Application of remote sensing technologies for engineering for onshore pipelines in active dune fields

Transcription

1 Application of remote sensing technologies for engineering for onshore pipelines in active dune fields Jason Manning, Arup Dr Matthew Free, Arup Dr Charlie Bristow, Birkbeck College, University of London Geological Remote Sensing Group (GRSG) & Oil & Gas Earth Observation Group (OGEO) Advances in Geological Remote Sensing ESA, Frascati, Italy 7-9th December 2011

2 Presentation Outline 1. Desert Geohazards 2. Remote sensing toolset 3. Engineering Geological Issues Sand Dune Mobility 4. Pipeline Engineering & Routing 5. Summary A. What is the issue? Direction of dune movement? How fast do dunes move? B. How has it been investigated? C. What is the solution? Questions / Answers 2

3 Engineering challenges to oil & gas developments in deserts Oil & gas engineering projects require detailed understanding of the ground to reduce risk (esp. true of desert environments, not benign). Geological understanding of the ground utilises a range of techniques and tools. Remote sensing tools from range of resolutions and techniques, integrated with geological knowledge.

4 Dune fields Dune migration Sand / dust & sandstorms Desert Geohazards Aggressive soils Flooding Wadi erosion & scour Groundwater Karst / piping Duricrusts Shallow bedrock Rugged terrain Swelling / shrinking soils Collapsible soils Salt mineralogy (gypsum, anhydrite) Slope instability A wide range of possible geohazards require careful identification, to allow for engineering solutions and mitigation

5 Remote sensing toolset SRTM Google Earth Pro GIS analysis Landsat SPOT / SPOT DEM ASTER / ASTER DEM GIS mapping Landsat742 Multispectral / Hyperspectral analysis Classification Radar Archive data Corona 1965 High Res optical (Worldview, Quickbird, Geoeye) High Res DEM (LIDAR / Satellite) Survey Air Photography Geophysics Remote sensing technologies and tools are essential for all stages of oil & gas development projects (Concept; Pre-FEED; FEED; detailed design and; operation/monitoring)

6 Relevant in-house staff set: Engineering geologists Geomorphologists Hydrologists / hydrogeologists Geotechnical engineers Pipeline engineers GIS analysts Seismic specialists Risk consultants Skills & Services Site supervision & trials Geological mapping Engineering solutions and foundation design GIS & terrain analysis Ground investigation Remote Sensing, GIS, survey specifications Field testing

7 Engineering Geological Issues in Active Dune Fields* Dune migration Encroachment on facilities. Encroachment and blockage of RoW Pipe over-burial. Scour of RoWand loss of support and free-spanning of pipe. Trench instability Running sand when dry. Instability when wet. Poor trafficability / RoW instability Not suitable for wearing surface. RoW cut and fill instability. Irregular topography Significant earthworks volumes Poor foundation performance Collapse potential on inundation Aggressive chemistry Wind blown sand Abrasion Health & Safety *Dune field hazards listed only interdune areas, sabkha and rocky deserts have additional hazards 7

8 Location of Major Desert Sand Seas and Dune Fields (7.5 to 16.5 % of World Surface) Algeria World distribution of deserts Deserts in Algeria Pipelines in Algeria Parsons & Abrahams (2009) 8

9 Recent Arup pipeline projects in Algeria Hassi Ba Hamou ( ) Isarene (2011) In Salah ( ) 9

10 Algerian Sand Seas 5 20 m Primary dune ridges with superimposed secondary dune networks m

11 Reconnaissance Ground Investigation Ground Penetrating Radar Provides images of the structure of sand dunes. Relative chronology of sand dune deposits. The thickness of sand in dune and interdune areas. Select sample locations for age dating. Compound dune structure superposition of multiple layers of smaller dunes. No core of older coarse sand. Survey line at 100 MHz 20m 3x vertical exaggeration 11

