APPENDIX K: ALTAMIRA REPORT ON INSAR ONGOING STUDY OF ... · ALTAMIRA INFORMATION, SLU C/ Còrsega,...

Surat North – Water Monitoring & Management Plan

QGC

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APPENDIX K: ALTAMIRA REPORT ON INSAR ONGOING STUDY OF SURAT BASIN 2012‐1014

ALTAMIRA INFORMATION, SLU C/ Còrsega, 381-387, 5b – E-08037 Barcelona – T. +34 93 183 57 50 – F. +34 93 183 57 59 Toulouse: Parc Technologique du Canal – 8-10, Rue Hermès – F-31520 Ramonville Saint Agne

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Title QCLNG ATP852

InSAR Ongoing Study of the Surat Basin Stage 2 2012-2014

Radarsat-2 July 2012- December 2014

Second delivery – April 2015

Addressed to:

Craig Noble, Patrick McKelvey

Type: Technical Report

Authors: M. Sánchez, P. Blanco

Approved by: P. Blanco

Ref.: AI_QGC_ATP852_D2_REPORT_20150430_010

Version: 01.0

Date: April 30th, 2015

30/04/2015 AI_QGC_ATP852_D2_REPORT_20150430_010.pdf 2/28

InSAR ground displacement monitoring on the Surat Basin

1. EXECUTIVE SUMMARY

This document presents the QCLNG tenements motion results corresponding to the second and final delivery of the “InSAR ground displacement monitoring on the Surat Basin” project. The motion temporal series at the dates of the employed images and the mean displacement rate are provided for every point in the area that is of sufficient quality.

These results were obtained by means of the application of Altamira Information’s Persistent Scatterer Interferometry technique (PSI) to a set of SAR Radarsat-2 images. This set was composed of 2 different frames with 27 SAR images each. These sets covered the period from July 2012 to December 2014.

Given the land cover characteristics of the tenements, the density of measurement points is high except over agricultural fields and forests where the number of measurement points is scarce due to the effects of the continuous temporal changes.

Consistent measurements have been obtained over the tenements. The following table shows the number of measurements obtained for this delivery:

The area of interest shows a general stable pattern (magnitude of ground motion below 5 mm/year). Nevertheless, some areas of subsidence have been identified, reaching a maximum magnitude of about 20 mm/y.

Delivery Measurements

D2 652,867



1. EXECUTIVE SUMMARY ....................................................................................................2

2. INTRODUCTION ..............................................................................................................5

3. AREA OF INTEREST AND IMAGE COVERAGE .....................................................................6

4. GLOBALSARTM METHODOLOGY ..................................................................................... 14

4.1. MILLIMETRIC MEASUREMENTS .......................................................................................................14

4.2. FORMAT OF THE PROCESSING RESULTS ..........................................................................................15

5. RESULTS OF THE STUDY ................................................................................................ 16

5.1. GLOBAL ANALYSIS OF THE RESULTS ................................................................................................17

5.2. IDENTIFIED AREAS WITH MOTION ...................................................................................................19

5.2.1. AREA A ......................................................................................................................................................... 20 5.2.2. AREA B ......................................................................................................................................................... 22 5.2.3. AREA C ......................................................................................................................................................... 24 5.2.4. AREA D ......................................................................................................................................................... 26

6. CONCLUSIONS .............................................................................................................. 28



CHANGE RECORD FOR THIS DOCUMENT

Version Date Sections Description of changes

01.0 30/04/2015 all Creation of the document

APPLICABLE DOCUMENTS AND REFERENCE DOCUMENTS (A/R)

Reference Date Title

DR1 03/10/2013 AI_QGC_031013_GROUND_MOTION_REPORT.pdf

DR2 30/04/2015 AI_QGC_ATP852_D2_PRODUCT_HANDBOOK_20150430_010.pdf

ACRONYMS AND ABBREVIATIONS

AOI Area of Interest

DEM Digital Elevation Model

PS Persistent Scatterer

PSI Persistent Scatterer Interferometry

SAR Synthetic Aperture Radar



2. INTRODUCTION

This document presents the methodology and results of the InSAR Ongoing Study of the Surat Basin Stage 2 - 2010-2014 commissioned by QGC in support of the QCLNG CSG project. This program has been conducted to evaluate the potential ground motion across QCLNG tenements in the Surat Basin, located in southern Queensland, Australia.

