Loei

Collaborating Authors

Ultrasonic Wave Properties of Weathered Sandstones in Khorat Group and Their Factors Affecting

Sukplum, W. (Khon Kaen University) | Wannakao, L. (Khon Kaen University)

OnePetroMay, 2019

Abstract: This research intends to use the ultrasonic properties of the rocks to classify weathering grade of sandstones and to correlate their physical and mechanical properties. Sandstone specimens were collected from Nam Phong (NP) and Phra Wihan (PW) Formations, Khorat Group, Northeast Thailand. Three weathering grades were categorized as fresh (I), slightly weathered (II) and moderately weathered (III). Petrofabric of both NP and PW sandstones at each degree of weathering were observed. Physical properties and uniaxial compressive strength tests were also conducted in the laboratory. Both ultrasonic compressional (Vp) and shear (Vs) wave velocities of the rocks were measured. The results of the research indicated that the ultrasonic wave velocities decrease as increasing of degree of weathering and porosity. On the contrary, the wave velocities increase as increasing percentage of quartz, density and uniaxial compressive strength. 1 Introduction The strength and other engineering properties of rock materials were usually reduced when the rocks are weathered. In generally, weathering is the process which changes the properties of rock mass due to changing the environment conditions such as physical, chemical and biological. Khorat Group, the non-marine red-beds sandstone, forms mostly in the Khorat Plateau, Northeast Thailand which is in tropical area (Figure 1). Sandstone is a sedimentary rock that composed of sand-sized grains of mineral, rock fragments, or organic material. It also contains the most common cementing materials that are silica and calcium carbonate; accordingly, it is very moisture-sensitive and easily weathered due to reaction with water. Thus, the authors interested in weathered sandstone of the Khorat Group. This Group was named by Ward & Bunnag (1964) who subdivided the group into 9 Formations, namely from older to younger sequences (Triassic to Cretaceous) as, Haui Hin Lat, Nam Phong, Phu Kradung, Phra Wihan, Sao Khua, Phu Phan, Khok Kruat, Mahasarakarm and Phu Thok Formations. The rock samples in this research were taken from Nam Phong and Phra Wihan Formations that Nam Phong Formation deposits in Triassic and Phra Wihan Formation deposits in Cretaceous. The Nam Phong Formation has a type section along the Nam Phong stream and distributes along with the Loei-Phetchabun Fold Belt and the western regime of the Khorat Plateau. The formation consists of resistant red-brown micaceous sandstone, siltstones, mudstones, and conglomerates of fluvi-atile origin (Chonglakmani 2011). The Phra Wihan Formation is widely distributed, occurring in the Phu Phan Rang and around the western and particularly the southern rims of the Khorat Plateau. Generally, the rock consists of light buff to gray, fine to coarsegrained quartzitic sandstones and rare siltstones and mudstones with occasional conglomerates (Meesook 2011).

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ISRM

ISRM-RDS-2019-022

ISRM Rock Dynamics Summit

Country:

Europe > Norway > Norwegian Sea (0.25)
Asia > Thailand > PheTchabun > Phetchabun (0.24)
Asia > Thailand > Loei > Loei (0.24)
Asia > Middle East > Turkey (0.15)

Geologic Time:

Phanerozoic > Mesozoic > Cretaceous (0.45)
Phanerozoic > Mesozoic > Triassic (0.45)

Geophysics: Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.46)

Industry:

Energy > Oil & Gas > Upstream (1.00)
Materials (0.89)

Oilfield Places:

North America > United States > Wyoming > Bighorn Basin (0.99)
North America > United States > Montana > Bighorn Basin (0.99)
Europe > United Kingdom > England > London Basin (0.91)

SPE Disciplines:

Well Drilling (1.00)
Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.87)
Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.70)

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Mounds and Boundstone Facies in the Late Carboniferous Early Permian Pha Nok Khao Formation-equivalent of the Loei Syncline, Loei-Phetchabun Foldbelt: Implications for Reservoir Quality

George, Annette | Lazar, Shahar (University Of Western Australia) | Booth, John (Auldana Advisors Corporation)

OnePetroNovember, 2011

Abstract Late Carboniferous-Middle Permian carbonate platforms are major petroleum reservoirs in the Khorat region of northeastern Thailand. Previous sedimentological work on these platforms in outcrop and core highlighted the dominance of platform interior (subtidal to intertidal) facies and platform margin (shoal) facies, with minor boundstone facies typically associated with the platform interior (e.g. phylloid algal mounds). Reservoir quality reflects depositional and diagenetic controls on porosity and permeability development, notably dissolution of skeletal components and dolomitisation of platform-margin bioclastic facies, and/or faulting and fracturing associated with post-depositional (Triassic and younger) collisional tectonics. An outcrop analog study of the Pha Nok Khao-equivalent platform in the Loei Syncline (northern part of the Loei-Phetchabun Foldbelt, LPF) shows that diverse platform-margin boundstones were locally developed. Three features of the study are highlighted:sandy shoal facies include diverse encrusting organisms (such as Tubiphytes) suggest local binding and stabilisation; phylloid algal mounds, including large mounds up to 10 m high and 30 m long grew in outer platform to upper slope settings and are associated with off-mound grainstones-rudstones that also contain clotted fabrics and in situ growths of calcimicrobes and/or calcareous algae; and calcimicrobes are a notable component in boundstones and other features such as abundant peloids in phylloid algal mounds also attest to microbial activity. The importance of boundstone/reefal facies as reservoirs is well known in Permian basins worldwide and recognition of more widespread boundstone facies in the LPF has important implications for the distribution and quality of reservoir facies in ongoing production in nearby fields and an active exploration program. A potential subsurface analogue may be recorded in the Dong Mun Field. The distribution of bound fabrics/mounds is consistent with the distribution of 'clean' skeletal facies and both indicate that higher energy oceanographic conditions prevailed along the western and northern/northwestern margins of the platform (modern-day orientation). Large mounds with stylolite-associated porosity and adjacent microbialite/grainstone facies represent an alternative exploration target to dolomitised grainstone-packstone facies with vuggy and intercrystalline porosity.

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doi: 10.2523/IPTC-15256-MS

IPTC

IPTC-15256-MS

International Petroleum Technology Conference