The re-entry technique, which is being used by some of the operating companies in the Neuquine basin, allows reconverting old inactive wells and reorienting them towards the production of hydrocarbons unconventional reservoirs.
The so-called re-entry to the wells is allowing to recover hydrocarbons in wells that seemed already forgotten, located in different blocks of the Neuquine Basin. According to the technical glossary of the Ministry of Energy of the Nation, the “well re-entered” is called the “well that begins using the engineering of another pre-existing one, by placing a diverting element (wedge) that allows a window to be opened in the well used pipe and whose objective is to reach some layer, formation or structure in a certain location or position ”. With this technique you can open a new operating grain in an already perforated column, deepen an existing well or make a lateral branch to extract oil from that reservoir again.
According to data from the Undersecretary of Hydrocarbons of the Province of Neuquén, in the last months 20 orders were received to make re-entries, with the aim of orienting them towards the production of shale oil, the type of hydrocarbon that is leading a true revolution in this basin and it’s the greatest evidence in his boom in Vaca Muerta. It is clear that not all inactive wells can be subjected to this technology. To define whether a non-productive well is a candidate for a re-entry, it must be studied in its entirety and determine the economic equation of the project based on its costs and benefits.
One of the benefits that encourages companies to opt for this alternative is to take advantage of existing locations and exploit the area at a lower cost than it would take to drill the wells from the surface. The analysis from a purely technical point of view should also take into account the ideal wells tubing diameter (production pipe), which must be at least 7 inches. A smaller diameter requires the use of much more expensive tools, in addition to the production achieved would be limited.
One of the most advanced firms has been Pan American Energy (PAE), the new operator of the Coirón Amargo Sur Este (CASE) block, in which the Canadian Madalena Energy and the provincial state-owned Gas and Petroleum of Neuquén (GyP) also participate as partners. There, two traditional wells were converted to be redirected to the production of shale oil. Last May one of them, CAS 14 (r) (h), reached the production of 210 barrels per day; while the other, CAS 15 (r) (h) obtained a production of 538 barrels per day. These “readmissions” allowed to reach in one case the 1000 meters and in the other, the 1500 meters of extension. The objective has been to deepen the existing wells to then be able to make lateral branches destined for Vaca Muerta formation.
Another company that has been involved in a re-entry program is Capex, operator of Agua del Cajón Neuquino block, with the aim of deepening 400 to 500 meters in its own wells to find the shale of unconventional Organic Molles. YPF has also entered into re-entry operations, for example in Las Lajas Este x-1 well of the Loma La Lata block, aimed at the Las Lajas formation for the production of tight gas.
Wells made so far in Vaca Muerta were mostly vertical. Although they could in the future be candidates to be converted into horizontal wells, most were made with narrow tubings, which is the biggest obstacle to achieving greater production. The advantage of horizontal wells is that they significantly improve the return on investment, by increasing the drainage area and reducing the number of wells required to develop a reservoir.
Specialists warn about the outdated regulations and recommend an update of the resolution 1040/2009 of the Ministry of Energy, which establishes the classification and nomenclature of wells to which companies must comply, with exploration permits and concessions of exploitation granted throughout the national territory.
