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Friday, July 27, 2012

WELL CONTROL SCHOOL

Here I put a valuable handbooks about well control for every operation in petroleum industry :



Book Contents
  • 1 PRESSURE BASICS
  • 2 KICK FUNDAMENTALS
  • 3 DETECTION OF KICKS
  • 4 KICK THEORY
  • 5 PROCEDURES
  • 6 WELL CONTROL BASICS
  • 7 WELL CONTROL METHODS
  • 8 COMPLICATIONS
  • 9 FLUIDS
  • 10 SURFACE EQUIPMENT
  • 11 SUBSEA WELL CONTROL
  • 12 SPECIAL TOPICS
  • 13 REMEDIAL OPERATIONS
  • 14 SUBSURFACE EQUIPMENT
  • 15 COILED TUBING
  • 16 SNUBBING
  • 17 WIRELINE UNITS
  • 18 MMS REGULATIONS
  • 19 SIMULATOR EXERCISES
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Script for the 10 Drilling CDs of Schlumberger

To help non-English-native oilmen and newpetroleum professionals to better understand the 10 Drilling CDs (Schlumberger training material).


The 10 CDs can be found from:
http://petropedia.blogspot.com/2012/04/schlumberger-cds-for-drilling.html

Let's improve ourselves together!


Here is the script link:

Kindly Share knowledge with your friends.


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Oil Traps

There are three basic forms of a structural trap in petroleum geology:
-Anticline Trap
-Fault Trap
-Salt Dome Trap

The common link between these three is simple: some part of the earth has moved in the past, creating an impedence to oil flow.
Anticline Trap
An anticline is an example of rocks which were previously flat, but have been bent into an arch. Oil that finds its way into a reservoir rock that has been bent into an arch will flow to the crest of the arch, and get stuck (provided, of course, that there is a trap rock above the arch to seal the oil in place).



Fault Trap

Fault traps are formed by movement of rock along a fault line. In some cases, the reservoir rock has moved opposite a layer of impermeable rock. The impermeable rock thus prevents the oil from escaping. In other cases, the fault itself can be a very effective trap. Clays within the fault zone are smeared as the layers of rock slip past one another. This is known as fault gouge.







Salt Dome Trap
Salt is a peculiar substance. If you put enough heat and pressure on it, the salt will slowly flow, much like a glacier that slowly but continually moves downhill. Unike glaciers, salt which is buried kilometers below the surface of the Earth can move upwarduntil it breaks through to the Earth's surface, where it is then dissolved by ground- and rain-water. To get all the way to the Earth's surface, salt has to push aside and break through many layers of rock in its path. This is what ultimately will create the oil trap.






Stratigraphic Traps
A stratigraphic trap accumulates oil due to changes of rock character rather than faulting or folding of the rock. The term "stratigraphy" basically means "the study of the rocks and their variations". One thing stratigraphy has shown us is that many layers of rock change, sometimes over short distances, even within the same rock layer. As an example, it is possible that a layer of rock which is a sandstone at one location is a siltstone or a shale at another location. In between, the rock grades between the two rock types. From the section on reservoir rocks, we learned that sandstones make a good reservoir because of the many pore spaces contained within. On the other hand, shale, made up of clay particles, does NOT make a good reservoir, because it does not contain large pore spaces. Therefore, if oil migrates into the sandstone, it will flow along this rock layer until it hits the low-porosity shale. Voilà, a stratigraphic trap is born!
An example of a stratigraphic trap





Combination Traps
As the name implies, a combination trap is where two (or more) trapping mechanisms come together to create the trap. In reality, many successful oil traps are combination traps.


geology formation basin trap oil:

