Copyright 2003, Offshore Technology Conference This paper was prepared for presentation at the 2003 Offshore Technology Conference held in Houston, Texas, U.S.A., 5–8 May 2003. This paper was selected for presentation by an OTC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Offshore Technology Conference or officers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference 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 where and by whom the paper was presented.

Abstract The challenges found in deepwater and ultra-deepwater drilling have, in a remarkable short period, forced the oil industry to develop new significant technologies and techniques. The characteristics of the deepwater environments have pushed design criteria, normally used in onshore and shallow water wells, to values beyond their traditional limits. All drilling phases of deepwater and ultra deepwater wells face challenges. The initial phases, generally composed of soft soil or just mud, have required a lot of experience in terms of jetting the conductor pipe to avoid sinking of the wellhead. In the intermediate phases, engineers must be very careful to avoid lost circulation due to the narrow window between pore pressure and low fracture pressure gradients. Besides, well bore instability, always an issue for directional drilling, often limits the length of the deepwater well departures to values considered small if compared to those obtained in shallow waters or onshore. In addition, the drilling of permeable rocks, many times just loose and unconsolidated sands, increases the chance of differential sticking. To complete the picture, watching closely well operation and drilling parameters to keep risks under control generally is not enough. Creativity is very often necessary to overcome the ultra-deepwater challenges. This paper describes Petrobras drilling experience in deepwater and ultra-deepwater. A number of historical cases are shown to illustrate the main obstacles an Operator normally faces when drilling in deepwater. The evolution of well design and drilling practices as the result of the increase of the water depth and its related problems, are also presented. Several experiences with new tools, rig performances and drilling fluid products specific for deepwater are described. Finally, deepwater projects that include extended reach drilling and other special studies are also discussed.

Introduction The discovery of important deepwater oil fields such as Marlim and Albacora has inspired Petrobras to look for new frontiers located in deeper waters. However, initially thought as simple adaptation of the work done in shallow water, a number of new challenges also followed this move. According to the oil industry, deepwater wells are those wells drilled in water depths ranging from 300 meters to 1,500 meters. Wells located in water depths higher than 1,500 meters are classified as ultra deepwater wells. Deepwater drilling with dynamic positioned (DP) rigs has been a reality in Brazil since 1984. Up to 1991, Petrobras used only these types of rigs to drill exploratory wells in the Brazilian Basins, including Campos Basin. After having drilled a number of wells in water depths higher than 1000 meters, Petrobras has started in 1990 an extensive program to drill development wells in deepwater oilfields using both, DP and anchored rigs. Fig. 1 shows a schematic map of the Brazilian Coast and the distribution of deep and ultra deepwater wells along it. Campus Basin, where the main oilfields are located, has the majority of the drilled wells. Though, Espirito Santos Basin, where a number of new discovery have been announced by Petrobras, is expected to have a considerable increase of drilling activities in the future years. Fig. 2 displays the number of wells drilled in deep and ultra deepwater versus time in years. A total of 302 exploratory wells have been drilled until the year of 2002 and other 6 wells have been drilled or were in progress in January 2003. In the same way, 453 developments and special wells were drilled in deep and ultra deep waters until 2002. Other 15 wells were drilled or were on the way until January 2003. As displayed in Fig 2, the number of wells in deep and ultra deepwater has increased since 1995. More seismic interpretations indicating new prospects and the development of a number of oil fields such as Marlim Sul, Albacora Leste and Roncador have contributed to boost drilling activity. Fig. 3 shows an interesting exploratory well distribution according to water depth. Until January 2003 and as mentioned before, 308 exploratory wells have been drilled in deep and ultra deep waters. Among the total, 224 wells are deepwater while 84 wells were drilled in waters considered

OTC 15233

Overcoming Deep and Ultra Deepwater Drilling Challenges Luiz Alberto S. Rocha, P. Junqueira and J.L. Roque /Petrobras

