Oil Basins Limited: Oil and Gas Explorer

Canning Basin – Backreef Area


Under the terms of the Backreef Play Agreement (BPA) dated 31 October, 2008 (refer OBL ASX Release) Oil Basins Limited (OBL) presently holds 100% beneficial rights to the Backreef Area.

OBL is the designated operator for the Backreef Area having successfully drilled Backreef-1 by 31 October 2011. OBL has a further farmin obligation well to be drilled by 31 October 2012.

Backreef Area

The Backreef Area comprises EP 129 Remainder R2 (part thereof), R3 & Production Licence L6, (part thereof) - refer to Figure 1.

Backreef Prospect

Backreef-1 was spudded on 11 October 2010 and was a vertical exploration land well located within the Backreef Area of Production Lease L6 in the onshore Canning Basin, approximately 70km east of Derby, Western Australia.

The well was deepened 200m from an originally planned TD of 1600m to a revised TD of 1800m to obtain further stratigraphic information (including the development of possible reservoir facies) deeper in the Clanmeyer Formation and investigate increasing mud gas indications including the presence of "heavies" (C3-C4) in addition to C1 and C2 which predominated in the upper part of the formation.

The primary exploration objective of Backreef-1 was to explore for reservoired hydrocarbons in sandstones within the Devonian-aged Clanmeyer Formation in the Kimberley Downs Embayment southwest of Harold-1 and northeast of the Blina Oil Field.  These sandstones were interpreted to have been deposited as a submarine channel / fan complex in the embayment between the margining Devonian carbonate platform to the north and the Blina reefal complex, comprising more isolated reefal build-ups to the south.  However, as the Clanmeyer Formation clastic sequence had not been drilled previously in Kimberley Downs Embayment, its stratigraphy in this region prior to Backreef-1 was essentially unknown.

The Backreef-1 well, within the Backreef Area is presently cased and suspended at plugged-back total depth 1155m MDRT (measured depth relative to rotary table) and the well has according to Weatherford petrophysicists delineated the following attributes:

  • Porosity circa 22% - with permeability tight
  • Reservoirs - Yellow Drum equivalent & Gumhole dolomites
  • Gross Reservoir interval 48.9m
  • Net Oil Pay interval 39.2m
  • Risked Net Free oil (pre-stimulation) 3.9m

During 1HY2011, OBL commissioned new geophysical and geological (G&G) work within the Backreef Area to collect and digitise some 16 vintage 2D seismic and to reprocess the newly digitized data and apply modern 3D techniques assist with its evaluation and interpretation of the potential new oil play area. Utilising advanced 3D Petrel ™ software has now defined a potential the New Oil Play first delineated by Backreef-1 well (Figure 2).

  1. OBL has delineated a ‘first-time revealed image’ of the overall extent of the potentially large regional stratigraphic trap circa 40sqkm to 60sqkm, possibly containing the Backreef-1 well location (Figure 2)
  2. This prognosed reservoir are the Yellow Drum dolomites extending from L6 into EP129R3 region within the Kimberley Downs Embayment.
  3. The feature mostly lies within Production Licence L6 and EP129R3 within the Backreef Area.
  4. In addition, there appears to be two distinct conventional roll-over ‘oil pool’ targets, namely Lead A (East Blina Lead) and the Backreef-1 prospect.
  5. The lateral extent and risk in the north and updip in the east is dependent upon an adequate seal being evident between the subcrop and unconformity at the base of the lower Grant formation (our geological/geophysical team considers that there is the likelihood of a lower Grant shaley member within the channel non-conformity).

Principal Petrophysical Findings – Backreef-1

An integrated analysis by Weatherford using nearby Blina fluid properties indicates a potential (in the absence of fluid sample from the well) for 39.2 m of net oil pay over a gross reservoir interval 48.9m in dolomitic carbonate reservoirs within the Laurel, Yellow Drum and Gumhole formations.  Water saturations (SWirr) as low as 20% with porosity as high as 22% were calculated using a formation water salinity of 80,000 ppm (salinity assumption was based upon the nearby down-dip Blina Oil Field in the absence of a FMT fluid sample).  The gas wetness ratio plot validates the OH log interpretation results in the detection of a predominantly oil column.

The net pay section has an average porosity (PHIE) of 13.6% and average water saturation (SWE) of 29.5%.  A risked conservative (unstimulated) moveable oil interval within the tight dolomites of around 3.9m circa 957 m to 961mMDRT has been determined in the Yellow Drum / Gumhole formations.

A cased hole production test is required to confirm the presence and producibility of oil.

