Developments in Acoustic Doppler Current Profiling and its Technical Application in Deepwater Drilling
Authors: van Smirren J.R. , Romeo John , Vogel Michael 
Published: October 2008

The continued expansion of E & P activities in deepwater has resulted in a growing demand for reliable ocean current measurements and criteria throughout the entire water column. To satisfy this demand there has been an increasing requirement for refinement of instrumentation, deployment systems and real time display and forecast software.

This paper describes the approach of oil companies, a service company and an instrument manufacturer to these requirements and shows how the close collaboration of these organizations has resulted in optimizing the data available to the operational decision makers and engineers. The paper discusses the developments in instrument technology, both hardware and firmware, optimization of data through system deployment approaches and the development of software appropriate for the offshore oil and gas industry.

Examples of floating structure, drilling rig and riser (BOP stack) deployed systems are presented, together with recorded data sets. Considerations in deployment configuration and real time software and their impact on overall data quality are reviewed.

Future requirements of the oil and gas industry in deepwater are considered. In particular achieving full water column profiling capability in depths beyond 1,000m and enhancement of real time current prediction.

Introduction

For the last ten years the exploration and production of oil and gas reserves have increased in the deep waters at the edge of the continental shelf. Deep water exploration is subject to the same environmental demands as shallow water exploration coupled with the complex problems associated with moorings and station keeping rigs in deep water and the increased significance of hydrodynamic forces on subsea components of the drilling operation. Currents at the shelf edge are often strong and variable and can potentially cause many operational challenges in the exploration and production of oil and gas reserves.

Requirements for current information include: vessel/rig selection (station holding), riser design, deployment and performance, and ROV operations. These requirements have led the industry to demand real time current measurements throughout the water column. The measurement of real-time currents requires instrumentation with commercial availability, economy, ease of installation, performance and reliability. RD Instruments has been manufacturing 75 kHz ADCP with ranges up to 600m for more than 10 years and has recently developed a long profiling range 38 kHz Phased Array (PA) ADCP in response to the deep water exploration requirement. This instrument uses a patented (Patent # 5,808,967) 2-D phased array transducer with selectable processing modes.

ADCP Installation And Operating Environment Considerations

Deep water exploration and production of oil and gas reserves have presented many operational challenges to offshore operators and drilling companies. With over 60 new deep water rigs being built, at an investment of more than $12 billion, oil companies are committed to solving the problems before them.