Engineering in the design of petroleum well completions

The first important thing is to understand the meaning of well completion, as some questions may arise, for example:

What makes an oil well completed?

When is an oil well incomplete?

Is engineering knowledge necessary for design in the completion of an oil well?

What phases are before and after the completion of oil wells?

Of all the questions posed, the one that can help us to build a manageable concept that is easy to understand is the last question, since there are some works that help to identify some phases that are described before and after the work and design of the completion of an oil well.

All this leads us to conceptualize about the completion of oil wells as the whole set of works or activities that are performed in an oil well once the drilling activities of an oil well are completed, considering that within the drilling activities are contemplated the drilling of the hole, the lowering of the casing and then its subsequent fixation with the walls of the well through the cementing process, these three activities can be generalized as drilling activities in all phases of drilling.

Once the drilling activities are completed, the well completion activities are carried out, in the well completion all the equipment such as production tubing, nipples, circulation sleeves, valves are lowered to the well, all with the intention that this equipment can serve as a conditioner so that the formation fluids (oil and/or gas) can be efficiently produced from the oil well from the bottom of the well to the surface.

Engineering insight into oil well completion design

Taking into consideration that after the completion of the drilling activities a well is not totally completed, then it is necessary to make corrective works in order to know which are the activities of the works that are necessary to put the well to produce oil and/or natural gas. These works are not the same in all cases and will depend on the geological characteristics of the producing formation, therefore engineering must be present in the planning, design and monitoring of the operations of the selected works.

A clear example of design by an engineer is to first determine which will make the producing formation, if for example the producing formation is of the geological age of the Miocene, then most likely you have to complete the well leaving the producing formation in a bare hole, ie without lowering casing or cementing, as the hole will be bare a grid containing small holes which will be packed with gravel is used, all this without in the case that in the Miocene the producing formation is quite consolidated, because in the case that it is little consolidated and landslides can occur, then the most convenient is to complete the producing hole lowering a casing and cementing the space between the walls of the well and the casing, and then lower some guns that can drill and make holes in the casing and cement, in the case that the formation produces much sanding then you have to lower the well packed with gravels.

As can be analyzed the completion design depends largely on the geological characteristics of the producing formation, however they are not the only requirements that must be taken into account, since for example it will also depend on the rate of production of oil and / or natural gas that is intended to obtain from the completed well.

Many times there are multiple geological zones of interest, which all together can be put to exploit, this conditions the design in such completion, the way in which the well will contribute, since it is not the same completion for a well where the same energy is sufficient to lift the column of oil and / or natural gas from the bottom of the well to the surface than a well that for example needs to install an electrosubmersible pump at the bottom to help in the production and pumping of oil to the surface.

As a last aspect to consider I am going to mention two that are very important, one of them is to take into consideration the arrangement of the subsurface equipment considering the future works of repair and reconditioning of the well, the other that will condition the design is the economic resources that are available at the time.

Conclusion

In the design of a completion, the design engineer must never lose the vision of design and planning that places as protagonist that design that communicates the formation or producing reservoir with the surface using the most economical design and that in turn provides the best productivity rates.

To achieve the most optimized well completion, it is necessary to have a design vision in which the best completion techniques, the best equipment and the best safety at the lowest possible cost can be selected.

Bibliographic reference consulted and recommended

Well Completion. Engineer Mario Arrieta. National Experimental Polytechnic University of the Bolivarian Armed Force (UNEFA).

Note: The cover image is my own and was created using Microsoft PowerPoint design tools.