French to English Tech/Engineering Petroleum Eng/Sci Hydrocarbon production

The term appears in the following point in a production sharing contract between the Republic of Chad and an oil and gas company:

"Lorsque les Travaux d'Abandon concernent des Puits de Développement ou de
Production, ces travaux comprennent trois phases principales :

(a) l’isolement du Réservoir de la surface et des différentes couches productrices ;
(b) le traitement des annulaires entre les trains de cuvelage ;
(c) la découpe et le retrait des parties supérieures des trains de cuvelage."

The following are the purposes of the contract as stated in article 2: legal nature subject of the contract:

(a) the conditions under which the Contracting Party shall carry out, on behalf of the State and entirely at its own risk, Exploration Operations within the Contractual Exploration Area and, in the event of the discovery of a Commercial Deposit, Development and Exploitation Operations within any Contractual Exploitation Area on the one hand;
(b) the conditions for the sharing between the State and the Contracting Party of the production resulting from any Commercial Deposit within the Contractual Area on the other hand, and
(c) finally, the conditions relating to the issuance of one or more Authorisations for Domestic Transport and the conclusion between the Carriage Contractor and the State of one or more Transport Agreements in the event of the discovery of a Commercial Deposit, without prejudice to the Applicable Law relating to the transportation of Hydrocarbons via pipelines.

I can't find any existing translation of the term "trains de cuvelage", and it only appears once in Google search when I search for it as a complete phrase.