2 OTC 15233

ultra deep. Similarly, Fig 4 shows that Petrobras has drilled a total of 468 development wells (producers, injectors and special wells) in water considered deep and ultra deep. Among this total, 436 are deepwater wells and 32 fall in the group of the ultra deepwater wells. Fig. 5 shows Petrobras deepwater records versus years. As shown, exploratory drilling has rapidly moved to new water depth frontiers and probably soon the 3000 meters mark will be beaten. The plot also shows that productions from water depths higher than 1800 meters have been a reality in Brazil since 1999. Likewise, productions in water depths higher than 2000 meters can be expected in the near future. Deepwater Challenges: Petrobras Experience Successful deepwater drilling is achieved if the total well depth in the desired hole size is reached safely and the designed casings are placed across the desired depth intervals [1]. Although the oil industry has accomplished performing this job, a number of drilling challenges may negatively affect deep and ultra deepwater drilling. Troubles in the shallowest zones, rig efficiency and equipments failures are good examples of factors that can reduce drilling performance. Problems such as fracture of weak formations by the annular pressure losses or total collapse of wellbore walls due to instability of the formations may be obstacles impossible to be overcome. This section summarizes the main problems faced by Operators in deep and ultra deepwater drilling.

Deepwater Geohazards

The following aspects can characterize typical deepwater environment:

Lower overburden stress due to the long water column, resulting consequently in a relatively low stress regime.

Structurally weak, low compacted and unconsolidated sediments, mainly in the shallow portion of the underground.

Besides these aspects, deepwater also faces a number of

problems at the sea floor or in the shallow well part. These problems are known in the oil industry as geohazards.

Geohazards are potential source of problems and include

among other [2] steep unstable slopes, irregular topography, overpressured sands at relatively shallow depths, active faults, landslides, gas hydrates, sea floor erosion, ground conditions raging from weak underconsolidated soils to rock and locally corrosive soils that could require special design of the conductor.

The actual implication of type of the geohazards

mentioned above depends on the current degree of geologic activity and engineering action going on at the specific area. In any case, geohazards are serious a source of problems and cannot be neglected. Shallow water flows (SWF) from pressurized aquifer sands and soil conditions that could cause problems during the jetting of the conductor pipe are typical examples of shallow geohazards that can cause severe economical losses.

Although, SWF or shallow gas flow haven’t been common in Brazil, the standard procedures used by Petrobras to predict geohazards include a number of technologies such as the use of 2D and 3D seismic data, Sonar, Multibeam and Sub bottom Profile (SBP). Piston coring and sea floor rendering are part of the detailed shallow hazard studies to assure that the well location is placed in the best spot. Also, in the case that shallow gas or water accumulations are anticipated, an 8 ½” pilot well may be drilled as a safety procedure.

Fig. 6 shows a seismic section in a deepwater area located

in the coast of the state of Espirito Santo, Southeast Brazil. In this particular case, the observed presence of a shallow fluid escape features by the seismic survey helped engineers to find a better location and avoid unnecessary risks.

Despite of all the procedures used by Petrobras to mitigate

geohazards, only three wells displayed shallow gas or shallow water flows. However, in all cases, changing well locations or simply using standard casing design (30”, 20”, 13 3/8” and 9 5/8”) were enough to drill the wells without operational problems.

Shallow hazards studies have also been extensively used

by Petrobras to determine the presence of hard formations, near to the sea bottom, that can cause problems during the jetting of the conductor pipe. Fig. 7 shows a typical example of the use of seismic data to evaluate soil hardness and formation tops, important information used to define the length of the conductor pipe to be jetted. Pore Pressure versus Fracture Pressure Gradient

Smaller tolerance between pore pressure and fracture pressure gradient resulting in narrow pressure margins while drilling is probably the most recognized deepwater challenge. Fig. 8 schematically shows the pore and fracture pressure gradients as function of depth for two different water depth scenarios. The decrease of the fracture pressure gradient observed in the deeper water case (graph on the left) is mainly due to the reduction of the overburden pressure gradient. In these circumstances, the operational window formed by the pore pressure and the fracture pressure gradient will reduce more and more as the water depth increases. Excessive number of casing strings, slim hole at total depth, unable to reach total depth and fracturing the formation during kick control operations are typical examples of how the reduced operational window affects deep and ultra deepwater drilling.

