BGP integrated OBN solutions for ADNOC, from shallow water to TZ

Summary

The ADNOC 3D survey. Currently being acquired by BGP Offshore is a large-scale seismic acquisition project offshore Abu Dhabi in water depths from zero to 30m. Differing seabed conditions and bathymetries introduce enormous challenges for seismic survey design, large volume data handling, operational organization and HSEQ, not least because of the Covid-19 pandemic. This paper focuses on how BGPO has developed an integrated solution to address the challenges such a large project presents in terms of equipment, key acquisition techniques, and including HSE measurement and control.

Introduction

Since the first shot in January 2019, BGP OFFSHORE has been acquiring OBN seismic data for ADNOC offshore Abu Dhabi covering an OBN area of 30,000km2and a TZ area of approximately  10,000km2. Considering the diverse nature of the geological targets in the survey area, the complex surface environment with a very large number of producing facilities and the differing seabed conditions, several different survey geometries have been selected for different survey sub-areas. In order to acquire the highest quality seismic data, BGPO has invested extensively in both equipment and technology. In this paper, we explain how our integrated seismic survey scheme has been able to solve the challenges posed by such large-scale operations in this complex oil production environment, including the equipment configuration chosen for each terrain, the OBN seismic methods employed, the organization of the operation and the measures selected to improve seismic data quality and ensure safety.

Integrated Acquisition Solutions

Integrated acquisition equipment solution

On the source side deep-water air-guns, shallow water air-guns and mini air-guns are used in water depths are greater than 6m, 4-6m and less than 4m respectfully. Explosives and land vibrators are deployed onshore close to the sea and on the various islands in the survey area. In the more challenging terrain, such as sabkha, a Transition Zone (TZ) vibrator was chosen as the optimum source solution. On the receiver side, a variety of marine and land nodes are deployed to record seismic data on the different terrains. Additionally different types of node handling vessels and other specialised vessels, such as mini workboats and Hegelong (TZ transport vehicles) are used for the survey.

Key OBN acquisition techniques

In the last five years, the industry has witnessed a dramatic increase in the volume of OBN seismic data volume being acquired  – from ~2TerraBytes/day in conventional acquisition mode, to ~10TerraBytes/day in blended acquisition mode, to ~15 TerraBytes/day in high-density acquisition mode. To handle such enormous data volumes, a series of OBN seismic techniques have been incorporated into this ADNOC offshore and TZ project, including KL-AGQC, KL-NodeQC, KL-FBP, GeoEast and other scalable seismic acquisition software developed by BGP, that allows us to undertake comprehensive source QC across multiple source vessels, continuous seismic data combing, node repositioning, and seismic data processing.

Operation organization

Since 2009, DOLPHIN, a sophisticated navigation system developed independently by BGP for OBC / OBN operation, has provided multi-source vessel operation and navigation, node deployment/positioning and multi-source vessel operation. Utilizing this navigation system and the VTS system we can monitor the production status of the vessel fleet in real-time, and forewarn vessels operating close to production facilities and  OFS vessels in transit in the survey area of any close passes or course adjustments required to ensure safe and secure operations in such high congested oil field production areas.

Measures to improve data quality

In order to reduce the effect of platforms and islands in the working area and improve the uniformity of coverage, BGP has implemented a number of methods to minimize the gaps in near-surface coverage such as increasing the density of shot points near obstacles and shooting offshore parallel to the island coasts in the survey area.

Measures to ensure safe operation

While ensuring the efficient operation of the project, BGP undertook additional safety measures, especially with regard to the prevention of Covid-19 on a large number of vessels (51) and crew (>2500), to ensure personnel safety. In addition to the extensive and rigorously enforced quarantine periods/C-19 testing require before personnel were allowed to join the vessel, weekly onboard H2S drills are carried out.

Application

Since 2019, the project has been operated safely and efficiently, whilst the seismic data quality has been of the highest standard as approved by ADNOC. By investing heavily initially and continuously during the execution of the project in the acquisition equipment, the production efficiency has been steadily improving, reaching a  maximum daily shot production of  74383 SPs/day. In 2022 we will introduce a shallow water electric-powered “hybrid” node and source vessel which will further enhance our SW/TZ capabilities.

Conclusions

Despite the impact of the global COVID-19  pandemic, the ADNOC large-scale shallow water and TZ seismic project has been a significant achievement, delivering the highest quality OBN data on an unprecedented scale. BGPO overcame many operational and logistical challenges to meet the high data quality, high safety standards and high-efficiency operation that ADNOC requires.

Acknowledgements

The authors thank the support from ADNOC during the seismic acquisition champion.