Research on Asphaltene Deposition During the Process of CO 2 Flooding Huang Lei 1 Shen Pingping 1 Jia Ying 2 Li Shi 1 1.State Key Laboratory of EOR (Research institute of Petroleum Exploration and Development,Petrochina) 2.Exploration and Production Research Institute, Sinopec For IEA EOR Meeting CNPC

1 、 Research Background 2 、 Asphaltene Precipitation Experiment study for CO 2 Injection 3 、 Asphaltene Precipitation Model for CO 2 Injection Process 4 、 Compositional simulator Considering Asphaltene Deposition 5 、 Conclusion content CNPC

Asphaltene deposition in the well hole Asphaltene deposition in the pipe line Research Background CNPC

 Asphaltene Precipitation: Asphaltene component to be seperated from oil and get together to form another phase different from oil phase  Asphaltene deposition: the process of precipitated asphaltene settling onto the surface of porous media Two Basic Concept Research Background CNPC

1 、 Research Background 2 、 Asphaltene Precipitation Experiment study for CO 2 Injection 3 、 Asphaltene Precipitation Model for CO 2 Injection Process 4 、 Compositional simulator Considering Asphaltene Deposition 5 、 Conclusion content CNPC

The Basic Properties and Composition of Experiment Oil Sampling Separator Sampling Reservoir Pressure （ MPa ） 32 Reservoir Temperatue （℃） 110 Bubble Point （ MPa ） 4 DOR （ m 3 /m 3 ） 12.9 FVF1.088 (g/cm 3 ) Dead Oil Density (g/cm 3 )0.886 CO C 1 +N C 2 ～ C C Wax of Dead oil ( ％ ) Asphaltene of Dead oil ( ％ ) EvaluationRepresentative Asphaltene Precipitation Experiment study for CO 2 Injection CNPC

Equipment for Precipitation Onset Point Measure Asphaltene Precipitation Experiment study for CO 2 Injection CNPC

Equipment for Precipitate quantity measure 注： 1-3. 手动高压泵 高压阀门 P1-P5. 压力表 A. 主平衡釜 B. 副釜 C. 转样釜 D. 空气恒温浴 E. 石油醚洗瓶 Asphaltene Precipitation Experiment study for CO 2 Injection CNPC

20.0MPa 26.0MPa 20.0MPa 23.0MPa 26.0MPa 29.0MPa 32.0MPa 35.0MPa 29.0MPa 35.0MPa 32.0MPa CNPC PLT response of asphaltene Precipitation process Asphaltene Precipitation Experiment study for CO 2 Injection

injection pressure MPa CO 2 mol% CO 2 mol% Asphaltene in oil wt% Asphaltene Precipitation wt% noCO Result of Asphaltene Precipitation Experiment Onset line saturation line Critical point CNPC Asphaltene Precipitation Experiment study for CO 2 Injection

1 、 Research Background 2 、 Asphaltene Precipitation Experiment study for CO 2 Injection 3 、 Asphaltene Precipitation Model for CO 2 Injection Process 4 、 Compositional simulator Considering Asphaltene Deposition and its Application 5 、 Conclusion content CNPC

Presumption  Because precipitated asphaltene is composed of heavy polarity and non-ideality molecules, which is solid-like precipitated liquid with strong viscosity under reservoir condition. Thus, equation of state incorporating association （ AEOS ） is used to describe the phase behavior of asphaltene  Ignoring resin component ， Precipitated Asphaltene is composed of asphaltene component  asphaltene component do not behave association in oil phase  During the process of asphaltene precipitation, no crystal formed Asphaltene Precipitation Model for CO2 Injection Process CNPC

 Because precipitated asphaltene is composed of heavy polarity and non-ideality molecules, the compress factor of association compound established by Anderko is introduced to describe the non-ideality of precipitated asphaltene where Compressible factor of Asphaltene Asphaltene Precipitation Model for CO2 Injection Process CNPC