The introduction of new tools such as pressure while

drilling (PWD) has been effective as a monitoring tool since it alerts engineers for dangerous augment of the annular pressure allowing preventive actions to keep the hole clean without fracturing the formation. The Evolution Well Spud and Well Design

Fig. 9 summarizes the main types of well designs used by Petrobras in its deep and ultra deepwater operations. This evolution is the result of years of experience and some points are described next.

OTC 15233 3

In the seventies, when drilling occurred in water depth up to 300 meters, a typical well configuration was composed by 30” conductor pipe in 36” hole, 20” casing in 26” hole, 13 3/8” casing in 17 ½” hole and the 9 5/8” casing in 12 ¼” hole. The 7” was also used as production casing or as contingency casing. A total of 45 to 60 days was the average time to reach a TVD of 3500 meters and most of the wells had four to five phases [4].

With drilling going to deeper waters, a number of

challenges appeared, affecting mainly the well spud in. The ineffective initial attempts, based on shallow water experience, proved that new deepwater procedures should be developed as soon as possible to avoid severe economic losses. For instance, the use of the temporary guide base (TGB), as in shallow water operations, often didn’t work as it inclined and sank totally in the mud line while drilling the 36” hole [5]. Sometimes, the use of casing configuration composed of 30” and 20”, both drilled and cemented, led the wellhead to be dangerously unstable as the cement jobs fractured the formations [3].

For a certain period of time, the use of lightweight cement

slurries (12.2 ppg) and the adaptation of a drive pipes (48”, 46” or 44” diameters) welded in the bottom of the TGB (Fig. 10) were good solutions for the problem of TGB’s undermining [3,5].

As the drilling moved to higher water depths, the well

design has also changed. Studies of the sea bottom resistance indicated that a 42” conductor pipe was enough. Based on this information, the 42” pipe was jetted and the 36” hole drilled to receive the 30” casing. The 7” liner was added to the last phase. A total of 35 to 45 days was the average time to reach a TVD of 3500 meters and most of the wells had five to six phases [4].

Later on, new studies of the sea bottom indicated that the

42” pipe could be simply replaced by the 30” conductor jetted. This new well design assumed also that a 20” casing was run and cemented in a 26” hole, a 13 3/8” casing was run and cemented in a 16” hole, a 9 5/8” casing was run and cemented in 12 ¼” hole. A 7”liner in an 8 ½” hole was also common after the 9 5/8” casing string. A total of 20 to 35 days was the average time to reach a TVD of 3500 meters and most of the wells had four to five casings strings [4].

An important step in terms of well design optimization was

obtained by eliminating a casing string of the casing configuration described above. The successful drilling of deepwater well in water depth of 858 meters proved that by the elimination of the 13 3/8” casing lead to a well design that met Petrobras safety criteria and saved rig time. Later on, after rigorous stress analysis another solution was proposed and experienced in 1998. The well was a deepwater well located in water depth of 692 meters. Following the experienced obtained in the previous wells; the 30” conductor was jetted at the depth of 749 meters. Next, a 17 ½” hole was drilled and a 13 3/8” casing was run and cemented at 1498 meters. Finally, a 12 ¼” bit drilled to 3770 meters and a 9 5/8” casing string

was run and cemented without any major problem [4]. Fig. 11 shows the wellhead used in such configuration.

The use of slender well design has become a standard in

the majority of the situation, including exploratory drilling. Jetting the 36” or 30” conductor has been the first choice to spud in the well. However, cementing a 30” casing in a 36” drilled hole is still used if seismic survey indicates the presence of harder rocks near to the sea bottom.

Despite of the spud in evolution, wellhead instability

problems are still occurring in some deepwater areas in wells where the 36” or the 30” conductor pipe was jetted. Actually, the problem was observed after drilling the 26” or the 17 1/2” hole. However, in such a situation, tensioning the conductor to keep the wellhead in the correct position while wait on cement of the 20” or 13 3/8” casing has succeeded in all cases so far.

