First Three Surface Casing While Drilling Operations in Brazil Demonstrate Technical Feasibility in Loss Circulation Scenarios

Abstract

Historically, casing while drilling (CWD) has not been largely deployed in Brazil land operations due to inconsistent results achieved in the past and also due to the lack of a clearly identified technical need. In some onshore fields located in the Northeast of Brazil, total or partial mud losses in many shallow surface sections, make those sections very expensive to drill. Apart from the large volume of mud required when lost circulation occurs, which heavily impacts the operation logistics, and the cost associated with remedial actions such as cement plugs and lost circulation materials, HS&E risks are typically the major concern. To validate a technically viable casing while drilling solution with a non-retrievable bit, a series of three surface hole sections were drilled through this severe lost circulation zone. This paper will describe the planning, implementation, results and lessons learned from the first three surface non-retrievable CWD onshore operations done in Brazil. These wells were drilled by land rigs equipped with a kelly and the operations were performed with specialized 12 1/4-in non retrievable casing bits and 9 5/8-in surface casing. It is important to mention that to perform these operations did not require any modification to the rigs. The results showed that the casing while drilling technique has considerable applicable in surface sections that are Polycrystalline Diamond Compact (PDC) drillable and where fluids losses make conventional drilling practices difficult or expensive. However, in those applications the casing bit design must be tailored to drill efficiently through the medium to hard tophole carbonates, to ensure reaching the desired casing point.