Fishing Technology (6)

Using Magnets for Fishing

Purpose

Fishing magnets are primarily used to pick up bit cones, but they can pick
up all types of small objects with magnetic properties.

Guidelines for using magnets

Magnets should be run on pipe instead of wire line so that you can circulate
and rotate. Fishing magnets run on wire line are usually made inside the
casing with clear fluid in the hole. There are adapters available to run
magnets on a wire line.
Note: Most, but not all tungsten carbide bit inserts are non-magnetic.

Checking magnet capacity

Check to see if the magnet is charged properly by attaching a 20-lb.
sledgehammer to the face of it. If the magnet will support the weight of the
sledgehammer, it will likely hold any small pieces of junk in the well bore.
The lifting capacity of the magnet is a function of its size, area, and charge.

Verifying size

The OD of the magnet should be ¼" to ½" less than the hole size.

Figure 2-1:
Fishing Magnet with a Cripple Type Guide Attached

Using a Junk Mill

Description

Junk mills mill up and break up large junk into smaller pieces that can be
recovered in a boot basket. Junk mills provide the surest method for
eliminating junk in the hole.

Types of mills

The following are examples of types of mills that are used for eliminating
junk:
1- insert type mill
2- crushed tungsten carbide mill
3- skirted flat bottom or concave type mill
4- blade type mill
5- cone buster mill
6- cement mill.

 

Figure 2-2: Cone Buster and P Mill

Figure 2-3:  Packer or Cement Mill

Milling guidelines

Some important guidelines for milling with junk mills include:
1- Provide adequate circulation to flush the cuttings and cool the mill.
2- A boot basket must be run directly above the mill to catch the metal
cuttings.
3- Always mill by torque and not by weight. If the mill is producing torque
and making progress, then the weight applied to the mill is sufficient.
Most people run too much weight on mills. A standard rule of thumb is
not to exceed 1,000 pounds per OD inch of the mill.
Note: Mills with stabilizer pads should be used inside the casing.
IF you are milling pipe that causes the drill string to bounce and vibrate,
THEN consider using a Bowen Shock Sub to cut down on vibration.

Calculating milling rates

The milling rates for the carbide mills are specified by the manufacturer in
Surface Feet Per Minute (SFPM). The surface feet per minute must be
converted to revolutions per minute (RPM) because the operator does not
have a way to measure surface feet per minute.
The rpm may be derived from the SFPM by multiplying the mill diameter
by the milling RPM. This result is then multiplied by a constant, 0.262. For
example, a certain mill’s diameter is 4.5" and the milling rate in RPM is
120. You would calculate the SFPM in this way:
4.5 x 120 x 0.262 = 142 SFPM.
Table 2-2 lists some standard milling rates. Other rates may be computed
by converting the milling rates in revolutions per minute to surface feet per
minute.

Collecting the junk

Mills and boot baskets go hand-in-hand. Boot baskets are always run with
mills because they collect the pieces of the junk that the mill grinds up.

Enhanced Oil Recovery ( THERMAL RECOVERY )

THERMAL RECOVERY

Thermal recovery comprises the techniques of :

 -Steam flooding.

 -Cyclic steam stimulation. 

     In situ combustion

STEAM FLOODING

Recovery by steam flooding is commonly used in

 heavy-oil reservoirs containing oil whose high 

viscosity is a limiting factor for achieving commercial

 oil-producing rates

 

Procedure:

 High-temperature steam is continuously injected into 

a reservoir. As the steam loses heat to the formation, 

it condenses into hot water, which, coupled with

the continuous supply of steam behind it, provides the

 drive to move the oil to production wells

As the formation heats oil, recovery is increased by: 

1.The heated oil becomes less viscous, making it easier to move through the formation toward production wells.

2.Expansion or swelling of the oil aids in releasing it from the reservoir rock.

3.Lighter fractions of the oil tend to vaporize, and as they move ahead into the cooler formation ahead of the steam they condense and form a solvent or miscible bank.

4.Finally, the condensed steam cools as it moves through the reservoir and results in what amounts to an ordinary Water flood ahead of the heated zone.

 

CYCLIC STEAM STIMULATION

("Huff-and-Puff')

(A well-stimulation method)

This method is sometimes applied to heavy-oil reservoirs to boost recovery during the primary production phase.

Procedure: 

A predetermined amount of steam is injected into wells that have been drilled or converted for injection purposes. These wells are then shut in to allow the steam to heat or "soak" the producing formation around the well.