Although wellhead equipments haven’t presented

problems so far, good operational procedures must be employed to reduce tension on wellhead and therefore reduce the risk of damaging it. The high weight of the BOP, the long extension of the drilling risers associated with high subsea currents (sometimes in different directions along to depth), the high tension on riser necessary to reduce the ball joint angle and the off-set of platform due to environmental conditions on surface transmit high stress to the wellhead. As consequence, the resultant transversal movements of the wellhead can generate dangerous situations that can lead to the fatigue of the material and collapse of the entire wellhead.

Borehole Instability

The already mentioned characteristics of the deepwater sediments associated to low overburden pressure gradient have been responsible for a number of mechanical instability problems such as caving in the well and total bore hole collapse.

Borehole Instability affects both, vertical and directional

wells, depending on the stress regime underground. In general, the vertical stress is the predominant stress compared to the two horizontal stresses (minimum and maximum horizontal stress). Except for specific situation such as drilling in salt dome areas, directional wells are, in general, more likely to exhibit high collapse pressure gradients due to well inclination. This, in turn calls for the use of higher mud weights in order to keep the bore hole walls from collapsing. In consequence, well trajectory in deep and ultra deepwater wells must be carefully designed to minimize borehole instability. Unfortunately, some of the procedures usually used by directional drillers are quite limited in deepwater situations. For instance, the common approach of lifting the kick off point (KOP) to reduce well inclination is not always possible in deepwater due to the characteristics of the shallow weaker sediments.

Directional Drilling

In deep and ultra deepwater scenarios, the low temperatures found near to the sea bottom often causes interruption of oil production due to hydrates and wax

4 OTC 15233

formation. In such situation, projects based on dry completion units (DCU) such as TLP or SPAR become technically attractive since oil will flow through directional wells instead of flowing throughout production lines placed on the cold sea bottom.

Similar to shallow water templates, developing a

deepwater oil field from a DCU requires directional wells departing from a central cluster in direction to their targets. However, it may also require drilling a number extended reach wells (ERW) in deep and ultra deepwater.

Despite of the benefits, the use of ERW in deepwater is

somehow limited due to the effect of water depth. The chances of fracturing the formation due to high annular pressure losses or having serious wellbore instability problems due to well inclination augment with both, the increase of water depth and well displacement. Fig 12 shows a schematic view of two well trajectories in two different water depths scenarios. As the length of sediments in deepwater location is smaller than the length of sediments in shallow water site, wellbore inclination in deepwater well must be higher. In consequence, bore hole instability will probably occur in the deepwater well.

In addition, the high horizontal displacement compared to

the total vertical depth, main characteristics of ERW, leads to a crucial problem, that is, the long well length and the associated increase in annular pressure loss with measured depth, is not followed by a correspondent increase of the fracture pressure gradient with depth. As a result, departures of deepwater directional wells are generally shorter compared to similar onshore and shallow water directional wells [6].

Fig. 13 displays the trajectory of deepwater directional

well drilled in Marlim Sul Oilfield, offshore Rio de Janeiro, Brazil. The initial assumption used to design this well was based on the fact that displacements of 5,000 meters and 7”OD production tubing would be enough to guarantee flow assurance by avoiding wax and hydrate formation. However, new studies indicated that reducing well displacement to 3200 meters would also assure the same oil production. Thus, a shorter well with the following characteristics was drilled:

Water depth (WD) = 1205 meters Displacement (D) = 3210 meters Total vertical depth (TVD) = 2903 meters Total Measured depth (MD) = 5211 meters Inclination of the Slant Section = 700 Ratio = D / (TVD-WD) = 1.89 Ratio = MD / (TVD-WD) = 3.07 Although well instability and fracturing the formation due

to high ECD were still concerns, drilling occurred without any problem, confirming all previous studies. However, malfunction of the BOP, after an unexpected blackout followed by disconnection of the riser, left the well open to the sea reducing the hydrostatic pressure inside the hole. The total collapse of the borehole walls observed after the situation was normalized, confirmed wellbore instability as a serious issue for this deepwater well. On the other hand, the lessons learnt

from this well and the subsequent wellbore stability and hydraulic related studies indicated that higher displacements are likely to be achieved in this area.

