HPHT Gas Well Cementing and Effect on Collapse

SPE 153986

HPHT Gas Well Cementing Complications and its Effect on Casing Collapse Resistance Zhaoguang Yuan, Texas A&M, Jerome Schubert, Texas A&M, Catalin Teodoriu, TU Clausthal, Paolo Gardoni, Texas A&M

Copyright 2012, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Oil and Gas India Conference and Exhibition held in Mumbai, India, 2830 March 2012. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

Abstract The failure probability of casing collapse is high in HPHT gas wells because of the cementing complications and the operational environment. In the life of a well, the cement sheath not only provides zonal isolation but also supports casing and increases casing collapse resistance. Due to the high temperature high pressure conditions, the cement sheath plays a more important role in maintaining wellbore integrity. During the production process in HPHT gas wells, the pressure differential inside the casing and the surrounding formation is larger than the conventional wells, this presents a greater challenge to the casing integrity.

Casing eccentricity, cement voids and cement channels usually are cementing complications in HPHT gas wells. Pore- pressure was also considered in this study. In the analysis, the finite element method was used and 2D simulation model was built to study the effect of cementing complications on casing collapse resistance. In the study, two cement systems, brittle cement system and elastic cement system, were used to analyze the effect of the cement property on the casing collapse resistance. In the sensitivity analysis, void location, void size and shape, casing eccentricity, pore pressure, casing internal pressure, horizontal stress, cement Youngs Modulus, cement Poisson ratio, hole diameter, and formation temperature were considered to study their effect on casing collapse resistance.

The results showed that an improvement of collapse resistance of 12% is observed in various conditions in elastic cement system. Casing collapse resistance is very sensitive to void location, cement Poissons Ratio, cement Youngs Modulus, and pore-pressure. Casing eccentricity and voids shape have minor effect on the casing collapse resistance. Simultaneous cement channeling and casing eccentricity is the worst case scenario in casing collapse resistance.

This study gives a better understanding of casing collapse failure in HPHT gas wells and helps improve cement and casing design to maintain wellbore integrity that can be expected to last for the life of the well.

Introduction Exploring and producing new hydrocarbon reserves may be a more and more challenging task, often requiring petroleum industry to contend with hostile downhole conditions. Although high-pressure, high-temperature wells are drilled, stimulated, produced and monitored in a way similar to wells with less-demanding conditions, the HPHT environment limits the range of available materials and technologies to exploit these reservoirs. The oil and gas industry has been contending with elevated temperatures and pressures for years.

Wells that present HPHT characteristics have been being drilled since the late 70s in the Gulf of Mexico and in the early 80s in the North Sea. HPHT wells have been split into three categories based on the temperature and pressure envelopes, namely HPHT, extreme HPHT and ultra-HPHT wells, with temperature higher than 400 0F and pressure greater than 20,000 psi (R.R. Paula Jr., et al., 2009). According to the Health and Safety Executive, British safety agency, the HPHT well (in the industry, these wells are known as high pressure and high temperature) is the one where the non-disturbed, bottom temperature, is superior to 3000F and the highest gradient of the pores pressure foreseen for any porous formation exceeds 0.8 psi/ft or the required working pressure for the equipment of well controlling (BOP) is superior to a 10,000 psi.

2 SPE 153986

As the pressure was increased, more gas can be stored per cubic foot in HPHT wells makes them very productive. But they are much more expensive to complete because of the more advanced technology required. Among the increasingly deep and unknown places operators are going are high-pressure, high-temperature gas wells, where the definitions of depth, pressure and temperature are ever expanding. HPHT environments result in higher drilling and completion risk and cost. The increased temperature drastically affects the stability and longevity of downhole electronics and must be properly considered to manage overall efficiency and cost. And simultaneously, because of the high pressure operation conditions, the partial pressures of CO2 and H2S exposed to wellbore tubular was increased significantly, there is the potential for severe corrosion and cracking. The corrosive rates are higher for HPHT wells and require expensive corrosion-resistant alloys for downhole tools, wellbore construction and surface pressure-control equipments.