12 Ground Penetrating Radar Profile of Compound Dune Slide removed 12

13 Reconnaissance Ground Investigation Observation trenches Penetration testing Sampling Laboratory testing Age Dating of Sand Optically Stimulated Luminescence OSL Optical dating determines how long since sand was exposed to light, i.e. the time of deposition and burial of dune sands. 13

14 A Dune Migration Rates Using GPR and OSL dating B C D A GPR profile C Relative chronology B Radar stratigraphy D Rates of migration (0.12myr -1 ) (Warsaw Dune, Namibia -Bristow, Lancaster and Duller 2005) 14

15 Lake deposits (Early to Mid Holocene?) Old dune deposits Current active dune deposits Calcrete capped old dune sands Calcrete on sandstone Older dune sands covered by calcrete Lake deposits on older sands 15

16 Geological Model Conceptual geological models developed based on geomorphological assessment from desk study & remote sensing data. Important tool to inform project team on key issues to guide mitigation measures. Geological model updated following ground-truthing and further investigations. 16

17 Dune Migration Rate Using Automated Change Detection Methods COSI-Corr 60 x 60 km ASTER scene Change Detail following slide Co-registration of Optically Sensed Imagery and Correlation (COSI-Corr) ASTER

18 Rate of Dune Migration Using Automated Change Detection Methods COSI-Corr 1. Direction of dune movement = NE to SW 2. Rate of dune migration = Average celerity 10-20m / yr Town 5km Change vectors between 2000 and 2008 ASTER 18

19 Rate of Dune Migration Using Automated Change Detection Methods COSI-Corr Detail following slide Pieter Vermeesch (Birkbeck) ASTER 19

20 Dune Migration Rate Using High Resolution Satellite Imagery A 2002 N 2009 B 2003 B 200m Detail from aerial survey ortho-imagery 2007 Migration of dunes A Migration rates for individual dunes: B Dune A ~22 m/year (110m in 5yrs) Dune B ~8.4 m/year (42m in 5yrs) 20

21 Engineering Solutions for Pipeline Construction in Active Dune Fields Dune migration Avoid by pipeline routing. Removal or re-profiling of sand dunes. Sand fences. Vegetation stabilisation. Surface stabilisation. Trench instability Batter trench slopes or provide support. Minimise open trench length. Scour resistant berm. Poor trafficability / RoW instability Provide wearing surface. Stabilise RoW cut and fill (as above). Irregular topography Avoid / optimise by pipeline routing (as above). Poor foundation performance Engineer site formation works. Minimise water ingress. Protect against aggressive ground. Wind blown sand Protect facilities against abrasion. Health & safety management strategy. 21

22 Pipeline routing - ASTER DEM shaded elevation Dune hazard mitigated by routing in interdune corridor 22

23 Pipeline Routing - Landsat base + ASTER DEM contours Dune hazard mitigated by routing in interdune corridor 23

24 Summary Engineering projects in desert areas require careful consideration of geohazards. A revised geological model is proposed for active dune fields in central Algeria. Engineering geological issues identified and investigated. Dune migration rates have been determined Primary dunes: 0.05 to 0.15 m/year Secondary dunes: varies with dune type 0.6 to 22 m/year Range of pipeline engineering solutions proposed. Remote sensing technologies essential to oil & gas development projects. Careful choice of applicable techniques required. Project team should include wide range of experts, including geologists, geomorphologists, geotechnical engineers and pipeline engineers. 24

25 Acknowledgements: In Salah Gas Petroceltic International Ltd Birkbeck College, University of London Charlie Bristow & Pieter Vermeesch Acknowledgements Jason Manning, Arup Dr Matthew Free, Arup Dr Charlie Bristow, Birkbeck College, University of London Geological Remote Sensing Group (GRSG) & Oil & Gas Earth Observation Group (OGEO) Advances in Geological Remote Sensing ESA, Frascati, Italy 7-9th December 2011