Pulse Communication Technology Enables Remote Actuation and Manipulation of Downhole Completion Equipment in Extended Reach and Deepwater Applications
Authors: Hopmann Mark , Smith Mike 
Published: December 2007

Pulse frequency communication techniques have been employed to remotely actuate electronically enhanced downhole completion tools. In extended-reach and deepwater applications, remote actuation systems based on pulse technology reduce rig time and costs required to actuate downhole completion tools, and eliminate the risks associated with conventionally actuated completions which require invasive well intervention.

Introduction

The need to minimize well completion time without compromising reliability, safety or ultimate profitability is growing, particularly with the expansion of extended-reach and deepwater drilling techniques. In these situations, where rig costs often exceed $100,000 per day, the ability to reduce or eliminate operations and reduce rig time can significantly impact operating expense and overall completion costs.

Conventional completion techniques can be time-intensive; require tubing manipulation, and many times require multiple well interventions- all of which make them less than desirable for extended-reach and deepwater applications.

A recently developed, one-way communication system that relies on pressure wave pulses has been adapted to remotely actuate downhole completion tools.

Wave Pulses

Definition. A wave pulse is an acoustic wave, which is defined as a wave that is transmitted through a solid, liquid, or gaseous material as a result of a mechanical vibration of the particles forming the material. The normal mode of propagation is longitudinal; i.e., the direction of motion of the particles is parallel to the direction of propagation of the wave, and the wave therefore consists of compressions and rarefactions of the material.

Wave Pulse Characteristics. To effectively communicate using pressure wave pulses, the pulse's velocity, amplitude, displacement, reflections, interval frequency, peak rise time and attenuation need to be defined.

Velocity of a compression wave is defined by the speed at which the wave pulse travels through a compressible medium. The velocity of a compression wave in water is equal to the speed of sound in water, which is 4921 ft per second.

Amplitude is the maximum height of the wave crest. (Figure 1) For a pressure wave pulse, the amplitude is the maximum pressure recorded. This is usually in reference to the pulse delivered or the first reflection.

Displacement is the volume of fluid required to generate a wave pulse of a given amplitude.

Reflection is the part of a wave pulse that gets reflected back to surface when the pulse passes a discontinuity in the tubular conductor (Figure 2). The depth of the discontinuity causing the reflection can be calculated since velocity is constant:

(1)

The interval frequency of a wave pulse sequence is defined as the time between wave pulses (Figure 3). It is measured in seconds as the wave crest passes a fixed point.

Peak rise time is the time that the initial pressure pulse takes to reach the maximum amplitude (Figure 1). This time is usually in tenths of seconds.

Attenuation is the deterioration of the wave pulse over time. The effects of attenuation are seen in the reflections created by the original pulse. Each reflection will suffer ever increasing displacement and ever-decreasing amplitude (Figure 4).

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