Because of the high cost of HPHT wells, the way to reduce the failure probability of HPHT wells and increase the wellbore service life are highlighted. In the completion process, the cementing complications may happen though the best efforts are tried. The study to know the effect of cementing complications and find methods to mitigate or avoid wellbore failure is important. Cement mechanical properties are the important input data for casing-cement system analytical analysis and finite element method study. Many experimental studies have been taken out to measure cement mechanical properties under different conditions. One of the earliest lab tests to simulate the field condition was taken to test cement sheath failure (Goodwin K.J. et al., 1992). The cement was cured at the temperature of 350 oF , with the maximum casing inside pressure of 10,000 psi and the annulus pressure of 500 psi. Another model with the cements cured under higher temperature was built for testing the long term HPHT condition on the properties of cements (D. Stiles et al., 2006). The cement was cured at the pressure of 2,133 psi with the temperature of 6450F. The cement was cured under the condition of 2,610 psi, and 212 0F (Catalin Teodoriu, et al., 2012). The experimental results can be used for the casing-cement-formation system analytical study (C. Atkinson., et al., 1996; Catalin Teodoriu, et al., 2010). However, the analytical analysis can only consider symmetry condition. The casing eccentricity, cementing voids and channeling is difficult to be studied under this condition.

Casing eccentricity usually depends on wellbore angle, the number of casing centralizers and wellbore dimension. The higher the wellbore inclination angle usually leads to higher value of casing eccentricity (Ferda Akgun, et al., 2004). The effect of casing eccentricity on the cementing operation was investigated (M.Courturier et al., 1990; Silva, M.G.P. et al., 1996). When the casing is off centered, the fluid favors the path of least resistance and flows more rapidly on the wide side than on the narrow side of the geometry. The consequence is that the velocity distribution is distorted and the displacing fluids may bypass the slowly moving drilling mud on the narrow side. Then at the end of displacement process, the annulus may be left with a long strip of inefficient cementing displacement of the drilling mud in a given interval depending on the local geometry. If casing eccentricity happens, cement channeling tends to build up simultaneously. Cement channeling allows for cavities to be filled with drilling mud, unset cement, or formation materials. To prevent cement channeling needs to design mud, spacer and the cement properties properly (Christopher F.Lockyear, et al., 1990). Some techniques can be used to detect and repair cement channels (P.E. Hart, et at., 1990).

Its also very import to know the effect of casing eccentricity and cement channeling on the wellbore integrity if the cementing problems exist. Finite element methods are good for studying cementing complications with complicated conditions. Using finite element methods, the stress distribution in the cement and the casing under perfect condition was well analyzed (W.J.Rodriguez et al., 2003). There is much difference for the Von Mises stress distribution in the casing between the high thermal properties cements with the thermal conductivity of 2.4 /Wm-1K-1 and the low thermal properties cements with the thermal conductivity of 0.66 /Wm-1K-1(Manoochehr Salehabadi et al., 2010). The maximum Von Mises stress in casing in wellbores cemented using high thermal properties cements does not increase significantly by increasing the degree of casing eccentricity. However, the maximum Von Mises stress in casings in wellbores cemented using the low thermal properties cements increases by increasing the casing eccentricity. In reality, most of the cements fall into the category of low thermal property cements. The effect of casing eccentricity, voids, cement channels and pore pressure decline on the collapse resistance of casing was studied (A.Berger et al., 2004). The presence of voids and cement channels can reduce the casing collapse significantly. The casing eccentricity has minor effect on casing collapse resistance. However, the voids size, location and sensitivity analysis was not considered. One more study (A.Nabipour et al., 2010) shows the same results that the casing eccentricity has minor effect on casing collapse resistance.

