ABSTRACT

A new electric wireline through-tubing inflatable bridge plug system has been developed which allows either permanent or retrievable bridge plugs to be run through the tubing string and set in large diameter casing below without the use of a workover rig. The system employs a downhole electric pump to filter and pressurize wellbore fluid for bridge plug inflation. After pressurization, the bridge plug can handle high differential pressures without the aid of sand or cement. The system is conveyed and powered by a conventional electric wireline unit.

The paper will discuss development of the system, system components and comparison of design andperformance characteristics with those provided by conventional bridge plug systems.

The paper addresses possible savings in costs and time as well as ease of performing well operations when the system is used to accomplish:

  1. selective stimulation, including acidizing, fracturing or other chemical treatments;

  2. selective water shutoff within a producing zone or the total abandonment of a producing zone, i.e. perform a workover without killing the well.

The authors have been instrumental in the development of this system and with its subsequent successful application in Prudhoe Bay. The authors will discuss field history and provide details and insights on operational procedures, applications and system limitations.

INTRODUCTION

The pursuit of technology to reduce production costs has changed traditional methods of well workover, maintenance, and stimulation. Performing required well service through tubing is now commonplace in several areas around the world. Prior to the advent of through-tubing well operations, any workover or well stimulation meant moving in a workover rig, killing the well and pulling production tubing. The production packer was removed, required work performed and the well recompleted. Before development of the new workover system discussed in this paper, the average operation at Prudhoe Bay, Alaska required about 21 days.

In 1987, inflatable packers and plugs that could be run on coiled tubing through the production tubing were introduced in Prudhoe Bay. By eliminating the workover rig and all ancillary operations required by conventional workovers, through-tubing servicing allowed wells to be returned to production in significantly less time. The inflatable packers and bridge plugs had improved expansion characteristics dictated by the rigors of going through tubing and setting in the casing below without sacrificing pressure holding capability. Today, inflatable packers and plugs run on coiled tubing are routinely utilized in Prudhoe Bay to perform selective stimulation and interval shut-offs.

Complementing this equipment and evolving through tubing technology even further is a new electric wireline through-tubing inflatable bridge plug system. The new system (Fig. 1) allows, without the use of a workover rig, either permanent or temporary bridge plugs to be run through the tubing string and set in large diameter casing below. The system employs a downhole electric pump system to filter and pressurize wellbore fluid for bridge plug inflation. After setting, the bridge plug is capable of withstanding high differential pressures. The system is conveyed and powered by a conventional electric wireline unit (Fig. 2).

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