Numerical Simulation of Steam Injection for Heavy Oil Thermal Recovery

Numerical Simulation of Steam Injection for Heavy Oil Thermal Recovery

Available online at www.sciencedirect.com ScienceDirect Energy Procedia 105 (2017) 3936 – 3946 The 8th International Conference on Applied Energy – ...

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Available online at www.sciencedirect.com

ScienceDirect Energy Procedia 105 (2017) 3936 – 3946

The 8th International Conference on Applied Energy – ICAE2016

Numerical Simulation of Steam Injection for Heavy Oil Thermal Recovery Guo Chunshenga, Qu Fangyia, Liu Yonga, Nian Xianboa, Chen Zianga, Zou Yongb,* a

Dynamics and mechanical & electrical equipment engineering technology research center , Shandong University, Weihai of Shandong Province,264209, China b School of Material Science & Engineering, Shandong University, Jinan of Shandong Province,250100, China

Abstract

The steam injection technology is widely used in heavy oil production. The higher the steam injection rate is, the more beneficial the exploitation of heavy oil is. In this paper, we choose the twodimensional rotati on axis symmetry model, using VOF model of steam injection wells, wet steam phase change, transient a nalysis of influence of different injection pipe string structure in vertical well section during the process o f steam injection on steam injection parameters and changes of single and dual steam injection steam inje ction well bore in steam parameters during the process of steam injection in horizontal wells. The analysis results show that the vertical well steam injection by high vacuum insulated tubing make minimize the dr yness of the steam; Toe end dry degree is higher than that of single tube steam injection when horizontal pipe steam injection, which is conducive to the balanced development of heavy oil.

© 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Selection and/or peer-review under of ICAEof the 8th International Conference on Applied Energy. Peer-review under responsibility of theresponsibility scientific committee Keywords:heavy oil thermal recovery; hot steam; vertical well; horizontal well; VOF model

1. Introduction With the global resources get rare, the unconventional oil and gas, represented by heavy oil, will play a more and more important role in the world. Heavy oil is a very large and difficult flow of unconventional 

* Corresponding author. Tel.: +86 531-88399872; fax: +86 531-88399872. E-mail address: [email protected]

1876-6102 © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.817

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Nomenclature mv ml

Mass of vapor phase transition λo Coefficient of thermal conductivity of oil Variable mass transfer in aqueous phase ρw Water density Phase change coefficient Cw Specific heat of water Tsat Saturation temperature λw Thermal conductivity of water speed Cv Specific heat of steam v λv Thermal conductivity of steam < > average velocity Liquid physical fraction r4 The diameter of horizontal single shaft w Steam physical fraction r5 Double inner tube diameter v Surface tension coefficient r6 Double tube outer tube diameter ! Interface curvature L Horizontal wellbore length ∀ r1 Inner diameter of thickened oil pipe h Enthalpy of mixture r2 Vacuum insulated tubing radius λ Coefficient of thermal conductivity Sh Phase change heat (or heat) r3 High vacuum insulated tubing radius Si Momentum source term H Vertical well depth Oil volume fraction M Dryness of steam injection o P0 Steam injection pressure of vertical well dV Basic volume unit Thermal conductivity of porous framework P Steam injection pressure of horizontal 0’ qT R thermal resistance P Reservoir pressure Material thickness T0’ Initial reservoir temperature # Tin Steam injection temperature ρo Crude oil density T0 Surface temperature Co Specific heat of crude oil ΔT Geothermal gradient crude oil, and in the global oil and gas account for a large proportion of. Steam injection thermal recovery is the main method of heavy oil production. By injecting hot steam into the heavy oil can increase the temperature of the reservoir and reduce the viscosity of heavy oil, and can increase the pressure of oil layer and drive oil easily. It is important to understand the heat loss of the wellbore in the process of steam injection, which has an important influence on analyzing the steam injection efficiency. Many scholars domestic and overseas have studied the problem of energy loss in steam injection process. At home Yu Haitao[1]had studied the effect of steam injection effect on oil, and Lin Huichun[2]studied some controllable factors of steam injection. Yang Lihua[3] analyzed the heat loss in steam injection process and the improvement measures. And Liu Wenzhang[4] used the physical simulation method to determine the overall heat transfer coefficient. Dong Xiaohui[5] et al. to established a prediction model for thermal physical properties analysis of horizontal well thermal multi screen. Zhai Jianhua[6] considered the temperature and pressure drop in steam liquid two-phase flow in vertical wells. Considering the ground pipeline and well bore, the steam pressure and the decline of the dry degree of the were discussed by Shen Huifang[7]. Squier[8] et al. overseas proposed a complete calculation method for hot water through the wellbore. Hasan and Kabir[9,10] studied heat passage of the multiphase flow in the well, and established the perfect physics and mathematics. Emami-Meybodi[11] et al. Developed a transient heat conduction model to evaluate the heat transfer from the horizontal well to the formation. The heat loss of the wellbore during the injection of a hot fluid or a cold fluid through a casing is studied by Moss and White[12], Fokeev and Kapyrin[13]. The theoretical and experimental results of wellbore heat loss during steam injection are given by Huygen and Huitt[14], and the importance of the radiation heat loss is pointed out at the same time. In this paper, the VOF model is used to analyze the innovation of the heat and mass transfer process of the oil reservoir and the heat injection; While we are in the process of setting up the model to select two