Fugacity Calculation for Asphaltene Phase Asphaltene Precipitation Model for CO2 Injection Process CNPC

where Vapor/liquid/Asphaltene equilibrium model: Asphaltene Precipitation Model for CO2 Injection Process CNPC

Judgement of asphaltene precipitation is as follows:  if ， asphaltene would precipitate ；  if ， asphaltene would not precipitate ；  if ， asphaltene begin to precipitate 。 Where is content of heavy components in oil. Phase stability analysis of precipitated asphaltene: Asphaltene Precipitation Model for CO2 Injection Process CNPC

Regression Result for Asphaltene Pricipitation onset point Asphaltene Precipitation Model for CO2 Injection Process CO2,mole% cal.Pb point cal.onset line cal.disappearance line expl.onset line exp.Pb line critical point CNPC

When injection pressure is constant, precipitated asphaltene increases with the increase of injected CO2 before CO2-oil system reaches saturation. Precipitated asphaltene reaches maximum at saturation state, and then precipitated asphaltene decreases with the increase of injected CO2 When the CO2 mole percents of CO2-oil system are constant, precipitated asphaltene reaches maximum at saturation pressure. The higher system pressure, the more maximum quantities of precipitated asphaltene Asphaltene Precipitation Model for CO2 Injection Process the relationship between asphaltene precipitation and CO2 mole percent at fixed pressure the relationship between asphaltene precipitation, gas phase mole percent and pressure at varied CO2 mole percent Asphaltene Precipitation,wt% Gas mole% Asphaltene Precipitation,wt% CO2,mole% pressure,MPa CNPC

1 、 Research Background 2 、 Asphaltene Precipitation Experiment study for CO 2 Injection 3 、 Asphaltene Precipitation Model for CO 2 Injection Process 4 、 Compositional simulator Considering Asphaltene Deposition 5 、 Conclusion content CNPC

where ， Conservation Equation for Component i Compositional simulator Considering Asphaltene Deposition Conservation Equation for Water Conservation Equation for Oil and Gas CNPC

Precipitated Asphaltnene is made of three parts ： deposit onto the porous media surface through adsorption ； deposit through mechanical entrapment ； suspended in the oil phase adoption by unit rock volume surface adsorption by unit rock mass follows a Langmuir isotherm ： mechanical entrapment ： suspended content in oil phase ： CNPC Compositional simulator Considering Asphaltene Deposition

Plugging Equations Using following equations established by Cernansky &Siroky （ 1985 ） to describe plugging process CNPC Compositional simulator Considering Asphaltene Deposition

Seq unia l Core length( cm) Perm ( mD ) S oi ( ％ ) P ex (M Pa) dp(MP a) Injection PV Exp. Re (%) New method Cal. Re (%) Conventional methed Cal. Re (%) Recovery factor matching for core flooding CNPC Compositional simulator Considering Asphaltene Deposition

Asphaltene deposition front is consistent with gas front, which indicates that CO2 injection lead to asphaltene pricipitate 0.1HCPV 0.2HCPV 0.3HCPV0.4HCPV CNPC Compositional simulator Considering Asphaltene Deposition

As pressure rises ， more asphaltene deposition lefted in core. CNPC Compositional simulator Considering Asphaltene Deposition

1 、 Research Background 2 、 Asphaltene Precipitation Experiment study for CO 2 Injection 3 、 Asphaltene Precipitation Model for CO 2 Injection Process 4 、 Compositional simulator Considering Asphaltene Deposition 5 、 Conclusion content CNPC

 AEOS can describe Asphaltene Precipitation behavior.  For a fixed pressure system, precipitated asphaltene increases with the increase of injected CO 2 before system reaches saturation, then precipitated asphaltene decreases with the increase.  When system composition is fixed, precipitated asphaltene reach its climax near saturation pressure.  Asphaltene Precipitation should be considered in CO 2 injection process of high Asphaltene content oil.  Asphaltene deposition front is consistent with CO 2 front.  As pressure rises ， more asphaltene deposition lefted in core. Conclusion CNPC