Remote Sensing

Assessing controls on hydrocarbon leakage and seepage

The objective is to develop a better understanding of how to use remote sensing techniques, specifically synthetic aperture radar, to reduce exploration uncertainty on scales ranging from margins to prospects

 Geoffrey W. O’Brien, Australian School of Petroleum, University of Adelaide, South Australia; Geoff Lawrence, TREICOL Ltd., Knebworth, Hertfordshire, UK; and Alan K. Williams, NPA Group, Edenbridge, Kent, UK

 A study of hydrocarbon leakage and seepage has been carried out over the Bonaparte and northern Browse basins in the Timor Sea, North-West Shelf, Australia (Fig. 1) using satellite-based Synthetic Aperture Radar (SAR) data. The SAR data have been integrated with regional geological data, open-file fault-seal analysis results and charge history investigations to provide a holistic assessment of the principal controls on seepage in the area. The study shows that, at a margin scale, seepage preferentially takes place at the edge of seal, in areas with generally thin seals, along major fault relay systems, and is associated with areas of strong Neogene subsidence. At a more localized scale, the study shows that the present day stress field plays a – perhaps the – key role in determining whether areas leak or not.

Fig. 1. Oblique view (looking northeast) of bathymetry of Bonaparte and Browse basins, showing principal tectonic elements expressed in present day physiography.

 In regions where the maximum horizontal stress is perpendicular to the fault arrays, leakage is typically rare to absent, almost irrespective of how much charge is present. In contrast, areas that leak profusely are those in which active hydrocarbon generation and a maximum horizontal stress, which is sub-parallel to the fault arrays, combine to produce an effectively “open” fault system. Such areas provide unique opportunities to assess the petroleum systems but represent risky exploration targets. Consideration of variables such as fault-seal integrity and hydrocarbon generation/ migration history has been shown to add enormously to the power of the SAR data. Conversely, interpretation of the SAR data can provide useful insights into variables such as fault-seal integrity.

  INTRODUCTION

 Bonaparte basin contains several commercial oil and gas accumulations that typically comprise fault-bound structural traps in which Early Cretaceous sealing shales overlie Jurassic or Triassic sandstone reservoir facies. Examples include the Skua, Jabiru, Challis and Laminaria oil fields, Fig. 2a. Other, as yet noncommercial oil and oil-gas accumulations, such as Talbot and Oliver, are also present in the region.

Fig. 2. a) Bathymetry of Australia’s Timor Sea, showing bathymetric and structural relationships within the Bonaparte basin region. b) Bathymetry of the Browse-Bonaparte transition zone (for area outlined in Fig. 2a), showing displacement (in ms) of Neogene faults from regional 2D seismic data.

 Despite these successes, however, the issue of fault-seal integrity represents a key exploration uncertainty across much of the region. Progressive plate collision during the Neogene resulted in significant structural reactivation, with the formation of a large and deep foreland system, the Timor Trough (Fig. 2a), adjacent to the outer margin of Bonaparte basin. The Pliocene was characterized by generally increased rates of regional Neogene subsidence and deposition, although localized and significant Pliocene depocenters, such as the Cartier and Nancar troughs, also formed around the southeastern margin of the Timor Trough.

 The combination of collisional tectonics and attendant crustal flexure induced by foreland formation produced widespread Pliocene faulting, with both the number and the displacement of these Neogene faults (Fig. 2b.) increasing dramatically northeast of the boundary between Bonaparte and Browse basins, since the southwestern limit of the Timor Trough is itself defined by this boundary. Neogene fault displacements of greater than about 100 m (~100 ms) are not uncommon throughout the Bonaparte basin. It is this faulting, combined with the fact that the Cretaceous sealing units in the basin are usually thin (<<100 m thick), which has induced the partial to complete breaching of many hydrocarbon accumulations in the region. ^{1 – 4}

 In contrast to Bonaparte basin, the adjacent Browse basin is characterized by the combination of relatively thick Cretaceous seals and minimal Neogene reactivation. Hence, Neogene trap breaching does not represent a significant exploration risk in Browse basin. 

