(1) Drilling & Allied Services (Petroserv)

Drilling & Allied Services (Petroserv)

Drilling & Allied Services (Petroserv) Directorate

Drilling Operations (DO)

Drilling Services (DS)

Construction & Engineering Support Services (C&ESS)

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Drilling Operations Drilling Engineering

Drilling Operations

Drilling Materials Planning

Drilling Services Drilling Fluids Services

Cementation & Stimulation

Rig Maintenance

Logistics

Construction & Engineering Support Services Mechanical Engineering

Civil Engineering


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Drilling rigs of OGDCL Rig N-1

Rig N-2

Rig N-3

Rig N-4

Rig N-5 (recently procured from China)

Rig N-6 (recently procured from China)

Rig N-55

Rig 307

Rig F-125

Rig K-750-T (Workover)

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Drilling

When it has been established that a petroleum reservoir probably exists, the only way to verify this is to drill a well.

Types of wells

Exploratory wells

Development wells


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Exploratory well An exploration well or ‘wildcat’ is one that is drilled

primarily for the purpose of determining that oil or gas actually exists in a sub surface rock formation.

Development well A development well is a well that is drilled after an

exploration wells has confirmed the presence of

petroleum in the formation.

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Drilling Methods

Cable Tool Drilling

Rotary Drilling

Coil Tubing Drilling


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Major systems of a rotary drilling rig

The hoisting system

The rotating system

The circulating system

The power system

The blow out prevention system

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The drillstring

Starting at the bottom, a basic drillstring for rotary drilling consists of the

bit,

drill collars and Bottom-Hole Assemblies (BHAs), and

drill pipe

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Drilling fluids

The term "fluid" includes liquids and gases. A drilling fluid that is mostly liquid is a drilling mud. Air, gas and foam are pneumatic drilling fluids. Pneumatic drilling fluids are used only in special cases.

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The liquid in a drilling mud typically is water, oil, or a stable mixture in which one liquid is suspended in minute globules in another. The suspended liquid is the internal phase of the emulsion; the suspending liquid is the external phase of continuous phase. An oil-base mud is a mud whose liquid portion is oil or, more frequently, a water-in-oil emulsion (called an invert emulsion). If the continuous liquid portion is water or an oil-in-water emulsion, the mud is a water-base mud.

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Water base muds are the most common drilling fluids. Fresh water muds are prepared by mixing swelling type clay (bentonite) in fresh water and treating the suspension with mud additives. In case of salt mud, salt water (brine) is used to build the mud system. Water base muds range from at native muds to lightly-treated muds to the more heavily treated, inhibitive water-base muds.

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Inhibitive muds reduce, or inhibit, the interaction between the drilling mud and certain drilling formations. Oil-base muds are naturally inhibitive. Water-based muds can be inhibitive if cations or encapsulating agents or both are present in sufficient quantities in the muds.

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Basic types of drilling fluids

Water base mud

Oil base mud

Invert emulsion

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Functions of drilling fluids

The eight basic functions of a drilling fluid are as follows:

Transport drilled cuttings and cavings to the surface.

Suspend drilled cuttings and cavings in the annulus when circulation is stopped.

Control subsurface pressure.

Cool and lubricate the bit and the drill string.

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Support the walls of the wellbore.

Help suspend the weight of the drill string and casing.

Deliver hydraulic energy upon the formation beneath the bit.

Provide a suitable medium for running wireline logs.

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Properties of drilling fluids SG

Funnel Viscosity

PV

YP

Gel Strength

Water Loss

Cake thickness

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Solids

Sand

Oil

Calcium

Magnesium

Chlorides

MBT

Flow line temperature

pH

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Mud Additives

Properties of the drilling fluids are maintained in the required ranges during different types of drilling, workover or production operations so that these fluids can perform various functions effectively. Mud properties are achieved/ tailored by mixing different types of materials (products), called "mud chemicals or mud additives", into the existing system which may be water, oil, liquid brine or mud. Examples are Barite, Bentonite, CMC-HV, CMC-LV, Defoamer, PHPA etc.

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Basic Drilling Fluids Calculations

BASIC DRILLING FLUIDS CALCULATIONS

CAPACITIES & DISPLACEMENTS Capacities (Inside volume per unit length)

Displacement of string (Displaced volume per unit length when the pipe is lowered into the fluid)

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VOLUMES

Pits

Hole

Drill String

Annulus – several sections

Total circulating volume

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CIRCULATING TIME Surface to bit (drill string vol./flow rate) Bit to surface (bottom up) (Annular vol./flow rate) Hole cycle (Hole vol./flow rate) System total cycle (hole +active system)/ flow rate.

NO. OF STROKES Surface to bit (string vol./Pump discharge per stroke) Bit to surface (Annular vol./Pump discharge per stroke) Hole Cycle (Hole vol./Pump discharge per stroke) System total cycle (total system + hole vol./Pump discharge

per stroke).

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MUD PUMPS

Triplex Pumps

Single Acting

Efficiency

Duplex Pumps

Single Acting or double acting

Efficiency

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DISCHARGE VOLUME OF PUMPS/STROKE

Volume per stroke (Depends on liner dia, length of piston & efficiency)

Consider triplex or duplex

Consider single acting or double acting

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FLOW RATE or PUMP OUT PUT

Pump discharge x pump speed

Liter per stroke x stroke per minute (ltr/min).

VELOCITY

Flow rate/ capacity of section.

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SPOTTING CALCULATIONS

Spot Black Magic SFT

Spot LCM Pills

Displacement Strokes of mud after black magic, LCM pills and cement jobs.

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WT. UP & CUT BACK CALCULATIONS

WT.UP

WITH VOLUME INCREASE

FIX VOLUME

CUT BACK

WITH VOLUME INCREASE

FIX VOLUME

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HYDROSTATIC HEAD

= 0.052 x mud wt. (ppg) x depth (ft)

----------- psi

= 0.1 x mud wt. (SG) x depth (m)

----------- kg/cm2

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Casing & Cementing

Casing Casing has several important functions during the

drilling and completing of a well. It is used to prevent the bore hole from caving in during the drilling of the well, to provide a means of controlling fluids encountered while drilling, to prevent contamination of fluids to be produced, and to protect or isolate certain formations during the course of a well.

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Casing & Cementing

Basic types of casings

Conductor casing

Surface casing

Intermediate casing

Production casing

Production liner

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Casing & Cementing

CEMENTING

Oil well cementing is the process of mixing and displacing a slurry down the casing and up the annulus, behind the casing, where is allowed to “set”, thus bonding the casing to the formation.

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Casing & Cementing

Some additional functions of cementing include:

Protecting producing formations

Providing support for the casing

Protecting the casing from corrosion

Sealing off troublesome zones

Protecting the bore hole in the event of problems

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Casing & Cementing

Cement Slurries

Water is added to dry cement to cause hydration and to make a pumpable slurry. To be used correctly, several properties must be known: the yield per unit (cubic feet per sack), the amount of water required (gallons per sack), and its density (pounds per gallon).

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Casing & Cementing

Cement Additives

Accelerators

Retarders

De-foamers

Extenders

Anti settling agents

Fluid loss additives of cements (FLAC)

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