Functions of a Drilling Fluid

Drilling fluid is a very important part of the drilling operation.
•Drilling fluid has many functions and is very complex
•The understanding of the uses of drilling fluid can make a drilling operation successful Ten functions of a drilling fluid:
1.Transport cuttings
2.Release cuttings at the surface
3.Control bottom hole pressure
4.Cool and lubricate the bit and drillstring
5.Provide borehole stability
6.Provide buoyancy for the drillstring
7.Suspend cuttings when circulation is interrupted
8.Facilitate the retrieval of information from the wellbore
9.Protect formation productivity
10.Transmit hydraulic energy to the tools and bit

Completion and Workover Fluids

completion and workover fluids are specialized fluids used during well completion operations and remedial workover procedures.
•These fluids are designed to cause the least amount of damage to the production zone
–The potential for damage to the zone is greater during the completion of workover operation
•Completion fluids are placed across the chosen pay zone after the well has been drilled but prior to putting it on production.
•Workover fluids are used during remedial work in producing wells, usually as an attempt to enhance or prolong the economic life of the well
•Functions of a completions or workover fluid:
–Control subsurface pressures.
–Minimize formation damage.
–Maintain wellbore stability.
–Control fluid losses to the formation.
–Transport solids.
–Maintain stable fluid properties
.•Types of completions and workover fluids:
–Clear, solids-free brines.
•These are the most common
–Polymer-viscosifiedbrines with bridging/weighting agents.
–Other fluids: oil-base, water-base, converted muds, foam


..•Brines are usually selected based on the appropriate density required to control the well

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Well Completion

•After the well is drilled, logged, tested and cased it is time to proceed to completing the well •Completion simply means making the well ready to produce oil and gas under controlled pressures and flow rates •The most common types of completions are open hole, gun-perforated, liner, and gravel-packed liner •Open hole completion –If the formation is competent and can hold together by iteself(such as a limestone or dolmiteformation) a simple open hole completion is adequate.

•Gun-perforated completion –In this case the casing or liner is ran and cemented right through the zone of interest –Perforations are shot through the casing or liner and cement in the formation •Slotted liner completion –a pre-perforated or slotted liner is hung from the bottom of the last string of casing. –If the producing formation is weak or poorly consolidated, sand and other solids will be carried into the well as the oil or gas is produced. –To prevent this “sand production,”the slotted or perforated liner may contain a wire-wrapped or a prepacked-gravel protective layer to keep the sand from entering the wellbore.

Gravel-packed liner –A gravel-packing operation consists of circulating and placing carefully sized gravel into the annular space between the liner and the wellbore wall –Used when there is a weak formation such as loose sand

Directional Drilling

•Sometimes wells must be drilled at high angles or even horizontally•Economic, environmental and technical reasons sometimes require that the well be dilled directionally•Deviated wells can sometimes access more of the reservoir than vertical ones •Large expensive offshore platform act as a central point for several deviated wells and can make these wells economical to drill •Specialized BHA’sare required to drill these wells –Include MWD (Measurements will drilling) tools –Mud motors –Stabilizers •Wells can be drilled in almost any direction now: S or U shaped, Horizontal

Mud logging

•Mud logging is a method of analysis that occurs while drilling

–Cuttings are examined for lithology and fluorescence –May indicate oil or gas shows –Downhole gasses are also analyzed for hydrocarbon shows –Mud loggers record parameters such as depth, ROP, lithology, and hydrocarbon shows

Blow Out Preventers

•
A large valve used to control wellbore fluids

•In this type of valve, the sealing element resembles a large rubber doughnut that is mechanically squeezed inward to seal on either pipe (drill collars, drillpipe, casing, or tubing) or the openhole.
•The ability to seal on a variety of pipe sizes is one advantage the annular blowout preventer has over ram-type blowout preventers Most blowout preventer (BOP) stacks contain at least one annular BOP at the top of the BOP stack, and one or more ram-type preventers below
•While not considered as reliable in sealing over the openholeas around tubulars, the elastomericsealing doughnut is required by API specifications to seal adequately over the openholeas part of its certification process

Drilling Rig Components

1
.Crown Block
2.CatlineBoom and Hoist Line

3.Drilling Line

4.Monkeyboard

5.Traveling Block

6.Top Drive

7.Mast

8.Drill Pipe

9.Doghouse

10.Blowout Preventer

11.Water Tank

12.Electric Cable Tray

13.Engine Generator Sets

14.Fuel Tank

15.Electrical Control House

16.Mud Pumps

17.Bulk Mud Component Tanks

18.Mud Tanks (Pits)

19.Reserve Pit

20.Mud-Gas Separator

21.Shale Shakers

22.Choke Manifold

23.Pipe Ramp

24.Pipe Racks

25.Accumulator

Exploration-Geophysics

Definition:•In hydrologic terms, the study of the physical characteristics and properties of the earth; including geodesy, seismology, meteorology, oceanography, atmospheric electricity, terrestrial magnetism, and tidal phenomena•We will only be briefly covering some surveying techniques

Knowing about the geology and the most likely traps that include hydrocarbons is important! Actually finding those traps is another thing altogether.
•Many methods have tried and failed to locate these reservoirs. The most important today are:
–Geological Exploration
–Ariel surveying
–Physical (Seismic) exploration
–Exploratory drilling

Geological Exploration•Actual surface observations by trained geologist can help to identify possible targets for exploration–Rock out crops–Canyon walls, road cuts, modern day structures•Geological maps can be made from these observations leading to the next phase of exploration

Aerial and satellite survey•High altitude surveys give a good picture of large anticlines or faulted regions that may be of interest•These surveys (either from aircraft or satellite) will help close in on further areas of interest.

Seismic Exploration
•The is the most common geophysical exploration method
•Shockwaves are aimed downwards into the rock strata and reflect back to sensitive surface equipment
•Different densities and hardness of the rocks reflect the waves at different rates of speed, seismologists interpret the variance in reflections and can model the strata below with the aid of complex computer programs

Seismic Exploration•New techniques such 3D seismic increase the success rates of finding reservoirs•Other geophysical exploration techniques include variations of gravity and magnetic properties to help detect subsurface formations.