Design and Optimization of Multistage Tubular–Mandrel System for Down-Hole Expandable Tubular

Abstract

The current work presents numerical modeling of cold expansion of down-hole expandable tubular through the multistage solid metallic mandrel. Down-hole tubular has demonstrated to be a promising technology in the oil and gas industry by providing optimum solutions for multiple unsolved issues. One of the challenges still confronting by researchers and field engineers is implementing and making this technology cost-effective while conserving tubular structural integrity. Furthermore, the requirement of a high expansion ratio ( $$\sim $$ 30%) by the field engineers also increases the cost of expansion. This ratio is practically not achievable in the one-pass of the expansion process, though multiple passes through single-stage mandrels are currently using to obtain the required expansion ratio. As a result, the cost of expansion and the probability of errors become higher. In the present work, the expansion of down-hole tubular through multistage mandrel is numerically investigated. Firstly, multistage tubular–mandrel is modeled, based on the concept of a single-stage system, to achieve expansion ratios of 16%, 20%, and 24% in one pass. The models are developed so that 16%, 20%, and 24% of expansion ratios can be achieved in the first, second, and third stages. Secondly, the multistage system’s finite element model is validated and found to be in good agreement with the experimental and simulation results. Thirdly, the multistage mandrel geometry is optimized based on the results of contact pressure, expansion force, and equivalent stress in tubular material. Finally, further simulations are performed to analyze equivalent plastic strain, thickness reduction, and length shortening. It is observed that the expansion force in the case of the multistage mandrel is approximately reduced by 57% as compared to three single-stage expansions. Moreover, maximum equivalent stress and contact pressure are 650 MPa and 620 MPa, respectively. These are within the allowable limits.