 In this article, we report on some of the results of a wider remote sensing investigation of the Bonaparte and northern Browse basins.⁵ The key goal of this article is to examine the large-scale, first-order controls on hydrocarbon leakage and seepage throughout the region, with the objective of developing a better understanding of how remote sensing techniques, specifically Synthetic Aperture Radar (SAR), can be used to reduce exploration uncertainty in the region. A large area of the Mesozoic and Tertiary parts of the Bonaparte basin, as well as the northern Browse basin, was investigated.

  METHODOLOGY USED

 The area included in the present study extended from northern Browse basin, at about 15°S and 122°E, north to about 10°S and 127°E, Fig. 3. The principal type of remote sensing data used during the study was satellite-based SAR. The SAR data were a mixture of weather-compliant, RadarSat Wide 1 and ERS data, which provided mostly double coverage or greater over the study area.

Fig. 3. Locations of SAR scenes used in the present study.

 SAR data can be used to map oil slicks and, to a lesser extent, condensate slicks, by detecting the smoothing or calming effect that liquid hydrocarbons, such as oil and to a lesser extent condensate, have on wind-induced rippling on the sea surface. Pollution-slicks are differentiated from seepage-slicks with varying levels of confidence by analyzing slicks and ocean characteristics mapped by SAR. SAR is a low-cost, regional tool that can provide an almost instantaneous radar snapshot of an area over 150 km square. SAR has a pixel size of about 20m, which means that individual slicks smaller than about 120 m long cannot be detected. 

  RESULTS AND DISCUSSION

 The principal results of the study are summarized in Figs. 4a and b.

Fig. 4. a) SAR slicks in Bonaparte basin.5 Second Rank slicks are larger purple dots, Third Rank are mauve dots. b) Slicks plotted on thickness of Early Cretaceous sealing units (from well data). Areas of thin (<50 m) seals are red; thick (>200 m) seals are blue.

 Regional leakage/ seepage patterns. Slicks that were mapped over the Mesozoic and Tertiary parts of the Bonaparte basin are posted on the present day bathymetry (Fig. 4a) and on the thickness of the regional Early Cretaceous sealing unit (Fig. 4b). Also shown on these figures are some key wells. The slicks are subdivided into two classes, namely Second Rank slicks, which are relatively intense (shown as larger, purple-filled circles) and Third Rank slicks (smaller, mauve-filled circles), which are smaller, less intense slicks. The slicks are widely distributed, and show that Bonaparte basin is very “seepy” compared to other Australian basins. The mapped slicks tend to fall into several discrete groups, as follows.

    At the edge of the regional seal. One large group is present in the far northeastern Browse basin (Yampi Shelf, Fig. 2a), immediately south of the Bonaparte-Browse transition inboard. These slicks occur inboard from the Cornea oil field,^6,7 and probably represent slicks derived from tertiary migration from the field. These edge-of-seal leakage points in the northern Browse basin form 1 – 5 km wide, and 30 – 70 km long zones that comprise numerous individual slicks. The individual slicks themselves are typically 250 – 1,000 m wide and 500 – 5,000 m long. A smaller but similar edge-of-seal leakage zone occurs immediately offshore from the northernmost tip of the Kimberley Block, shown in blue on Figs. 4a and 4b.

    Along margin-scale relay zones. The northwest trending boundary between Bonaparte and Browse basins is clearly a migration and leakage/ seepage focal point that is acting as a hydrocarbon catchment along its length.⁸ This boundary zone is a major fault relay zone, and divides areas with markedly different Neogene (stress?) histories.

    Neogene depocenters are topographic depressions which define areas of rapid Neogene subsidence and deposition. It is clear that a large number of slicks are focused either within, or around, these depressions, invariably over large displacement Neogene faults. 