However, the sensitivities of mechanical properties to stress distribution in casing-cement-formation system are still seldom studied and they are the important parameters to improve the cement design. In this analysis, the sensitivity of casing and cement mechanical properties, voids location, voids size and shape are taken into account and tried to figure out which parameter is the most important and its effect on casing collapse resistance.

Finite Element Methods

Finite element methods are the effective tool for structural analysis and thermal analysis. ANSYS 12.0 was the platform to develop codes for this study. In the thermal analysis, the element of PLANE77 was used. PLANE77 is a higher order version of the 2-D, 4-node thermal element. The element has one degree of freedom, temperature, at each node. The 8-node elements have compatible temperature shapes and are well suited to model curved boundaries. The 8-node thermal element is

SPE 153986 3

applicable to a 2-D, steady-state or transient thermal analysis. After the thermal analysis was done, the results of element temperature are loaded for structural analysis. The element of PLANE82 was used for structural analysis. PLANE82 is 2-D 8-Node Structural Solid element. It provides more accurate results for mixed (quadrilateral-triangular) automatic meshes and can tolerate irregular shapes without as much loss of accuracy. The 8-node elements have compatible displacement shapes and are well suited to model curved boundaries. The 8-node element is defined by eight nodes having two degrees of freedom at each node: translations in the nodal x and y directions. The element may be used as a plane element or as an axisymmetric element. The element has plasticity, creep, swelling, stress stiffening, large deflection, and large strain capabilities.

The elements generated are shown in figure 8. In the first step, in the environment of thermal analysis, using the element of PLANE77, the temperature of each node is calculated and stored in a file. Then, the file was loaded in structural analysis environment, using the element of PLANE82, the thermal expansion and thermal stress of the casing-cement-formation system is solved. Together with the displacement boundary and pressure boundary conditions, the stress distribution in the system was calculated (shown in figure 9 to figure 32).

Model Dimension and Boundary Conditions The wellbore conditions are from one typical high pressure high temperature gas well in south Texas which produces gas in sand formation. The well depth is 18,000 ft with the pore-pressure gradient of 0.9 psi/ft. The 23.2 lb/ft, 5 in. OD, Grade P110 Casing was used for well completion with the hole of 6 in. In the simulation, two cement systems are used, elastic cement and brittle cement system, to study the effect of cement mechanical properties on casing collapse resistance.

Table 1 Model Dimension and Boundary Conditions

Casing ID. (in.) 4.044

Casing OD. (in.) 5

Hole Diameter (in.) 6

Formation Radius (in.) 20

Maximum Horizontal Stress (psi) 11,950

Minimum Horizontal Stress (psi) 11,820

Pore Pressure (psi) 11,000

Bottomhole Pressure (psi) 10,000

Reservoir Temperature (0F) 300

Bottomhole Temperature (0F) 260

Table 2 Material Mechanical Properties Casing Elastic Cement Brittle Cement Formation

Youngs Modulus (psi) 3e7 2e6 4e6 3e6

Poissons Ratio 0.3 0.35 0.2 0.3

Specific Heat (Btu/lb.0F) 0.11943 0.5231 0.5008 0.2385

Coefficient of Thermal Expansion (/0F) 1.3e-5 9e-6 1e-5 1e-5

Thermal Conductivity (Btu/hr ft 0F) 8.668 0.5425 0.6149 0.5726

4 SPE 153986

Sensitivity Analysis

Probabilistic sensitivities are important in allowing you to improve the design toward a more reliable and better quality product, or to save money while maintaining the reliability or quality of the product. A sensitivity plot for any random output parameter in the model can be made to show the sensitivities of the random input variables on the random output random variables.

