The growth of the world population has caused us to have increasingly higher rates of energy demand, industrialization and technological progress in urban planning, transport and infrastructure has made industrialized countries demand large amounts of oil and natural gas, so understanding in a general and basic way the processes of exploration and production of these hydrocarbons can place us as a society aware of our production based on a harmonious awareness of balance between consumption and rational use of this important resource.
These three big areas that I will name next represent almost in its entirety the essence of the oil activity and where the oil engineering plays a primordial role:
[1] Hydrocarbon exploration.
[2] Drilling and construction of an oil well
[3] Production of hydrocarbons.
The development and understanding of these three major areas seeks to highlight the importance of working with multidisciplinary teams, where geologists, petroleum engineers and mechanical engineers are an essential part of hydrocarbon exploration and production activities.
The task begins with the search for possible areas where there is oil and natural gas. This is where the importance of geology comes in, where prospective seismology studies provide the first indications for drilling the first exploratory wells.
The certainty of finding oil ends once we finish drilling an exploratory well where important petrophysical and geological information is collected for the development of the producing field with the drilling of new wells in that particular oil field. In the drilling of the oil wells, taking into account the complexity of the equipment to be used, the operations and supervision tasks in the construction of the oil well are carried out with the knowledge that the geologists can contribute, especially in the registration of lithological information.
The mechanical engineer is a fundamental part as a supervisor in the maintenance and repair tasks of the drill rig, the oil engineer is an essential part in building the design of the well construction and carrying out the supervision in the activities of undressing, moving, dressing of the drill, together with supervising the drilling activities in the different phases in the construction of the well, being this one the main responsible for the success or failure in the completion of the well construction.
Once the hydrocarbon content enhancing area is discovered, it is necessary to open that communication channel between the subsoil and the surface. This communication channel is the drilling of a well where fluids such as oil and gas will be taken from the rock where it is stored to the surface, it sounds very simple but the reality is that it involves a series of techniques and engineering so that these fluids can be used and marketed by all of us.
The different production methods mean that depending on the energy that the reservoir can provide, the wells are produced by methods such as: artificial gas lifting, mechanical pumping (rocker arm), electro-submersible pumping (ESP) or natural flow. The way in which the well will be completed once the construction of the well is finished will depend on the production method that is chosen.
Exploration of the hydrocarbon
The exploration or search for hydrocarbons is carried out based on a set of techniques that carry intrinsic knowledge in very important areas such as physics and mathematics that are applied to establish communication between the fluids that may be present in the subsoil and the seismic records that are recorded on the surface.
These records are studied by the geologists, and once the prospective evaluation task is completed, the decision is made as to whether that studied area is a candidate for drilling and to find out more about the lithological and pressure study found in the subsurface.
As it was mentioned in several opportunities in the hydrocarbon exploration, the geologist takes a leading role, since he is the one in charge of carrying out the geophysical prospecting studies, apart from the fact that when the drilling activities of an oil well are being carried out, he contributes by keeping a strict lithological control of the formations that are being drilled while the well is being drilled.
When I did my internship with the company Datalog de Venezuela C.A. I did it as a mudlogger, that is, as a recorder of information of the drilling mud cuts. During these internships in drilling PDV-09 I was able to reflect on the importance of geological information in both exploratory and development wells.
The mudlogger's activity consisted of collecting a sample of mud and drill bit cuttings from the shale, they were taken to be analyzed, a dry sample was analyzed after being taken to the oven and another wet sample was packed and taken to be analyzed by the company in the laboratories outside the location.
The dry sample that was analyzed on site was very important to keep a lithologic record every 10 feet of drilling to know the type of formation that was being crossed, this with the intention of helping with information to other wells that are intended to be drilled in the area, with this we can be prevented for example to know at what depth we can make a change of wick, because if at a certain depth we know that we are going to meet with some limestone, for its hardness is advisable to use wicks with a greater cutting capacity.
Within the exploration activities it is very important that we understand in a simple way what a field is, since it is a term that from now on will be very touched in most of my publications, and that apart from this is directly involved with the exploration methods used to determine the hydrocarbon content area.
