18 Months of Metocean Measurements in the Pearl River Basin Block 29/04 in the South China Sea
Authors: Sharma J.N. , Mu Shaoji , Soeraas P-E. 
Published: October 2008

To support ongoing drilling operations and possible future production operation, Amoco collected wind, wave, and current profile data continuously for 18 months (from August 1987 to February 1989) in the Pearl River Basin Block 29/04 in the South China Sea. This paper briefly describes the measurement program and presents samples of oceanographic features being investigated.

The measuring instruments consisted of (i) currents using two acoustic Doppler current profilers (ADCP), four Aandera current meters (RCM-4S), and an ultrasonic current meter (UCM-30), (ii) waves using the Marex and directional Wavec buoys, (iii) wind using two instruments on the Marex buoy and at four different elevations on a drilling rig, and (iv) other metocean parameters such as water and air temperatures, salinity, air pressure, tidal elevation, and oxygen content.

The initial overall goal was to obtain marine environmental data, including wind, wave, and current, for at least 80% of the time. The actual data recovery was substantially higher (about 95%) because of careful planning, redundancy in measuring equipment, and strict Quality Assurance/Quality Control (QA/QC).

The results of the measurement program are presented in 19 data reports, each covering about one month of operation. These reports contain acceptable data for preliminary (Quality No. 2 as defined on p. 21 of API-RP2A 1989 edition) design and operational planning purposes. Metocean data in several typhoons were used in evaluating wind, wave, and current hindcast models for this area.

Samples of wind, waves, and current data are presented. Of particular interest are the current velocity profiles resulting from large scale oceanic circulation of a local eddy feature, monsoons, and typhoons.

Introduction

The Pearl River Basin area is a prolific fishing ground and busy shipping lane. However, little systematic scientific study of the area has been carried out. In 1959-61, a hydrographic survey of the area was conducted and the results were published as a report by Wyrtki (Reference 1). In 1979-1982, Academia Sinica conducted several oceanographic surveys in the area. Western visiting scientists went on many of these cruises. A summary of the collected data has been published as a report in Chinese (Reference 2). Results of these surveys are useful in understanding the oceanography of the area. However, the surveys did not include collection of wind, wave, and current data for calculating operational and extreme design conditions.

Therefore, to gather badly needed metocean data Amoco initiated a unique and comprehensive metocean measurement program in its Pearl River Basin Block 29/04 (Figure 1). To maximize recovery of high quality data, the measurement program incorporated many special features, such as quality assurance and quality control, redundancy in measuring instruments, and clear division of responsibility in the project organization. Early experiences were presented in a paper presented at the 1988 SPE Conference in Tianjin, Chma when measuring instruments were still in place (Reference 3). This paper provides an overview of the completed measurement program. Samples of data showing oceanographic features of interest are presented and discussed.

Measurement Program

The measurement program has been distinctive in several ways.