Chow Weng Sum

Review on microfossil records of the Kinta valley sequences

Kinta valley was a focus of interest in search of geological resources for the last ten decades. Most of those studies were oriented to reveal the genesis of tin mineralization. Few workers including the current authors have identified some micro faunal (bivalves, gastropods, rugose corals, foraminifera, crinoids) records for relative dating of the limestone sequences. Even though present day accessibility of the reported fossiliferous sites is limited; areas which are dated based on the fossil records in Chemor (Silurian to Devonian), near Batu Gajah (Devonian), Malim Nawar (Carboniferous), Tualang limestone (Carboniferous to Permian), Kampar (Permian), and Kampung Sungai Keruh (Permian), are part of the Kinta valley limestone. The age difference in the limestones is interpreted as a result of migration of the coral reefs in the palaeodepositional setting. This current study will review the fossil collections of the JMG in Ipoh in order to test these original age determinations. We will demonstrate how these historic collections and macrofossil will contribute to our new research project. Furthermore, we will outline how these data will contribute to our ongoing research into defining a reference stratigraphic section that will enable correlation between scattered outcrops in the western Belt of Peninsular Malaysia.

Lithostratigraphy of Paleozoic Carbonates in the Kinta Valley, Peninsular Malaysia: Analogue for Paleozoic Successions

Tectonics of the Paleo-Tethys resulted in the formation of three distinct stratigraphic zones in Peninsular Malaysia, namely western, central, and eastern zones. The western zone encompasses extensive carbonate sediments, among which is the Kinta Limestone, which forms a major Silurian to Permian lithological unit. Subjection to diagenetic and thermal alteration of this succession and paucity of unweathered and accessible outcrop sections posed constraints on precise characterization of lithofacies. A few localities in the northern part of the valley indicate preservation of primary sedimentary/geochemical features with variable thermal alteration. Drilling campaign to recover a continuous succession, followed by geophysical logging allowed lithological characterization and detection of stratigraphic surfaces. The present study attempts to characterize the other monotonous Kinta Limestone into mappable units with defined stratigraphic surfaces that were not obvious from outcrops. Core profiles, natural gamma-ray, density, and caliper logs were used to interpret stratigraphic surfaces. Low gamma-ray and density values with near-shale baseline spontaneous potential were noted on the studied sections. Major caving and higher peaks of gamma-ray corresponding to siliciclastics were resulted perhaps from potassium and thorium. The lower gamma-ray readings of the Kinta Limestone may also show presence of little detrital mixing in the carbonates. This is in good agreement with the mineralogical composition that showed the dominant occurrences of calcite, followed by dolomite and low detrital silica. The stratigraphic surfaces between the siliciclastics and limestone are represented by sharp contact surfaces. The logs showed synergy with lithological and stratigraphic interpretations on the cores and outcrops, and this may facilitate local and regional correlations. This may advance the understanding of the Paleozoic basins and serve as analogue for wireline log signature in the Paleo-Tethys basins.

Bilinear Extrapolation for Geocellular Reservoir Connectivity and Flow Simulation

Reservoir connectivity is one of the main subsurface uncertainties in the assessment and improvement of many oil and gas fields. The main objective of this paper is to analyze the static and dynamic connectivity of the selected shallow-marine sandstone facies through construction of gridded-based units for flow behavior/patterns. Prior to the generation of the sandstone facies connectivity and flow simulation, outcrop log data are input into the modeling software. The exposer used for the facies connectivity and flow simulation was ranging from 1 to 500 cm. The measurements of permeability values were taken on each of the grid, which were bilinear extrapolated, to populate the surface with permeability variation. Detailed analysis of the sedimentology and interpretation of three major sandstone facies is used as a framework to build the geocellular facies connectivity and flow simulation. The sandstone facies of HCSS shows more uniform and have linear connectivity, fallow by sub-layer gridding. In case of HBCBS, horizontal sweep is more effective as compared to vertical, because of thin mudstone deposited at the base of each layer boundaries which resist to sweep vertically. Whereas TCBS, WFBS, and BS show the distribution of different qualities of sandstones and bioturbation in the grid block model, burrows filled with mud which acts as impermeable pathways within moderate to low-quality sandstone.

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

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, O = 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, O = 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, O = 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, O = 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, O = 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, O = 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, O = 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.

Construction in Terrain with Subsurface Karstic Limestone Bedrock

About 80 % of the Kinta Valley and 40 % of the Kuala Lumpur area, both of which are densely populated, are underlain by limestone bedrock. Dissolution of the limestone bedrock by the slightly acidic rainwater which seeps into the bedrock along discontinuities gives rise to a subsurface karstic morphology with features like steep pinnacles and deep troughs, overhangs, boulder floaters, an intricate network of cavities beneath the bedrock surface and sinkholes. At the interface between the bedrock and the overlying soil, there is a pocket of very soft, compressible soil with zero SPT value. All these features and characteristics pose a big challenge to engineers in the design of foundation of buildings. To obtain a comprehensive profile of the karstic bedrock, it would be prudent to conduct an integrated geophysical survey utilizing georadar, seismic and resistivity methods complemented with a few boreholes for ground truthing.

Palaeogeographic Evolution of the Southeast Asia Palaeozoic Carbonate Complexes

Amalgamation and accretion of Southeast Asia continental blocks has occurred during the Late Devonian to Late Cretaceous tectonic movements, its consequences led to the closure and opening of oceanic basins, and orogeny. The Southeast Asia carbonate complexes shared the same regional tectonic history of uplifting, faulting and compressional strains. The main Terranes of the present Southeast Asia were located within the palaeo-Thethys in an equatorial latitudinal setting in Permian period and the geological dating of the carbonates imply presence of regional relationship between carbonate buildups. Paleomagnetic data in northwestern Malaysia, biogeographic evidence throughout India, Australia, and China with palaeoclimatic conditions in the region were favored carbonate growth and might suggest that the Palaeozoic limestone formed continuous carbonate chain in the region, from Malaysia to Thailand. In addition to the microfossils, the absence of siliciclastics within the limestone sequences and syndepositional slope structures are considered as evidences for deeper depositional setting.