Usually, the researchers use lognormal distribution to describe material mechanical properties because for lognormal distribution, the values of material mechanical properties are positive. This is true. However, according to the characteristics of lognormal distribution, there is a small probability that the values for lognormal distribution reach positive infinity and nearly zero. In reality, the values of material mechanical properties cannot reach positive infinity or nearly zero. A Beta distribution can better describe the material property with the lower boundary and upper boundary. A Beta distribution of a random variable X has four distribution parameters, namely the shape parameters r and t, the lower limit a and the upper limit b. The probability density function of a Beta distribution is:

( ) ( )( )( )

1 1

1( , , , ) ,

q r

q r

x a b xBet a b q r

B q r b a

+ + = ,

With parameters range , , , a b< 0 q< 0 r< a x b In which Beta Function

( ) ( ) ( )( ),q r

B q rq r

= +

And Gamma Function

( ) ( )10

expkk u u = du

Inherently, Monte Carlo simulations always vary all random input variables at the same time, thus if interactions exist then they will always be correctly reflected in the probabilistic sensitivities. Monte Carlo simulations method is used for the sensitivity analysis with 1,000 repetitions which means every random input variable has 1,000 sample points as shown in wellbore diameter distribution in figure 3. For probability analysis, the Monte Carlo simulation takes 5 hours to generate 1,000 samples for each random input variable and to finish the solution.

Table 3 Random Input Variables and Distribution

Distribution Type a ( Minimum value) B

(Maximum value) q

(Shape Factor) r

(Shape Factor)

Casing Inside Pressure (psi) Beta Distribution 2000 14000 2 3

Wellbore Diameter (in.) Beta Distribution 5.8 7.5 2 5

Casing Youngs Modulus (psi) Beta Distribution 2.5e7 3.5e7 2 2

Casing Poissons Ratio Beta Distribution 0.25 0.35 2 2

Cement Youngs Modulus (psi) Beta Distribution 1e6 5e6 2 3

Cement Poissons Ratio Beta Distribution 0.15 0.4 2 3

Formation Youngs Modulus (psi)

Beta Distribution 1e6 3e6 2 2

Formation Poissons Ratio Beta Distribution 0.15 0.35 2 2

SPE 153986 5

Usually, the cement sheath fails before the casing fails because the cement sheath cannot provide enough support for the casing. Thus, in the sensitivity analysis, the cement stress distribution is more important than the casing stress distribution. In the analysis, the cement maximum Von Mises stress and maximum shear stress are used as random output variables

The evaluation of the probabilistic sensitivities is based on the correlation coefficients between all random input variables and a particular random output parameter. To plot the sensitivities of a certain random output parameter, the random input variables are separated into two groups: those that are significant (important) and those that are insignificant (not important) for the random output parameter. The sensitivity plots will only include the significant random input variables. The probabilistic design system will plot only the sensitivities of the random input variables that are found to be significant. However, insignificant sensitivities are printed in the output window. In the plot, a positive sensitivity indicates that increasing the value of the random input variable increases the value of the random output parameter for which the sensitivities are plotted. Likewise, a negative sensitivity indicates that increasing the random input variable value reduces the random output parameter value.

Figure 1 and figure 2 show that the cement maximum Von Mises stress and the cement maximum shear stress are sensitive to cement Youngs modulus and formation Youngs modulus. The casing inside pressure, wellbore diameter, casing youngs Modulus, casing Poissons ratio, cement Poissons ratio and formation Poissons ratio are insignificant parameters in the sensitivity analysis. In reality, formation Youngs modulus is uncontrollable parameter, only cement Youngs modulus can be designed and controlled. Reducing the value of cement Youngs modulus can reduce the cement maximum Von Mises stress and provide a better cement sheath support for the casing. On the other hand, reducing the value of cement Youngs modulus will increase the cement maximum shear stress which may lead to bad cement sheath support. The balance has to be weighed between the advantage and disadvantage of reducing the cement Youngs Modulus. Within the limit of cement shear failure, the value of cement Youngs modulus can be designed to minimum if economically available.