In particular, this document presents the QCLNG ATP852 area motion results corresponding to the second and final delivery of the “InSAR ground displacement monitoring on the Surat Basin” project. The first delivery was held in October 2013 and comprised the same dataset employed in the present study but covering the initial period from July 2012 to July 2013. The corresponding results were presented in DR1.

The results were obtained by means of the application of the GlobalSARTM methodology to a set of Radarsat-2 images covering the 1,156 km2 of the QCLNG’s AOI. This set was composed of 2 different frames with 27 SAR images each. The corresponding image sets covered the period from July 2012 to December 2014. The analysis over the area of interest allowed the retrieval of 652,867 measurement points, which represent a mean density of about 564 Persistent Scatterers per square kilometre.

Following this introduction, the document is divided into several sections. Section 3 describes the area of interest and the available dataset. Section 4 is dedicated to the description of the GlobalSARTM methodology used to measure ground motion. Section 5 deals with the results of the application of the technique and the measurement of ground motion in the area of interest. The conclusions of the overall project followed by some recommendations are discussed in section 6.

In addition to this report, the delivery includes a set of files (vector files) with the measurements which are explained in the product handbook (reference document DR2) which presents formats, precisions and guidelines for the handling of the data.



3. AREA OF INTEREST AND IMAGE COVERAGE

The area of interest is located in the Surat Basin, where ATP852 area given by QGC’s QCLNG are studied. Figure 1 shows the processed AOI that has a total of 1,156 km2.

Figure 1: QCLNG ATP852 area of interest.

The employed image dataset includes two Radarsat-2 ascending frames. Each frame covers approximately 150 km x 150 km. Figure 2 shows those frames along with the QCLNG ATP852 AOI. The frame labels correspond to the SBC frame labeling where a total of five Radarsat-2 frames are considered.



As seen, the two frames are grouped into one consecutive ascending frame, as they belong to the same track. In general terms, a track represents a long strip of data composed of several frames which are sequentially acquired so it can be considered that each track represents a satellite pass (or equivalently, a date of measurement). In order to ensure track continuity, frames belonging to the same track present some overlapping.

The present satellite configuration was chosen as it represents the best disposable data to monitor the area in terms of coverage and available number of acquisitions for the AOI.

Figure 2: Frames corresponding to the Radarsat-2 set of images employed in the study superimposed to the QCLNG ATP852 AOI.

Radarsat-2 has a working frequency of 5.3 GHz (C-band) which is equivalent to a wavelength of 5.6 cm. The images were acquired in Extended Fine Mode presenting a pixel size of 8 m in ground range and 5 m in azimuth. The incidence angle varied from 32 deg. in near range to 38 deg. in far range.

3

2



27 images were acquired with each frame. Table 1 summarizes this information. The image sets were built-up by scheduling the acquisitions with a repeat cycle of 24 days from July 2012 to October 2013 and 48 days from October 2013 to December 2014. Radarsat-2 has a revisit period of 24 days.

Table 1: Radarsat-2 data archive per frame. A total amount of 54 - SAR – images have been used.

The acquisition dates and the orbit number processed for frame 2 and 3 are listed in Table 2 and Table 3 respectively. Although they belong to the same track they have been split in two because on frame 2 the 16-Jun-2014 acquisition failed so a new programming was performed acquiring 10-Jul-2014 image.

Table 2: Radarsat-2 frame 2 image set.

