- •Rig types & components rig processes
- •June, 2002 Contents
- •Drilling programme
- •Casing and cementing programme
- •Bits and Hydraulics programme
- •Mud programme
- •Drilling procedures programme
- •Figure 02
- •Semi-submersibles
- •Figure 03
- •Drill ships
- •D. Platform rigs
- •The drilling types
- •Rotary drilling:
- •Cable tool drilling:
- •Land rig components
- •1. Mast or Derrick
- •Figure 07
- •2. Substructure
- •Figure 08
- •1 0. Tongs
- •11. Prime Movers (Engines )
- •12. Transmission
- •13. Draw Works
- •Figure 12
- •Figure 13
- •14. Drilling Line
- •15. Rotary Table
- •Figure 14
- •19. Top drive
- •20. Heave (Motion) Compensation
- •Drill string Compensator:
- •Riser and Guideline Tensioners
- •Figure 18
- •21. Drill String
- •Figure 19
- •Figure 20
- •Figure 21
- •I) Hole Openers
- •Figure 22
- •22. Casing head
- •23. Mud pumps (Slush Pumps)
- •24. Kelly Line-Rotary Hose (Mud Hose)
- •25. Shale Shaker
- •26. Desanders and Desilters
- •27. Degassers
- •28. Mud Pits
- •29. Bop’s (Blow-Out Preventers)
- •Figure 25
- •Figure 26
- •Rig personnel
- •List of Common Drilling Terms
- •3.The drilling mud
- •Composition and nature of drilling muds
- •Types of mud
- •Mud Properties Termenology
- •De nsity
- •Gel strength:
- •Filtration
- •Alkalinity
- •Chloride Content
- •Installing Christmas Tree
- •Directional Drilling
- •Drilling to total depth (td)
- •Conventional coring:
- •Sidewall coring
- •Tripping
- •Figure 27
- •Stuck pipe
- •1. Differential sticking
- •2. Mechanical sticking
- •Fishing
- •Wireline logging (electric) logging
- •Cement Figure 30
- •(Figure 31)
- •Completing the well & Setting Production Casing
- •Perforating production casing
- •Drill Stem Test (dst)
- •Acidizing
- •Fracturing
- •Installing the Christmas Tree
- •5.Mud Logging Definition
- •Types of mud logging units
- •Duties & responsibilities
- •I) mud logging unit captain
- •6.The mud logging theory & lag
- •Answers
- •Trip-out monitoring procedures
- •7.Sample collection and description
- •Preparation for collection of cutting sample
- •Shaker Samples
- •Sample Descriptions
- •Rock Types
- •Describing and logging oil shows
- •Acetone Test
- •Heat Test
- •Hot Water Test
- •Acid Test
- •Some Criteria & Procedures For Rock & Mineral Identification Testing Methods:
- •General remarks on sample escription
- •Contamination of cuttings
- •8.Gas system
- •Gas Curve
- •Types of recorded gases
- •1) Cuttings gas (formation gas)
- •2) Background gas
- •3) Trip gas
- •4) Connection gas
- •4) Circulation gas
- •Gas detection and analysis monitoring equipment
- •Gas trap assembly
- •Fid gas detector
- •Fid gas chromatograph
- •9.Sensors
- •Sensors specifications
- •1.Hook load sensor
- •2.Torque sensors Electric torque type:
- •Mechanical torque type:
- •3.Standpipe and choke pressure sensors
- •1. Strain gauge type:
- •2. Current loop type:
- •7.Analog rotary speed sensor
- •8.Pit volume sensors
- •9.Flow out sensors
- •10.Mud temperature sensors
- •11 .Mud density sensor
- •12. Mud conductivity sensor
- •13. Depth sensor
- •14. Pump stroke sensor
- •15. Digital rotary speed sensor
- •16.Gas trap assembly
- •17. Hydrogen sulphide gas detector - h2s
- •Basic Mud Logging
8.Gas system
Factors affecting size of the gas show .
