Enhanced Solids-Removal Techniques From Ultralow-Pressure Wells Using Concentric Coiled-Tubing Vacuum Technology

摘要

The removal of solids from the Tyonek field gas wells has proven to be a major challenge for the operator. The field has an exceptionally low bottom hole pressure gradient of ~0.1 psi/ft. This means that traditional two phase sand removal operations using coiled tubing had not been successful. Even following the development of engineered cleanouts, the bottom hole pressure was just too low to support economic returns. The option of reverse circulating would also not be feasible due to the massive quantities of nitrogen required to succeed. Following reviews, the most efficient method of cleanout was identified as using a Concentric Coiled Tubing Vacuum Technology (CCTVT) system. The CCTVT essentially provides a second annular return route for wellbore solids while simultaneously boosting the return pressure. This permits the cleanout to be performed with fluid only, a significant logistical and financial saving over two phase operations. This paper will describe the system technology, engineering planning, well control considerations, system limitations and the observed operational and production results of a five well campaign from the first CCTVT operations conducted in Alaska as well as the first application on an offshore platform.