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axisymmetric model to replace the traditional 3D model and 2D model, 3D model calculation is fast, and accurate calculation using a two-dimensional model. 2. Physical model Reservoir steam injection diagram is shown as figure 1. Steam injection process is divided into two sections, one for the vertical well, and the other one was horizontal well section. Steam variation condition is ignored around the corner for vertical well and horizontal well in the process of calculation.

Fig.1. Schematic diagram of steam injection process

Fig.2. Vertical well steam injection simulation diagram

Fig.3. Horizontal well steam injection simulation diagram

Simulation in this paper is divided into two steps correspond with the mode(Vertical Wells steam injection simulation, horizontal well steam injection simulation). Figure 2 is the simplified diagram for vertical well steam injection model. Injected steam transfer heat to stratum through medium such as wellbore, cement. And stratum is homogenous porous media. Figure 3 is horizontal well steam injection simulation diagram, steam through exports into the screen, and then steam exchange heat with the reservoir, and reservoir is homogenous porous media filling of crude oil. Steam injection along the horizontal section is divided into single pipe steam injection and double tube steam injection. In addition to have an opening in the end of the bottom, horizontal single tube steam injection also have some exit in

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the side of wellbore; double tube steam injection has the same exit with the single tube. However, it only has one exit at the bottom as shown in figure3. 3. mathematical model In order to carry out the simulation calculation, the following assumptions are made in this article: (1) The physical parameters of the strata are constant and not change with the change of temperature; (2) Sealing between the wall of the tube well is well with no leakage phenomenon; (3) There is only water- steam -oil three-phase in the reservoir; (4) The area of the reservoir is uniform porous medium which is rigidity and non-distortion ; (5) The flow of the fluid in the wellbore is fully turbulent flow and the flow in the reservoir is laminar flow; The control equation can be looked at the appendix A. Give the model initial parameters. The vertical well steam injection simulation related to the surface temperature of T0 ,geothermal gradient T, steam injection pressure P0 , steam injection temperature Tin; The initial conditions of horizontal well steam injection are the reservoir temperature T0, steam injection pressure P0, injection temperature Tin, reservoir pressure P and other parameters. 4. Simulation results 4.1.Steam injection parameters The related numerical simulation to simulate the required prior to the start of parameters, are shown in appendix B. 4.2.Vertical well steam injection simulation results Starting from the formation entrance steam injection, increasing with the depth of steam injection, the pressure loss gets more. So steam injection tubing string in fluid pressure shows declining trend. Figure 4 describes that the steam injection tubing string including thickened oil pipe, vacuum heat insulation oil pipe, and high vacuum insulated tubing have the wellbore pressure drop, known from the figure thickened oil pipe steam injection pressure drop is small, the vacuum insulated tubing with high vacuum heat insulation oil pipe steam injection pressure drop is bigger. Because the upset tubing steam injection wellbore diameter is large, so three kinds of pressure change trend is not the same: The curves of steam injection pressure of insulated tubing are approximately linear, while the upset tubing steam injection is nonlinear. Because saturation pressure is associated with saturation temperature, the temperature change curve should be parallel to the stress change curve. In three different steam injection cases, different coupled wall boundary conditions lead to the steam injection wellbore dryness changes within difference, steam quality in wellbore is shown. The thickening of the tubing and the formation of the heat transfer is better, so the loss of steam injection energy is larger, resulting in a decline in the injection steam dryness, decreased from 80% to 80%; The vacuum tubing compared with high vacuum tubing and upset tubing, has better heat preservation performance, so the heat steam heat loss is small; High vacuum heat insulation oil pipe relative to the vacuum heat pipe heat loss will be slightly less, so in 100 m steam injection vacuum heat insulation oil pipe, the outlet steam quality is 74.2%;In the high vacuum heat insulation oil pipe steam injection 100 m, outlet steam quality is 74.4%.

