In order to study the profile control characteristics of emulsions in porous medium, the heterogeneous experimental model was established, by which the experimental scheme was designed with different permeabilities, matching degree of particle size and concentration of emulsions. Based on experimental results of physical simulation, the concept of distributing rate and changing coefficient was introduced to quantitatively evaluate the profile control characteristics of emulsions. The results of the study show that, as the permeability ratio and emulsion concentration increase, the profile control characteristics of emulsions will enhance. The profile control characteristics of emulsions will be the best. The profile control scheme with emulsions was implemented in Bohai X oil field, The research results can be used for reference to design the profile control scheme in Bohai heterogeneous reservoir.
When the multiple-zone commingled production is in progress, the interlayer interference phenomenon exists obviously, which has a great impact on oil field development [
Combined injection and separating device for parallel sand filling pipe was used as experimental equipment, including constant flux pump, intermediate container, high permeability sand pack, low permeability sand pack, incubator, PMU and collector. Experimental oil was compounded according to the viscosity of formation oil in Bohai X oil field. Experimental water was compounded according to the analytical data of formation water and injecting water provided by working field.
Based on the basic experimental scheme, three groups of contrastive experiments was designed by different permeability, matching degree of particle size and concentration of emulsions to study the influence of the profile control effect (
R = d m d e (1)
In which, R is the particle size matching factor; dm is the pore diameter of porous medium; de is the diameter of the emulsion droplet.
The pressure of Initial water flooding and Emulsion flooding was measured under constant flow condition, the yield of water and oil of the sand filling pipe was measured. The experimental steps are as follows: First, the sand filling pipe was made, in which the air permeability was measured after oil washing and drying. Then the process of filling water to saturation state was done, after which the oil flooding was finished, the bound water was produced. Second, based on the basic scheme, the two sand filling pipes was paralleled, the process of water flood was done with constant speed of 3 mL/min. In this process, the data of pressure and production of each sand filling pipe was recorded. Third, the
Name | Permeability ratio | Particle size matching factor | Concentration of emulsions % |
---|---|---|---|
Basic scheme | 4.0 | 1.0 | 100 |
Scheme one | 2.17 | 1.0 | 100 |
Scheme two | 15.8 | 1.0 | 100 |
Scheme three | 7.0 | 4.5 | 100 |
Scheme four | 4.0 | 1.2 | 100 |
Scheme five | 4.0 | 1.0 | 10 |
Scheme six | 4.0 | 1.0 | 50 |
Scheme seven | 4.0 | 1.0 | 100 |
process of oil washing and salt washing was done, then the bound water was produced again. The emulsion flooding experiment was in progress with the same flooding speed. Then the data of pressure and production of each sand filling pipe was recorded. Fourth, based on the contrastive experiments, the first step to the third step was repeated.
The concept of distributing rate was introduced to study the profile control characteristics of the heterogeneous parallel pipe:
f f = Q low Q high + Q low × 100 (2)
In which, ff is distributing rate of low permeability pipe, %; Qlow is flow rate of low permeability pipe, mL/min; Qhigh is flow rate of high permeability pipe, mL/min.
The bigger the distributing rate is, the better the effect of the profile control characteristics were.
In order to analyze the profile control characteristics of emulsions and to comparatively analyze follow-up experiment,the basic experiment was designed to carry out water flooding experiment and emulsion flooding experiment. Then the distributing rate of low permeability pipe was recorded to analyze its increased range. The results of the experiment are shown in
gradients in emulsion flooding, we can know that the process of “plugging, plugging removal and plugging” often happened when the emulsions were transporting in the sand filling pipes. The distributing rate and pressure of emulsions both fluctuated, but the changing trend of them was the same. The larger the distributing rate of low permeability pipe was, the larger the seepage resistance was. Conversely, the lower the seepage resistance was, the lower the pressure was. This proofed that temporary plugging of emulsions was the primary cause of the profile control characteristics. Because of the temporary plugging, the emulsions would move to the deeper layer, which made the residual oil moving, then the recovery rate was increased.
the emulsions was, the bad the stability of emulsions was. So when the emulsions were used for profile control, based on the stability of emulsions was better, we should choose the emulsions with a suitable diameter.
of emulsions was, the more obvious accumulation effect was, the better the profile control performance of emulsions were.
In order to validate the profile control performance of emulsions, two typical wells of Bohai X oil field were chosen to make profile controlling. The Bohai X oil field was a typical multi-layer combined production reservoir which was put into production in 2005. There are five small layers exploited by A-1 well, the I and II oil bearing strata were divided to make stratified test. There are ten small layers exploited by A-2 well, the I and II oil bearing strata were divided to make stratified test. The operating frequency of electric submersible pump was 30 Hz. The test data of the two test wells were shown in
The practical application proofed that, according to the A-1 well, the bigger the particle size of the emulsions was, the better the profile control performance of emulsions was. After profile controlling, the daily output increased 24.1 m3/d, the effect of profile control is remarkable. According to the A-2 well, the concentration of emulsions was properly reduced, the daily output of which increased 25.2 m3/d. The above proofed that the effect of profile control by emulsions was better than others, this technology has good generalization to increase the recovery rate.
1) The percolation characteristics of emulsions with microscopic model of different permeability gradations were studied. The profile control characteristics and percolation mechanism of emulsions in porous medium were analyzed.
Well number | Test layer | Effective thickness /m | Permeability | Matching degree of particle size | Concentration of emulsions/% | Daily output before profile controlling/m3 | Daily output after profile controlling /m3 | ||||
---|---|---|---|---|---|---|---|---|---|---|---|
/10−3 μm2 | liquid | oil | water | liquid | oil | water | |||||
A-1 | I | 14.8 | 1500 | 4.5 | 100 | 22 | 11.2 | 10.9 | 98.3 | 35.3 | 63.1 |
II | 25.6 | 5300 | 171.4 | 62.6 | 108.8 | 133.1 | 58.1 | 75 | |||
A-2 | I | 17.6 | 450 | 4.5 | 50 | 69.8 | 55 | 14.8 | 115.2 | 80.2 | 35 |
II | 35 | 900 | 216.4 | 32.5 | 184 | 204.5 | 26.5 | 178 |
2) The experimental results show that, when the permeability gradation was large enough, the stronger the heterogeneity was, the better the profile control performance of emulsions was. When the particle size of emulsion was bigger than the size of pore, the effect of the profile control was very good. As the concentration of emulsions increases, the effect of the profile control becomes better.
3) The application of profile control by emulsions in Bohai oil field proved that this technology has good generalization to increase the recovery rate.
The authors declare no conflicts of interest regarding the publication of this paper.
Yang, D.D., Wang, M.N., Miao, F.F., Wang, S.P. and Zhang, J.T. (2018) Research and Practice on the Profile Control Characteristics of Emulsions in Bohai Oil Field. Journal of Geoscience and Environment Protection, 6, 52-59. https://doi.org/10.4236/gep.2018.68005