eric rop reservoir engineer kengen, · 2019-09-02 · kengen, kenya. investigation of the...
TRANSCRIPT
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