Drilling Fluids

Environmental friendly, easy to handle, good chemical inhibition, versatile composition and good transporting capability are some of the main characteristics a drilling fluid must have to overcome the following challenges:

- Keep chemically reactive, fragile and unstable

formations in place, - Allow high rates of penetration, - Deliver caliper under the desired tolerance, - Be economically feasible.

Both, water base mud and oil base mud have been used by

Petrobras in its drilling operations. A summary [7,8] of its usage is presented next.

Water Base Mud In the earlier stage of deepwater drilling in Brazil, saline

fluids, treated with hydrated calcium and amide, fabricated with seawater were utilized. However, problems such as borehole enlargement, wellbore instability and fluid density management required mud engineers to look for other solutions. A number of alternatives were tried with limited success before the use of saline-drilling fluids treated with cationic polymers. This type fluid has succeeded in more than 200 wells drilled in water depths up to 2800 meters.

Oil Base Mud By the end of the eighties, environmental regulations had

already forbidden the use of diesel base mud in Campos Basin. After 1995, with the increment of horizontal drilling activities, new types of drilling fluid were tested and recently a synthetic fluid, specially developed by Petrobras engineers, have proved to be quite effective. High lubricity capacity, good inhibition properties, relative low cost and environmental acceptance friend are some of the main characteristics of this new drilling fluid. Rig Efficiency

Although rig efficiency generally is not seen as a deepwater challenge, it was included here as one of the most critical obstacle most Operators face to succeed in deepwater environments.

A good example is the experience obtained by Petrobras in

the years of 1999 and 2000, when an increase in drilling activities occurred and a number of fully automated deepwater drilling rigs were just brought to Brazil. Some rigs were brand new and others were the result of expensive upgrades. Coincidently, rig related problems were serious drawback during these two years. BOP malfunction, rig misoperation, unprepared rig team, crashes of the drill string handling system and minor failures of a number of small equipments have been responsible for 58% of the non-productivity time

OTC 15233 5

(NPT) observed in 25 deepwater and ultra deepwater wells drilled in this period.

The results obtained in the subsequent years of 2000 and

2001 showed that the effort made by Petrobras to improve rig efficiency was successful. In these two years, NPT related to rig, although high, has fallen to 29%.

Safety Program

Having in mind that the safety in deepwater drilling operations must always be a priority, Petrobras coordinated the so-called Dynamic Positioning Safety Program (DPPS). This important program, that has had drilling contractors as partners, started with 11 projects and has as main objective to reduce (or eliminate) DP incidents or minimize their effects in the case it occurs.

Future Years

After having broken the 2000 meter and getting very closer to the 3000 meters water depth barrier, Petrobras is again motivated by the challenges to go even deeper. The PROCAP-3000, an R&D program on ultra deep water, has launched several projects to support deepwater drilling operations. These projects include:

• Extended Reach Wells in Ultra-Deepwater, • Design Wells in Ultra-Deepwater, • High-Rate Production Wells in Ultra-Deepwater, • Drilling, Well Test Evaluation & Completion in

Ultra-Deepwater, • Light Fluid and Underbalanced Drilling in Ultra-

Deepwater • Intelligent Completion in Deepwater

In addition to that PROCAP 3000, Petrobras has also

started an Excellence in Drilling program, named PeX. The objective of PeX is to keep Petrobras drilling operations among the top top class companies of the world. PeX covers a number of topics that include:

• Performing routinely benchmarking, • Implementing standard procedures in the

whole company, • Putting into practice new and more

productive systematic • Establishing better relationship with contractors,

Conclusions Until January 2003, Petrobras has drilled a total of 776 wells in deep and ultra deep waters in several offshore locations of the Brazilian Coast. Among the total, 308 are exploratory and 468 are development wells. A number of drilling challenges have been described as potential source of severe economic losses. Geohazards, spud in the well, smaller tolerance between pore pressure and fracture pressure gradient and borehole instability are good examples of challenges Operators face when moving to deep and ultra deep waters. Particularly, Petrobras drilling experience to overcome these challenges has been described in a number of different situations. Acknowledgements The authors would like to thank Petrobras for permission to publish this paper and the professionals of the Petrobras E&P Production Group in the Headquarters and in the Operational base in Macaé for their comments and suggestions. References

1. Dutts, N.C., “Deepwater Geohazard Prediction Using Prestack Inversion of Large Offset P-Wave Data and Rock Model”, The Leading Edge Magazine, US, pages 193-198, Vol. 21, N0. 2, February 2002.