    Carbonate bank systems are confined to the margins of Neogene depocenters. It has been proposed⁹ that the development of many of these carbonate banks within the Bonaparte basin has been localized over active hydrocarbon seeps.

    Thin regional seals may seem obvious. It is clear from Fig. 4b that most slicks that were mapped in this study occur in areas with generally thin (i.e., colored red) sealing facies. It is also evident that the margin-scale relay zone separating Bonaparte and Browse basins characteristically has thin sealing sequences along its length. Areas with thicker seals, as outlined by blue colors, have generally low slick densities compared to other areas. Clearly, areas with thin seals are much more prone to trap (i.e., fault seal) failure, even if the amount of trap reactivation and attendant faulting is only mild.

 Areas with higher densities of slicks also correlate well with areas where the presence of a thermally mature, Late Jurassic or Early Cretaceous oil source-rock system has been demonstrated. Areas such as the Permo-Triassic Ashmore Platform and Londonderry High,¹⁰ where a Late Mesozoic source system is absent, tend to have low densities of slicks, despite the fact that the sealing facies in these areas are thin (which would favor seepage if charge were present). This is consistent with the observation that no commercial discoveries have been made in those areas to date.

 It is interesting to note that several seepage-slick clusters occur within the deepwater parts of Timor Trough, perhaps suggesting the presence of a liquids-prone source system in that area.

 An obvious question with regard to Figs. 4a and 4b is this: Have the SAR data been successful at directly detecting hydrocarbon accumulations within the Bonaparte basin region? In the Laminaria field area, a large and intense cluster of Second Rank slicks occurs to the southwest of the accumulation, but none occur over the accumulation itself. Farther south, the Oliver oil and gas field has a significant group of Second Rank and Third Rank slicks inboard from its location, though none are present immediately over the field. Both Jabiru and Challis have small groups of slicks relatively close by, but neither has interpreted natural oil slicks (excepting pollution slicks that are not shown in Figs. 4a and 4b) directly over them. Talbot oil field has no slicks near it, whereas Skua oil field does. 

 The variability in these observations suggests that the processes that determine whether a field has a slick immediately over it, has one relatively close by, or does not have one at all, are probably relatively involved.

  TRAP-SCALE LEAKAGE/SEEPAGE PATTERNS

    The Nancar Trough-Laminaria High is located immediately south of Laminaria field, Fig. 5. The trough itself is a prominent topographic low and Neogene depocenter that fluid-inclusion data indicate contains one minor breached oil accumulation, with little evidence for oil accumulation in other traps in the trough.¹¹ The trough is highly fault reactivated, with the majority of the faults reaching seafloor.¹² Moreover, the Neogene faults cut through the center of the Neogene depocenter, rather than just extending along its margins. 

Fig. 5. Location map showing the Nancar Trough and the Laminaria High. Stress vectors (Shmax) are also shown.13

 The results of the SAR study are summarized in Fig. 6. The slicks show a very pronounced distribution. Virtually all of the more robust, Second Rank slicks are distributed in the southern part of the area, within the Nancar Trough itself, and closely follow the edge of the carbonate bank system (the Karmt Shoals). The close relationship between the location of slicks and carbonate banks is clear from the seismic line shown in Fig. 7. A few Second Rank slicks are located farther to the north, northwest of Corallina and Laminaria fields, Fig. 6. The Third Rank slicks are mostly scattered between the Karmt Shoals and the Laminaria-Corallina areas.

Fig. 6. Location map in Nancar Trough-Laminaria High area. Second Rank slicks are larger purple dots; Third Rank are mauve dots. Location of seismic line in Fig. 7 indicated.

Fig. 7. Seismic line running NNW from the Eider Horst into the Nancar Trough. The Nancar Trough is characterized by intense slick development around carbonate bank systems.

 It is clear from Fig. 6 that SAR is not successful at accurately identifying large commercial accumulations on the Laminaria High, namely Laminaria and Corallina. In fact, the fields actually define an anomalous area characterized by almost no seepage indicators. SAR was, however, very successful at “bulls-eyeing” the Neogene depocenter comprising the Nancar Trough.

