Study of Porosity Analysis for Silisiclastic Reservoir Rock Based on Log Data in Talangakar Formation, Field "X"€, North West java Basin.

Abstract

"€œX€" Field is exploration field on Cipunegara Blok that becomes concession area of PT. Pertamina EP Jakarta. The exploration target of this are focused on Talangakar Formation. Scanning of data recording of wireline logs results on wells show reservoir heterogenity induce on silisiclastic reservoir rocks porosity (sandstone) so that impact on reservoir quality. Therefore, analysis study for reservoir rocks porosity required. The porosity study for reservoir geology could performed based on quality with identify litology type, identify kinds of fluid, analyze the facies and sedimentation environment and in quantity performed through petrophysic account (porosity, permeability, water saturation, water resistivity, and volume shale) with data value reading of well log. In this research used by a research method in the form of descriptive and analysis that is analysis with the method of shaly sand interpretation. Wells on research area (HRY#1, HRY#2 and HRY#3) arranged by rocks such as sandstone, limestone, siltstone, coal, and shale. The porosity value of silisiclastic reservoir rocks (sandstone) that is 3-26%, the volume shale are > 15%, and permeability is good enough (5 – 100%). Development facies on each well are shallow marine sheet sandstone facies, crevasse splay facies, swamp, distributary channel, distributary mouth bar. The facies sedimented on sedimentation environment fluvial meandering stream – delta and shallow marine / inner nertitic. The difference of sedimentation environment causes diversity of reservoir quality. Increasingly toward land (fluvial sedimentation environment) then reservoir quality would be worst because the porosity value get smaller (7%). As on contrary, increasingly toward marine then the porosity value get bigger (13 – 15%) and causes the reservoir getting better. After the reservoir quality and values from petrophysic calculation identified, then it could be determine that is prospect zone for hydrocarbon. Prospect zone of hydrocarbon at Well HRY#1 was exist at depth of 2790,0-2796,0 meter and 2825,5 – 2831,5 meter. Prospect zone of hydrocarbon at Well HRY#2 was exist at depth of 2632,0 – 2635,5 meter; 2637,5 – 2641,5 meter and 2729,0 – 2731,5 meter and prospect zone of hydrocarbon at Well HRY# 3 was exist at depth of 2840,0 – 2848,0 meter. Key word : Talangakar, Log, Petrophysic, Porosity