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Fig.4. Variation of pressure and dry degree in vertical well

4.3 .Horizontal well steam injection simulation results 4.3.1. Horizontal single pipe steam injection simulation

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Horizontal well steam injection relative to the vertical steam injection is relatively complex, this is because the vapour-liquid two-phase flow for the sake of oil vapor - liquid - phase flow. Figure 5 describes that the horizontal well steam injection tubing string along the axis of the pressure change trend, similar to the vertical well steam injection, stress is a declining trend. Figure 6 shows the steam injection after a period of time the single tube steam temperature changes, due to the continuously in the process of steam injection transfer energy to the reservoir, the temperature fell slightly. Figure 7 shows changes of the dryness along the axis direction. The figure shows that in the curves of dryness has three obvious mutation, corresponds to the horizontal wellbore lateral three export, in the three exit we can see dryness decline significantly. Compared with steam injection after 1, 3, 5 days, we can find that the longer the steam injection, the greater the steam quality in wellbore. This is due to the increased with the increase of steam injection time outside the wellbore temperature high and within the wellbore heat transfer coefficient decreases, so the steam within the wellbore heat loss is small.

Fig.5. Variation of steam injection pressure in single tube

Fig.6. Variation of steam injection temperature in single tube

4.3.2.double pipe horizontal well steam injection simulation

Fig.7. Variation of steam injection dryness in single tube

Figure 10 and figure 11 show two pipe horizontal well steam injection process, the steam injection tube and steam injection tube steam injection respectively 1, 3, 5 days later, the tube with hot steam quality distribution in the inner tube. Figure illustrates the steam injection in the outer tube steam quality change rule and single pipe steam injection dryness change rule are quite similar. In three lateral wellbore steam mouth dryness change rule changes; while the effect of injecting steam saved by the tube, the steam dryness drop is small. In three lateral wellbore steam mouth dryness change rule changes; while the effect of injecting steam saved by the tube, so the steam dryness drop is small.

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Fig.8. Variation of steam injection pressure in double tube

Fig.10. Variation of steam injection dryness in outside tube

Fig.9. Variation of steam injection temperature in double tube

Fig.11. Variation of steam injection dryness in inside tube

5.Conclusion In this paper, we establish a two dimensional axisymmetric model. Combined with Mathematical model simulation of water vapour oil three phase flow, we analyzed the changes of dry and pressure in vertical well and horizontal well in the process of thermal recovery of heavy oil. This paper argues that in the steam injection wellbore, the smaller heat loss of steam dryness, the less heat loss in the process of steam injection. According to the numerical analysis of the model, this paper gets the following conclusion. First of all, in vertical well steam injection, steam injection wellbore type has an important influence for the vapour injection effect. This article studies the three steam injection tubing string (upset tubing, vacuum heat insulation oil pipe, high vacuum heat insulation oil pipe). Thickening of the tubing in the steam injection wellbore dryness decline is the largest, high vacuum heat insulation oil pipe of steam injection has the smallest drop in dryness, and the vacuum heat insulation oil pipe of steam injection dryness decline is slightly superior to high vacuum heat insulation oil pipe. From the results, a single horizontal well steam injection process in three lateral outlet steam dryness decreases faster. Double pipe steam injection has the similar changing rule with the dry degree. In the dual process of steam injection pipe in the steam dryness decreased linearly, and the decline is very small. With the increase of the time of steam injection in horizontal wells, the steam injection at the end of the steam injection well is obviously increased. Compared to single tube steam injection, steam pipe steam injection wellbore in the dry degree is higher, as a result, the pipe gas injection is better than single steam injection.