 These responses may potentially be explained by Fig. 5, which shows the directions of the maximum horizontal stress (S_hmax) in this area.¹³ The area is presently very leaky (the Ludmilla-Mandorah region on Fig. 6) and characterized by S_hmax being sub-parallel to the ENE-trending fault arrays which bound the traps in the Nancar Trough. Farther north, in the Laminaria-Corallina area, the fault orientations swing more E-W, at the same time as S_hmax rotates into a more N-S trajectory. As such, under the present-day stress field, the Laminaria-Corallina area would not be expected to suffer from fault-seal failure, whereas the faults in the Nancar Trough would be very prone to reactivation, leakage and seepage. This is exactly what is observed on the seepage data. The fields show no evidence of leakage at present because of high inherent fault-seal integrity, whereas prolific seepage takes place away from the fields, in areas of poor fault seal.

 The Nancar Trough is clearly a very dynamic and active petroleum system, and yet generally there is a scarcity of either accumulations or palaeo-accumulations within it.¹¹ The most probable interpretation of all data from this area is that the source rock system in the Nancar Trough has been invigorated (or more likely, reinvigorated) by Neogene subsidence and deposition. The Neogene tectonism has also led to extensive fault reactivation within (and across the axis of) the trough, with the result that many of the Pliocene fault arrays extend all the way to the seafloor. The faults within the Nancar Trough are favorably oriented (with respect to S_hmax) for leakage, and the Pliocene fault arrays provide ready conduits to the seafloor. The combination of strong present-day hydrocarbon migration (i.e., a dynamic petroleum system) and poor fault-seal integrity has produced a very leaky system.

 It thus appears that the Nancar Trough is now a dynamic petroleum system, but one that appears to have little prospectivity because of low present-day fault-seal integrity. In contrast, the faults in the Laminaria High area are oriented in such a way to favor preservation of the hydrocarbon columns. 

 The central parts of the Cartier Trough are a Neogene depocenter that is effectively an unfaulted sag. Unlike the Nancar Trough, significant Neogene fault arrays are restricted solely to the flanking margins of the Cartier Trough, where numerous large displacement Neogene faults are present. Fluid inclusion data^2,3 show that the previously oil-bearing Oliver structure, on the eastern margin of the basin, has been almost completely gas-flushed. This gas-flushing has probably taken place within the last 3 – 4 million years, as a result of increased sediment load and source rock maturity in the center of the sag.²

 The SAR data over the Cartier Trough show that oil seepage within the Trough is restricted exclusively to the trough margins, Fig. 8. In particular, slicks are clustered directly up-dip from the Oliver accumulation, with their distribution appearing to be localized to where large displacement (>75 m, 50 ms) Neogene faults cut to the seafloor, Fig. 9. These slicks occur about 6 km inboard (southeast of) the Oliver structure, and stretch for about 10 km along strike (i.e., in a northeast direction), appearing to closely mimic the field outline.

Fig. 8. Cartier Trough positions of Second Rank (large purple dots) and Third Rank (smaller, mauve dots) slicks are indicated. White dots are mapped from regional 2D seismic grid of Neogene faults having displacements of more than 50 ms. SAR slicks are focused inboard from Oliver field. Seismic line in Fig. 9 is shown.

Fig. 9. Seismic line that runs north-west across the Cartier Trough.

 The most reasonable interpretation of the slicks seen near Oliver field is that gas generated from over-mature source rocks in the central Cartier Trough is progressively displacing oil from the Oliver structure, which is then leaking to the surface up seaward-dipping Neogene fault arrays to the southeast of the accumulation. The Cartier Trough thus represents an active petroleum system where Pliocene gas generation has flushed previously oil-charged accumulations. Oil prospectivity probably exists up-dip from the Oliver trend.

 The fact that no slicks are observed along the axis of the Cartier Trough is probably due to the center of the trough being unfaulted; hence, no conduits for leakage exist. 

