2.1- Filtrate Invasion Page-1

2.1- Filtrate Invasion

Depth

Time

Surface Casing, Cementing, Circulation

Surface hole

Intermediate Casing, Cementing, Circulation

Intermediate hole

Production Casing, Cementing, Circulation, Completion, perforations

Production hole

The Drilling ProcessDepth-Time Line

The Drilling ProcessDepth-Time Line

2.1- Filtrate Invasion Page-2

2.1- Filtrate Invasion

OverviewThe hole is drilled in stages and at the end of every stage, casing is put into the hole and cemented into place. After the well has been drilled to final depth and all of the casing has been cemented into place, the well is completed.

2.1- Filtrate Invasion Page-3

2.1- Filtrate Invasion Typical Formation Pressures and the minimum mud density needed to balance this pressure (P = h ρ g)

P= 2000 psi, mud-density= 1.2 gm/cc

P= 3000 psi, mud-density= 1.6 gm/cc

P= 2900 psi, mud-density= 1.4 gm/cc

P= 3500 psi, mud-density= 1.4 gm/cc

P= 4500 psi, mud-density= 1.8 gm/cc

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2.1- Filtrate Invasion

Blow Out

Blow Out

Blow Out

Blow Out

What happens if we drill one hole size From Surface to TD and use one mud type:

P= 2000 psi, mud-density= 1.2 gm/cc

P= 3000 psi, mud-density= 1.6 gm/cc

P= 2900 psi, mud-density= 1.4 gm/cc

Mud Density: 1.2 gm/cc

P= 3500 psi, mud-density= 1.4 gm/cc

P= 4500 psi, mud-density= 1.8 gm/cc

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2.1- Filtrate Invasion

FractureLost Circulation

FractureLost Circulation

What happens if we drill one hole size From Surface to TD and use one mud type:

P= 2000 psi, mud-density= 1.2 gm/cc

P= 3000 psi, mud-density= 1.6 gm/cc

P= 2900 psi, mud-density= 1.4 gm/cc

Mud Density: 1.8 gm/cc

P= 4000 psi, mud-density= 1.7 gm/cc

P= 4500 psi, mud-density= 1.8 gm/cc

2.1- Filtrate Invasion Page-6

2.1- Filtrate Invasion

BOREHOLE FormationBorehole mud M

ud c

ake

Invaded ZoneFiltrate filled

Virg

in Z

one

Tran

sitio

n Zo

ne

Rt

Rxo

Res

istiv

ityMud

Formation Water

2.1- Filtrate Invasion Page-7

2.1- Filtrate Invasion

Invasion Process1. Mud in the borehole will slowly invade the Virgin Zone2. The solids in the mud will accumulate at the borehole wall (too large

to enter the pores). Some small particles may enter.3. The mud liquid (filtrate) will enter the pores, expels the formation

water and some of the HC4. Progressively, more filtrate will invade the pores5. This invasion process will stop when enough solids accumulate at

the borehole walls create an impervious barrier. 6. We will then have

MudMud cakeInvaded ZoneTransition ZoneOriginal Virgin Zone

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2.1- Filtrate Invasion