What criteria should be taken into account in an drill bit program?

Hello friends of the hive platform and to all those who love engineering and STEM content in general.

This time I want to present you this very own article of engineering, since for the drilling of wells is very important the planning, as I have already mentioned in many of my post the drilling and construction of an oil well must be planned taking all the possible factors and elements, that is why to select the drill bits that will be used in the drilling and construction of a well must be selected such drill bits following a set of criteria all very rigorous, now you may be wondering:

What factors can be taken into account when selecting a drill bit?

In order to answer this question, it is necessary to have implicit in our ingenuity a series of analyses that will make us answer this question in a way that is quite easy to understand.

The first thing to think about in order to know what criteria to take into account for such selection is to know the function of the drill bits in the construction process of the hole, I think it is very easy to understand that the function of the drill bit is to crush the subsoil formation as it goes deeper into the hole, knowing this function makes us reflect that we must know the characteristics of the formation found in the subsoil, because if the lithological formation is what will crush or cut the bit, then it is very convenient to know the characteristics of the lithological formation of the subsoil.

However, those of us who know engineering know that almost always program designs are not limited to only one factor to consider in order to select something, and for this case, apart from the characteristics of the formation, we must also know the characteristics of the design of the drilling program, since depending on the diameter of other tools and equipment, the selection of the drilling bit set depends to a considerable extent.

Nowadays we can find a great diversity of oil well drilling bits in the market, however not all of them can be used in the drilling of wells without first having our drilling program detailed, where the type of bit that we are going to use for the drilling and construction of each particular hole is specified.

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Why not choose a general type of drill bit for drilling and constructing an oil well?

The reasons are many, but one of the things that most characterize engineering is resource optimization, as this translates into cost reduction, which is why you can not choose a single type of drill bits for all the drilling of the hole, for example there are diamond drill bits that are very expensive and should only be used for very hard lithological formations, this makes us conclude that the economic factor is an element to consider when following the selection criteria to develop a drill bit program.

Procedures in bit program planning

The first thing we must do as design engineers is to make a preliminary planning, i.e. to make a planning based on the most obvious criteria in the drilling and construction and drilling of a well, for this you must choose a set of bits specifying for which hole will be used each type of bit, but of course this initial selection of the bits will be made based on criteria that personally I think are the most fundamental and that can serve as an initial guide, these are:

• Objectives to be met during drilling, such as the depth in each of the holes.

• Operational risks involved during drilling, these risks refer to whether there may be formation collapse, pipe sticking, among others.

• The geometry of the hole, it is known that the diameter of the hole will never be perfect, perhaps this is one of the factors that we are not taught in college, but we learn once we have the opportunity to be in the field attaching the practice with the theory, however although the diameter of the hole will never be uniform, we can consider some type of bit that is as consistent with the formation so that the geometry of the hole is as perfect as possible, since with this we can achieve that the cementation of the well is as uniform as possible.

The beauty of petroleum engineering is that any design that involves the construction of a well makes it possible to compare certain parameters of other wells that have already been completed based on the one we intend to build, which is why the other thing that can be recommended for the development of the drill bit program is to incorporate in the program a detailed study of the bits that were used in the neighboring wells of the one we intend to build, and with this we can get an average of the bits used to build the wells of the oil field in which we intend to build our new well.

What types of augers are available on the market?

As I mentioned in the introduction of the post, there is currently a great diversity of drill bits, one of the characteristics that we can find among the bits that are on the market is that they differ from each other, you may wonder: How do they differ and why?

First of all, when we have the opportunity to see many of these bits, we can realize that the difference between them lies basically in two factors which are its cutting structure, that is, the way in which the bit is configured to cut the subsoil formation, and the other difference between them is in its bearing system, these two differences exist because the drilling bits have to cut different types of rocks in the subsoil, which is why we can get in the market:

• Tricone drill bits.

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• Diamond bit .

• Polycrystalline diamond drill bits (PDC).

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From my work experience I can tell you that these three types of bits were used in the construction of wells for which I personally was the drilling operations engineer. The tricone bits were generally used in the conductor and shallow holes, since these holes are constructed where there is a poorly consolidated lithological formation (soft formations). Diamond bits were used in the intermediate hole, where the lithology changed to a less soft rock type, and PDC bits were used to drill the production hole, which regularly reached very high depths such as 15,000 to 18,000 feet deep, and where hard lithological formations made it necessary to drill with polycrystalline diamond bits.

Conclusion and recommendations based on the design in the bit program.

From the different bits available in the market, a type of bit must be selected according to the conditions of the lithological formation, since if for example we are drilling the conductor hole, we must be aware that in the drilling and construction of this hole there are few consolidated formations and where a tricone bit can be easily selected.

For hard formations, which are generally found at depths greater than 10,000 feet, it is recommended that diamond bits and polycrystalline diamond bits (PDC) be selected.

One of the aspects to be taken care of in the well is the geometry of the hole, although from experience in the field it is known that it is impossible to keep a hole with a constant diameter and without variations, the idea is to choose a program of drill bits under which a hole with the best possible geometry can be built.

There are bits that do not maintain directional control because suddenly the drill bit has been selected that is not the most suitable for certain lithological formation, this makes the directional control that has been programmed in the verticality or directionality in the well trajectory is lost, it is advisable to make a bit program that involves directionality as an important criterion at the time of the direction of the well.

Another criterion that perhaps many do not take into account is the rotation system that we have in the drilling rig, since it is not the same to select a type of bit for a top drive rotation system than for a rotation system that includes a rotary table.

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Within the drilling fluid circulation system is the drilling fluid, depending on the drilling fluid that we are handling in a certain phase of the well, it is important that the drilling bit selected is in accordance with the drilling fluid being used.

Observations

The cover image was created using Microsoft PowerPoint design tools and the following Image Source

References

Drilling Optimization: The Essential Role of Drill Bit Selection

Advances in drill bits improve efficiency, performance

Drill Bit Optimization. Halliburton

Drill Bits