ERIC ROP

RESERVOIR ENGINEER

KENGEN, KENYA

INVESTIGATION OF THEPOSSIBILITY OF USINGHYDRAULIC FRACTURING ASA METHOD OF ENHANCING WELLPRODUCTIVITY AND INJECTIVITY INOLKARIA, KENYA.

INTRODUCTION

• Geothermal prospect areas in Kenya• Located within the Kenyan Rift system• 1st power plant of 45 MWe (1981-1985)• Field size about 204 km2

• Divided into seven (7) sectors• Total installed capacity 212 Mwe• Present assessment-additional 900 Mwe• Implementation phase of 280 mwe

LOCATION OF OLKARIA GEOTHERMAL AREA

OLKARIA DIVIDED TO 7 SECTORS

OLKARIA 280MW PROJECT

• Total of 66 wells drilled; both injection and production

• Costs 2.7 Million Dollars in Olkaria per well• Average power per well of 7 Mwe• Target average was 5 Mwe• Some wells are dry or poor producers but

with temps above 300 c00

• Tight with poor permeability• Failure to strike natural fractures

WELL PRODUCTVITY AND INJECTIVITY IMPROVEMENT

• Three possible ways of improving well permeability:

1. Hydraulic fracturing-pumping water propant mix at high pressures to break rocks

2. Explosive fracturing –use of explosives to break rock

3. High energy gas fracturing-propellants burn more slowly and push fractures some distance from the well bore

HYDRAULIC FRACTURING

• First treatment was pumped in 1947 on a gas well operated by Pan American Petroleum Corporation in the Hugoton field

• To compare with acidizing• successfully used well stimulation method

in petroleum industry• Involves pumping propant water mix at

high pressures enough to fracture formation

HYDRAULIC FRACTURING CONTD

• Propant not commonly used in geothermal applications –expensive

• Improves permeability on damaged wells during drilling

• Increases injectivity index or productivity index

• Economic viability of EGS projects critically dependant on the method

HYDRAULIC FRACTURING JOB DESIGN LAYOUT

WELL STIMULATION IN OLKARIA

• Step pumping done at 1000 lpm,1300 lpm,1600 lpm and 1900 lpm

• Improves well permeability by reducing skin effect

• Pumping rates too low to cause appreciable fracturing

• Enables the evaluation of well injection capacities and permeability

PRESSURE BUILD IN OW-915

PRESSURE BUILD IN OW-907A

OLKARIA PUMPING TEST RESULTS

• sudden decrease in pressure after 2 1/2 hrs pumping in OW- 915

• sudden decrease in pressure after 7 1/2 hrs pumping in OW- 907A

• Indication of improved permeability• Possibly through reduced well bore

damage or• Formation fracturing

CASE STUDY 1: WAYANG WINDU GEOTHERMAL FIELD

• Injection test done on 4 wells, WWQ-2 WWQ-3, WWA-2 and WWQ-4

• pumping rate was increased in 8 steps from 22 l/s to 54 l/s

• Steam production improved by 100% from 4 kg/s up to 8.5 kg/s in WWQ-2

• Steam production improved by 50% from 4 kg/s up to 6 kg/s in WWA-2

• Open fracture created in WWQ-3, no fracture in WWQ-4 due to insufficient pressure

PRODUCTION TEST RESULTS FOR WWQ-2

CASE STUDY 2: GEOTHERMAL WELL STIMULATION IN THE US

• Done under DOE Geothermal Reservoir Well Stimulation Program (GRWSP) in 1979

• 7 experiments were conducted• Experiment 1- Reverse flow technique used • Resulted in 5 times productivity improvement• Experiment 2-convetional hydraulic fracture

treatment used• 50000kg/hr flow rate achieved• Experiment 3 & 4-planar- type hydraulic

fracture

CASE STUDY 2: GEOTHERMAL WELL STIMULATION IN THE US

• Achieved production improvement of 114% yielding commercial flow of 90 tonnes/hour

• Experiment 5- nonproductive, 70 m isolated using an experimental high temperature Otis packer with EDPM elastomeric elements.

• Post-stimulation tests indicated a fracture had been successfully created

• single fracture 100 m high and about 160 m long created

• Experiment 6 -HCl etching treatment was done

CASE STUDY 2: GEOTHERMAL WELL STIMULATION IN THE US

• No productivity improvement was achieved

• Experiment 7- high viscosity fracturing fluid with sintered bauxite proppant

• Tests indicated highly conductive fracture was achieved with a length of over 100 m.

• Unfortunately poor productivity achieved

CASE STUDY 2: GEOTHERMAL WELL STIMULATION IN THE US

• Fracture treatments in Raft River and those in Baca succeeded in getting significant production from previously non-productive intervals

• In fractured systems, new fractures are created or reopened

• they run parallel to existing permeable fractures and do not connect to them

• Medium producing wells should also be tested

CASE STUDY 3: HYDRAULIC FRACTURING AT THE EUROPEAN

HDR/HFR SITE• Performed successfully in the Hdr/fr test site in

Soultz-SOUS -FORÊTS (France)• Underground heat exchanger formed by a

hydraulically stimulated fracture system.

• High injection rates and pressure created large fracture systems in the crystalline basement between 3 and 5 km depth

• Injectivity and productivity of the boreholes GPK1 and GPK2 enhanced by more than 100%

EGS DEVELOPMENT CYCLE

CONCLUSION

• Hydraulic fracturing greatly improves well permeability

• Well injectivity and productivity index can improve

• Success of EGS systems depends on hydraulic fracturing technique

• Investment in hydraulic fracturing should be encouraged by the stakeholders to improve the technology

• Drilling projects costs can be greatly reduced

Thank you for your attention