 Fault-seal analysis of the Oliver structure itself¹⁴ showed that this structure has high (modeled) fault-seal integrity, consistent with the fact that the trap has been gas-flushed, and is not leaking at the present day. One of the key reasons for this trap’s high integrity is that the bounding fault has an unusually low dip.¹⁴  

 The southern Swan Graben contains a partially breached oil field (Skua field), the undrilled Spruce prospect, located at the northeastern end of the Skua horst block, as well as several completely breached traps, including Swift, East Swan and Eclipse.^2,3,9 These structures are distributed along the southern boundary fault of the Swan Graben, the principal Late Jurassic source rock depocenter in the region.

 The SAR response in this area (Fig. 10) was characterized by Third Rank slicks that were focused right over Skua field (particularly near the Skua-2 and Skua-3 wells), over the undrilled Spruce prospect (located to the northeast of Swift-1), and near Birch-1. These slicks could be related directly to “leaky” fault segments visible on seismic data, Fig. 11. Several Second Rank slicks were detected along the fault tips at the southern end of the Swan Graben, southwest of Skua field. No slicks were detected northeast of Birch-1, with breached accumulations such as East Swan and Eclipse characteristically having no slicks associated with them. The SAR tool appears to respond principally to traps or areas that have “live” hydrocarbon accumulations present within them. 

Fig. 10. SAR results from the southern Vulcan Sub-basin. SAR slicks are color-coded as before; slicks are focused around the Skua-Swift area. Location of seismic line in Fig. 11 is shown.

Fig. 11. Seismic line over Skua oil field. SAR slicks are associated with the seismically defined hydrocarbon-related diagenetic zones (HRDZs)1,2,8,9

 2D and 3D basin modeling results indicate that the principal liquid hydrocarbon migration event in this region took place by the Early Tertiary, in contrast to the dynamic migration scenarios seen previously in the Nancar and Cartier Troughs. Present-day generation in the southern Swan Graben is interpreted to be largely comprised of dry gas. Moreover, the location of the slicks detected over Skua field corresponds precisely to the location where fault-seal modeling¹⁴ indicates that the structure has its poorest fault-seal integrity. 

 Combining all of these observations together, it would appear that the SAR tool is detecting leaky (commercial) oil accumulations, but is not detecting breached accumulations. It is likely that this is due to a combination of two factors. First, the breached accumulations in this area, such as East Swan and Eclipse, are presently only receiving a gas charge, which, even if it leaked continuously into the water column, is not readily detectable on SAR data. Secondly, when a charged field such as Skua leaks – and both the seismic data and the fault-seal modeling suggest that it does – it is likely that it leaks a considerable volume. These relatively large hydrocarbon volumes can be readily detected using SAR.

  SUMMARY

 The leakage and seepage characteristics of the Bonaparte basin and the northern Browse basin, northwestern Australia, have been investigated using a combination of satellite-based synthetic aperture radar supported by some seismic and charge history data and published fault-seal analysis. This has been undertaken at scales ranging from margin- to prospect-scale.

 It is clear that the distribution of the slicks results from predictable inter-relationships and interactions between top seal thickness, present-day fault-seal integrity, and the hydrocarbon generation/ migration history of the respective areas.

 At a margin-scale, preferred areas of seepage include regions within thin seals, along large relay zones, and within and around areas with high rates of Neogene subsidence.

 At a more localized scale, areas that have high present-day fault-seal integrity tend to leak little, if at all, even in regions receiving active charge and over traps containing large hydrocarbon volumes. Examples in this study include Laminaria and Oliver fields. It is naïve to expect that such accumulations, with high fault-seal integrity, will show any clear evidence of seepage at the present. Rather, the prospectivity of such areas/ prospects is perhaps best assessed either down-dip or up-dip from them (i.e., along the migration fairway), in locations where fault seal, or perhaps even top seal, is interpreted to be poor.

