Abstract

Some of the most important aspects to consider during the design, construction and productive life of a well are the amount and nature of the risks associated with the conveyance of downhole instruments to acquire critical formation evaluation (FE) data while the hole is open and downhole tool strings needed to service the well after installing the completion and production hardware.

With the increase in popularity of long, deep and tortuous wells, mainly in the high-cost operating environments, these risks have become more acute.

A new methodology, based on forces modeling and best practices gathered over decades, has been developed to take full advantage of new conveyance technologies intended to alleviate or eliminate these risks.

This paper describes the new conveyance risk-reduction technologies and their areas of applications, the newly developed risk management methodology and the economical value these innovations bring to our industry.

To demonstrate the merits and practical aspects of such an enterprise, we discuss here the following case study:

  • A perforating job successfully completed using wireline and downhole tractors in a highly deviated well that was planned using the new methodology subject of this paper.

Introduction

As it became more difficult to discover large oil and gas fields in relatively shallow and friendly environments, the industry stepped out into more complex and less familiar territories requiring the creation of new technologies and methods designed to drill, complete and produce longer, deeper and more deviated and tortuous wells.

Advances in directional drilling technology increased the ability to exploit small-to-medium-sized reservoirs from a single drilling location. This resulted in large improvements of the productivity and the profitability of offshore projects that were previously considered marginal. During the initial well construction phases, any well operations delays encountered defer production in the well under construction and in the production from all subsequent wells that will be drilled from the same location. These changes to the reservoir exploitation strategy demand the use of top-of-the-range drilling technologies which provide improved drilling performance in this demanding environment.

As the complexity of the wells increased, the aggregated cost of all well interventions increased. In particular, the rig cost resulting from the amount of time required for these operations became a point of serious concern when planning the well intervention operations.

The use of traditional conveyance methods in this type of complex wells typically required longer deployment times than in more conventional wells. Consequently, the projects overall costs were much higher due to the increased rig time costs needed to avoid the perceived risks associated with deploying equipment in these wells using less conventional technologies.

To illustrate such a situation, consider what was commonly done to execute an openhole formation evaluation program in a low-angle, 20,000 ft well that included a 5,000 ft openhole section with an average deviation of 65 degrees:

  • The use of unassisted wireline logging methods was ruled out early in the process due to perceived risks associated with the borehole geometry anomalies which could prevent the logging tools from reaching total depth resulting in the failure to acquire logging data in the critical intervals. Additionally the high amount of rig time required by several wireline runs, and the chance of the logging toolstrings becoming stuck resulting in costly fishing jobs were major concerns that followed.

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