GNS Science Consultancy Report 2006/0XX

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Figure 8. Temperatures ranges of onshore and offshore abandoned oil and gas wells. In contrast to onshore wells about 92% of abandoned offshore wells (97 wells) have bottomhole temperatures >50 o C (Figure 8) because these are all drilled deeper than 700m. One offshore well, Clipper-1 in the Great South basin, has a calculated bottomhole temperature of nearly 185 o C at 4742m. A plot of total depth versus estimated bottom hole temperatures (Figure 9) show three onshore wells with thermal gradients higher than most wells: Rotokautuku-1 in the East Cape, Bounty-1 in the West Coast and New Plymouth-2 in Taranaki (Figures 2 and 9). Rotokautuku-1 is located in a region of active landmass uplift in the Raukumara Peninsula where the surface heat flow is high at 170 mW/m 2 believed to be caused by the advection of rising hot fluids from depth (Field et al, 1997). The thermal gradient in Rotokautuku is about 80 o C/km. Well Bounty-1 in the West Coast is 3131m deep, drilled in an isolated region with a heat flow of 80 mW/m 2 heat flux (Figure 3) where the landmass is rapidly rising (Allis and Shi, 1995). Well New Plymouth-2 is drilled to 4451m in a region of 70 mW/m 2 heat flux and is located near the Pliocene to Quaternary Sugar Loaf Islands and Paritutu volcanic centres which may still possess vestigial heat at depth. The thermal gradient is about 40 o C/km in wells Bounty-1 and New Plymouth-2. The three offshore wells with the highest thermal gradients at 40-50 o C/km are wells Takapu-1 and Clipper-1 in the Great South basin and well Cook-1 in offshore Taranaki. GNS Science Report 2007/23 10
Figure 9. Depth versus estimated bottom hole temperatures of all offshore and onshore abandoned hydrocarbon wells and possible uses of geothermal fluids. GNS Science Report 2007/23 11
Page 2 and 3: Abandoned oil and gas wells - a rec
Page 4 and 5: CONTENTS ABSTRACT..................
Page 6 and 7: ABSTRACT There are 349 abandoned on
Page 8 and 9: Figure 1. Temperature, depth and pe
Page 10 and 11: 2.0 ABANDONED OIL AND GAS WELLS IN
Page 12 and 13: Figure 5. Map showing the distribut
Page 14 and 15: Figure 6. Drilled vertical depths o
Page 18 and 19: Table 1. Number of wells within a r
Page 20 and 21: 3.3 REASONS FOR ABANDONING WELLS Mo
Page 22 and 23: Assuming a flow of 4 L s -1 , the 2
Page 24 and 25: 5.0 CURRENT GEOTHERMAL USE OF ABAND
Page 26 and 27: In New Zealand temperature may be p
Page 28 and 29: Figure 16. Abandoned hydrocarbon we
Page 30 and 31: 10. Determine how geothermal produc
Page 32 and 33: Isaac M J, Herzer R H, Brook F J an
Page 34 and 35: APPENDIX 1 NOTES ON THE GEOTHERMAL
Page 36 and 37: Speaker Company/Agency Topic Main P
Page 38 and 39: Table 6. Basic well data for onshor
Page 40 and 41: Well Name NORTH ISLAND TARANAKI Dat
Page 42 and 43: Well Name SOUTH ISLAND WEST COAST D

GNS Science Consultancy Report 2006/0XX

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