 Areas that are receiving active, liquid-prone charge, but have low fault-seal integrity, leak profusely. Such areas represent high-risk exploration targets per se, but provide unique opportunities to assess the petroleum systems of the respective regions. An example of such an area is the Nancar Trough. Within such “leaky” areas, regions that actually show little evidence of seepage, if confirmed to relate to structural highs, may actually represent attractive exploration targets, since they may have higher fault-seal integrity.

 Charged traps (e.g., Skua) in areas with moderate fault-seal integrity do leak, but perhaps only along specific fault segments. 

 Breached traps in regions no longer receiving oil charge tend to show no SAR response, perhaps because insufficient volumes of liquid hydrocarbons are now leaking from the traps.

 This study clearly indicates that the best outcome is obtained from the interpretation of SAR data if the leakage/ seepage results are closely integrated with the results obtained from seismic interpretation and attribute analysis, fault-seal analysis and hydrocarbon generation/ migration modeling. Such a holistic approach can provide a truly integrated assessment of the petroleum systems present in the area under investigation.  

  ACKNOWLEDGMENTS

 Geoff O’Brien thanks Geoscience Australia, where he was employed when much of this work was undertaken. He also thanks the Australian Petroleum Cooperative Research Centre (APCRC), and the Australian School of Petroleum (University of Adelaide) whose support allowed this study to be completed. The authors especially thank RadarSat International for its support of this cooperative project, and Maria de Farago Botella, OBS Operations Manager for Nigel Press and Associates, who performed all of the weather compliance research for this paper. Mark Webster from Geoscience Australia did great work for this study.

  LITERATURE CITED

  ¹ O’Brien, G. W. and E. P. Woods, “Hydrocarbon-related diagenetic zones (HRDZs) in the Vulcan Sub-basin, Timor Sea: Recognition and exploration implications,” APEA Journal, Vol. 35, pp. 220 – 252, 1995.

  ² O’Brien, G. W., Lisk, M., Duddy, I., Eadington, Cadman, S. and M. Fellows, “Late Tertiary fluid migration in the Timor Sea: A key control on thermal and diagenetic histories?” APPEA Journal , Vol. 36, pp. 399 – 427, 1996.

  ³ O’Brien, G. W., Lisk, M., Duddy, I. R., Hamilton, J., Woods, P., and R. Cowley, “Plate convergence, foreland development and fault reactivation: Primary controls on brine migration, thermal histories and trap breach in the Timor Sea, Australia.” Marine and Petroleum Geology, Vol. 16(6): pp. 533 – 560, 1999.

  ⁴ Shuster, M. W., Eaton, S., Wakefield, L. L. and H. J. Kloosterman, “Neogene tectonics, greater Timor Sea, offshore Australia: Implications for trap risk,” APPEA Journal, Vol. 38, pp. 351 – 379, 1998.

  ⁵ O’Brien, G. W., Lawrence, G., Williams, A., Webster, M., Cowley, R., Wilson, D. and Burns, S., “Hydrocarbon migration and seepage in the Timor Sea and Northern Browse basin North-West Shelf, Australia: An Integrated SAR, Geological and Geochemical Study,” AGSO Report and GIS. Record 2001/11.

  ⁶ O’Brien, G. W., Lawrence, G, Williams, A, Webster, M., Wilson, D. and S. Burns, “Using integrated remote sensing technologies to evaluate and characterise hydrocarbon migration and charge characteristics on the Yampi Shelf, north-western Australia: A methodological study.” APPEA Journal, Vol. 40, pp. 230 – 255, 2000.

  ⁷ O’Brien, G. W., Cowley, R., Quiafe, P. and M. Morse, “Characterising hydrocarbon migration and fault-seal integrity in Australia’s Timor Sea via multiple, integrated remote sensing technologies,” in “Applications of geochemistry, magnetics, and remote sensing,” D. Schumacher and L. A. LeSchack, eds., AAPG Studies in Geology No. 48 and SEG Geophysical References Series No. 11, pp. 393 – 413, 2002.

