drilling and completions_3

8/10/2019 Drilling and Completions_3

1/33

Faculty of Chemical Engineering

Drilling and Completions

Drilling techniques

Verticaldrilling straight down into reservoir (in early days)

Horizontaldrilling horizontally to reach the target zone e.g.

drill to penetrate the reservoir at a very shallow angle or toexpose more of low permeability reservoir to the wellbore so

that production rate is increased

Directional drillingthe process of directing a wellbore along

some trajectory to a predetermined target


2/33



Drilling techniquesWellhead


3/33



Application of directional drilling


4/33





5/33





6/33





7/33Faculty of Chemical Engineering






Drilling techniques




Casing and cementing

What is casing?

Large-diameter steel pipe lowered into a borehole and

cemented in place





Purpose of casing:

To prevent contamination of fresh water sands

To enhanced the probability of drilling to total depth (TD) To sealoff weak, fractured and unconsolidated

formations

To control pressure during drilling

To meet production requirements

To confine production to the wellbore

To protect the hole from the mud

To prevent water migration(from mud) to producing

formation e.g. shale tends to draw water out of the

mud causing them to swell





Casing program





Casing program

Surface casing

Drilling operation begins by drilling the large-diametersurface hole to penetrate unconsolidated

formation(near to surface) and any potable water

zones

Normally a few hundred feet deep (3005000ft)

depending on local conditions encountered

Surface casing is usually cemented to the surface





Casing program

Function of surface casing

Prevent fresh-water aquifer from being contaminatedwith drilling mud, gas, oil or salt water

State and federal regulations for the protection of

underground fresh-waters reservoirs are usually quite

specific about the setting depth of surface casing

Maintain hole integrity by preventing cave-in and

washout of loose formations

Minimize lost circulation into shallow, permeable zone

Provide a mean for attaching the BOPs





Casing program

Function of Intermediate casing

Main application of intermediate casing is to case offthe troublesome formations that prevent the well from

being drilled to the target depth e.g. shallower weak

zones (rupture, lost circulation or stuck pipe)

Occasionally, intermediate casing is used to isolate salt

or anhydrite (calcium sulphate)formations, which may

cause drilling fluid contamination, or perhaps leak out

to such an extent as to cause pipe sticking





Casing program

Production casingthis string is set at a depth slight above

midway through or below the pay zone Functionisolate the producing zone from other

formations

Protect the tubing and other equipment used in the well





Cementingobjective of cementing is to create sheath

cement of hard cement completely filling the annular space

between the outside of the casing and the hole, therebyblocking fluid movement and pressure up or down the annulus


19/33





Cementing

When bottom plugs lands on

the float valvethin rubberdisc ruptures

Pumping continues as the

cement is pumped around the

shoe and up the annulus

When the last of the cement

has been pumped, a solid

rubber (no rupture disc) follow

plug is inserted into the casing

and mud is pumped in behind it


21/33





Scratcher


23/33


24/33


25/33


26/33


27/33


28/33


29/33

TYPICAL CASING CONFIGURATION

Conductor (20 30 OD)

Surface Casing

(13- 3/8 20 OD)

Intermediate Casing

(9-5/8 16 OD)

Production Casing

(4-1/2 9-5/8 OD)

Liner

4-1 2 13-3 8 OD


30/33

TYPICAL HOLE & CASING SIZE

HOLE SIZE CASING SIZE DESCRIPTION

36 30 Conductor

26 20 or 18-5/8 Surface Casing

17 13-3/8 IntermediateCasing

12 9-5/8 ProductionCasing

8 7 Liner


31/33

TYPICAL CASING FUNCTIONS & SETTING DEPTH

RANGES

CasingType

Functions Setting Depths(from seabed)

Conductor To seal off unconsolidated

formationsto prevent erosion

Enables circulation of drillingfluid

150600 ft

Surface

Casing

Seal off any fresh water sands

Support the wellhead and BOPequipment

Prevent lost circulation

10005000 ft


32/33

Casing Type Functions Setting Depths(from seabed)

IntermediateCasing

Isolate troublesomeformations between surfaceand production casing

Normally set in the transitionbetween normal andabnormal zone

Depends on the number ofproblems encountered

1,00010,000 ft

ProductionCasing

Separate producing zonesfrom other formations

Conduit for production andtestin tubin

Set across orabove pay

zone

TYPICAL CASING FUNCTIONS & SETTINGDEPTH RANGES


33/33

Casing Type Functions Setting Depths(from seabed)

Liner

(less than 5000ft casing string

which issuspended

from a linerhanger)

Replace intermediate

casing for deeper drillingeconomic

Separate producing zones

As required

TYPICAL CASING FUNCTIONS & SETTINGDEPTH RANGES

drilling and completions_3

Documents