Olkaria reservoir response36Ofwona3.3 Injection / re-injection in Olkaria IWell OW-3. A tracer and injection test experiment was done in well OW-3 from April to September1993 (Ambusso, 1994). Cold fresh water at 18°C from Lake Naivasha was injected in this wellcontinuously for 172 days at an average rate of 100 t/hr (27.78 kg/s). 125 kg of Sodium fluoresceindye was introduced as a slug after 45 days of injection. Production and chemical changes wereobserved in wells OW-2, 4, 7, 8, 10 and 11. Chloride decline occurred in wells OW-2 and 4 during theinjection period and tracer returns were observed in wells OW-4, 2 and 7 with OW-4 registering thehighest recovered mass of about 38 %, well OW-2, 0.1 % and well OW-7, 0.07 % (Ofwona, 1996).Hot re-injection of separated brine from wells OW-27, 31 and 33 has been going on in this well (OW-3) since May 1995 at approximately 13 t/hr (3.6 kg/s).Well OW-12. Tracer/injection test experiment was done in this well from 12.7.96 to 1.9.97. Coldfresh water from Lake Naivasha was injected continuously at an average rate of 100 t/hr (27.78 kg/s)for 416 days. 500 kg of Sodium fluorescein tracer was introduced as a slug after 20 days of injection.Wells around OW-12 were monitored for chemical and output changes. High tracer returns wereobtained from wells OW-15, OW-16 and OW-19. The same wells also experienced drastic decline inchloride concentration and enthalpies with big increase in water flow.Well OW-R3. Tracer/injection test experiment was done in this well from May 1995 to July 1.9.96.Cold fresh water from Lake Naivasha was injected continuously at an average rate of 100 t/hr (27.78kg/s) over the duration of the experiment. 500 kg of Sodium fluorescein tracer was introduced as aslug after 27 days of injection. Wells close to OW-R3 were monitored for chemical and outputchanges. Very little tracer returns were obtained from wells OW-25, OW-29 and OW-30 and nonefrom the closest wells OW-32 and 34. There was also very little or no change at all in the fluidchemistry as well as production output from the neighbouring wells.3.4 Hot re-injection in Olkaria NortheastHot re-injection in Olkaria Northeast field is infield and is done in wells OW-R2, OW-R3, OW-703and OW-708. By the end of 2004, a total of 4,895,726.5 tones of hot brine had been re-injected intothe field with 1,186,266 tons flowing into OW-R2, 1,057,768 tons flowing into OW-R3, 1,105,296tons into OW-703 and 1,546,397 tons flowing into OW-708 (Mwawongo, G. M., 2004). Tracer testshave been conducted in well OW-708 and returns were observed in wells OW-712. Monitoring ofthese wells for the effect of re-injection is ongoing but preliminary results show that there is positiverespone.Cold condenser blowdown from Olkaria II plant is injected in wells OW-201 and OW-204 in OlkariaCentral field. By end of 2004, a total of 708,261.5 tons had been re-injected into the two wells.3.5 Pressure response due to productionDue to high demand for steam, no wells within Olkaria I production field were available formonitoring pressure response due to production. Only well OW-3 and well OW-9 were consideredunsuitable for production and could have been used for this purpose but well OW-3 was used for fieldinjection experiments and well OW-9 had internal flow and was also later on plugged due to its closeproximity to the project offices. However, well OW-8 offered some good pressure decline history.This well was first drilled to 1080 m in November 1978 and intercepted permeable zones at 600 - 700m and 900 - 1080 m depth. It was then deepened to 1600 m in 1983 intercepting more permeablezones at 1300 – 1400 m. It remained shut-in from 1979 to 1983 and again to September 1985 when it
Ofwona37Olkaria reservoir responsewas connected to the steam supply system. Production from this well continued until October 2000when it was shut-in. It has remained shut-in to date and is now used as pressure monitoring well.
Change language