Reservoir Characteristics of Turbidite Sediments in Kedungjati Area, Grobogan Regency, Central Java, Indonesia

OR CHANMOLY, Dr. Sugeng Sapto Surjono, S.T., M.T.

2011 | Tesis | S2 Teknik Geologi

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Measuring stratigraphic sections (on Kerek Formation) have been done to understand the stratigraphy and facies distribution in study area. According to Ghibaudo’s classification (1992), there are four kinds of lithofacies of turbidite sedime-nts in Kedungjati area, that are Facies Sand (S), Facies Sand-mud couplet (SM), Facies Mud-sand couplet (MS), and Facies Mud (M). Based on the the physical properties of lithofacies, the sediments were deposited by turbiditic currents; and facies association indicate the dynamic sedimentation during deposition process from middle fan to outer fan of deep sea (Southeast to Northwest). The candidate facies which are the potential for reservoir rocks are facies Sand (S) and facies Sand-mud couplet (SM) in which the thicknesses of sandstones range from 0.8 to 2.5 meter. Based on the petrophysic analysis, the porosity is generally good, ranges from 8.23% to 36.34%; and the permeability is generally poor, ranges from 0.00 to 9.67 mD, except two samples are quite good permeability which reach to 96.22 and 431.30 mD. Moreover, as a result of the petrography, the sandstones are usually fine grains, rarely consist of quartz, commonly consist of planktonic foraminifera and plagioclase, and consist of much micrite and cement. Because the rocks consist of much micrite and cement that it is the reason of poor permeability. Indeed, Facies S and SM which are good porosity and permeability will lead the researchers to explore more detail of reservoir rock by shifting study area to more proximal; and facies which are poor porosity or/and poor permeability could be the second prospect of reservoir rocks.

Kata Kunci : Kerek Formation, lithofaci-es, facies association, porosity, permeability