2. Campbell, Kerry J., “Deepwater Geohazards: How Significant Are They", The Leading Edge Magazine, US, pages 514-519, April 1999.

3. Oddone, Décio Fabrício da Costa et al, “The Evolution of Deepwater Drilling in Brazil”, SPE 21158, presented at the SPE Latin American Petroleum Engineering Conference, Rio de Janeiro, Brazil, October 14-19, 1990.

4. Saliés, J.B et al, “Evolution of Well Design in the Campos Basin Deepwater”, SPE/IADC 52785, presented at the SPE/IADC Drilling Conference, Amsterdan, Holland, March 9-11, 1999.

5. Nakashima, Fernando K. H. et al, “The Evolution of Spud in and Conductor Cementing in Deep Water Wells”, presented at the Deep Offshore Technology Conference, Rio de Janeiro, Brazil, 1995.

6. Rocha, L.A, Andrade, R. M. and Soffried K, “How Water Depth Affects Extended Reach Drilling”, OTC 15326, submitted 2003 Offshore Technology Conference held in Houston, Texas, U.S.A., 5–8 May 2003.

7. Moura, Eliabe M. and Taíra, Hélio S., “Sucesso na Aplicação de Fluidos Catiônicos em Poços de Lâmina d’Água Profunda e Ultra Profunda”, XIII Congresso Latino Americano de Perfuracion (COLAPER), Caracas, Venezuela, October 2002.

8. Moura, Eliabe M. et al., “Desenvolvimento de Fluidos Sintéticos de Baixa Toxicidade na Plataforma Marítima Brasileira”, XIII Congresso Latino Americano de Perfuracion (COLAPER), Caracas, Venezuela, October 2002.

6 OTC 15233

Figure 1 – Map of Brazilian Coast and deep and ultra deepwater well distribution.

OTC 15233 7

3 15

11

29

21

8 7

26 27 28

48

70

8188

15

2 1 1 4 5 8

1812

9 611

8

18

32

1913 14

1015 12

24 2633

6

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Years

Num

ber

Wel

ls

Development Wells Exploratory Wells

Figure 2 – Number of deep and ultra deepwater exploratory and development wells versus year. The number

of wells showed in 2003 referred to January 25, 2003.

148

7662

14 8

308

0

50

100

150

200

250

300

350

300 to 1000 1001 to 1500 1501 to 2000 2001 to 2500 2501 to 3000 Total

Water Depth Range (meters)

Num

ber o

f Exp

lora

tory

Wel

ls

Ultra Deep WaterDeep Water

Figure 3 - Number of Exploratory Wells versus Water Range. A total of 224 wells were drilled in deepwater (green

bars) and 84 were drilled in ultra deepwater (red bars).

8 OTC 15233

341 379505 458 501

943

1164

1565

13931254

923831

1158

1801

1415

1776

1560

1906

26622777 2787 2853

437 439

752847

980 950

630

824954 972 976

1877 1861 1879 1841

1853

0

500

1000

1500

2000

2500

3000

3500

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

Years

Wat

er D

epth

(met

ers)

Exploratory Wells

Development Wells

Figure 5 – Highest water depth of exploratory and development wells versus years

343

93

32

468

0

50

100

150

200

250

300

350

400

450

500

300 to 1000 1001 to 1500 1501 to 2000 Total

Water Depth Range (meters)

Num

ber o

f Dev

elop

men

t Wel

ls Ultra Deep WaterDeep Water

Figure 4 - Number of Development and Special Wells versus Water Range. A total of 436 wells were drilled in deepwater (green bars) and 32 were drilled in ultra deepwater (red bars).

OTC 15233 9

Water Depth= 678 m

Mud (Soft Clay)

Mud + Sand Intercalations

Water Depth= 678 m

Mud (Soft Clay)

Mud + Sand Intercalations

Figure 7 – Seismic section used to define the length of the conductor pipe.