- After a sufficient time has elapsed to allow adequate heating, the injection wells are back in production until the heat is dissipated with the produced fluids.

 

This cycle of soak-and-produce, or "huff-and-puff," may be repeated until the response becomes marginal because of declining natural reservoir pressure and increased water production.

-At this time a continuous steam flood is usually initiated to continue the heating and thinning of the oil and to replace declining reservoir pressure so that production may continue.

-When the steam flooding is started, some of the original injection wells will be converted for use as production wells, along with the others drilled or designated for that purpose.

 

Oilfield Steam Generator 

 

 

 

Insulated Steam Injection Tubing: 

The Thermal Tube 3-H tubulars employs a high vacuum as the insulating medium offering the highest thermal performance for oil field steam injection projects

IN SITU COMBUSTION or "Fireflooding

This method is sometimes applied to reservoirs containing oil too viscous or "heavy" to be produced by conventional means.

 Burning some of the oil in situ (in place), creates a combustion zone that moves through the formation toward production wells, providing a steam drive and an intense gas drive for the recovery of oil.

Procedure:

This process is sometimes started by lowering a heater or ignitor into an injection well. Air is then injected down the well, and the heater is operated until ignition is accomplished.

-After heating the surrounding rock, the heater is withdrawn, but air injection is continued to maintain the advancing combustion front.

-Water is sometimes injected simultaneously or alternately with air, creating steam which contributes to better heat utilization and reduced air requirements.

Notice in the accompanying illustration that the lighter steam vapors and combustion gases tend to rise into the upper portion of the producing zone, lessening the effectiveness of this method. Injection of water alternately or simultaneously with air can lessen the detrimental overriding effect.

Fishing Technology (5)

FISHING FOR JUNK

Overview

Any undesirable object that is stuck or accidentally dropped in a well is
referred to as “junk.” Junk may include bit cones, tong dies, broken slips,
reamer parts or debris created by a fishing or milling operation, or any other
small debris that could impede normal drilling operations. Because of the
wide variety of junk that can be in the hole and the likelihood that the
customer may not know what the junk is, you will have to be fairly creative
in planning a junk fishing operation. However, because of the time and
money spent on fishing operations, you will need to devise a method for
fishing the junk that involves the fewest trips and equipment as possible.

Deciding How to Fish Junk

Evaluating the junk

Any debris or junk in the borehole must be thoroughly evaluated before any
successful fishing attempt can be made. Depending on the properties of the
junk, it can either be milled up, recovered, or pushed back (walled-off) into
the formation.
Consider the following questions before proceeding with a fishing job:

•  What is the size, weight, and condition of the junk?
•  Is the junk magnetic?
•  Can the junk be picked up?
•  What are the dimensions of the bit cone or cones?

The company man would ideally know exactly what the junk in the hole
consists of. When the nature of the junk is unknown, you must be creative
in your approach to fishing the junk.

 Impact of the junk size, weight, and condition

Try to determine the size, weight, and condition of the junk. This
information will help you determine the best method for fishing the junk.
For example, if you have junk that is:

•  large and/or irregularly shaped, you might try a poor boy basket
•  smaller, you might try a magnet, core type, or reverse circulating basket.

For very large pieces of junk, you may need to use a junk shot to break it
into smaller pieces before attempting to fish.

Determining if the junk is magnetic

Try to find out what the junk is made of. If it has a high ferrous content, it
is probably magnetic. The easiest method for fishing magnetic junk is using
a magnet.

Determining is the junk can be picked up

If the OD of the junk is significantly smaller than the ID of the hole, than
there is a good chance that it can be picked up. However, if the OD of the
junk is fairly large, it will be harder to get a fishing tool over it. In this case,
you will probably have to mill the junk to break it up and collect the pieces
in a boot basket.

Determining cone dimensions

If you know the junk is a bit cone, the dimensions of the cone must be
known before deciding which tool to run. Find out the size of the bit from
which the cone was lost, and verify the maximum OD of the cone. Select a
tool that has an ID at least 1/8" larger than the OD of the cone.
For example, a 7 7/8" bit cone is 5 15/64" OD. A 7 1/8" OD Bowen Itco
Type Junk Basket has an ID size of 5 28/64". This tool will get over the bit
cone.
Standard rock bit cone dimensions are shown in Table 2-1. Note: This
information can also be found in the Bowen user manuals.