EVALUATION ON THE APPLICATIONS OF SMALL SIZE COILED TUBING IN WELL SERVICES

Abstract

Today, one of the most important key for hydrocarbon production in the oil & gas industry is economic justification. In the later state of the well’s production, the aging wells may introduce many problems such as scale, sand and liquid load-up. These impede the hydrocarbon production and prevent all the reserve to be fully produced. In order to fight this impedance, the use of conventional coiled tubing (CT) unit is a common practice. The use of conventional CT unit is impossible on the small platform, low crane rating and without barge support. These are commonly found in most of the marginal field development. Hence, many wells reach their abandonment state before producing all reserve. The use of small size CT is a promising practice, although has its own limit. Therefore, the objective of this study is to evaluate the range of applications for well services with small size CT. The evaluation utilizes the computer modeling which is used to determine the hydraulic and mechanic operating conditions. The determination of operating conditions involves critical velocity, system pressure losses, runability, capability to push/pull and combined stresses in various well scenarios. The effects of operating parameters in various oil & gas well scenarios are investigated for 1” and 1.25” CT. The proper choice for the CT size (i.e. fit for purpose CT) is the key for successful operations. The study found the small size CT is more suitable for well services than the industry used to believe. The 1” CT is viable for well servicing in the low inclination well scenarios with the lower requirement on pumping rate. For small wellbore in particular, the use of large size CT can lead to the severe pressure losses in annuli, reduce efficiency of the cleanout or unloading. Although, the 1.25” CT is not the best choice for such conditions, but can be used in all of well services applications and scenarios.