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Thursday, July 26, 2012

Drilling Fluids

A drilling fluid is any fluid which is circulated through a well in order to
remove cuttings from a wellbore. This section will discuss fluids which
have water or oil as their continuous phase. Air, mist and foam, which can be used as drilling fluids, will not be discussed at this time.
A drilling fluid must fulfill many functions in order for a well to be drilled successfully, safely, and economically.
The most important functions are:
1. Remove drilled cuttings from under the bit
2. Carry those cuttings out of the hole
3. Suspend cuttings in the fluid when circulation is stopped
4. Release cuttings when processed by surface equipment
5. Allow cuttings to settle out at the surface
6. Provide enough hydrostatic pressure to balance formation pore
pressures
7. Prevent the bore hole from collapsing or caving in
8. Protect producing formations from damage which could impair
production
9. Clean, cool, and lubricate the drill bit
Occasionally, these functions require the drilling fluid to act in conflicting
ways. It can be seen that items #1-3 are best served if the drilling fluid has
a high viscosity, whereas items #4-5 are best accomplished with a low
viscosity. Items #6 & 8 are often mutually exclusive because drilled solids
will tend to pack into the pore spaces of a producing formation.
Make-up of a Drilling Fluid
In its most basic form a drilling fluid is composed of a liquid (either water
or oil) and some sort of viscosifying agent. If nothing else is added,
whenever the hydrostatic pressure is greater than the formation pore
pressure (and the formation is porous and permeable) a portion of the fluid
will be flushed into the formation. Since excessive filtrate can cause
borehole problems, some sort of filtration control additive is generally
added. In order to provide enough hydrostatic pressure to balance abnormal
pore pressures, the density of the drilling fluid is increased by adding a
weight material (generally barite).
In summary, a drilling fluid consists of:
The Base Liquid
• Water - fresh or saline
• Oil - diesel or crude
• Mineral Oil or other synthetic fluids
Dispersed Solids
• Colloidal particles, which are suspended particles of various
sizes
Dissolved Solids
• Usually salts, and their effects on colloids most is important
All drilling fluids have essentially the same properties, only the magnitude
varies. These properties include density, viscosity, gel strength, filter cake,
water loss, and electrical resistance.
Normal Drilling Fluids
Though this type of drilling fluid is easy to describe, it is hard to define and
even more difficult to find. In the field, a normal fluid generally means
there is little effort expended to control the range of properties. As such, it
is simple to make and control. General rules include:
1. It is used where no unexpected conditions occur
2. The mud will stabilize, so its properties are in the range required
to control hole conditions
3. The chief problem is viscosity control
Formations usually drilled with this type of mud are shales and sands.
Since viscosity is the major problem, the amount and condition of the
colloidal clay is important. To do this, two general types of treatment are
used:
1. Water soluble polyphosphates
(a) they reduce viscosity
(b) can be used alone or with tannins
(c) if filter cake and filtration control is required
- add colloidal clay to system
2. Caustic Soda and Tannins
(a) they also reduce viscosity
(b) used under more severe conditions than phosphate treatment
The upper portions of most wells can use “normal” muds
1. Care must be taken not to add chemicals which may hinder the
making of special muds later on
2. Native clays used to make the mud are usually adequate
Special Drilling Fluids
These drilling fluids are made to combat particular abnormal hole
conditions or to accomplish specific objectives. These are:
1. Special Objectives
(a) faster penetration rates
(b) greater protection to producing zones
2. Abnormal Hole Conditions
(a) long salt sections
(b) high formation pressures
Lime Base Muds
1. Water base mud
2. Treated with large amounts of caustic soda, quebracho, and lime.
Added in that order
3. Ratio of 2 lb caustic soda, 1.5 lb quebracho and 5 lb lime per 1
barrel of mud
4. Will go through a highly viscous stage, but will become stable at
a low viscosity
5. Good points
(a) can tolerate large amounts of contaminating salts
(b) remains fluid when solids content gets high
6. Weakness - it has a tendency to solidify when subjected to high
bottom-hole temperatures
Lime-Treated Muds
1. Similar to lime based mud - differ only in degree
2. A compromise attempt at overcoming the high temperature
gelation problem
(a) use less lime than lime-base mud
(b) not nearly so resistant to salt contamination
Emulsion Muds - Oil in Water
1. Oil can be added to any of the normal or special muds with good
results
2. No special properties necessary
3. Natural or special emulsifying agents hold oil in tight suspension
after mixing
4. Oils used are:
(a) Crude oils
(b) Diesel
(c) any oil with an API gravity between 25 and 50
5. Oil content in mud may be 1% to 40%
6. Advantages are:
(a) very stable properties
(b) easily maintained
(c) low filtration and thin filter cake
(d) faster penetration rates
(e) reduces down-hole friction
7. Major objection is that the oil in the mud may mask any oil from
the formations
Inhibited Muds
1. Muds with inhibited filtrates
2. Large amounts of dissolved salts added to the mud
3. High pH usually necessary for best results
4. Designed to reduce the amount of formation swelling caused by
filtrate - inhibit clay hydration
5. Disadvantages
(a) need specialized electric logs
(b) requires much special attention
(c) low mud weights cannot be maintained without oil
(d) hard to increase viscosity
(e) salt destroys natural filter cake building properties of clays
Gypsum Base Muds
1. A specialized inhibited mud
(a) contained large amounts of calcium sulfate
(b) add 2 lb/bbl gypsum to mud system
(c) filtration controlled by organic colloids
2. Advantages
(a) mud is stable
(b) economical to maintain
(c) filtrate does not hydrate clays
(d) high gel strength
3. Disadvantages
(a) fine abrasives remain in mud
(b) retains gas in mud
Oil Based Muds
1. Oil instead of water used as the dispersant
2. Additives must be oil soluble
3. Generally pre-mixed and taken to the wellsite
4. To increase aniline value, blown asphalt and unslaked lime may
be added
5. Advantages
(a) will not hydrate clays
(b) good lubricating properties
(c) normally higher drill rates
6. Disadvantages
(a) expensive
(b) dirty to work with
(c) requires special electric logs
(d) viscosity varies with temperature
Inverted Emulsions
1. Water in oil emulsion. Oil largest component, then water added.
Order of addition is important
2. Have some of the advantages of oil muds, but cheaper.
Somewhat less stable
Salt Water Muds
1. Can be used either completely or partly saturated
2. Weight can vary up to 10 lb/gal when saturated
3. No filter cake building properties, easily lost to porous
formations
Silicate Muds
1. Composed of sodium silicate and saturated salt water
2. Has a pickling effect on shales which prevents heaving or
sloughing
3. Will be 12 lb/gal or higher
4. Corrosive, expensive and gives poor electric log results
Low Solids Muds
1. Keeps amounts of clays in the mud at a minimum, which
promotes faster and safer drilling
2. Three ways to remove solids from mud
(a) water dilution
(b) centrifuging
(c) circulate through large surface area pits
3. When clays are removed, a minimum of viscosity control
chemicals are needed
Inverted Emulsions
1. Water in oil emulsion. Oil largest component, then water added.
Order of addition is important
2. Have some of the advantages of oil muds, but cheaper.
Somewhat less stable
Salt Water Muds
1. Can be used either completely or partly saturated
2. Weight can vary up to 10 lb/gal when saturated
3. No filter cake building properties, easily lost to porous
formations
Silicate Muds
1. Composed of sodium silicate and saturated salt water
2. Has a pickling effect on shales which prevents heaving or
sloughing
3. Will be 12 lb/gal or higher
4. Corrosive, expensive and gives poor electric log results
Low Solids Muds
1. Keeps amounts of clays in the mud at a minimum, which
promotes faster and safer drilling
2. Three ways to remove solids from mud
(a) water dilution
(b) centrifuging
(c) circulate through large surface area pits
3. When clays are removed, a minimum of viscosity control
chemicals are needed

