Abstract

Reeled tubing technology has proven to be beneficial in solving both economical and production problems in the Coal Bed Methane (CBM) industry of the Black Warrior Basin near Tuscaloosa, Alabama. The primary benefit from using reeled tubing technology is one of economics. Operators can now prepare CBM wells for production quicker than was previously possible.

CBM completions must be cemented, the wellbore cleaned and zones selectively stimulated. Reeled tubing technology can be used in cleaning cement residue from the casing ID and in cleaning frac sand, frac balls and perforating debris from the wellbore. Isolation bridge plugs can be retrieved and debris washed from the well. Five hundred wells plugs can be retrieved and debris washed from the well. Five hundred wells have been cleaned of unwanted cement residue using high pressure submerged fluid jets and in excess of two thousand wireline-set retrievable bridge plugs have been retrieved using reeled tubing technology in the Black Warrior Basin.

Introduction

With the large volume of CBM wells planned for the Black Warrior Basin, an economical means of preparing wells for production is required. Completion design dictates that all of the wells must be (1) cemented (2) the wellbore cleaned and (3) multiple zones selectively stimulated. Using reeled tubing technology, submerged fluid jets allow an operator to effectively remove cement residue from the casing wall, clean frac sand and/or frac balls remaining from the stimulation process, and retrieve bridge plugs that have been used to isolate the various coal seams.

WELL CLEANOUT
SUBMERGED FLUID JET CLEANOUT OF CEMENT/RESIDUE

Submerged fluid jet cleanout of cement/residue has become an everyday operation in the Black Warrior Basin. The cleaning procedure calls for a pre-frac cleanout of the well and offers the following benefits:

  1. the cleanout effectively removes contaminants such as cement, pipe dope, scale and mill varnish, which might otherwise reduce the well's productivity (i.e. entering the fractures with the frac sand)

  2. productivity (i.e. entering the fractures with the frac sand)

  3. following the pre-frac cleanout, contaminated fluids are easily replaced by clean, filtered completion fluids

  4. the gauge ring. incorporated as part of the downhole cleaning assembly, gauges the hole to ensure proper wellbore ID and

  5. the removal of cement and other harmful residues prepares the way for downhole logging tools and bridge plugs.

The jet cleaning tool assembly is shown in Figure 1.

CALCULATIONS FOR JOB PREPARATION

A computer program is used to calculate the jet size, number of jets, pump rate, vertical pipe travel rate, job time, total fluid and mixed polymer (friction reducer) required to perform the jet cleanout polymer (friction reducer) required to perform the jet cleanout operation.

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