1. Feasibility Study on DCA Microspheres for Deep Profile Control Technology in High Permeability of High Temperature and High salt Reservoirs
Changchun Yang
(doctoral supervisor:Xiang’an Yue)
China University of Petroleum(Beijing)
July 21, Brisbane

2. Laboratory of Enhanced Oil & Gas Recovery
Basic Information
Laboratory of Enhanced Oil & Gas Recovery
in Complex Reservoir

3. Distribution of high temperature and high salt reservoirs
of major oil and gas fields in China
Tarim Oilfield
Qinghai Oilfield
Zhongyuan Oilfield

4. The problems in high-temperature and high-salt reservoirs development
What are the main features?
High-temperature and high-salt reservoirs
What are the problems it brought about?
What are the problems it brought about?
High-temperature and high-salt
Heterogeneous
● Serious channeling
● Low sweep efficiency
● Low production and
production capacity.
● rapid rising of water cut
● Conventional agents of high
temperature and salinity
tolerance is poor.
● Cross-linking reaction time is
difficult to control.
● The validity period of the
operation measures is short.
What should we do？
Deep profile control

5. The challenges in high-temperature and high-salinity reservoirs deep profile control
Better temperature resistance of profile control agent
Profile control
Good injection property
Stronger plugging capability
The permeability of the remaining oil area is much lower, for the purpose of flooding the remaining oil, the profile control agent must have stronger plugging capability
Why??
Generally speaking, the profile agent used in high-temperature and high-salinity reservoirs must satisfy these three demands.

6. The commonly used deep profile control agents
Weak cross-linked polymer gel
Linked polymer solution （LPS）
Colloidal dispersion gel （CDG）
polymer concentration and cross-linking agent concentration
New profile control agents are needed
Because of low polymer concentration and low cross-linking agent concentration, the cross-linking reaction is easily influenced by formation conditions, such as salt, temperature, shearing degradation and chromatographic separation of cross-linking agent, thus can not suit the deep profile control in high-temperature and high-salinity reservoirs.
Pre-cross-linked water swellable particles
Solid polymer gel particles, with good injection property, but weak plugging capability and washing-out resistance, the validity period is short.

7. The elastic water swellable DCA microsphere
The elastic water swellable DCA microspheres have been developed based on linked polymer solution for about more than eight years.
（a）
（b）
Hydration layer
Cross-linked polymer layer
Gel core
● Like the gels, the elastic water swellable microspheres have cross-linked 3D networks structure.
● Unlike the gels, the cross-linked 3D networks structure is built by covalent bond not coordinate bond, so the microspheres have many advantages compared with other polymer type deep profile control agent.
●DCA microspheres have a three-layer structure which is the outer layer of the hydration, intermediate layer of cross-linked polymer, inner layer of gel core.

8. Plugging step by step, till the deep profile control is carried out.
Plugging mechanism
Plugging step by step, till the deep profile control is carried out.
● Temporarily plug the large pores and throats near wellbore, cause the water flow to divert and displace the remaining oil in the small pores and throats.
● When the pressure gradient is high enough, they will deform and traverse the pore throat, and recover to their original shape and size rapidly.
●Finally, they move into the deep area of oil formation and effectively plug the large pores and throats there, because of a relative low-pressure gradient. Thus, the water flow is diverted again and the remaining oil in the deep area of oil formation is also displaced.

9. Temperature Resistance of DCA microspheres
Temperature performance of DCA microspheres and HPAM were measured in an oxygen environment by thermal gravimetric analyzer (TGA).
HPAM
DCA microspheres
● The temperature capability of HPAM and DCA microspheres were 193 ℃ and 300℃
respectively.
● According to relationship between viscosity and temperature, HPAM adapted to
reservoir temperature from 70℃ to 80℃.
●According to decomposition temperature, DCA microspheres adapted to the target
reservoir temperature above 130 ℃.

