Sandstone Facies Reservoir Properties and 2D-Connectivity of Siliciclastic Miri Formation, Borneo

Abstract

Reservoir connectivity and modeling in siliciclastic deposits are quit challenging in terms of its distribution and quality prediction. The objective of this paper is to demonstrate the different aspects of reservoir properties to construct static connectivity model and its heterogeneity distribution in siliciclastic Miri Formation, Borneo. Field description in terms of facies, distribution, and dimensions of sand bodies and rock samples, for grain-size and petrographic analysis, were used to quantify and examine seven different types of sandstones: (i) hummocky cross-stratified sandstones, with medium-to fine-grained sand with 86.4\% sand and 13.6\% mud, phi = 20.4-32.07\%, k = 6.78 md; (ii) herringbone cross-bedded, with coarse to fine-grain having 92.7\% sand and 7.3\% mud, phi = 12.2-31.3\%, k = 17.7 md; (iii) trough cross-bedded sandstones, with very-fine-to medium-sized grains having 86.6\% sand and 13.4\% mud, phi = 16.8-35.5\%, k = 5.97 md; (iv) wavy-to flaser-bedded, silty sand to very-fine-grained sand with 48.1\% sand and 51.9\% mud, phi = 7.6-19.4\%, k = 2.31 md; thickness varies from 2-9 m; (v) cross-bedded sandstone, with fine to medium grain having 89.2\% sand and 10.8\% mud, phi = 10-12.8\%, k = 12.2 md; thickness from 2-3 m; (vi) bioturbated sandstone, having silty sand to fine-grained sand with 72-86\% sand and 28-14\% mud, phi = 2.4-6.8\%, k = 5.2 md; the sandstone thickness from 1-3 m; and (vii) massive sandstone, with very fine to medium grain representing 94.8\% sand and 5.2\% mud, phi = 14-25.8\%, k = 4.3 md; thickness from 1-5 m. The results show that sandstones of HCSS and HBSC are better sorted, with minimal mud content, with the depositional pattern with increasing vertical and lateral connectivity, even in bioturbated rich sand, as compared to other sandstone facies. On the other hand, sandstones of BS and CB are of poor quality in terms of grain sorting and poro-perm. This may reflect the heterogeneity in different facies and affect the connectivity with in sand bodies.