  ⁸ O’Brien, G. W., Morse, M., Wilson, D., Quaife, P., Colwell, J., Higgins, R. and Foster, C. B., “Margin-scale, basement-involved compartmentalisation of Australia’s North-West Shelf: A primary control on basin-scale rift, depositional and reactivation histories,” APPEA Journal, Vol. 39, pp. 40 – 63,1999.

  ⁹ O’Brien, G. W., Glenn, K., Lawrence, G., Williams, A., Webster, M., Cowley, R. and S. Burns, “Influence of hydrocarbon migration and seepage on benthic communities in the Timor Sea, Australia,” APPEA Journal, Vol. 42, pp. 225 – 240, 2002. 

  ¹⁰ Patillo, J. and P. J. Nicholls, “A tectonostratigraphic framework for the Vulcan Graben, Timor Sea Region. APPEA Journal, Vol. 30, pp. 27 – 51, 1990.

  ¹¹ Brincat, M. P., O’Brien, G. W., Lisk, M., deRuig, M., and S. George, “Hydrocarbon charge history of the northern Bonaparte basin,” APPEA Journal, Vol. 41, 2001.

  ¹² Bishop, D. J., and G. W. O’Brien, “A multi-disciplinary approach to definition and characterisation of carbonate shoals, shallow gas accumulations and related complex, near-surface structures in the Timor Sea,” APPEA Journal, Vol. 38, pp. 93 – 114, 1998.

  ¹³ De Ruig, M. J., Trupp, M., Bishop, D. J., Kuek, D. and Castillo, D. A., “Fault Architecture in the Nancar Trough/ Laminaria Area of the Timor Sea, Northern Australia”, APPEA Journal, Vol. 40, pp. 174 – 193, 2000.

  ¹⁴ Mildren, S. D., Hillis, R. R. and J. Kaldi, “Calibrating predictions of fault seal reactivation in the Timor Sea,” APPEA Journal, Vol. 42, 187 – 202, 2002.

THE AUTHORS
	Geoffrey O'Brien is a researcher and consulting geoscientist with the Australian School of Petroleum, University of Adelaide. He was previously Research Group Leader and Senior Scientific Specialist with the Petroleum and Marine Division of the Australian Geological Survey Organization (AGSO). His work focuses on applying multi-disciplinary research strategies to basin evaluation and environmental management on the continental margins. Dr. O'Brien has also worked for BHP and for Western Mining Corp. He is a member of PESA (PESA Australian Lecturer, 1992), AAPG and AGU.
	Geoff Lawrence (BSc, PhD, FGS, FIMM) founded The Really Easy Imaging Co. Ltd. (TREICoL) in 1992 after 10 years as Manager of Satellite Remote Sensing at BP Exploration. TREICoL joint-ventured with the NPA Group to develop Offshore Basin Screening (OBS) using satellite radar to map hydrocarbon seepage and pollution offshore. They have screened 310 basins in 150 OBS projects from 66 countries to become the leaders in this technology. Previously, he was a Visiting Industry Associate at NASAs JPL and Senior Geologist and Exploration Manager in 40 countries of Africa, Middle East Southeast Asia and Australia with international consultants Hunting. He was the founding President of the Geological Remote Sensing Society.
	Alan Williams earned a BSc (Hons) in Geology from the University of Wales (Swansea) in 1965 and an MSc in Geochemistry from the University of Leeds in 1966. He spent 1970-‘78 as a remote sensing geologist for Hunting Surveys and Consultants before joining BP Exploration in 1979, initially as a geological geochemist, later heading up the interpretation team for BP's ALF Project and finally managed BP’s Integrated Seepage Detection team. In 1992, he joined World Geoscience Corp. to manage the latest version of the ALF technology from Guildford, UK. In 1995, he moved to National Remote Sensing Centre Ltd in Farnborough, and in 1999, joined NPA Group as exploration business manager. He is a member of AAPG, SEG, IPA, PESGB and APPEA.