rotary bha ingold r3x

Self Introduction

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Trainees introduce themselves

Note: Generally speaking, drillSafe is fairly accurate for common sizes but is often

inaccurate for exotic BHAs.

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inaccurate for exotic BHAs.

Discussion:

Discussion:

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Discussion:

The uncertainty (lack of control) when using a slick assembly leads to unpredictable results.

Thus, this type of BHA is not used in deviated wells.Thus, this type of BHA is not used in deviated wells.

The tangency point moves down with the increase in WOB.

The greater the hole inclination, the higher the pendulum force.

A condition of zero net side force may be achieved at some point.

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A condition of zero net side force may be achieved at some point.

If we use stiffer drill collars, a larger pendulum force results. A higher weight on bit must be

used to achieve a balanced condition. It may not even be possible.

In a field unknown, it is usually easier to predict what stabilizer spacing will do rather than

stabilizer gauge.stabilizer gauge.

With stabilizer gauge, blade digging may happen or the stab can wear out thus producing

more or less than planned.

A BHA where inclination can be controlled with WOB may be classified in some cases as a

“double geometry” BHA.

Generally speaking the higher the hole to collar ratio the higher the BUR that can be

obtained with a full Buildobtained with a full Build

A single stab BHA can fail to build as in the 9 7/8 showed. With a stab placed 60 ft above,

the BUR would have doubled.the BUR would have doubled.

The 17 ½ BHA could have worked fine with less WOB. This BHA could have produced from 3

to 5 per 100

A stabilizer 30 ft above the bit would have allowed building at twice the BUR obtained on

the 6” BHA.

If stabilizer # 2 is undergauge, this BHA may be a double geometry BHA.

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The simplest multi-stabilizer BHA has a near-bit stabilizer (3'-6' from the bit to the leading

edge of the stabilizer blade) and a second stabilizer some distance above this.

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edge of the stabilizer blade) and a second stabilizer some distance above this.

For a given weight on bit, the distance from bit to first stabilizer (L1) and between the

stabilizers (L2) determines the tangency point.

This chart shows the influence of inclination on bit side force.

A 90 ft Build is consistently higher than a 45 or 60 ft build but as the WOB increases A 90 ft Build is consistently higher than a 45 or 60 ft build but as the WOB increases

the gap between the 60 and the 90 ft shrinks.

If the second stabilizer is under gauge and placed right, it becomes easier to build angle.

The more under gauge, the greater the effect.

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The more under gauge, the greater the effect.

In lock BHAs, the second stabilizer is usually undergauge. The objective is to reach a

condition of zero net side force at the bit.

Discussion:

Typical lock up BHA with 4 stabilizers

Notes:Mention to class to find the mistake: the stabilizer has a left hand spiral (wrong)….

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Notes:Mention to class to find the mistake: the stabilizer has a left hand spiral (wrong)….

Blades work against the flow

The BHA affects the well bore trajectory. The design of BHA can vary from very simple (bit,

drill collars, drill pipe) to a complicated hookup (bit, shock sub, roller reamers, stabilizers,

non-magnetic drill collars, steel drill collars, crossover subs, extension subs, jars, heavy

weight drill pipe and drill pipe).

Discussion:

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Stiffness coefficient is a measure of component rigidity.

It is important to take drill collar stiffness into account when designing BHA's. MWD tools

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It is important to take drill collar stiffness into account when designing BHA's. MWD tools

are normally more limber than same size DCs.

DLS achieved may differ greatly when MWD is placed above a NB.

Discussion:

If collar size is multiplied by rigidity is increased by 16.

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If collar size is multiplied by rigidity is increased by 16.

In the real world, the level of sag will reduced by the weight and forces acting on

either side of each stabilizer.

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either side of each stabilizer.

Sag will also be affected by how much movement the hole will allow.

Full gauge Near Bit Stabilizer could be build or hold, depending on the WOB

Undergauge Near Bit Stabilizer will result in slow drop

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It is clear from this chart that with low WOB the difference in side force is huge when the

stabilizer is over 1/8th under.stabilizer is over 1/8th under.

As the WOB increases, it is not so bad.

A stabilizer placed 40 to 60 ft above the bit is too far away to create a build tendency.

However it is still close enough on many BHAs to allow flexing collars with WOB and to

create a build tendency.

How does the hole gauge affect a Building BHA and a dropping BHA?

In soft formations, hole erosion occurs due to high annular velocities. Attempts at holding

or building inclination are more difficult (impossible to keep sufficient weight on bit).

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or building inclination are more difficult (impossible to keep sufficient weight on bit).

Sometimes it may be necessary to drill a pilot hole first and follow up with a hole opener.

Examples of commonly used BHA's for building inclination. Rates of build of the order of

3.4°/100' are possible with BHA No. 9, depending on the geology, inclination and drilling

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3.4°/100' are possible with BHA No. 9, depending on the geology, inclination and drilling

parameters.

BHA No. 3 is used as a slight-to-medium building assembly, depending on how much under

gauge the middle stabilizer is and how responsive to weight the BHA is.

