Abandoned Wellsites

Environmental Assessment of Abandoned Petroleum Wellsites in the Cooper Basin, South Australia

Michael Malavazos (Chief Engineer, Petroleum & Geothermal Group, PIRSA)

Introduction

As part of the PIRSA Petroleum and Geothermal Group's strategy to implement a transparent regulatory framework for the upstream petroleum industry in South Australia, a concept known as goal attainment scaling (GAS) for assessing and reporting environmental restoration practices of the industry has been adopted.

For the case of wellsite restoration activities, this concept has been trialed and developed over the past few years in consultation with industry and community stakeholders. An outcome of this has been the recent publication of PIRSA's Field guide for the environmental assessment of abandoned petroleum wellsites in the Cooper Basin, South Australia which outlines the objectives and assessment criteria for these activities. The criteria for each objective are given in Table 1, and photographs for assisting in the assessment against each of these criteria are provided in the guidelines. Examples of these photographs are provided below.

The Guidelines

These guidelines, prepared to assess the level of environmental rehabilitation of abandoned petroleum wellsites in the Cooper Basin region in South Australia, are intended for use by government agencies, industry and the community. They are an integral part of PIRSA's auditing procedure and, as part of a working document, will be subject to periodic review.

Assessment tool

The assessment is based on the concept of GAS in which stakeholders are required to participate in evaluating and seeking consensus on the most important aspects of the goals to be achieved within a particular time frame, and the range of expected outcomes of the activities undertaken. Expected outcomes are documented as:

Score Outcome

-2 much less than expected
-1 less than expected
 0 expected
+1 more than expected
+2 much more than expected

The guidelines use descriptive outcome criteria supported by colour photographs. The photos are provided as an example only and do not represent an absolute situation. Where multiple outcomes are applicable to a particular site, the final score will be the lowest, reflecting the lesser expected outcome.

The aim of the assessment is to ascertain the level of attainment of objectives at abandoned wellsites and to ensure that appropriate action is undertaken to reduce the environmental impact of wellsites which score -1 or -2.

Environmental objectives

Fatchen and Woodburn (1997) studied the environmental impact of wellsites and seismic lines in the Cooper Basin and concluded that the impact is mainly visual and not ecological. They suggested that a return of the physical configuration of an affected region would be an acceptable indicator of the level of return of the regional ecology. When setting the objectives, the focus was therefore on those which could be assessed visually:

  1. minimise the visual impact through earthwork restoration, blending wellsites and associated access tracks into the surrounding contours and ensuring soil colour and material is returned to a level compatible with that of the surrounds
  2. revegetation of indigenous species.

The Objective 1 assessment consists of two parameters:

  • the effectiveness of the earthwork in restoring the original contours of the site
  • the extent to which the site is stabilised against erosion.

Three categories of outcome criteria are set for this objective; one relates to the wellsite access track and the others to the wellsite location (plain or dune).

Revegetation is dependent on the vegetation type, soil type and moisture content in the soil which, in turn, is dependent on the timing and amount of rainfall in the region after earthwork restoration. From field observations in the Cooper Basin (Malavazos and Dobrzinski, 1995), a five- year period was selected as sufficient time for revegetation of wellsites (provided that earthwork restoration was effective). For an interval of less than five years, the assessment is carried out on an 'enabling' objective, ie a reliable short-term indicator for the achievement of long- term revegetation outcomes. Therefore, two categories of outcome criteria were set up for Objective 2, one for wellsites restored for less than five years and one for five years or more.

The guidelines are intended to ensure consistency in the assessment against these objectives by minimising the subjective judgement often associated with such qualitative assessment. From the operational viewpoint, it is considered that managing the visual impact will assist field staff in managing for minimal impact on the biological and physical environment. This in no way reduces the importance of long-term ecological consequences which are the subject of ongoing investigation and consultation.

Table 1: Summary of criteria for assessing the restoration of abandoned wellsites in the Cooper Basin.