Nearby Oil Infrastructure – Blina Oil Field

The largest nearby structure in the immediate region of the Backreef Area is the Blina oilfield which was the first commercial oil discovery in the Canning Basin. It is presently wholly owned and operated by Buru Energy Limited. Its discovery in 1981 led to a mini exploration boom in the basin. The Blina field is located in onshore Production Licence L6 in the Canning Basin, 105 kilometres east-southeast of Derby. The field was discovered in May 1981, by Home Oil Australia with the drilling of Blina 1, which intersected two distinct reservoirs, namely the Upper Devonian (Famennian) Nullara Limestone Formation (Nullar Oil Pool) and the Lower Carboniferous dolomitic Yellow Drum Formation (Yellow Drum Oil Pool). The development of vugs in these carbonate reservoirs has resulted in excellent permeability. A drill-stem test of the Nullara Limestone produced 35.7degree API (American Petroleum Institute) oil at a rate of 144 kL/d (905 bbl/d) through a 12.7 mm (1/2") choke. A drillstem test of the Yellow Drum Formation produced 36.7° API oil at a rate of 5.7 kL/d (36 bbl/d). A total of eight wells have now been drilled in the field, four of which produced from the Nullara Limestone (1, 2, 3 and 5) and two from the Yellow Drum Formation (4 and 6). The other two wells did not intersect reservoirs. Blina 4 was subsequently re-completed and produced from the Nullara Limestone.

Production from the Blina field commenced on 17 October 1983 and todate over 1.5 million barrels of oil has been produced.  Produced oil is gathered, separated and stored on site for road transport to Kwinana via the Gibb River Road (presently the pipeline to and the Erskine truck terminal on the Great Northern Highway are under care and maintenance as combined volumes from PL6 and PL8 operations are only circa 50 bopd).

Current Status

The Company presently has a 100% net beneficial rights interest in the Backreef Area. Backreef-1 is presently cased and suspended at PBTD 1155m with 178mm (7 inch) diameter liner fully cemented to the surface. 

The Company’s proposed Backreef Area Work Program for 2012 and in particular the proposed Backreef-1 Cased Hole Production Test, will have the following clear objectives:

  1. Conduct a routine and standard cased hole modern (closed chamber within packer) production test of Backreef-1
  2. To recover hydrocarbons (i.e oil) to the surface either by closed chamber sampling or flow to surface.
  3. Characterise the previously poorly defined reservoir permeability and fluid properties (so as to better calibrate the Weatherford Petrolog CPX logs).
  4. Establish steady state down hole and surface reservoir pressure, fluid production rates, static fluid level (applicable to pumping) and hydrocarbon and reservoir fluid composition.
  5. Better define the extent and nature of the possible contingent resources.

Figure 1: Backreef Location Map - click to view.

Figure 2: Oil Basins Interpretation of Backreef Area - click to view.


Latest News

Update on Backreef Ownership & New Deep Oil Case Assessment    
July 29, 2013 (PDF)

Backreef Area USG Prospectivity Overview    
March 4, 2013 (PDF)

East Blina-1 Operations Latest Report    
October 31, 2012 (PDF)

East Blina-1 Update – Rig Contract Executed    
September 18, 2012 (PDF)

East Blina-1 Update    
August 14, 2012 (PDF)

Backreef-1 - Oil Discovery    
May 29, 2012 (PDF)

Backreef-1 Production Test now expected to commence 24 May 2012    
May 22, 2012 (PDF)

Backreef-1 Production Test to commence circa May 20    
May 16, 2012 (PDF)

Update Backreef-1 Production Test    
May 7, 2012 (PDF)

Commencement of Onsite Preparations for Backreef-1 Production Test    
April 13, 2012 (PDF)

Oil Basins Farmout of up to 20% Backreef Area for up to $3.6 Million    
April 2, 2012 (PDF)

Rig Contract Executed for Backreef-1 Production Test
March 22, 2012 (PDF)

Backreef Area Prospective Resources
January 16, 2012 (PDF)

Backreef Area Prospective Resources
November 24, 2011 (PDF)

Postponement of Production Test
October 18, 2011 (PDF)

Backreef-1 Production Test  
September 16, 2011 (PDF)

Proposed Backreef-1 Production Test  
August 3, 2011 (PDF)

Backreef Area Update  
June 20, 2011 (PDF)

Canning Basin Update  
January 13, 2011 (PDF)

Backreef Area – Increase in Beneficial Interest Ownership to 100%  
November 23, 2010 (PDF)


Independent Expert Report

Backreef Area Prospective Resources
November 24, 2011 (PDF)

CSG & USG Potential of Backreef Area  
July 7, 2010 (PDF - 3.0 meg download)