Exploration with Wireline Logs

The information from wireline logs is used to enhance two principle
objectives in the exploration program:
Rock & Reservoir Properties Hydrocarbon Evaluation
a. Environment of Deposition a. Correlation
b. Lithology & Mineralogy b. Structure
c. Radioactivity c. Permeability Traps
d. Porosity Type d. Porosity Type
e. Fluid Properties & Distribution e. Salinity Traps
f. Formation Pressure
g. Temperature
h. Rock Strength & Elastic Properties
There are several complicating factors which must be dealt with in order to
arrive at acceptable values for those formation and hydrocarbon variables.
The three most common factors are:
• The borehole is a dynamic system. The mud system will
penetrate the rocks surrounding borehole, and the borehole wall
is affected by the drilling process and time (time difference
between drilling and the wireline logging runs).
• Matrix and Pore Fluids affect certain tools differently.
• Tool Depth of Investigation is relatively shallow.
Classification of Wireline Logging Tools
1. Lithology Logs - These logs are designed to:
a. Identify permeable formations
b. Determine boundaries between permeable and non-permeable
formations
c. Provide lithology data for correlation with other wells
d. Provide a degree of certainty for quantifying the formation
lithology.
Examples of lithology logs are:
Spontaneous Potential
Gamma Ray
2. Porosity Logs - These logs are designed to:
a. Provide accurate lithologic and porosity determination
b. Provide data to distinguish between oil and gas
c. Provide porosity data for water saturation determination.
Examples of porosity logs are:
Sonic/Acoustic
Neutron
Formation Density
3. Saturation (Resistivity) Logs - These logs are designed to:
a. Determine the thickness of a formation
b. Provide an accurate value for true formation resistivity
c. Provide information for correlation purposes
d. Provide a quick indication of formation pressure, hydrocarbon
content and producibility.
Examples of saturation logs are:
Normal and Lateral Devices
Laterologs
Induction Logs
There are a number of auxiliary wireline services which can provide
additional information to augment the interpretation of formation
characteristics. These include: 1) caliper logs, 2) directional logs, 3)
dipmeter logs, 4) sidewall coring, and 4) formation testers.

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