Viscosity in situ

Figure 6.9 A submersible oscillation viscometer for in situ viscosity measurements in a continuous process vessel. From Schramm [92]. Copyright 1989, The Petroleum Society.

In a discussion of rheology, one important parameter is viscosity. First, we should be aware of the different terminologies related to viscosity. Bulk viscosity is the viscosity measured in a viscometer, which was discussed previously. In situ viscosity in porous media, which is one of the subjects in this section. 

Using the measured in situ viscosities and suspension densities determined from discrete samples (Figure 24), bitumen globule rise velocities have been estimated (66) from equations 1-3. In Figure 25, Stokes rise velocities are calculated for 0.26 mm diameter globules as a function of depth in the vessel. For bitumen globules at a depth of 0.8 m in the vessel (just below the slurry feed plate), the zero NaOH addition... 

For example, the observed decrease in the shear viscosity with the addition of MAH and PENTA leads to lower pressure in the filling of the mold in the mold-injection operation. In fact, the injection pressure diminishes from 40,680 kPa for PET to 24,822 kPa in the system PET-clay-MAH (1 wt%) and to 13,790 kPa in the system PET-clay-PENTA under the same processing conditions. This corresponds to a threefold decrease in the viscosity. However, it is necessary to point out that the viscosity curves reported are built from simple shear rheometric flows. In the actual process operation, the fluid that fills the mold is subjected to a nonhomogeneous stress field, which is likely to develop slip at the walls and another complicated flow behavior [62]. In these circumstances, the in situ viscosity is probably lower than that measured in the rotational rheometer. Measurements of pressure drop versus flow rate made on the fluid that enters the mold would surely provide a more reliable value of the process viscosity, and hence a better evaluation of the effect of the nanoparticles on the flow behavior of PET. 

The in-situ viscosity, rj C, v ) referred to above is a function of both polymer concentration and the flow rate (aqueous-phase velocity, v ) in the porous medium. If the polymer solution is purely shear thinning in flow through the porous medium, then one possible model to describe the effective in-situ shear rate within the aqueous phase, is the two-phase generalisation of the capillary bundle model discussed previously (see Chapter 6) ... 

However, there is no consensus formula which could give the best prediction on the relationship of in situ viscosity and in situ shear rate. Generally, we need data both from viscometer and coreflooding experiments. Viscometer data is easy to obtain. If we do not have coreflooding data, we will need to match other available data by adjusting the shear rate coefficient C in Equation 12. Gogarty (1967) stated that the shear rate coefficient is... 

Calcium ion contamination due to anhydrite dissolution caused in situ viscosity loss which-affected the effectiveness of polymer solution. 

Practical considerations for the polymer solution are that (1) it must be injectable into the reservoir, (2) it must survive, and (3) it must be able to move through the reservoir and provide the required viscosity. Field tests were done to verify injectivity, biological stability, and in-situ viscosity. Falloff tests, done after injection at variable rates, were conducted to investigate the non-Newtonian behavior of the polymer bank in the reservoir. Falloff test results and in-situ viscosity estimates were given previously. A three-dimensional reservoir simulation, not covered in this paper, used field-generated data to project an oil production schedule for the final economic analysis. 

Polymer flooding being a proven EOR technique in high permeable sandstones onshore, it is assttmed that if the in-situ viscosity of the polymer is in line with the retained design, after passing through the whole set of injection facihties specific to deep offshore implementation, incremental recovery should be as expected. 

Like steam injection, in-situ combustion is a thermal process designed to reduce oil viscosity and hence improve flow performance. Combustion of the lighter fractions of the oil in the reservoir is sustained by continuous air injection. Though there have been some economic successes claimed using this method, it has not been widely employed. Under the right conditions, combustion can be initiated spontaneously by injecting air into an oil reservoir. However a number of projects have also experienced explosions in surface compressors and injection wells. 

Miscibility or compatibility provided by the compatibilizer or TLCP itself can affect the dimensional stability of in situ composites. The feature of ultra-high modulus and low viscosity melt of a nematic liquid crystalline polymer is suitable to induce greater dimensional stability in the composites. For drawn amorphous polymers, if the formed articles are exposed to sufficiently high temperatures, the extended chains are retracted by the entropic driving force of the stretched backbone, similar to the contraction of the stretched rubber network [61,62]. The presence of filler in the extruded articles significantly reduces the total extent of recoil. This can be attributed to the orientation of the fibers in the direction of drawing, which may act as a constraint for a certain amount of polymeric material surrounding them. 

Strong elongational deformation and use of matrix polymers whose viscosity is higher than that of TLCP phase are better to ensure uniform and fine fibril formation. But application of compatibilizing techniques to in situ composite preparation can be useful to get the most desirable products. These can reduce the high costs of the liquid crystalline polymers and expensive special engineering plastics used for the in situ composite preparation and reduce the processing cost, whereas they can increase the performance of produced in situ composites, hence, their applications, too. 

Thermal recovery methods involve the use of steam and in-situ combustion. Thermal EOR processes add heat to the reservoir to reduce the viscosity of the oil or to vaporize it. In addition, these processes use steam or oil combustion... 

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