Bài giảng Cơ sở khoan dầu khí - Chương 7: Well completion and stimulation

WELL COMPLETION and STIMULATION

Bài giảng được soạn bởi

Bộ môn Khoan – Khai thác Dầu khí

Khoa Kỹ thuật Địa chất và Dầu khí

Đại học Bách Khoa TP. HCM

Tel: (08) 8647256 ext. 5767

GEOPET

CONTENTS

1. Basic Completion Methods

2. Completion Procedure

3. Perforating

4. Stimulation

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1. BASIC COMPLETION METHODS

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INTRODUCTION

^Once the design well depth is

reached, the formation is tested

and evaluated.

PLATFORM

^To complete the production well,

casing is installed and cemented,

and the drilling rig is dismantled.

SEA BED

30’’ CASING

^A service rig is brought in to

perforate the production casing

and run production tubing along

with downhole equipments.

20’’ CASING

13 3/8’’ CASING

7’’ LINER

Production casing (9 5/8)

^Production begins after surface

safety equipment installation

inished.

RESERVOIR

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WHAT IS COMPLETION?

Well completion creates a

dependable pathway to the surface

for the hydrocarbons.

The term ‘completion’ describes

the assembly of downhole tubulars

and other safety equipments that is

required to enable the safe and

efficient production of oil or gas

from the well after it has been

drilled.

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BASIC WELL COMPLETION TECHNOLOGY

^Each drilled wellbore awaiting completion is unique. Even nearby wells

drilled to the same reservoir can have differencies in:

^.depths,

^.formation characteristics,

^.and hole sizes

^A wide variety of equipment designs and procedures have been

developed to provide safe, efficient conduits from subsurface

reservoirs to the surface in different situations.

^The ideal completion design

^.minimizes initial completion and operating costs,

^.providing for the most profitable operation of an oil or gas well over

its entire life.

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TYPE OF COMPLETION

Natural Completions

Natural completions are those in which little or no stimulation is required

for production. Sandstone and carbonate systems with good permeability

and mechanical stability are ideal for natural completions.

Stimulated Completions

These completions are generally applied to improve the natural drainage

patterns of hard, low-permeability formations. It is used to remove

barriers that prevent easy passage of fluids into the wellbore.

Sand-Control Completions

Sand-control completions support the formation while allowing the flow of fluids.

They are performed in young, unconsolidated or less mechanically competent

sandstones.

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TYPE OF COMPLETION

The design of a particular completion depends on:

1. The number and type of productive zones,

2. The expected pressures and flow rates,

3. The need to control sand production,

4. The need for artificial lift or stimulation the regulations

governing operations in the area.

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WELL COMPLETION ACTIVITIES

Well completion activities include:

^Conducting well test

^Setting production casing

^Running production tubing along with

downhole equipments

^Installing surface safety equipments

^Starting production flow

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BASIC COMPLETION METHODS

 Once we drill to the target and evaluate our well by

. Mud analysis: density & viscosity

. Well logging (electrical, ascoustic, nuclear, etc…)

. Coring: at bottomhole or sidewall

. Welltest: bottomhole pressure vs time -> reservoir properties

Next decision is whether to complete or abandon it????

 In the latter case:

. set a cement plug or plugs in the hole,

. possibly recover whatever casing can be removed,

. and return the drill-site to its original condition.

 The more fortunate is one in which our well not only is productive, but

economically justifies a completion.

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BASIC COMPLETION METHODS

The next step usually involves the running of the final string of casing - the

production string.

The manner in which this is done determines the basic completion

method and may follow one of several configurations: (interface between

the wellbore & reservoir)

^.the openhole completion,

^.the liner completion,

. the cased and perforated completion

• Without liner

• With liner

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BASIC COMPLETION METHODS

^The openhole completion: the producing formation is not isolated by

the casing, which extends only to the top of the producing interval.

^The slotted liner completion: which is not cemented and not "tied back"

to the surface.

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BASIC COMPLETION METHODS

^The cased and perforated completion

^.Without liner: cementing the production casing across the

productive interval and then perforating the casing for production

^.With liner: a liner is cemented and perforated as a cased and

perforated completion

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BASIC COMPLETION METHODS

^One of these configurations will be the basis for the completion design,

which may incorporate:

^.one or multiple strings of tubing: single, dual, or triple, etc

^.and a variety of tubing components to facilitate production

(production method): pumping, flowing, etc.

^.from one or multiple zones: single or multiple zones

^For our purposes, a cased and perforated well with a single tubing

string will serve to illustrate the typical completion procedure.

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SUBSEA COMPLETION

Subsea production systems are wells

located on the sea floor, as opposed to

at the surface. The safety equipments

are installed underwater on the seabed.

They enable early production from

deepwater, remote, and marginal fields.

Subsea production system offer a

means of producing field extremities not

reachable by directional drilling from

existing platforms, or where field

economics do not justify the installation

of one or more additional platforms.

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2. COMPLETION PROCEDURE

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COMPLETION PROCEDURE

^After the contract casing crew runs the final casing,

cementing follows the usual procedure, although stage

cementing may be necessary to cement an extremely long

string.

^The production string has been hauled out to the location

and the inside diameter checked to make sure that

imperfections will not prevent the subsequent running in of

tubing and packers after the string is set.

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COMPLETION PROCEDURE

^Special care: to prevent the possibility of future leaks.

^If stage cementing is necessary:

^.the bottom section is first cemented in place and then

^.a series of plugs are pumped down the casing to open ports that

allow the upper end of the annulus to receive cement.

^After the cement has set, the inside of the casing must be

^.drilled out and

^.flushed clean of cement and other debris to a depth below that of

the proposed completion.

 It is important that the inside diameter of the production casing be

clean and smooth.

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COMPLETION PROCEDURE

It is also important that the cement

form a competent seal between the

casing and borehole over the entire

openhole interval. To ensure this,

^an acoustic cement bond log is

sometimes run on wireline

^to determine if voids exist

between casing and hole

because cement has bypassed

the drilling fluid.

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COMPLETION PROCEDURE

^If the bond is poor in an area, particularly if the area is between

productive formations, a cement squeeze will be required.

^Often the cement bond log is run in conjunction with a gamma ray log

and a casing collar log. The drilling engineers can correlate this

gamma ray log with the logs run earlier during formation logging.

^This correlation is important because as we zero in on the target - the

productive formation - our need to locate tools precisely relative to that

formation is critical.

 The open hole logging sondes are subjected to a greater amount of

"drag" when being pulled up the hole, the depths at which formations

are recorded may differ somewhat from the formation depths on the

gamma ray log run inside the casing.

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