Satellite Frame Orientation Images per frame

RADARSAT-2

2 Ascending 27

3 Ascending 27

Acquisition date Orbit number


1 20-Jul-2012 24006 15 15-Jul-2013 29151

2 13-Aug-2012 24349 16 01-Sep-2013 29837

3 6-Sep-2012 24692 17 25-Sep-2013 30180

4 30-Sep-2012 25035 18 19-Oct-2013 30523

5 17-Nov-2012 25721 19 06-Dec-2013 31209

6 11-Dec-2012 26064 20 23-Jan-2014 31895

7 4-Jan-2013 26407 21 12-Mar-2014 32581

8 28-Jan-2013 26750 22 29-Apr-2014 33267

9 21-Feb-2013 27093 23 16-Jun-2014 33953

10 17-Mar-2013 27436 24 03-Aug-2014 34639

11 10-Apr-2013 27779 25 20-Sep-2014 35325

12 4-May-2013 28122 26 07-Nov-2014 36011

13 28-May-2013 28465 27 25-Dec-2014 36697

14 21-Jun-2013 28808



1 20-Jul-2012 24006 15 15-Jul-2013 29151

2 13-Aug-2012 24349 16 01-Sep-2013 29837

3 6-Sep-2012 24692 17 25-Sep-2013 30180

4 30-Sep-2012 25035 18 19-Oct-2013 30523

5 17-Nov-2012 25721 19 06-Dec-2013 31209



Table 3: Radarsat-2 frame 3 image set.

Figure 3 and Figure 4 show the temporal distribution of the Radarsat-2 images for frame 2 and 3 respectively. 24-day and 48-day acquisition cycles are noticeable, having a very regular sampling. As also shown three scheduled acquisitions failed. These took place in 24/10/2012 and 21/07/2013 for frames 2 and 3 and in 10/07/2014 for frame 2. In all cases they were replaced with the consecutive acquisition.

It is important to mention that each acquisition will represent a motion measurement. For each ground measurement point, a displacement result at each image date will be given in the temporal series.

Figure 3: Time distribution of the frame 2 images.

Figure 4: Time distribution of the frame 3 images.

In order to illustrate the acquired Radarsat-2 images, the mean amplitude of the image stack corresponding to frame 2 has been generated and it is shown in Figure 5 (in radar geometry). The mean amplitude is the result of an enhanced average calculation of each amplitude image of the stack.

The shading from black to white is related with the scatter of the wave on the surface and its back-response towards the satellite. Bright white values correspond to a high amount of backscattering, while dark values are related with a low backscatter of the wave towards the satellite (e.g. water bodies and vegetated areas) This strongly depends on the geometry of the illuminated surface. Dihedrals will backscatter most of the incident energy, resulting in bright white pixels. On rough surfaces, the more the roughness is similar to the radar signal wavelength, the more the backscattered energy (grey levels). On the contrary, flat areas (in terms of the radar wavelength) will result in dark pixels.

01/07/2012 30/12/2012 30/06/2013 29/12/2013 29/06/2014 28/12/2014

01/07/2012 30/12/2012 30/06/2013 29/12/2013 29/06/2014 28/12/2014

6 11-Dec-2012 26064 20 23-Jan-2014 31895

7 4-Jan-2013 26407 21 12-Mar-2014 32581

8 28-Jan-2013 26750 22 29-Apr-2014 33267

9 21-Feb-2013 27093 23 10-Jul-2014 34296

10 17-Mar-2013 27436 24 03-Aug-2014 34639

11 10-Apr-2013 27779 25 20-Sep-2014 35325

12 4-May-2013 28122 26 07-Nov-2014 36011

13 28-May-2013 28465 27 25-Dec-2014 36697

14 21-Jun-2013 28808



A comparison between the radar image and the optical image of a gas field is made in Figure 6 and Figure 7 respectively. The different land covers are represented by a different backscatter coefficient (level of grey) allowing for the detection of the extraction spots.