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Acknowledgements It is gratefully acknowledged that financial support for this work has been provided for those foundation items: 1.Natural Science Foundation of Shandong (ZR2015PE016), China; 2.Nature science foundation of China (51305238); 3.China postdoctoral science foundation(2015M572023). References [1] Yu Hai-tao. The effect of Steam dryness effects on oil displacement effect. Science Technology and Engineering 2012, 12 (12);2981-2982. [2] Yang Hui-Chun. The controllable factors influencing the dryness of steam injecting. Value engineering 2014,19(13):32-33. [3] Yang Li-Hua. Steam injection system of heat loss and improving measures. New Technique and Material 2016,42(2):64-66. [4] Liu Wen-Zhang. Heavy oil steam injection thermal recovery project. Beijing : Petroleum Industry Press,1997 [5] Dong XH, Liu HQ, Zhang ZX, Wang CJ. The flow and heat transfer characteristics of multi-thermal fluid in horizontal wellbore coupled with flow in heavy oil reservoirs. J Petrol Sci Eng 2014;122:56–68. [6] Zhai jian-hua. Two phase flow in vertical pipe flow pressure drop calculation. Mechanics In Engineering 1985,2:32-37. [7] Shen Hui-Fang. eavy oil steam stimulation Wells surface pipeline and wellbore thermodynamic calculation. Oil Drilling & Production Technology 1990,13(4):55-64. [8] Squier D P, Smith D D, Dougherty E L. Calculated Temperature Behavior of ot-Water Injection Wells,J.Per. Tech 1962: 436-440 [9] Hasan AR. Kabir CS. Modeling two-phase fluid and heat flows in geothermal wdls. JPetrol Sci Eng 2010,71:77-86. [10] Hainan AR, KabirCS.Wellbore heat-transfer modeling and applications. Jpetrol Sci Eng 2012, 86:127-136. [11]Emami-Meybodi H, Saripalli HK, Hassanzadeh H. Formation heating by steam circulation in a horizontal wellbore. Int J Heat Mass Transf 2014, 78:986–92. [12] Moss J T, White P D. How to Calculate Temperature Profiles in a Water-Injection Well, Oil and Gas J 1959, 57: 11,174 [13] Fokeev V M, Kapyrin Y V. Calculation of Wellbore Heat Losses, and the Effect of Injection of Large Quantities of Water on the Temperature Distribution in the Romashkin Rerervoir (in Russian),Neftyanoe Khozaistvo 1961,12,33. [14] Huygen H A, Huitt J L. Wellbore Heat Losses and Casing Temperatures During Steam Injection, Prod.Montlily 1966, 30, 8. [15] Lee, W. H. A pressure iteration scheme for two-phase flow modeling. Washington DC, Applications, Hemisphere Publishing 1980. [16] Brackbill, J. U, Kothe, D. B, Zemach, C. A continuum method for modeling surface tension, Journal of Computational Physics1992, 100: 335-354.

Biography Guo Chunsheng is a post doctor student in the Scholl of Material Science and Engineering at Shandong University. He worked on reservoir simulation, flow slip theory between pours media and free flow, loop heat pipe technologies, and enhanced heat transfer technology.

Appendix A. A.1. The control equation

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VOF mode is adopted because water- steam -oil three-phase are involved ,in the process of steam injection. VOF model has good interface tracking performance and can analyze mass flow density in mass transfer process [14]. The calculation model use standard k- turbulence model and the governing equations adopt the Navier-Stoke equation by the Reynolds average method for processing. Quadrilateral mesh is used in computational grid, and pressure boundary condition is adopted in grid boundary. The SIMPLE method is used to calculate. The momentum and volume fraction using QUICK equation, and the momentum equation employ the first order upwind equation. There is flow and heat transfer of water-steam two-phase flow in steam injection process, transformation of water- steam two-phase flow using the phase change model [15] proposed by W.H.Lee. In the formula , mv ml said the steam and water phase mass transfer; for phase change coefficient; Tsat for saturation temperature. (1) T Tsat m v m l T ∃ Tsat ( evaporation process ) l %l Tsat

m l

m v

v

%v

T

Tsat Tsat

T % Tsat ( condensation process )

(2)

A.1.1.Steam injection control equation of vertical well There is only steam-liquid two-phases in the vertical well, the continuity equation is as follows: 1 (3) w ! v ∀α w m dV ! # & (vαw )dV = w (4) ∀t ρw ∀α v m dV ! # & (vαv )dV = v (5) ∀t ρv In the formula, the n express speed, m/s;using the average speed of liquid flow in the reservoir , steam through the interface of wellbore and reservoir enter into the reservoir while the speed keep continuous, namely v=< >,aw and av express the volume fraction of oil, water and steam in the unit. The momentum equation is as follows, k– turbulence equations is needed when solving.



(ρv) !#& (ρvv)

#p !#& [∃(#v !#v )]+ρg+FV T

(6)

∀t The density and viscosity of the mixture are shown in the following diagram.

ρ = ρw α w + ρv αv

(7)

μ = μ w α w + μv α v

(8) CFS model is built to transform the continuous surface tension force into the volume force by Brackbill[16], In the formula 9 , express coefficient of surface tension and express interface curvature. the values of is 5.25.

