Technology Focus: Wellbore Tubulars (July 2020)

Abstract

Why steel casing or tubing? What does that choice have to do with sustainability? Is it time to change? These are a few of the questions we need to think about to move from the status quo, and we need to use technology, engineering, and innovation to reduce not only the surface footprint but also the downhole footprint. Composites are making inroads and continue to replace steel in other industries such as aerospace, automotive, and the renewable-energy segment. The follow-up question is, “Is it sustainable and relevant to our industry under harsher and deeper environments?” Different types of components exist, including reinforcement and the matrix, that can be adjusted and modified to be used for downhole conditions without compromising well integrity. There are compelling answers to those questions. Composites have high strength-to-weight ratios that result in low weight and high energy absorption. They have high stiffness and high durability, including corrosion resistance, less fracture toughness, and dimensional stability. Added distinctive advantages of composites are that they are excellent electric and thermal insulators. On the other hand, there are challenges very specific and unique to our industry such as anisotropic properties, modulus matrices, ability to with-stand thermomechanical loading, unknown stress/strain under tension/compression, unknown failure envelopes under internal pressure, bending loads, external pressures, tensile loads, and torsional load conditions. Addition-al challenges include material-properties degradation under wear conditions and composite-to-metal joining if necessary. For this, a phased approach may be necessary. Development of new products will require conservative design consisting of modeling with improved physics and improved models with experimental results involving compression state, buckling, and collapse for various slenderness ratios. Nonetheless, we are making inroads with composites. Looking to the future and considering sustainability, switching to composite casings in the coming years is necessary. I have selected papers that are structured toward using composites and, to some extent, answering the questions I have raised.