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Why a holistic approach is integral to geo-hazard risk and assessment

17 December 2014

A sharp increase in the global energy industry’s demand for specialist, integrated geo-hazard and risk assessment services is a strong sign that the market is starting to recognise the importance of a more holistic approach. Phil Edwards, Head of Survey and Geo-Engineering at LR Senergy, provides an overview of this rising trend, including why operators and contractors need to understand indemnity regimes and audit trails.

Drape sonar
Drape sonar

Safety and risk management lie at the core of successful survey and geo-engineering services – and this can be applied both onshore as well as offshore – but the importance of this can regularly be overlooked.

Often, it is the case of there being a disconnect between the survey work and the subsequent construction or drilling operation. More concerning is that there can be similar disconnects between time-separated, multi-phase site investigation operations.

These are serious issues which can subsequently lead to poor quality assurance and high risks from the outset of a project as well as throughout its lifecycle.

But the assurance of all-encompassing survey and geo-engineering services significantly overcomes such issues and is fundamental to de-risking a project in both the oil & gas and alternative energy sectors. 

Essentially, integrated survey and geo-engineering services could be described as HSE cases whereby the design, management, assessment and interpretation of survey data identifies risks and potential issues, and ultimately prevents incidents arising. As a result of taking into account all eventualities, it goes beyond that extra mile to protect personnel, the environment and other resources such as equipment.

Covering indemnity regimes with auditable trail

Having an auditable trail is crucial yet operators or developers are sometimes unaware of the indemnity regimes in place between them and the contractor, and what they actually mean. It is important that this is recognised and that any indemnity provision based on site investigation data is reviewed in detail prior to providing such provisions to the contractor.

By using this data, risks can be assessed and and hazards identified for a given operation and this allows the operator to take mitigating measures. As part of this process, data needs to be critically appraised and feedback provided on its applicability to provide a hazard and risk review. This review phase is essential to ensure the interpretation and any assessment conducted is aligned to best industry practice and takes into account the geology, the proposed operations, and particular location requirements.

As the industry enters a challenging new era that involves encapsulating the full energy mix spectrum for the future security of supplies, the demand for integrated, risk-based solutions which are designed to reduce uncertainties and advance mitigation strategies will no doubt continue to rise.   

Seismic chair
Seismic chair

Onshore case study

A recent onshore project undertaken by the company shows that this experience, capability and heritage is transportable from an offshore environment to onshore.

Together with the LR Senergy’s geo-mechanics team, a proposed onshore well programme was assessed for shallow drilling hazards and also possible overpressure issues.

In order to de-risk both the drilling and casing planning, a review of pore pressure and fracture gradient from available data was undertaken. All offset wells were reviewed to select study wells based on those with best data sets. The available drilling records from all the offset wells were then assessed to identify any pore pressure and fracture-related incidents from losses or gains, cavings and leak-off tests to remote field testing and managing drilling risk of stuck pipe related to depth and formation. This was collated in a drilling incidents’ database to assist with calibration.

Following this, a pore pressure and fracture gradient model was established, calibrated to log and drilling data. The study wells formation tops and properties were extrapolated to three prognosed drilling locations. Estimations of pore pressure and fracture gradient were then extracted for the proposed wells. Log-based modelling was supplemented by extraction of interval velocity data from available seismic at the prognosed well locations. A Monte Carlo uncertainty approach was used to provide a high, mid and low case outcome for well planning purposes.

The study found that no reports of significant pore pressure related incidents in the three primary offset wells. However, interval velocity data was particularly important in the first planned well where the planned well is due to drill deeper formations in the Paleozoic than those previously encountered in the offset wells.

Thus, although log data from the closest offset formed the basis of the prognosis at this location, it was supplemented by interval velocity data. This increased the uncertainty associated with the prognosis. The possible impact of gas buoyancy from anticipated reservoir thickness was also incorporated in the risk assessment. Although the de-risking was sufficient to allow informed well planning, real-time and relevant-time monitoring was advised to reduce the uncertainty by allowing update on pore pressure as the wells are drilled.

Using available 2D and 3D seismic data, and offset well data, we also mapped and assessed the overburden zone and its key halite component. Numerous small channel sand bodies were imaged and examined with anomalies assessed for shallow gas geo-hazard risk. Studies included the review of ring and polygonal faulting while other possible drilling geo-hazards were identified and reviewed.

The final result was, in effect, a risk assessment of the entire well path.

3D slice channels
3D slice channels

Offshore case study

Recently, the company was awarded a major contract to support GDF SUEZ E&P UK in the forthcoming offshore construction phases of its major Cygnus gas project in the North Sea. The work spans construction survey, positioning and trenching assurance.

Since 2007, we have already provided survey project management and geosciences engineering consultancy services on the project, which is located in the southern North Sea (Blocks 44/11 and 44/12 – license number P1055), including management of 15 rig and platform site and pipeline route surveys and geotechnical investigations.

The latest contract involves being retained to support the global operator in vital onshore survey quality assurance and quality control and positioning management services.

This includes providing offshore survey representatives for the load out and installation of the Alpha and Bravo platforms, subsea structures, lay, trench, backfill and rock-dumping of the export pipeline, infield pipeline and control umbilicals, spool metrology and tie-ins. In addition, we will provide the developer with oversight of the trenching and backfill systems and operations for the pipeline assets.

The work will also see us deploy our proprietary web-based GIS (Geographic Information Systems) and project information system, IRIS. The application enables project teams to track real-time vessel locations and access key project status information and as-built survey and video data – all through an internet browser. Through deploying IRIS, we will be able to demonstrate the full power of the system which provides close visibility to the real time progress and status to GDF SUEZ throughout the project.

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About the author:

Phil Edwards is Head of Survey and Geo-Engineering and Global Business lead at international energy services company LR Senergy. He studied Marine Physics between 1985 and 1988, then spent a number of years with GSI before joining Gardline in 1992 as an offshore geophysicist and then becoming part of the marketing team. He joined LR Senergy Survey and Geo-Engineering (S&G) as Commercial Director before taking on the leadership role in 2010.


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