Figure 1 Cement Maximum Von Mises Stress Sensitivity Analysis

6 SPE 153986

Figure 2 Cement Maximum Shear Stress Sensitivity Analysis

Figure 3 Wellbore Diameter Distribution

SPE 153986 7

Cementing Complications Analysis

In the simulation, seven different cases were studied (figure 9 to figure 29). Casing Centered in the hole without any cementing complications is the perfect case. In the cementing complication analysis, casing eccentricity, void, and cement channel were considered. In the cementing void analysis, the effect of the void location on the wellbore integrity was studied. Finally, casing eccentricity and cement channel were studied together in the last case.

In the analysis, the 0.3 in. eccentricity stands for the center of the casing moves 0.3 in. toward the wellbore. From table 4, figure 4, the casing eccentricity alone doesnt have much effect on the casing and cement. The maximum Von Mises stress difference is only 0.27% for the 0.3 in. eccentricity and the casing centered in the hole. The void location is the most important factor on casing stress. If the voids locate near the casing, the maximum von Mises stress in the casing increase significantly comparing to other cases. The Von Mises stress in the contact area between the casing and the voids is beyond the casing yielding strength a lot. Water or drilling mud is trapped in the voids. Water and drilling mud has very lower compressibility and they behave like incompressible material comparing to casing and cement. This may cause the very high stress in the contact area between the voids and the casing.

Casing eccentricity and cement channel usually happen simultaneously. This is the second highest failure probability scenario. If casing is not centered, the cross section area fluid flow velocity is different during the cementing process. This may contribute to the cement channel problem in the lower clearance area. Cement channel leads to the third highest von Mises stress in the casing. The stress in this scenario is 60% higher than the stress in the perfect condition. Casing eccentricity, voids in the center of cement and voids near formation doesnt have much effect on the casing von Mises stress comparing to the perfect condition.

There is a little bit lower Von Mises stress developed in the casing under the condition of the elastic cement. However, using the elastic cement doesnt improve the stress distribution in the casing significantly. The stress in the casing under the condition of elastic cement is 12% lower than stress in the casing under the condition of brittle cement.

For the stress developed in the cement, from figure 5, voids in the center of the cement, voids near casing and 0.3 in. eccentricity & cement channel are the three worst cases. For brittle cement, voids near formation and cement channel also develop very high stresses in the cement. Cement channel and cement voids near formation increase the Von Mises stress in the cement significantly comparing to the perfect cement condition. It is obviously that the elastic cement has much better behavior than brittle cement. The stresses in the three worst cases are almost reduced 33% to 43%. This trend is also seen in the scenario of voids near formation and cement channel.

Table 4 Casing and Cement Maximum Von Mises Stress Distribution

Brittle Cement Elastic Cement

Casing Von Mises Stress (psi)

Cement Von Mises Stress (psi)



Casing Centered in the Hole 49,598 15,418 46,246 14,658

0.3 in. Eccentricity 49,730 15,949 46, 697 14,832

Voids Near Casing 189,570 49,010 178,266 27,912

Voids in the Center of Cement 53,010 47,234 46,770 28,878

Voids near Formation 54,016 26,719 51,767 15,477

Cement Channel 79,043 30,134 62,276 17,792

0.3 in. Eccentricity & Cement Channel 103,254 45,975 91,864 30,625

8 SPE 153986

Fig.4 Maximum Von Mises Stress in Casing

Fig.5 Maximum Von Mises Stress in Cement Voids Shape and Size Effect In the two dimension simulation, rectangle and circle void shape are used in the analysis. For the circle voids, the radius was increased from 0.1 in. to 0.2 in. As shown in table 5 and figure 6, the voids shape and size doesnt have much effect on the maximum Von Mises stress developed in the casing.

However, from figure 7, the maximum Von Mises stress developed in the cement with 0.2 in. radius circle void is 27% higher than that in cement with 0.1 in. radius circle void. For brittle cement, the cement with the rectangle void and the 0.2 in. radius circle void has the highest Von Mises stress. The brittle cement is more sensitive to the void shape. For elastic cement, the void shape has minor effect on the cement stress distribution. As the void size increases, the maximum stresses developed in the cement also increase. No matter from the voids location, voids size and voids shape, the elastic cement shows much better behavior than the brittle cement.