Figure 5: Mean amplitude of the frame 2 Radarsat-2 stack of images in radar coordinates (flipped vertically for convenience).



Figure 6: Mean amplitude of a gas field in the AOI in radar coordinates (flipped horizontally for convenience).



Figure 7: Optical image of a gas field in the AOI.



4. GLOBALSARTM METHODOLOGY

The delivered results were obtained by processing Radarsat-2 radar satellite images with the GlobalSARTM methodology developed by ALTAMIRA INFORMATION. GlobalSARTM combines several processing techniques and algorithms to obtain the best possible accuracy of measurements for all ranges of ground motion, even strong non-linear deformation patterns. The GlobalSARTM technique achieves the highest possible density of Natural Reflectors, even in areas with difficult ground conditions, such as vegetation. As long as there are no drastic changes to the surface, such as major construction work, GlobalSARTM provides reliable natural measurement points, regardless of the intensity of the motion.

GlobalSARTM uses different methodologies to create a homogeneous ground deformation map in order to provide user-friendly information for the final user. All information is delivered with the same format in a single file package. This simplifies the usage and exploration of data.

The specific techniques used in this study are described in the following sections.

4.1. MILLIMETRIC MEASUREMENTS

The algorithms used to detect millimetric motion belong to the PSI (Persistent Scatterer Interferometry) family of software developed by ALTAMIRA INFORMATION. These algorithms are capable of extracting precise displacement and position information of the radar stable points.

PSI algorithms work by identifying high quality reflectance points in the radar imagery. Model fitting methodologies are applied to these points to derive the precise height and displacement measurements. During the process, the atmospheric effects are compensated. Points that do not present enough reflectance quality due to major surface changes are rejected.

The algorithms are applied to a set of input interferograms. Interferograms are images that represent the radar phase differences between a pair of SAR images. In an interferogram the phase value is related to the geometric configuration of the image pair, motion that has occurred during the period, atmospheric effects and noise.

The basis of the technique is the separation of the different components (deformation, topographic error and atmospheric effects) from the input data. Step-by-step, the data is processed taking into account the physical behaviour of each component characterized in terms of the radar signal reflectance and image geometry. Finally, the atmospheric effects are estimated and eliminated as spatially low-wavelength and temporally high-frequency effects. Afterwards a high resolution analysis is carried out to extract the precise values of the deformation as well as the precise DEM correction values.

This technique offers millimetric precision of the ground displacements not higher than approximately 20-25 cm/year. Figure 8 shows the main flow chart of this processor.



Figure 8: Millimetric measurements processor main flow chart.

4.2. FORMAT OF THE PROCESSING RESULTS

The motion of each measurement point is determined via the analysis of a stack of radar images as explained previously. Therefore, for each point the accumulated displacement rate (for each of the measurement periods) and its relative height correction with respect to the DEM are obtained. These values are given in the delivered database.

The reference document DR2 (Product Handbook) describes the format and method for using these products.



5. RESULTS OF THE STUDY

In this section an analysis of the obtained motion results is performed.

Motion results are presented as mean displacement rate maps as well as time series. The magnitudes are expressed in millimetres per year and millimetres in the time series, both along the Line of Sight Direction. Only those points with enough quality (high signal to noise ratio) are represented.

Mean displacement maps allow to identify the motion affected areas, in terms of extension and magnitude. Temporal series allow extracting the motion temporal behavior, describing some possible non-linear trends accounting, among others, for motion acceleration or stabilization.

The maps are represented in GDA-94 zone 55 south ground projected coordinate system. The background is supplied by Bing Maps © Microsoft Corporation.

The chosen colour scale is shown in Figure 9. Stability has been set to 5 mm/year, where green represents points which have remained stable over the period of study, blue points showing uplift and red points that have undergone subsidence. The quantification levels have been set in order to ease the characterization of the motion areas and considering the expected motion rate precision for the employed dataset.