A reservoir is an entity that accumulates hydrocarbons in a natural way. In order for the reservoir to exist, a series of geological requirements must be met, such as geological traps that stop the oil from migrating and storing it in these reservoirs, which must have porous and permeable characteristics so that the oil can be extracted in an optimal and commercially productive manner.
Within the parameters that can vary from a reservoir are the thickness of the sand containing the hydrocarbon, its lithology, pore pressures, porosity, permeability, all this will depend on the geological conditions and trapping to which it was subjected during its formation and accumulation stage.
Drilling of oil wells
The drilling of oil wells is done with the intention of creating a communication mechanism between the reservoir (in the subsoil) and the surface, since through this conduit (well) the oil in production will circulate from the subsoil to the surface.
Drilling operations are very complex activities that demand a large amount of equipment to be used, a contingent of personnel involving engineers, supervisors, workers, which make us have income from the extraction of this valuable resource such as oil.
Each well is unique, no matter how much information is collected from neighboring wells, the geological characteristics, pressures and even the operational form in which the wells are drilled vary among them, so it is advisable to assume an alert behavior before the drilling operations to the future problems that may arise such as casing glue, early wear of the drilling wick, loss of circulation of the drilling fluid, casing glue, high reservoir pressures among others.
Design in the construction of an oil well
What is shown in the image above is only one design diagram among the many that can be proposed for the drilling and design in the construction of an oil well, however the changes made from one design to another will depend on the lithological characteristics found in the zone where the well is to be drilled and also depends on the equipment and tools available to be lowered into the well.
In order to start producing the well, a string of pipes must be lowered to the bottom of the well with a set of explosives cannons in order to drill the cement-lined-formation to create this communication channel between the formation and the well.
The way in which the well is going to produce will depend on the completion of the well and the way in which it is decided to produce, for example if the reservoir is going to produce by natural flow is completed as shown in the mechanical diagram with production sleeve. However this form can vary to an electrosubmersible pump, mechanical pumping (rocker arm) among other methods.
Production of hydrocarbons
For the production of oil wells, it is important to make decisions when choosing the production method to be applied. For example, in my experience in the drilling area, I was able to see that although the wells being drilled in the Barúa-Motatán-La Ceiba zone could produce by natural flow, because a large part of the energy of those reservoirs was sufficient to lift that column of oil fluid under pressure, The decision was made to complete the wells by natural flow with a production sleeve but at the same time an electrosubmersible pump was lowered, since this pressure declined rapidly and thus the time to recondition the well to lower a pump was avoided, thus minimizing production costs in the drilling and completion of the wells.
It is important to emphasize that the design of the production method depends on the supply and demand production curve, this consists of a graph where the flowing bottom pressures are plotted against the accessory pressures of the well, if the supply curve that is the pressure with which the oil is estimated to flow is greater than the pressure losses that have to be broken for that oil to reach the surface then the well will flow naturally, otherwise some alternative artificial production method must be chosen such as
Mechanical pumping, the rocker arm is the pump that extracts oil from the subsoil to the surface in a mechanical way, generally the wells that are completed with this method of production are the shallow wells, an example of this are the wells on the eastern coast of the Lake such as Bachaquero, Mene Grande, Lagunillas and Cabimas.
Conclusion and contributions of this publication within the engineering
The processes involved in the exploration and production of hydrocarbons are very important within its description for future petroleum engineers to obtain a degree of discipline and management organization when they go to put their knowledge into practice, since many times it is believed that this is a linear process in which all operations are executed under the same order of ideas, and it turns out that when we study the process of production and exploration of hydrocarbons we realize that we need a complex set of knowledge that includes seismic studies to discover the area where we are going to exploit the oil, then going through the drilling and construction of wells where a lot of skill and precision is needed in the design of these activities until arriving at the systems and methods to put an oil well into production by the best method of production that best optimizes the production of hydrocarbons.
As a general knowledge for everyone not involved in this process, it is also important to get involved with learning these activities from an engineering point of view, since oil marketing and production is linked to our modern life system.
Recommended references
Overview of the oil and gas exploration
and production process