SPE 153986 9

Table 5 Casing and Cement Maximum Von Mises Stress Distribution for Different Voids

Brittle Cement Elastic Cement





Casing Centered in the Hole 49,598 15,418 46,246 14,658 Rectangle Void in the Center of Cement 53,010 47,234 46,770 28,878

Circle Void in the Center of Cement (0.1 in. radius) 50,559 39,592 49,314 34,542

Circle Void in the Center of Cement (0.15 in radius) 53,035 44,455 51,685 39,899

Circle Void in the Center of Cement (0.2 in. radius) 56,925 48,378 55,414 43,872

Figure 6 Maximum Von Mises Stress in Casing

Figure 7 Maximum Von Mises Stress in Cement

10 SPE 153986

Conclusions 1. The cement maximum Von Mises stress and the cement maximum shear stress are sensitive to cement Youngs

modulus and formation Youngs modulus. Reducing the value of cement Youngs modulus can reduce the cement maximum Von Mises stress and increase the cement maximum shear stress. Within the limit of cement shear failure, the value of cement Youngs modulus can be designed to minimum if economically available.

2. The casing eccentricity alone doesnt have much effect on the casing and cement. The maximum Von Mises stress difference is only 0.27% for the 0.3 in. eccentricity and the casing centered in the hole.

3. For the stresses developed in the cement, voids in the center of the cement, voids near casing and 0.3 in. eccentricity & cement channel are the three worst cases. For the stresses developed in the casing, voids near casing, and Casing eccentricity & cement channel are the worst two cases.

4. The elastic cement has much better behavior than brittle cement. The stress in the casing under the condition of elastic

cement is 12% lower than stress in the casing under the condition of brittle cement. The stresses developed in the cement in the three worst cases (voids in the center of the cement, voids near casing and 0.3 in. eccentricity & cement channel) are almost reduced 33% to 43%.

5. The voids shape and size doesnt have much effect on the maximum Von Mises stress developed in the casing. The

brittle cement is more sensitive to the void shape than the elastic cement for the stress developed in the cement. Acknowledgments This study was supported by Research Chevron Center for Well Construction and Production of Crisman Institute for Petroleum Engineering in Texas A&M Petroleum Engineering Department. We gratefully acknowledge these supports.

References

A. Gerger, W. W. Flecknestein, and A. W. Eustes:Effect of Eccentricity, Voids, Cement Channels, and Pore Pressure Decline on Collapse Resistance of Casing, SPE 90045, SPE Annual Technical Conference and Exhibition, 26-29 September 2004, Houston, Texas.

A.Nabipour and B.Joodi:Finite Element Simulation of Downhole Stresses in Deep gas Wells Cements, SPE 132156, SPE Deep Gas Conference and Exhibition, 24-26 January 2010, Manama, Bahrain.

C. Atkinson., and D. A. Eftaxiopoulos:A Plane Model for The Stress Field around an Inclined, Cased and Cemented Wellbore, International Journal for Numerical and Analytical Methods in Geomechanics, 1996, Vol. 20, 549-569.

Catalin Teodoriu, Ignatius Ugwu and Jerome Schubert:Estimation of Casing-Cement-Formation Interaction Using a new Analytical Model, SPE 131335, SPE EUROPEC/EAGE Annual Conference and Exhibition, 14-17, June 2010, Barcelona, Spain.

Catalin Teodoriu, Zhaoguang Yuan, Jerome Schubert and Mahmood Amani:Experimental Measurements of Mechanical Parameters of Class G Cement, SPE 153007, SPE/EAGE European Unconventional Resources Conferences and Exhibition, 20-22 March 2012, Vienna, Austria.

