1.2.3.2.3 Dewhurst Gas Exploration Pilot wells

Santos was granted approval from the NSW Government in July 2014 to expand its Dewhurst Gas Exploration Pilot under the Energy NSW CSG Exploration and Appraisal Program (RPS Australia East, 2013b). The Dewhurst CSG wells are shown on Figure 11 . The recently approved activity within PEL 238 involves drilling two new horizontal wells at each of the Dewhurst 16H, 17H and 18H pilot wells to target additional coal seams at the existing Dewhurst 13–18H pilot well set. Two additional vertical-triple-stacked wells (Dewhurst 30 and 31) have also been approved to be added to the previously approved Dewhurst 26–29 pilot well set. The Dewhurst 30 and 31 well pair is scheduled to be drilled in the second or third quarter of 2014 (RPS Australia East, 2013b). The Dewhurst Gas Exploration pilot wells did not require approval under the EPBC Act as the proposed action was not considered likely to be significant if undertaken in a particular manner. Any proposal to convert the pilot wells into production wells will be included in the Narrabri Gas Project discussed in Section 1.2.3.2.1 (GHD, 2014).

The tri-stacked wells are expected to be pumping and producing from three different coals seams. The total well depth is estimated to reach approximately 1000 m while the total length of the directional wells is about 2000 m (inclusive of vertical depth). The lateral wells would be operated by electric submersible pumps; for the vertical wells progressive cavity pumps are proposed. Maximum gas flow rates of 1000 million standard cubic feet per day are expected at an estimated operating wellhead pressure of 275 kPa (gauge pressure). Mean water production is predicted to be approximately 250 m³/d (RPS Australia East, 2013c).