08 primary cementing
DESCRIPTION
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PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Primary Cementing
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
reservoirreservoir
reservoirreservoir
Conductor
Surfacecasing
Intermediatecasing
Production liner
Production casing
Cement
Sequence of Well Construction
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Learning Objectives
• To describe functions and types of cement
• To explain cement properties and their importance
• To recognise surface and downhole cementing equipment
• To explain cementing operations
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
•Objectives of Cementing•Types/Class of Cement•Cement Properties•Cementing equipment
– Surface– Downhole
•Cementing Operations
Content
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Two principal functions of primary cement :
• To support the casing
• To restrict fluid movement (communication) between formations/reservoirs behind pipe
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
What can happen to cement behind casing ?
• Complete displacement and seal• Channeling behind pipe• Incomplete displacement• Micro-annulus• Gas or fluid migration• Unset cement
Well cured cement have permeability of 0.001 md with pore size of 2 microns and porosity of 35 %. Gas migrating within cement slurry before curing can create a network of pores of up to 0.1 mm with permeabilities of 1 to 5 md.
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
What can happen to cement behind casing ?
Incomplete displacement
Gas or fluid migration
Channeling behind pipe
Micro-annulus
Complete displacement & seal
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement Component
Principal component of Portland cement
>50% Tricalcium silicate/ C3S (3CaO.SiO2)>25% Dicalcium silicate/ C2S (2CaO. SiO2)>10% Tricalcium aluminate/ C3A (3CaO.Al2O3) >10% Tetracalcium aluminoferrite/ C4AF (4CaO. Al2O3.Fe2O3)>10% other oxides
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement properties
• Use standard API specification to describe equipment and procedures for testing
Cement Testing Procedures :
Operating Thickening Time Test• time taken for cement slurry to set/harden• most important properties of an oil/gas well cementing
slurry• insufficient thickening time - cement set in casing, tubing
or drillpipe• excessive long thickening time - long waiting on cement
(WOC) time
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement properties
Determination of Slurry Density• should be used in the field to monitor cement slurry quality
Operating Compressive Strength Test• useful for establishing WOC time and monitoring the stability
of the set material• in general, a compressive strength of 500 psi is adequate for
most operations
Determination of Normal and Minimum Water Content• to assess field slurry problem relating to water- to- solid ratio.
High water content can cause free water break out and solid settling, low water can cause undesirable high slurry density
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary CementingAPI Cement Types
API Class A and Class G
• Predominantly used cement• Class A refer to ‘construction cement’• may normally used to a depth 6000 ft• Class G normally used in neat slurry to a depth
8000 ft
Other API Classes• Class D, E, F use for high temperature but not
widely distributed• Class J is specifically intended for high
temperature - does not set at BHST less than 230 deg F. Not widely available
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement Additives
Properties that are modified by additives :
For slurry;• thickening time (acceleration,retardation)• density (extenders/weight increase/reduction• friction during pumping• fluid loss (by filtrate)• loss circulation resistance (whole slurry loss)
For set cement;• compressive strength• strength retgrogression (loss with time)• expansion and contraction
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cementing Equipment
Surface Equipment
• Mixers or blenders
• Pumping/displacing unit
• Cementing or plug release
head
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Mixing Equipment
Jet Mixer Pneumatic Blender(for batch mixing-accurate )
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Pump-skid Truck
The pumping unit draws slurry from the mixer. The slurry is followed by the displacing fluid (gauged).
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary CementingCementing Head
(with manual plug release)
•Provide connection frompumping unit and rig-pump lines into casing andreceptacle for plugs
•Modern heads equipped
with quick change cap forinsertion of cement plug
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Downhole Equipment(Conventional casing job)
• Predetermined volume of slurry is pumped into the casing betweem two wiper plugs
• The bottom plug ruptures when it seats (top plug is solid)
• The top plug is displaced with mud or completion fluid, flow stops and pressure builds up when the top plug lands
• Check valve in the float shoe prevents backflow of heavier column of slurry
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Commonly used shoes and collars
• A round-nosed shoe is run on the bottom joint to guide casing to pass borehole irregularities
• The collar also act as a seat for pump down plugs
Downhole Equipment
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Wiper plugs
Downhole Equipment
• To separate cement from preceding or following fluids
• The bottom plug also removes mud from the wall of the casing, prevents mud from accumulating beneath the top plug and being deposited around the lower casing joints
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Stage-Cementing and Methods
• Conventional placement of cement slurry around the lower portion of a casing string followed by placement of successive upper stages through ports in a stage or port collar
• Stage collars are most commonly used - contain ports initially isolated by a sliding sleeve which can be moved downward/upward to open and close the port. Two types of collar opening methods : displaced plugs and free fall plugs
• Port collars can be opened or closed by mechanical action of an inner string such as drillpipe - rotation or vertical manipulation
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Free Fall Plug MethodDisplacement Type Method
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary CementingLiner Cementing
Typical equipment used for liner cementing Typical liner cementing procedures
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement Evaluation
Evaluation of cement job can determine :
• failure of cement to fill the casing-borehole annulus to minimum acceptable height
• failure to provide a seal at the casing shoe, or at the top of a liner
• failure to provide effective isolation of the zone(s) of interest
PE Skill Group 10
BASIC WELL COMPLETION
May 2003
Primary CementingPrimary Cementing
Cement Evaluation
Common evaluation technique include :
• temperature survey• radioactive tracer log• cement bond logging• pressure inflow test• production testing, production logging