-flood experiments is that the selected surfactants produced effective nitrogen-based foams at extreme conditions of salinity and hardness in oil-free porous media under reservoir conditions (2). 

Figure 6. Adsorption levels measured in 96 core-flood experiments with foam-forming surfactants.

The present study utilizes a microwave attenuation tech nique to study oil bank formation and propagation during linear core tests. This technique, first developed by Parsons (12), was employed to monitor the dynamic in-situ water concentration during the alkaline core flooding experiments. 

LOTSCH, T., MULLER, T. and PUSH, G. "The Effect of Inaccessible Pore Volume on Polymer Core Flood Experiments", SPE 13590, Arizona, April 1985... 

In the core flooding experiments the waterflood residual oil saturation was established in the usual manner, i.e., the core was evacuated, flooded with brine, then with oil and again with brine until no more oil was produced. The core was then flooded with a finite (0.13 pore volume) surfactant slug, followed by a biopolymer drive (Table 1). The most important variable in these experiments was the salinity of the polymer drive. The flooding rate was 1 ft/ day. The surfactant mixture contained Witco s TRS 12B (62% a.i.)... 

The results of the core flooding experiments are summarized in Table 1. In the 30 cm core and in experiment 1, all aqueous solutions (connate water, waterflood, surfactant slug, polymer... 

The adsorption results from Wang s core flood experiments are interesting, but some critical comments are relevant ... 

Hydrodynamic retention of polymer is the least well defined and understood retention mechanism. The idea arose from the observation that, after steady state was reached in a polymer retention experiment in a core, the total level of retention changed when the fluid flow rate was adjusted to a new value (Desremaux etai, 1971 Maerker, 1973 Chauveteau and Kohler, 1974 Dominguez and Willhite, 1977). An example of this is shown for a core flood experiment using HPAM from the work of Chauveteau and Kohler (1974) in Figure 5.3. As the flow rate increased from 3m/day to 10.3m/day in this experiment, more polymer was retained from the mobile aqueous phase, as shown by the dip in the polymer effluent concentration. When the flow rate is lowered back to 3 m/day the polymer effluent concentration rises above the input value (400 ppm), denoting a drop in the retained level. This trend of increasing polymer retention with flow rate is consistent with the observations of other workers (Maerker, 1973 Dominguez and Willhite, 1977). For... 

The main objective of this chapter is to include the above phenomena in a suitable transport equation to describe the flow of polymer species through porous media. It has been found that terms describing these effects may be included in generalised convection-dispersion equations which appear to give a satisfactory macroscopic description of the processes in that they reproduce the main features observed in laboratory core flood experiments. It is these single-phase transport equations which provide the basis for simulation of polymer transport through porous media in the multiphase... 

Figure 7.1. Schematic diagram of a polymer/tracer core flood experiment showing a typical measured effluent profile.

Measurement of transport parameters The main measurement of interest under this heading is of the excluded/inaccessible pore volume (IPV) of polymer relative to tracer as parameterised by the core permeability. If this quantity is known, then it should be included in the simulation studies since it may have some effect on the relative breakthrough times of polymer and tracer. However, it has been found that the IPV effect is usually dominated by the frontal retardation of the polymer as a result of adsorption/retention, and it is not generally of major importance in the assessment of the outcome of the polymer flood. Other measurements, such as of polymer dispersion coefficient and viscous fingering parameters, are primarily of importance for interpreting detailed core flood experiments since they do not scale in a simple way to the field and cannot therefore be used directly in the polymer field-scale simulations. 

Lotsch, T., Muller, T. and Pusch, G. (1985) The effect of inaccessible pore volume on polymer core flood experiments. SPE 13590, Proceedings of the SPE International Symposium on Oilfield and Geothermal Chemistry, Phoenix, AZ, 9-11 April 1985. 

Fluid samples were bottled under controlled conditions and brought back to our research laboratory for core flood experiments. Fluid entry profiling of the well was done before,... 

The viscosity and screen factor measurements made on produced samples of sheared polymer were related to polymer effectiveness as a mobility control agent by means of core flooding experiments conducted in the laboratory. These core flooding experiments used field samples back produced from the polymer injection well. 

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