The Effects of Diagenetic and Presences of Ductile Components To Sandstone Reservoir Porosity of Batu Ayau Formation, East Part of Kutai Basin, East Kalimantan

Astuti, Tri Rani P.; Putra, Ksatria Yudha; Dita, Rosmalia; Surjono, Sugeng Sapto
Geological Engineering, Gadjah Mada University, Sleman, Indonesia.

During deposition process, the compound of grain framework derived from pre-existing rock were gathered and deposited in depositional environment. Soon after deposition, burial and diagenetic process occurred. Diagenetic event has transformed primary minerals to secondary minerals, supplemented by cementation, dissolution, combined of mechanical and chemical compaction. The presences of ductile components (i.e. detrital clay matrix, platy minerals, glauconite and rock fragments) may undergo mechanical compaction and lose initial porosity and permeability more rapidly, especially related to their distribution, orientation and amounts of them. In presence of cementation, the degree of reservoir quality can increase or even decrease. Loosely packed of pore filling cements may modify primary pores to micro-intercrystalline porosity, whereas thin-enveloping of quartz overgrowth in early phase strengthen grain against further compaction and preserved adjacent pores. Replacement and dissolution process play role in enhance total pore value by creating micro-intercrystalline porosity and secondary dissolution. This paper presents results of the study on outcrop samples taken from Ritan river, Upper Kutai sub-basin, East Kalimantan. Measured section of studied area has done, added by optical petrography and scanning electrone microscope analyses. Sandstone facies of Batu Ayau Formation in Middle - Late Eocene shows poor to well visible pores, represented by primary intergranular, secondary dissolution, fracture and micro-intercrystalline pores. Overall results show that the distribution and amount of ductile components as well as authigenic minerals have in-significantly reduced porosity hence reservoir quality and this certainly valuable addition to our understanding over permeability behavior of silisiclastic rocks.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012