f Microseismicity Records Active Reservoir at Karachaganak Field, West Kazakhstan

Karachaganak Petroleum Operating b.v. has been continuously monitoring using a microseismic array in the east-central part of the giant Karachaganak Field, West Kazakhstan, since February 2009. The field is producing from low porosity carbonates reservoirs comprising of a 600m Carboniferous isolated platform overlain by Permian carbonate pinnacle structures. A 200m thick oil rim is overlain by a 1000m gas column. The 8-level microseismic array is deployed in a well between 3500m and 4100m sub-sea, and each geophone level is recording with 4-component data. Until the end of March 2010, over 1200 microseismic events have been located, most of which lie within a 4 km radius of the array. They are interpreted to be due to instability at, or near, top reservoir, or to dynamic response of fault and fractures zones in the reservoir due to hydrocarbon production activities. The distribution of the former set will form part of the hazard mapping for future drilling activity and potential savings could be many rig days, a costly side track or even avoiding a junked well. The latter type indicates some of the lateral and vertical reservoir boundaries or baffles and will result in a refinement of the static and dynamic reservoir models.