Feasibility Study on DCA Microspheres for Deep Profile

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, 2016 Brisbane

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

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

The problems in high-temperature and high-salt reservoirs development What are the main features? What are the problems it brought about? High-temperature and high-salt reservoirs High-temperature and high-salt ● 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？ What are the problems it brought about? Heterogeneous ● Serious channeling ● Low sweep efficiency ● Low production and production capacity. ● rapid rising of water cut Deep profile control

The challenges in high-temperature and highsalinity reservoirs deep profile control Better temperature resistance of profile control agent Profile control Good injection property Stronger plugging capability Why? ? 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 Generally speaking, the profile agent used in high-temperature and high-salinity reservoirs must satisfy these three demands.

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 Because of low polymer concentration and low cross-linking agent Newreaction profile is easily influenced by concentration, the cross-linking formation conditions, such as salt, control temperature, shearing degradation are and chromatographic separationagents of cross-linking agent, thus can not suit needed and high-salinity reservoirs. the deep profile control in high-temperature 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.

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 3 D networks structure. ● Unlike the gels, the cross-linked 3 D 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.

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.

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 ℃.

Plugging Ability of DCA microspheres Experimental temperature: 115℃ ; Salinity of formation water: 26. 9× 104 mg/L ; Particle size distribution : 2 -399 μm ; Concentration of the microspheres: 1000 ppm; Gas permeability : 1400 m. D; 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

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.

Effect of profile control and water shutoff of DCA microspheres Experimental temperature: 115℃ ; Experimental pressure: 20 Mpa ; Particle size distribution : 2 -399 μm ; Concentration of the microspheres: 1000 ppm; 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 : 220 m. D and 1400 m. D. （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.

Method optimization of effect of profile control and water shutoff of DCA microspheres Experimental temperature: 115℃ ; Experimental pressure: 20 Mpa ; Particle size distribution : 2 -399 μm ; Concentration of the microspheres: 1000 ppm; 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 : 220 m. D and 1400 m. D. 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.

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.

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 102249 Tel: 86 -10 -89733960 M: 86 -13621210958 E-mail: yxa@cup. edu. cn

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