38 introduction to ubd

8/11/2019 38 Introduction to UBD

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UB DRILLING - JOBS

1997 Underbalanced Drilling Jobs

Geographic Distribution

Canada

US Europe

South America

Middle East

Far East

1998 Spears & Assoc.


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Underbalanced Drilling in the United StatesUnderbalanced Drilling in the United States

YEAR

95 96 97 98 99 00 01 02 03 04 05

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

TOTA L

UNBDE

RBALA

NC

EDWELL

S

LOW

HIGH


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UBD Definition

Formation Pressure isequal to or greater than

Circulating Pressure


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Barriers to UB Drilling


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REGULATORY BARRIERSto

UnderBalance Drilling

The regulatorsneed assuranceand details


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BARRIERS TO UB D&C

RegulatoryLack of Standards

Lack of knowledgeLittle statistical history

Concern about well control

Environmental questions


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OPERATORS BARRIERS

The Operatorneedsexperience and

confidence.


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OPERATORS PROBLEMS

Unfamiliar with the systemrisk of the new

Lack of experienced peopleEconomics - Too expensive

Concern- liabilityConcern- well bore stability


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REASONS FOR UB GROWTH

There aredriving

economicreasons


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UBD Forecast by Region

UBD Forecast by Region

-

200

400

600

800

1,000

1,200

1996 1997 1998 1999 2000 2001 2002

Wells

US

Can

Eur

SoAm

ME/Afr

FE

1998 Spears & Assoc.


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Depleted reservoirs

Awareness of skin damageLimits of lost circulation matl.

Cost of differential sticking


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Service co. competition

Trade journal publications

Horizontal drilling

Consultants available


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TECHNICAL IMPROVEMENTS

We were notready to put all

of this togetheruntil the 1990s


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Compressor EvolutionHammer drills

NitrogenIncreased availability

Reduced costOn site generation


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Recyclable foam systemsBetter gas separators

Closed loop circulationHydraulics models

Improved rotating headsWire line wet connect


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Improved MWDRig assist snubbing units

Coiled tubing equipmentNon-damaging drilling fluids

Top drive


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Reasons for UB drilling

Lost circulation Faster Drilling


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Lost circulation Faster Drilling

No DifferentialSticking


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... Reduce

Reservoir

Damage


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... Reduce

Reservoir

Damage

Improve Prod.

Evaluation


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Effect of Skin on Production Rates

0

200

400

600

800

1,000

SKIN

BOPD

5 10-2 0 15-3 -1


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UBD is another tool in the toolbox,

not a Panacea.

Physical Limitation to UBD

Borehole Instability

Unconsolidated Sands Weak Formations

Geopressured Shales

Salt Beds

Inadequate Casing


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Production Limits to UBD

Permeability isso low the zoneneeds to be

fracked

Zones must beisolated


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MISTFOAMLIQUID GASAERATED

LIQUID

Types of Flow Regimes


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GeneralizedFluid Systems


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Shaffer Rotating Blow-Out Preventor

2,500 psi rotating - 5,000 psi static

Equipment - Rotating Head


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Closed Loop Circulation

System

Closed Loop Circulation

System

SEPARATOR

OILTANKS

WATER

TANKS

NITROGENPUMPERS

MUDTANKS

RIG

RIG

PUMPS

R-BOP

TOPDRIVE

SYSTEM

CATCHERS

SAMPLE

CHOKEMANIFOLD

FLARESTACK

N2 / FLUID

MIX

CUTTINGRETURN


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Stainless Steel

Liquid Nitrogen(-320OF)

Carbon Steel

Gaseous nitrogento well

80O

F, 0-10,000psi

Pump

Vaporizer

6.11.3

Equipment - Gas Source


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AIR DRILLING

A brief summary


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Air Drilling

Air/Gas drilling (dust) is a technique used inareas where the formations are Dry i.e., thereis no influx of water or liquid hydrocarbons.

This medium requires significant compressedgas volumes to clean the well with average

velocities of over 3,000 ft per minute.


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Air Drilling Dusting


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Air Drilling Benefits

Increased Rate of PenetrationReduced Formation DamageImproved Bit Performance

Lost Circulation ControlContinuous Drill Stem Test


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Air/Dust Drilling Layout


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Misting

Addition of 6 to 30 bbl/hr offluid to the air stream.

Cleans and lubricates the bit

Carries the cuttings to thesurface as a mist or more

normally in a modified twophase flow.


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TT96-86 39

FOAM DRILLINGFOAM DRILLING

Basic Comments


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Foam Drilling

The most versatile of the gas-generatedsystems.

Effective operating range from 0.2 to 0.6 s.g. Mixture of gas phase and foaming solution.

Foam flow varies with depth in the hole.

Adjustable effective BHP.

Enhanced lifting and well bore cleaning.

A displacing medium, not a propellingmedium.


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Foam (Heading)


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Improved Hole Cleaning


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Foam Drilling Benefits

Faster Penetration rate Low Air requirements

Low fluid requirements

Low Hydrostatic head No damage to formation

Continuous Drill Stem test

Best for large holes


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Mist or Foam Drilling Layout


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GASEATED

OR

AERATED

DRILLING


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Gaseated

Mist

TransitionWater

Gas


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Aerated Fluid

Gasification of Primary Drilling Fluid.

Initially designed as a technique to lightenmud to reduce lost circulation.

Methods

Standpipe injection Jet Sub

Parasite String

Dual Casing String

As an UB fluid, it is easiest to control in smallholes.


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Small injection string run simultaneously

with intermediate casing. Injected gas does not affectbit hydraulics.

Injected gas does not effectMWD

Parasite String


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Aerated Fluid Layout


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Compressor/N2Cost

Rotating BOPs

Solid/Liquid/GasSeparation

Corrosion

Vibration

High Torque/Drag

Borehole StabilityMWD Transmission

Hydraulic Calculations

Cuttings Lifting

Fluid Influx

Fire/Explosions

UnderbalancedCompletion

Aerated Drilling Problems

38 introduction to ubd

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