Couturler, M., Guillot, D., Hendriks, H. and Callet F.:Design Rules and Associated Spacer Properties for Optimal Mud Removal in Eccentric Annuli, SPE 21594, CIM/SPE International Technical Meeting, 10-13 June 1990, Calgary, Alberta, Canada.

D. Stiles:Effects of Long-Term Exposure to Ultrahigh Temperature on the Mechanical Parameters of Cement, IADC/SPE 98896, 21-23 February, 2006 IADC/SPE Drilling Conference, Miami, Florida

Ferda Akgun, Shedid A. Shedid and Hamed H. Al-Ghadban:Simulation Investigation of Casing Eccentricity Estimation for Different Inclination Angles and Tensile Forces Using Finite Element Method, SPE 91811, SPE International Petroleum Conference in Mexico, 7-9 November 2004, Puebla Pue., Mexico.

SPE 153986 11

Goodwin K.J., and Crook R.J.:Cement Sheath Stress Failure, SPE Drilling Engineering, December 1992, Volume 7, Number 4, Pages 291-296.

Hart P.E. and Wilson L.C.:Improved Channel Repairs with Small-Phased Circumferential Perforating Guns, SPE 20424, SPE Annual Technical Conference and Exhibition, 23-26 September 1990, New Orleans, Louisiana.

Lockyear, Christopher F., Ryan, Daniel F., Gunningham and Marcus M.:Cement Channeling: How To Predict and Prevent, SPE Drilling Engineering, September 1990, Volume 5, Number 3 Pages 201-208.

Manoochehr Salehabadi, Min Jin, Jinhai Yang, Rehan Ahmed and Bahman Tohidi:Effect of Casing Eccentricity on Casing Stability Analysis in Wellbores Drilled in Gas Hydrate Bearing Sediments, SPE 131236, SPE EUROPEC/EAGE Annual Conference and Exhibition, 14-17 June 2010, Barcelona, Spain.

R.R. Paula Jr., P.R. Ribeiro and O.L.A. Santos:HPHT DrillingNew Frontiers for Well Safety, SPE 119909, SPE/IADC Drilling Conference and Exhibition, 17-19 March 2009, Amsterdam, the Netherlands

Silva, M.G.P., Martins, A.L., Barbosa, B.C. and Garcia Jr. H.:Designing Fluid Velocity Profiles for Optimal Primary Cementing, SPE 36136, SPE Latin America/Caribbean Petroleum Engineering Conference, 23-26 April 1996, Port-of-Spain, Trinidad.

W.J.Rodriguez, W.W.Fleckenstein, and A.W.Eustes:Simulation of Collapse loads on Cemented Casing Using Finite Element Analysis, SPE Paper 84566, SPE Annual Technical Conference and Exhibition, 5-8 October 2003, Denver, Colorado.

12 SPE 153986

Figure 8 Casing, Cement and Formation Elements

(Casing Centered in the Hole)

Figure 9 Casing, Cement and Formation Von Mises Stresses Distribution


SPE 153986 13

Figure 10 Casing Von Mises Stress


Figure 11 Cement Von Mises Stress


14 SPE 153986

Figure 12 Casing, Cement and Formation Von Mises Stress

(Voids near Casing)


(Voids near Casing)


(Voids near Casing)

SPE 153986 15


(Voids in the Center of Cement)

Figure 16 Casing Von Mises Stress (Voids in the Center of Cement)


(Voids in the Center of Cement)

16 SPE 153986


(Voids near Formation)





SPE 153986 17


(Cement Channel)


(Cement Channel)


(Cement Channel)

18 SPE 153986


(0.3 in. Eccentricity)





SPE 153986 19


(0.3 in. Eccentricity & Channel)





20 SPE 153986

Figure 30 , Cement and Formation Von Mises Stress

(Circle Void in the Center of the Cement, 0.2 in. radius)





Documents

HPHT Gas Well Cementing and Effect on Collapse