The rate of increase in inclination (buildup rate, in °/100') is very important. The safe

maximum is about 5°/100‘ with 8” DCs.

If the BUR is high at a shallow depth, key seats may form when drilling ahead.

If the curve is cased, the casing may show high wear when drilling the lower part of the

hole.

Clients may set a DLS limit as low as 1.5°/100‘ on deep holes (15000 ft plus).

It's important to be aware of the client's acceptable limit for buildup rate. The effective

stiffness of a drill collar increases as RPM is increased. This leads to a reduced buildup rate.

As hole inclination increases, it becomes easier to build angle. Thus, where MWD is

available, it is advisable to survey every single during the buildup phase. This allows the DD

to avoid unnecessary and unwanted doglegs. Weight on bit may need to be reduced and/or

reaming initiated where such an acceleration in buildup rate occurs.

Excessive WOB can also cause reverse bending. An 8” DC in a 17 ½ hole or larger can

reverse bend with 50000 lbs plus.reverse bend with 50000 lbs plus.

In order to keep the hole inclination within a small "window", a condition of zero net side

force on the bit has to be aimed for.

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force on the bit has to be aimed for.

This type of BHA must be stiff. The stiffness of the BHA also helps to control bit "walk".

In practice, slight changes in hole inclination often occur. The objective is to get a complete

bit run without needing to POOH for a BHA change.

BHA No. 1 can have either a building or a dropping tendency. This BHA using 8" collars in

17-1/2" hole in soft formation may barely hold inclination.

In 12-1/4" hole with 8” DCs a BUR up to 1.0°/100‘ can be obtained with high WOB.

Reducing the gauge of the second stabilizer may gives the same result as displacing the

second stabilizer up. For directional control in a field unknown, working with spacing works

better than working with stab gauge.

This is a typical lockup BHA for 12-1/4" hole at 30° inclination. If a slight build is called for,

the second stabilizer should be reduced in gauge - typically down to 12“.

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the second stabilizer should be reduced in gauge - typically down to 12“.

The DD would be well advised to have at his disposal a range of under gauge stabilizers

from 11-1/2" up to 12-1/8" in increments of 1/8". .

BHA No. 5 (60' pendulum) is the most common where a high drop-off rate (1.5°-3°/100') is

needed, i.e., in "S"-type directional wells.

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needed, i.e., in "S"-type directional wells.

“S"-type wells are normally planned to have a drop-off rate of 1°- 2°/100'. A common

approach is to start the drop-off early with a less-aggressive BHA.

A drop-off rate of about 1°-1.5°/100' is often achievable until the inclination drops to about

15° (at which point the gravity force is much less).

A round trip can then be made with a more aggressive drop BHA. This plan although safe,

should be discussed with the client before the job starts. An "extra" trip is involved.

Rate of drop-off usually slows significantly below 10° inclination. When the inclination falls

to 2°, the well is considered vertical. However, the inclination should continue to be

monitored.

There is very little control over hole direction when using a pendulum BHA. Sometimes the

well walks excessively when using a tri-cone bit during the drop-off. The DD should thus

have some tolerance available in hole direction when he starts the drop-off. RPM should be

kept high (this also helps the drop-off rate).

A lock-up BHA incorporating an under gauge near-bit is known as a semi-drop BHA. This

type of BHA is often used in slant wells where the DD is "above the line" and wants to drop

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type of BHA is often used in slant wells where the DD is "above the line" and wants to drop

into the target with a nice slow drop-off rate (typically 0.1°-0.5°/100'). The drop-off rate

achieved is determined by how much under gauge the near-bit is.

In case "spudding" of the drill string is required, the shock loading on the MWD tool is not

excessive (formation is soft).

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excessive (formation is soft).

Jetting has the advantage that the well can be kicked off along the required direction and

may allow a single run to drill a curve.

Jetting is a safer anti-collision approach than using a mud motor.

Precautions to be taken when running a jetting BHA:

1. Plan the job! Pick up enough drill collars in the BHA (kickoff point is shallow) to allow

sufficient BHA weight for spudding/slacking off as required.

2. Avoid running drilling jars in a jetting BHA.

3. Do not jet too long an interval! Check dogleg severity on each single. Wipe out

excessive doglegs by reaming/washing and re-surveying.

5' to 8’ per joint should be enough. Check the resulting dogleg severity and ream if

necessary.

Gilligan BHAs were mostly used for side tracks on vertical holes before 1980.

They were sometimes used in the ‘80s and ‘90s to build a few degrees on challenging high

angle wells.

It's vital to take surveys at close intervals to “track" the BUR. Again, as hole inclination

increases, BUR increases.

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increases, BUR increases.

G1 and G2 are typical Gilligan BHAs while the other two are very classic.

Discussion:

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Tricone with milled tooth or inserts may require very high WOB.

If you have been using a trricone and all of a sudden have to switch to a PDC you may want

te review your BHA.

rotary bha ingold r3x

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