Types of recorded gases.
Gas detection system
Gas trap
FID gas detector
Operating principle
Out put of the system
Advantages of FID system
FID gas chromatography
FID gas detector
FID gas chromatograph
General factors affecting the size of a gas show:
Amount of hydrocarbons present in the formation.
Type of hydrocarbons present
Porosity and permeability of the formation.
Mud weight overbalance (or underbalance) and amount of flushing.
Mud flow rate.
Mud properties, specifically viscosity.
Mud temperature.
Mud type in use.
Hole size.
Rate of penetration.
Type of bit ;affecting size of cuttings and amount of cuttings gas released into the mud.
12-Efficiency of gas trap, sample line and gas detectors.
Gas Curve
The amount of gas that enters mud as it passes through the system is recorded on one channel of the chart recorder against time. These gas values are converted to a gas curve against depth by use of the lag for plotting on the log.
The recorded amount of gas passes through several processes before being detected.
Gas enters the wellbore through two primary mechanisms. First it may be in the pore spaces of the rock being drilled, this gas is released by the bit and is known as liberated gas.
Second, it may be pushed into the wellbore by the pore pressure called produced gas, and it may come from any depth unlike liberated gas which only caroms from the bit face.
Wells are normally drilled with an amount of differential pressure i.e the hydrostatic pressure exceeds the pore pressure . Adding the annular pressure drop to the hydrostatic pressure then we have the Equivalent circulating density (ECD). This means that there is an amount of considerable forces above the hydrostatic pressure exerting on the rock ahead the bit. This force drives mud filtrate into the rock at the bit face flushing the rock of any fluid that may be originally present. Core analysis data indicates that 90 - 95 % of the formation fluid is usually flushed away.
The feature commonly called “Background” may come from two sources.
The First source is, it is a produced gas from up the hole. Many shales are drilled underbalance allowing small quantities of gas to continually bleed into the wellbore from these low porosity, low permeability form-actions.
The second source is, “Recycled Gas”; Not all the gas that enters mud is removed by the surface equipment and some of it will be recycled through the hole. It may be distributed through the entire mud volume and be seen as a constant reading background. Or, it may be in varying concentrations causing varying readings on the gas detector. If this is the case; so then the recycled peak should occur at a delay equal to the time required for a complete -Pit to Pit- circulation of the system ( including the active pit volume). Recycled gas tends to be the less volatile components; heavy components of the hydrocarbon series as these are harder to be removed by the surface equipment.
Gas that is not strictly produced or liberated can also be seen. This is gas that is retained in the cuttings after they have been removed from the rock face and due to expansion, separates itself from the cuttings at some depth up the hole This can cause gas shows to spread out after the gas lag giving an exaggerated value to the show.
The mud composition can interfere with the gas response by holding certain portions of gas affecting either the volume of the gas released and/or the nature of the gas released. As an example; as the mud weight or salinity increased so the ability of the mud to dissolve gas decreases and the quantity of gas released increased.
In oil based mud (OBM) the solvent for gas is the oil phase, which has a much higher dissolution capacity than water so gas shows will be lower. The oil also has a greater affinity for the heavier hydrocarbons so that the “heavies” may not be seen at the surface.
Apart from the varied capacity of mud to dissolve gas, the physical characteristics of the mud can enhance or reduce the size of a gas show. The lower the mud viscosity, for example, the more efficient the gas trap, the higher the gas shows.
Natural gas is a hydrocarbon gas composing of methane(CH4) and its homologues(Cn H2n+n).
Natural gases also often contain small amounts of carbon dioxide (CO2) hydrogen sulphide (H2S) and nitrogen (N2) At normal temperature and pressure.
Natural gases are always present in oil pools in the dissolved state while in some cases they evolve over the oil in the free state. This is the so called “Associated Gas” which is produced together with the oil.
This natural gas recorded while drilling is given different specific definitions according to the conditions associated to its appearance. On the coming pages we will go through these definitions.