Indication of Fluid FLowIndication of Fluid FLow

Figure 6 - Indication of underground fluid flow in an offshore area, Southeast Brazil

10 OTC 15233

Fracture

Pore Pressure

Fracture

Pore Pressure

Operational Window

Fracture

Pore Pressure

Fracture

Pore Pressure

Operational Window

Figure 8 – Typical pore and fracture pressure gradients for different water depths.

Figure 9 – Wells designs used by Petrobras in deep and ultra deepwater drilling.

OTC 15233 11

HIGH PRESSURE HOUSING 16-3/4” x 13”BOP ISOLATION TEST TOOL 13”

WEAR BUSHING13” x 9-5/8”METAL TO METAL SEAL 13”CASING HANGER 13” x 9-5/8”

SLENDER WELL PROJECT

ABB Oil & Gas Division - BrasilAv. Dos Autonomistas, 1496, Vila Campesina

Osasco - SP, CEP: 06020-902Phone: 5511 7088-9218

Fax: 5511 7088-9508ABB Oil, Gas & Petrochemicals

HIGH PRESSURE HOUSING 16-3/4” x 13”BOP ISOLATION TEST TOOL 13”

WEAR BUSHING13” x 9-5/8”METAL TO METAL SEAL 13”CASING HANGER 13” x 9-5/8”

SLENDER WELL PROJECT

ABB Oil & Gas Division - BrasilAv. Dos Autonomistas, 1496, Vila Campesina

Osasco - SP, CEP: 06020-902Phone: 5511 7088-9218

Fax: 5511 7088-9508ABB Oil, Gas & Petrochemicals

ABB Oil & Gas Division - BrasilAv. Dos Autonomistas, 1496, Vila Campesina

Osasco - SP, CEP: 06020-902Phone: 5511 7088-9218

Fax: 5511 7088-9508ABB Oil, Gas & Petrochemicals

ABB Oil & Gas Division - BrasilAv. Dos Autonomistas, 1496, Vila Campesina

Osasco - SP, CEP: 06020-902Phone: 5511 7088-9218

Fax: 5511 7088-9508ABB Oil, Gas & PetrochemicalsABB Oil, Gas & Petrochemicals

Figure 11 - Schematic view of a Slender Wellhead

1111

Figure 10 - Schematic view of the wellhead and driving pipe

12 OTC 15233

True

Ver

tical

Dep

th [m

]

0 220 440 660 880 1100 1320 1540 1760 1980 2200 2420 2640 2860 3080

0

220

440

660

880

1100

1320

1540

1760

1980

2200

2420

2640

2860

3080

30"

20"

13 3/8"

9 5/8"

Displacement (meters)

700

7-MLS-42H

True

Ver

tical

Dep

th [m

]

0 220 440 660 880 1100 1320 1540 1760 1980 2200 2420 2640 2860 3080

0

220

440

660

880

1100

1320

1540

1760

1980

2200

2420

2640

2860

3080

30"

20"

13 3/8"

9 5/8"

Displacement (meters)

700

7-MLS-42H

True

Ver

tical

Dep

th [m

]

0 220 440 660 880 1100 1320 1540 1760 1980 2200 2420 2640 2860 3080

0

220

440

660

880

1100

1320

1540

1760

1980

2200

2420

2640

2860

3080

30"

20"

13 3/8"

9 5/8"

Displacement (meters)

700

7-MLS-42H

True

Ver

tical

Dep

th [m

]

0 220 440 660 880 1100 1320 1540 1760 1980 2200 2420 2640 2860 3080

0

220

440

660

880

1100

1320

1540

1760

1980

2200

2420

2640

2860

3080

30"

20"

13 3/8"

9 5/8"

Displacement (meters)

700

7-MLS-42H

Figure 13 - Extended reach well drilled in deepwater

Seafloor

Sea Level

Target / Reservoir

DeepwaterShallow water

β

α > β

α

Seafloor

Sea Level

Target / Reservoir

DeepwaterShallow water

β

α > β

α

Figure 12 - Two directional wells trajectories reaching the same target. Due to the small sediment thickness, the deepwater well displays higher angle than the shallow water well trajectory.