FV σ

αwρwςw# w !αv ρvςv#αv 0.5(ρw +ρv )

(9)

The energy equation in the wellbore is as follows. In the equation ,H is the enthalpy of the mixture, J; is the thermal conductivity of the mixture ,W/m; the Sh is the phase change heat (or heat absorption).

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∀ ∀t

(ρh) !#& (ρvh) #& [λ (# T)]+S

(10)

h

h=

αw ρw hw + αv ρv hv αw ρw + αv ρv

(11)

hw Cpw, (T T0)

(12)

hv Cpv, (T T0)

λ = λwαw +λv αv

(13)

∋-m s Hc,saturation is gas phase Sh ( )m s Hc,saturation is liquid phase

(14)

The formation heat conduction equation is as the follow formula 15:

∀2T l ∀2T 1 ∀T 1 ∀2T ∀2 T =  2 + + +  ∀t %c ∀r r ∀r r 2 ∀& 2 ∀y2

(15)

A.1.2.Steam injection control equation of horizontal well Different from vertical well, the horizontal well section is an open well end containing water- steam- oil three phase, so the control equation is more complex than the vertical well, the same equation in the wellbore and reservoir expression is also slightly different. The equation in horizontal well was same with the equation in vertical well. In reservoir, the momentum equation is different as shown in equation 16. ∀ ∀t

∋ v ) !#& (ρ∋ vv )



#

p

∋v

!#& [∃(#

∋v

!#

T

)] ! ρg+FV +Si

(16)

In order to capture the flow characteristics near the interface between the wellbore and the reservoir, the Si is used to express the momentum source terms in the Forhheimer-Ward formula.

μ 1 S = - ∋ v -C ρ∋ v ∋ v i k 2

(17)

A.2.boundary conditions In this paper, the rotation axis symmetry model is established, so the axis of the steam injection wellbore is a rotational symmetry axis. Steam injection port is constant flow inlet. The vertical well exit is a constant pressure boundary, and the horizontal well exit is a fluid coupling boundary where fluid can be freely passed, and the boundary of steam reservoir in horizontal well is a constant pressure boundary. The interface between horizontal well steam injection pipe and reservoir use the continuous boundary conditions of shear stress put forward by Neale and Nader . (18) ∀ ∀∗ +



∀



 !

∀

 

In horizontal wells, there are annular hot air, casing, cement ring and so on. In order to simplify the calculation, the multi layer medium is coupled into one interface. The physical parameters of the interface can be obtained by calculating. According to the relationship between the thermal resistance and thermal conductivity. because the cross-sectional area have the same size, the cross-sectional area can be ignored,

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we can think R= , R is the thermal resistance, is the thermal conductivity, is the thickness of the material . The materials are connected in series with R=R1+R2+R3+R4 #∗+∗#∗()∗#∗,)∗#∗−)∗#∗. , so we can calculate coupling wall thermal conductivity. We can do the same coupling calculation of wall surface density, heat capacity etc..

Appendix B. B.The initial parameters of simulation Table 1. Parameters of steam injection Parameters

units

symbol

values

Surface temperature

o

C

T0

20

Geothermal gradient

o

C/100m

ΔT

3

Inner diameter of thickened oil pipe

mm

r1

75.9

Vacuum insulated tubing radius

mm

r2

60.32

High vacuum insulated tubing radius

mm

r3

60.32

Vertical well depth

m

H

100

M

0.8 10

Dryness of steam injection Steam injection pressure of vertical well

MPa

P0

Steam injection pressure of horizontal well

MPa

P0’

9.5

Reservoir pressure

MPa

P

10

Initial reservoir temperature

o

T0’

23

Crude oil density

kg/m3

ρo

980

Specific heat of crude oil

kJ/(kg·K)

Co

1.5

Coefficient of thermal conductivity of crude oil

W/m·oC

λo

0.18

Water density

kg/m3

ρw

998

Specific heat of water

kJ/(kg·K)

Cw

4.178

Thermal conductivity of water

W/m·oC

λw

0.065

Specific heat of steam

kJ/(kg·K)

Cv

6.73

C

o

Thermal conductivity of steam

W/m· C

λv

0.079

The diameter of horizontal single shaft

mm

r4

79.5

Double inner tube diameter

mm

r5

40.32

Double tube outer tube diameter

mm

r6

79.5

Horizontal wellbore length

m

L

100