Score

Objective 1

Objective 2
 

To minimise the visual impact

The revegetation of indigenous species(a)
 

Access tracks

Interdune and floodplain wellsites

Dune wellsites

Less than five years since wellsite abandonment

At least five years since abandonment
-2 The track is prominent because of a scraped surface, windrows along its edges or gully erosion. The site remains as a prominent consolidated surface with a distinct edge. Extensive gully erosion down theface of the dune and/or a steep site edge are prominent. The site remains as a consolidated surface. There is no revegetation.
-1 The track surface has been contoured into the surrounding landscape; but the colour of foreign material contrasts with the surroundings. The site surf ace and edge have been contoured into the surrounding landscape, but the colour of foreign material contrasts with the surroundings. The edge of the site has been restored into the natural contour of the dune, but the colour of foreign material contrasts with the surroundings. The colour of foreign material contrasts with the surroundings. The revegetation mostly consists of annuals and biennials; in contrast to the surroundings there are few perennials.
0 The track contours and colour blend with the surroundings, but the earthwork disturbance (e.g. ripping, rolling or respreading of original material) is still prominent. The site contours and colour blend with the surroundings, but the earthwork disturbance (e.g. ripping, rolling or respreading of original material) is still prominent. The edge and colour of the site blend with the surroundings. The site contours are visible only when viewed from the top of the dune; they cannot be seen from the base. Erosion gullies are present down the face of the dune, but they are not extensive or prominent. The site surface has been appropriately restored (e.g. ripping or respreading of original material) to facilitate revegetation The revegetation consists of annuals, biennials and perennials, but there are some bare patches which are inconsistent with the surroundings.
+1 The track contours and colour blend with the surroundings and the earthwork disturbance is also beginning to blend. The site contours and colour blend with the surroundings and the earthwork disturbance is also beginning to blend. The edge and colour of the site blend with the surroundings. The site contours are visible only when viewed from the tp of the dune; they cannot be seen from the base. There are no eroion gullies down the face of the dune. The revegetation is extensive and consists of annuals and biennials; in contrast to the surroundings there are no perennials. The revegetation, mostly perennials, is consistent with the surroundings, but there is a contrast in maturity between the two.
+2 The track contours and colour blend with the surroundings and the earthwork disturbance is indistinguishable. The site contours and colour blend with the surroundings and the earthwork disturbance is indistinguishable. The edge and colour of the site blend with the surroundings. The site contours are indistinguishable whether viewed f rom the top or base of the dune. The revegetation is extensive and mostly consists of annuals and biennials; perennials are beginning to establish which is consistent with the surroundings. The revegetation type, density and maturity is indistinguishable from the surroundings.

(a) See Wiltshire and Schmidt (1997) for identification of vegetation.

An example of Objective 1: Minimise visual impact - interdune and floodplain wellsites.

-2 score. The site remains as a prominent, consolidated surface with a distinct edge.

Landscape - site remains as a prominent, consolidated surface with a distinct edge

 

-1 score. The site surface and edge have been contoured into the surrounding landscape, but the colour contrasts with the surroundings

.Landscape - The site surface and edge have been contoured into the surrounding landscape, but the colour contrasts with the surroundings

 

0 score. The site contours and colour blend with the surroundings; but the earthwork disturbance (eg ripping, rolling, respreading) is still prominent

Landscape - The site contours and colour blend with the surroundings; but the earthwork disturbance (eg ripping, rolling, respreading) is still prominent

 

+1 score. The site contours and colour blend with the surroundings and the
earthwork disturbance is also beginning to blend.

Landscape - The site contours and colour blend with the surroundings and the earthwork disturbance is also beginning to blend

 

+2 score. The site contours and colour blend with the surroundings and the earthwork disturbance is indistinguishable.

Example of landscape where contours and colour blend with the surroundings and the earthwork disturbance is indistinguishable


References

Fatchen, T.J. and Woodburn, J.A., 1997. Criteria for the abandonment of seismic lines and wellsites in the South Australian portion of the Cooper Basin: identification and evaluation of assessment criteria. Report for MESA. South Australia. Department of Primary Industries and Resources. Open File, DME 389/1994 (unpublished).

Malavazos, M. and Dobrzinski, I., 1995. Goal attainment scaling applied to assessing environmental impact of petroleum production operation in the Cooper Basin. South Australia. Department of Primary Industries and Resources. Open File, DME 16/1990 (unpublished).

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