Utilizing a Micro-Vacuuming Jet Pump and Concentric Coiled Tubing to Clean Mud Damage and Fill from Wellbores with Small Completion Size and Low Bottom Hole Pressure

Abstract

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractIn instances of ultra-low bottom hole pressure (BHP) where the results of conventional cleanout methodologies range from inefficient to ineffective, wellbore vacuuming technology has proven to be a reliable alternative. Technology using concentric coil-in-coil tubing (CCT) design was developed in 1995 and is being used as an effective method to remove both unwanted liquids and solids from wells where formation pressure is prohibitively low for conventional cleanout techniques.The process involves pumping a work fluid down the internal string through a venturi nozzle assembly. A localized pressure drawdown is created at the bottom hole assembly (BHA), drawing wellbore liquids and solids into the return flow with the work fluid. The combined flow is returned up the outer coiled tubing string to surface. This process does not expose the wellbore to the hydrostatic pressure of the workover fluids.More than 600 wells have been treated to date with the wellbore vacuuming technology. Recently, the wellbore vacuuming technology has been revisited and extended to smaller internal diameter (ID) completions; this required a BHA and process redesign. Outlined in this paper are details of the research, development and testing of the 1.75" (44.5 mm) micro-vacuuming tool with recommended procedures, design criteria and operational practices for liquid and solids removal. Case histories from shallow gas wells <2,200 ft (670 m) and deep gas wells >10,000 ft (3050 m) with formation pressure gradients as low as 0.03 psi/ft (0.68 kPa/m) are presented. As well, engineering challenges, best practices and lessons learned from the microvacuuming process are summarized.