Figure 9: Colour table used for the mean displacement rate maps.

Firstly, in section 5.1 the mean displacement rate map of the complete AOI is presented. A general evaluation is done.

Secondly, in section 5.2 , the most significant motion areas that have been identified are located. The corresponding mean displacement rate maps for those areas are presented, along with the temporal series of some selected points at the area.



5.1. GLOBAL ANALYSIS OF THE RESULTS

Figure 10 shows the mean displacement rate in millimeters per year calculated for the QCLNG areas of interest. A total of 652,867 measurement points are presented, reporting an average density of approximately 564 PS/km2. This is summarized in Table 4.

Total number of PS PS density

652,867 564 PS/km2

Table 4: Number of measurement points and equivalent Persistent Scatterers density in the AOI.

Figure 10 shows that the AOI presents a general stable behavior, considering the selected stability threshold. Nevertheless, some motion affected areas have been identified. In the central part of the AOI several small motion areas have been detected. They have been grouped in two big areas for the following analysis with an approximate extension of 81 km2 each and a maximum subsidence magnitude of about 33 mm/y (area C) and 30 mm/y (area D).

It is also important to notice that the areas that present a low density of measurements points correspond to vegetated and cultivated areas, strongly affected by temporal decorrelation.



Figure 10: Mean displacement rate map of the AOI.



5.2. IDENTIFIED AREAS WITH MOTION

Figure 11 shows selected areas where localized motion was identified and have been selected for individual analysis. The following sections show each case separately, describing the principal characteristics and including some representative ground motion time series.

Figure 11: Mean displacement rate map of the AOI, locating the identified motion areas, labelled from A to D.

A

C

D

B



5.2.1. Area A

Figure 12 shows the mean displacement rate map of motion area A. In it a subsidence affected area is detected with a localized spot that reaches a magnitude greater than 15 mm/year. Figure 13 shows the temporal series of three motion points in the area.

Figure 12: Mean displacement rate map of motion area A.



Figure 13 : Representative time series of area A



5.2.2. Area B

Figure 14 shows the mean displacement rate map of motion area B. There, two subsidence affected areas are detected reaching a magnitude greater than 15 mm/year. Figure 15 shows the temporal series of three motion points in the area.

Figure 14: Mean displacement rate map of motion area B.



Figure 15 : Representative time series of area B.



5.2.3. Area C

Figure 16 shows the mean displacement rate map of motion area C. There, a subsidence affected area is detected having two spots reaching a magnitude greater than 15 mm/year. Figure 17 shows the temporal series of three motion points in the area.

Figure 16: Mean displacement rate map of motion area C.



Figure 17 : Representative time series of area C.



5.2.4. Area D

Figure 18 shows the mean displacement rate map of motion area D. There, a subsidence affected area is detected reaching a magnitude greater than 12.5 mm/y. Figure 19 shows the temporal series of three motion points in the area.

Figure 18 : Mean displacement velocity rate of motion area D.



Figure 19 : Representative time series of Area D



6. CONCLUSIONS

GlobalSARTM methodology has been applied to a stack of 54 Radarsat-2 Extended Wide Swath images over the QCLNG Area of Interest, covering the period from July 2012 to December 2014. The number of measurements points obtained is of 652,867, which represents a density of 564 PS/Km2. Low density areas are mainly composed of vegetated and cultivated fields.

The mean displacement rate and the temporal series for each measurement point have been generated. The AOI presents a general stable behaviour. Nevertheless some subsidence areas have been identified and described maximum subsidence rate larger than 15 mm/year.

Further analysis is recommended to understand the origin of the ground motion. The analysis of the correlation of the time series of motion with the ground works information jointly with the knowledge of the ground geology can help to determine the nature of the detected displacements.

APPENDIX K: ALTAMIRA REPORT ON INSAR ONGOING STUDY OF ... · ALTAMIRA INFORMATION, SLU C/ Còrsega,...

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