Importance of correctly applying the knowledge of hydraulics in the drilling of an oil well.

One of the main aspects of drilling a well is the speed with which it is drilled, this speed in the drilling is translated to the feet that progresses as it deepens. in the strata for the time that elapses, this speed is known as the drilling rate, also known as penetration rate (known as ROP for its acronym in English and measured in foot / minute), now if we analyze the elements or variables of which depends on whether the penetration rate is slow or fast, we need to name the following:

1. Need to have a controlled rate: In many cases already the drilling programs give the value of the penetration rate with which the specific hole will be drilled, for example it is not the same to use the same rate drilling for the drilling of the conductive hole that the same penetration rate for the intermediate hole, since the geological formations that are traversed are different, and maintaining a controlled penetration rate helps us to avoid landslides of the formation.

2. Bad design in hydraulics: it is necessary to adjust the parameters of the models we study in fluid mechanics, such as models and programs that take into account the drilling fluid circulation rate and the size of the jets of the wicks, this means that taking into account, the characteristics of the formation to be drilled, the characteristics and properties of the fluid, we must design the flow rate of the drilling fluid adjusted to the size of the jets of the wick.

3. An inefficient cleaning at the bottom of the pit: This variable I think is the one that most influences even for a drilling of an oil and / or gas well can be stopped completely until you can not drill a foot of more length, since if the cuttings product of the drilling are not removed efficiently by the drilling fluid, it may be failing or the design of the hydraulics or the properties of the drilling fluid as density, viscosity, yield point, filtering among others more properties.

With everything explained above, we can ask the following question:

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Note: in the image we can illustrate a similarity of what the driller's cabin represents, where we can observe very important drilling parameters such as the ROP.

How do we improve the penetration rate?

For this we have to analyze in detail the situation, for example if we are drilling the shallow hole at a depth of 2500 feet in a little consolidated formation, and we are required according to the drilling program to drill a ROP of 20 ft / minute, if all the properties of the fluid are correct and adjusted to the drilling program, and we did not reach the goal of 20 feet per minute, and we are just beginning the hole, where the fuse has not had any wear and tear, it is likely that this Failing the hydraulic, here is the importance of making a readjustment and perform a new redesign in hydraulics.

A very effective method applied when you want to have an effective cleaning of the hole and increase the ROP is to be able to provide maximum hydraulic power (horsepower) by means of the drill bit. The maximum hydraulic power method is based on effectively cleaning the hole by spending the maximum energy available in the bottom. The other method applied is the maximum hydraulic impact, where it is sought to remove the cuts using the impact force of the drilling fluid that comes out of the jets of the wick hitting the bottom of the well maximized. This energy to my way of understanding translates into maximum pressure at the bottom of the hole, which is why the smaller diameter of the jets of the wick, the greater the impact pressure we will find at the bottom of the hole.

Knowledge associated with hydraulics that are an essential part of well drilling.

The models explained above are in summary the center of hydraulics applied to oil drilling, but to be able to adjust these models to the different conditions that may arise during drilling the well, it is necessary to know the following:

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• Capacity of the mud pump: the mud pump must move the drilling fluid from the mud tanks, pass through the whole pipe that takes it from the tanks to the jets of the wick, therefore the The pump must have enough energy to compensate for the energy losses that occur in the circulation of the mud, if the pump is already has a time of use, and what is the flow and pumping pressure would no longer be at standard conditions, situation that forces a hydraulic design to compensate for the losses that are lost due to the lack of energy of the mud pump and valve accessories, elbows among others.

• Flow regime: In most cases, the flow regime used in the oil industry is turbulent, as through this flow regime the fluid particles move in opposite directions, colliding with each other. others at high speeds, a situation that favors the cleanliness of the hole.

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• Lost by friction: As mentioned above in the fluid circulation system there are pressure losses, in which to calculate these losses mathematically it is necessary to know the lengths and diameter of the pipes through which the fluid circulates of drilling, the annular space existing between the hole and the drill pipe, it is also necessary to know certain properties of the drilling fluid such as: the density of the mud, plastic viscosity of the fluid, and it is not less important to know the flow rate of fluid of drilling that we have it as data in the panel of the driller's controller (driller's cabin).

Consequences that an inadequate hydraulic design can cause.

It is necessary that we can compensate the energy of the pump by means of the hydraulic design, either by the maximum hydraulic power method or the maximum hydraulic impact method, with this we will avoid failures by unnecessary requirement in the pumping equipment, which means that A design that is not adjusted to pump energy compensation, to the later will cause it to be damaged.

There is a serious evil that occurs in the drilling operations of oil wells and / or natural gas, and is that of the glue pipe, there are many factors that can influence the glue of pipes, among them is the differential glue, which occurs when the hydrostatic pressure of the fluid exerts a very large pressure differential compared to the reservoir pressure, the other is when the removal of gravel is very poor, causing accumulation of cuttings at the bottom of the well, a clear warning of that this is happening is when we observe that the ROP gradually decreases to the point that the perforation is slowed down, without being able to continue drilling and afterwards the pipe is stuck to the parents of the hole, having few possibilities to detach it, this brings as consequence that all the pipe string can stay at the bottom of the hole bringing considerable economic losses.

In conclusion, a bad design in the oil well drilling hydraulics means that the mud pumps can be damaged, the pipe string can be stuck with high-cost equipment such as the bottom motor, ballast, heavy pipe, pipeline perforation, stabilizers, all this subsoil equipment that is lost at the bottom of the hole represents a considerable amount of money, which although the well can pay when it starts to produce, is an event that if planned well with a correct Design in hydraulics can be avoided so as not to generate greater evils.

Technical vocabulary used.

1. Hydraulics: Only in the case of industry and oil knowledge is known the hydraulic as the part that studies the behavior of the fluid adjusted to the needs of compensation of energy in the form of pressure, taking into account pressure losses and flow models taking the Reynolds number as a starting point among other parameters.
2. ROP: is the penetration rate with which it is penetrating the subsoil layers, that is to say when we drill, we penetrate into the formation a certain length measured in feet per unit of time measured in minutes.
3. Jets of the wick: Are the holes located in the drill bit where the fluid will come out while it is drilling, using the maximum hydraulic impact method, we will take advantage of it by reducing the diameter of the jets to generate more pressure at the bottom of the hole, and with this maximize the cleanliness of it.
4. Mud pump: The three pumps used in an oil location are called a mud pump to pump the drilling fluid (also called drilling mud) from the tanks to the bottom of the tank. well, until completing its circuit until it reaches the tanks again. These pumps in drilling operations are usually used two and one that is kept in reserve in case one of the two in use fails.
5. Flow regime: is considered flow regime to the behavior of the fluid at the rate of direction and direction, speed that the fluid particles follow in the circulation system it has, this type of regime flow is determined by the Reynolds number, where a Reynolds less than or equal to 2100 is considered a laminar flow. Rare a Reynolds between 2100 and 4000 is considered a flow in transition. And for a fluid whose Reynolds is greater than 4000 it is considered to be governed by a turbulent behavior (the one most used in the oil industry).

References consulted:

1. Well drilling book of the postgraduate program in Petroleum Engineering of the Petroleum Training and Training Center of Venezuela and its subsidiaries.

2. Fluid mechanics. Frank M. White University of Rhode Island. Editorial Mc Graw Hill. Fifth edition

Note: Part of the writing and sense of the publication is product to my profession (Oil Engineer) with 3 years of experience that I conceived in PDVSA in the area of ​​drilling operations PDVSA SERVICIOS PETROLEROS S.A

Greetings to all, until the next opportunity to present you with all my enthusiasm more publications of this nature.