17.08.2015   IAEA RADIATION TECHNOLOGY SERIES No

LEYTE GEOTHERMAL FIELD (PHILIPPINES)

I.5.1. Problem

The Tongonan-1 sector of the Leyte geothermal production field (LGPF) in the Philippines (Fig. 67) has been experiencing declines in output in some of its production wells, which have been mainly attributed to injection returns from brine injected into one of the wells situated near the production area. Routine production well chemistry monitoring indicated physicochemical changes in the production wells attributed to migration of the reinjected brine back to the production sector since 2001, when the injection load from South Sambaloran was transferred to Tongonan-1.

TABLE 16. CONCENTRATION OF 125I IN PRODUCER WELLS (net cpm/g)

Monitoring period (d)

Well

HCE-7A

HCE-7B

HCE-7C

HCE-9B

HCE-28A

7

—

715

887

445

—

14

2804

246

460

—

—

22

—

244

—

508

—

57

2351

—

—

212

1387

71

1712

189

483

721

126

92

89

—

—

—

8792

107

—

216

291

157

2367

121

409

—

—

—

760

134

436

107

218

210

268

ЮООО 8000 ■

cpm/gr

•

6000 4000 — 2000 — n —

•

/

/

f

•

• л

57

72

91

107

121 135

image125

Time Monitoring (days)

FIG. 66. Tracer experimental response curve obtained at the production well HCE-28A.

image126

FIG. 67. Location map of the LGPF showing tracks of wells drilled (in red lines). Inset delineates the area where the tracer test was conducted. Well 1R8D is the tritium injector well.