Recent Developments in Pumpdown Tools and Techniques
Authors: Loth W.D. 
Published: October 2008

As described in previous papers, pumpdown tool techniques have been proven for completion and servicing of subsea wells. Previous pumpdown tool use has been limited to 2-inch tubing in conventionally completed wells with short completion intervals. This paper describes the development and testing of larger diameter and new tools, all of which extend pumpdown tool capability.

Tools tested include 3-inch locomotives, jars, running and pulling tools, and paraffin cutters, as well as a number of tools not available in the smaller diameter. New tools include gas-lift valves which can be run and retrieved in multiples, a pumpdown choke assembly, an oriented perforating system for completion of long producing intervals, and a formation patch tool. The capability was established to pump long lengths of extension tubing, in conjunction with the orienter or patch tool, without destroying the mechanical integrity or alignment of the extension tubing.

All of the above tools have been tested extensively in a land well with satisfactory results. This testing program has proven the capability to complete and service high production volume subsea wells which incorporate large-diameter tubing, long perforated intervals and multizone production.

INTRODUCTION

To date, offshore production operations have usually been conducted from the decks of fixed platforms with wellheads being located above water, at platform cellar deck level. Under these circumstances, well completion, workover, and servicing may be conducted conventionally utilizing wireline, tubing, or drill pipe introduced vertically into the well. As production moves into deeper water, economics and technical constraints may require that wellheads be located subsea. With subsea wells, vertical access becomes more difficult and costly as high cost and weather sensitive floating vessels are required and as risers, subsea blowout preventers, and other extensive auxiliary equipment becomes necessary.

For efficient completion, workover, and servicing of subsea wells, new methods have been developed for utilizing tools and equipment pumped from the surface through the flowlines. Figure 1 schematically illustrates a pumpdown tool operation. Multiple flowlines provide a fluid circulation system for pumping tools into and out of the well. Positive downhole depth location (and directional orientation if needed) is accomplished by preinsta11ed nipples designed to accept only selected components.

Basic pumpdown tool (PDT) technology has previously been developed.1–5 Extensive testing has been conducted on 2-inch diameter tools and techniques, including:Subsurface flow control devicesStanding valvesSafety valvesSand-consolidation proceduresSand-washing procedures and equipmentSliding-sleeve shifting devicesGas-lift methodsCasing perforatorsFishing tools and procedures

Several operations, such as sleeve shifting, oriented perforating, and multiple-point gas lift had not been proven entirely successful. It also appeared that additional capabilities were required if pumpdown techniques were to be seriously considered as the prime method for wellbore operations and that capability for operation in larger-diameter tubing would be necessary for high-volume subsea wells. Accordingly, a new development and testing program was initiated.