The Karachaganak Field is an oil and gas condensate reservoir in northwest Kazakhstan. This field covers an area of 280 square kilometres, with a hydrocarbon column extending over 1 km in thickness - from the Permian pinnacle reefs down into the Carboniferous and Upper Devonian platform carbonates. Discovered in 1979, this field now has over 230 wells, with data from these wells showing a very heterogeneous reservoir that is difficult to characterize. The current Formation Evaluation (FE) database contains a mix of older vintage wells (Former Soviet Union logs, cores, well tests) and new wells with recently acquired core, logs, production logs and well tests. With Karachaganak nearing full-field development, an investigation is underway to determine the optimal FE acquisition necessary to evaluate the reservoir. A recent well, consisting of a 45 degree main bore and a lateral sidetrack, was chosen as a test well to run a variety of wireline and LWD logs. In addition to logging, over 250m of core was taken in the 45 degree portion of the main bore. The LWD string run in the 8 ½" main bore was the most complex ever run in Kazakhstan, with the full suite of standard logs (Gamma Ray, resistivity, neutron, and density), full-waveform sonic, magnetic resonance and formation pressure tester. The pipe conveyed logs also contained a full suite of data comparable to that run on LWD (minus the magnetic resonance). Image logs and formation pressures were obtained from both LWD and wireline tools. All of this data was thoroughly evaluated and integrated with core analyses results. Based on this evaluation, an optimal FE acquisition strategy has been developed for future wells. Examples from this test well, showing log-core integration, along with LWD-to-wireline comparisons will be presented as part of this paper.
Located in northwest Kazakhstan, the Karachaganak Field is a giant oil and gas condensate reservoir, comprising of more than 1,200 million tons of oil and condensate and over 1.35 trillion m3 gas. The reservoir lies about 4 km below the surface and at the crest is over 1.5 km in thickness and covers an area more than 280 km2. The reservoir is a carbonate massif that consists of heterogeneous reef (Permian) and platform carbonates (Carboniferous, Devonian) – primarily limestone and dolomite, with overall low porosity and permeability.
(Figure in full paper)
Discovered in 1979, Karachaganak has been operated since January 1998 by a joint venture now known as Karachaganak Petroleum Operating b.v. (KPO). This joint venture is made up of four international parent companies: BG Group and Eni, each with 32.5% interest, Chevron with 20% and Lukoil with 15%. Prior to 1998, over 220 wells were drilled by Russian or Kazakh oil companies. Since late 2001, KPO has deepened several existing wells which had previously terminated above the reservoir in what is referred to as Phase 2. KPO has also drilled several new wells from surface - including high angle or horizontal wells and several multi-lateral wells - in what is referred to as Phase 2M.
