Field survey expertise ensures success for first wells offshore Senegal in more than 20 years.

Overview

Cairn Energy (Cairn) is one of Europe's leading independent oil and gas exploration and development companies.

Cairn has been active in Senegal since 2013; the SNE deep-water field was discovered in 2014 with the drilling of the SNE-1 exploration well. The SNE deep-water field is located in the Rufisque, Sangomar and Sangomar Deep Licence Blocks, located within the Senegalese portion of the Mauritania-Senegal-Guinea Bissau Basin. The SNE-1 well, along with the nearby FAN-1 exploration well, were recognised as the largest global oil discovery in 2014 opening a new hydrocarbon basin on the Atlantic Margin. The SNE-1 field was further evaluated with drilling campaigns undertaken between 2015 and 2017 comprising a further nine exploration & appraisal wells. These series of drilling campaigns were the first to be drilled offshore Senegal in more than 20 years and the first in the deep-water licence areas.

Cairn and its Joint Venture partners’ extensive evaluation plan to drill the appraisal and exploration wells in the SNE field had been approved by the Government of Senegal. Following results from the drilling campaigns Cairn began the process to develop the field to extract the hydrocarbons. A phased development of the SNE field using a standalone Floating Production, Storage & Offloading Facility (FPSO) with subsea wells and expansion capability is planned. As part of the field development Cairn required a seabed, shallow soils and site investigation survey to be conducted across the site to optimise the field design concept and assist in front-end engineering design (FEED).

How we helped

We assisted Cairn early in the field development concept, undertaking several desk studies, comprising metocean, regional geohazard and a study of the continental shelf area to assess possible routing options for an export pipeline from the field to the Senegalese mainland.  Our desk studies included data sources that comprised 3D exploration seismic, site survey reports and publicly available information. Following completion of the desk studies, and based primarily on the regional geohazard study, a Seabed and Shallow Soils Ground Model were developed by to assist and provide key survey requirements for the field design.

Based on the expertise and experience in offshore site surveys and information drawn from the ground model, we compiled the necessary survey scope of work documents. An ITT was subsequently issued to potential survey contractors. We were instrumental in providing Cairn the assistance in evaluating the technical capability of survey contractors and their tender responses prior to selection for the survey campaign in 2017.
The survey was conducted in two phases undertaken from separate vessels; a geophysical and environmental survey was conducted from the Fugro Searcher and the geotechnical sampling site investigation survey from the Fugro Scout. We provided project management support through both phases of the survey campaigns. The results from the survey provided Cairn and its JV partners with the relevant information to then progress with the next stage in field development.

We have continued to provide post-survey support to Cairn until September 2018, in the quality control (QC) of survey contractor’s reports and technical oversight of the geotechnical laboratory testing requirements.

The transfer of operatorship to Woodside Energy and the FEED award for the FPSO facility and subsea infrastructure is planned in the fourth quarter of 2018 with the FID in 2019 and first oil targeted 2021-2023.

The impact

The pre-survey support desk studies and ground model were completed in a timely manner and the results informed and optimised the field survey scopes of work for Cairn. Our project management support and technical expertise were considered integral to the success of the project. The results from the field survey undertaken in 2017 have been used by Cairn and its JV partners to optimise their field layout design and have also been used in the formal tendering of contractors for the FPSO and subsea infrastructure. The results from the survey continue for the detailed concept definition work leading to the front-end engineering design (FEED).

- Risk and costs were reduced due to a better understanding of the site for field development.
- The desk studies and the construction of the ground model at an early stage in development helped provide an enhanced overview of the site conditions, informing a detailed concept field design and optimised the field survey scope requirements.