10. Plugging Ability of DCA microspheres
Experimental temperature: 115℃ ; Particle size distribution :2-399 μm ;
Salinity of formation water: 26.9×104mg/L ; Concentration of the microspheres: 1000ppm; Gas permeability : 1400mD; Length and diameter of the core : 30 cm and 2.5 cm respectively.
The pressure distribution along the cylindrical core was monitored in real time.
Microstructure of DCA microspheres in injection original liquid and recovery solution

11. Plugging Ability of DCA microspheres
The plugging ability of DCA microspheres was characterized by residual resistance coefficient were calculated by the using of the
is permeability of the core after injecting microspheres;
is permeability of the core before injecting microspheres.
● the residual resistance coefficient along the cylindrical core was greater than 2. The highest value of residual resistance coefficient was 1777.
● The microspheres have a stable plugging ability to migrate into all the measure points of the core to achieve the deep plugging.
●DCA microspheres show high-strength deep plugging in reservoirs.

12. Effect of profile control and water shutoff of DCA microspheres
Experimental temperature: 115℃ ; Experimental pressure: 20Mpa ;
Particle size distribution :2-399 μm ; Concentration of the microspheres: 1000ppm;
Length , width and height of the core : 30 cm, 4.5 cm, and 4.5 cm respectively;
Gas measured permeability of low and high permeability : 220mD and1400mD.
（a）model appearance before saturated oil
（b）model appearance after DCA microspheres
plugging and subsequent water flooding
● The rate of enhanced oil recovery reached 10.18% and the water cut dropped by 20.73% after injecting only the slug of the DCA microspheres.
● The low-permeability region of the model was a white color inside yellow circle in Figure（b）.
●The remaining oil of the unswept regional, whose relative permeability was lower, was started.

13. Appearance of produced liquid of carbon dioxide flooding
Method optimization of effect of profile control and water shutoff of DCA microspheres
Experimental temperature: 115℃ ; Experimental pressure: 20Mpa ;
Particle size distribution :2-399 μm ; Concentration of the microspheres: 1000ppm;
Length , width and height of the core : 30 cm, 4.5 cm, and 4.5 cm respectively;
Gas measured permeability of low and high permeability : 220mD and1400mD.
Appearance of produced liquid of carbon dioxide flooding
● After subsequent water flooding, the further method was carbon dioxide flooding and the rate of enhanced oil recovery reached 19.64%.
● The crude displacement with carbon dioxide enhanced oil recovery and one important mechanism of carbon dioxide emulsified crude oil.

14. Conclusions
● DCA microsphere had a three-layer structure and have better suspension. The temperature capability of DCA microspheres was up to 300 ℃ and had better temperature resistance.
● The residual resistance coefficient along the cylindrical core was greater than 2. The microspheres have a stable plugging ability to migrate into all the measure points of the core to achieve the deep plugging.
●The rate of enhanced oil recovery reached 10.18% in stage of the subsequent water flooding. On the basis of the subsequent water flooding, the rate of enhanced oil recovery reached 19.64% in stage of carbon dioxide flooding.
●Feasibility methods which was the plugging of DCA microspheres and carbon dioxide flooding on deep profile control technology in high permeability of high temperature and high salt reservoirs have been proposed.

15. Acknowledgements
● Thanks to my co-authors for their contribution to synthesis and performance evaluation of high-temperature and high-salinity tolerance polymer microspheres:
Changchun Yang, Xiang’an Yue, Jie He, Daiyu Zhou, Rui Xu,
Ji Zhao, Chaoyue Li, Xuenan Zhang
●Xiang’an Yue, Ph.D, Professor (doctoral supervisor)
Laboratory of Enhanced Oil & Gas Recovery in Complex Reservoir,
College of Petroleum Engineering
China University of Petroleum，Beijing
No.18 Fuxue Road,Changping,Beijing
Tel: M:

16. Thank You…
Questions ??