Abstract

A novel deployment system for open hole logging tools has been developed that reduces the risk and cost of accessing high angle wells and wells with bad hole conditions. The tools are conveyed inside drill pipe where they are protected while running-in. Wireline tools are used for data quality reasons, but are modified to operate without a wireline to give speed, logistical and safety benefits relative to wireline pipe conveyed logging. Savings are also made relative to logging-while-drilling where real time formation evaluation data is not a critical requirement.

The new system has been used in the Western Canadian Sedimentary Basin where the majority of horizontal wells have not been logged previously for reasons of accessibility, cost, and/or perceived lack of value, all of which are now addressed. In particular, the value perception has been challenged by applying formation evaluation data to issues of reservoir quality and boundary definition, confirmation of zone structure, and identification of fluid interfaces for the planning of completions and stimulations.

Introduction

High angle, horizontal and extended reach wells are challenging environments for the acquisition and interpretation of formation evaluation data.(1,2) The established acquisition methods are pipe conveyed logging (PCL) using conventional wireline tools, and logging while drilling (LWD) using instrumentation behind the bit. In a minority of cases, wireline tools are conveyed on coiled tubing (CT). Each method has technical and commercial weaknesses so that many horizontal wells (particularly in land locations) yield no more than a measurement-while-drilling (MWD) gamma ray. In the Western Canada Sedimentary Basin, for example, we estimate that as few as 10% of horizontal wells return porosity-resistivity-acoustic data due to perceived high cost and/or because of bit size and bend radius restrictions. The challenge of interpreting log data from horizontal wells is also pertinent.

The introduction of Compact open hole logging tools in 1998 was the catalyst for the development of wireless deployment techniques that address the issues of cost, operational complexity, and data quality and consistency.

In the simplest of the wireless conveyance techniques - Memory Pipe Conveyed Logging (Memory PCL) - the measurement string is run in the well on the end of drill pipe. In some cases the method is used as a faster, more reliable alternative to conventional wireline PCL, while in others it is the only technical logging solution.(3)

Over 80 Memory PCL jobs have been run in horizontal wells.(4) We analyzed the value contributed by the data before justifying a further development to address the issue of tool safety in uncased build sections, where tools are most vulnerable. Although memory and wireline PCL techniques both use dampers to help prevent excessive loading of the measurement string, conveyance in open build sections remained potentially hazardous. Putting the tools inside the drill pipe was the solution, and Well Shuttle was the result.

DESCRIPTION OF THE LOGGING TOOLS

The logging tools used in the Well Shuttle are new generation Compact format tools characterised by small size, low weight and low power consumption. They have significant advantages over conventionally-sized tools:

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