Abstract

Coiled tubing is used extensively in Colombia as the preferred alternative to conventional workover operations for reasons of costs, logistics, and security. However, wellbore conditions make few jobs "routine" and extensive pre-job planning is required for each well intervention. Even with precautions, unforeseen situations occur that are unique to Colombia.

This paper presents an overview of the types of wells in Colombia. Depths, wellbore schematics, formation interval lengths, fluids produced, etc. are given as background information. Wellbore conditions that affect the use of coiled tubing are detailed to show the difference between Colombia and other areas utilizing coiled tubing.

A complete description of the types of jobs run in Colombia with coiled tubing is presented along with problems encountered while doing these jobs. The types of computer modeling used to design and implement each job are also given. Two actual case histories are used as typical examples of problems encountered on a daily basis during well interventions as well as the solutions to remedy these problems.

A set of guidelines gained primarily through experience in running coiled tubing in Colombia are presented and may help others encountering similar wellbore conditions in other areas of the world. The concluding section of the paper lists the areas requiring more technological advances for running coiled tubing in Colombia.

Introduction

The Cusiana and Cupiagua fields of Colombia are highly prolific oil producing fields. Most of the gas is re-injected with the oil processed through two plants and then exported by pipeline to the coast of Colombia. The area is highly faulted and tectonically active which presents many drilling problems. These same problems continue into the completion and workover phases of operation, which complicate the use of coiled tubing.

The three primary producing zones are the Guadalupe, Barco, and Mirador; as a result of faulting, these zones may repeat in the same wellbore. The zones themselves range from 15,000 to 17,000ft in depth and are highly permeable. The bottom-hole-temperatures vary from 270 to 290 degrees F.(Table 1)

The rock is extremely hard and penetration by even the most advanced perforating charges results in short perforation tunnels. In addition, these perforation tunnels are easily damaged by debris being pumped into them, which makes coil intervention rather than bullhead techniques essential. (Table 2)

Typical completions for Cusiana and Cupiagua are either packer style or mono-bore. The tubing and liners are 13% chrome varying in size from 4 ½ to 7 in. Tubing and liners for water injectors and gas injectors are primarily 7 and 7 5/8 in. carbon steel. Refer to Figures 1, 2, and 3 for typical wellbore diagrams for oil producers, gas injectors, and water injectors.

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