THESIS — PIT N
A five-well, source-led reconstruction of Seams A1–D that keeps core lithology, clay partings, gamma-ray and density response, marker correlation and three-dimensional interpolation in one auditable chain. The model is strongest inside the borehole-control polygon; depositional and geometric certainty decreases beyond it.
ALBUM
51 records
The geological map fixes the spatial problem before any facies or model interpretation begins: Pit N, mapped coal traces and the borehole collar distribution are shown in one reference frame. Boreholes constrain the subsurface only where they exist, so confidence should decrease away from collars and along extrapolated seam edges.
The stratigraphic column orders the Muara Enim coal succession and its intervening clastic units from Seam D upward to A1. It provides the naming framework used by the core panels, electrofacies and three-dimensional surfaces, but does not by itself establish thickness continuity.
The Pit N view is dominated by an anthropogenic open-pit landscape—excavated benches or walls, haul access, spoil and exposed working surfaces—with residual natural low hills around the operation. Calling the entire scene a natural geomorphic unit would erase the process that now controls slope form, drainage and exposure.
The source places Seam D at about 142–147 m in RTB 09 and 181–185 m in RTS 01; the correlated coal interval is approximately 4 m thick and is described as banded coal, locally with a clay band or parting. In the thesis evidence chain, the photograph records recovered material and superposition but does not directly demonstrate between-well continuity.
Seam C is traced through five boreholes and is described as an 8–14 m banded-coal interval containing a clay parting; the larger control count makes it better constrained laterally than Seams D, B2, B1, A2 or A1.
The C–D interburden is represented by very fine- to fine-grained sandstone and siltstone, locally coarser, with flaser, wavy and lenticular bedding. Those heterolithic structures record alternation between traction and suspension fallout, but they do not, on their own, distinguish tidal modulation from other fluctuating-current processes.
The panel correlates Seam B2 at approximately 104–109 m in RTB 11, 107–112 m in RTS 74 and 161–165 m in RTS 06. Across those three wells the source treats it as a roughly 4–5 m banded-coal interval.
The B2–C interburden is dominated by very fine sandstone and siltstone. Its heterolithic character is the principal core observation; environmental assignment requires bed-boundary relationships, sedimentary structures and lateral persistence rather than a log motif alone.
Seam B1 is correlated through RTB 11, RTS 74 and RTS 06 as a comparatively thick, approximately 9–14 m coal body. Clay partings of roughly 0.5–2.5 cm are recorded within the seam and must be carried into any clean-coal thickness or quality calculation.
Between B1 and B2, the source describes pale grey claystone and siltstone with fine heterolithic layering. This interval is a correlation separator as well as a depositional record, so thickness changes must be distinguished from drilling loss, core breakage and marker-pick uncertainty.
Seam A2 is represented in three boreholes as an approximately 12–15 m banded-coal interval. The source records clay bands or partings about 2–15 cm thick, so the apparent seam envelope is not equivalent to uninterrupted clean coal.
The A2–B1 package contains heterolithic fine-grained clastics and the Suban marker used in the source correlation. Its value lies in the conjunction of lithology, marker position and log response; none of those components should be treated as an independent chronostratigraphic datum without regional calibration.
Seam A1 is correlated in RTB 11, RTS 74 and RTS 06 at approximately 29–37 m, 14–24 m and 87–96 m respectively. The source describes a variable 3–10 m seam with clay bands or partings about 2–8 cm thick beneath a mudstone–shale roof.
Seam A1 is correlated in RTB 11, RTS 74 and RTS 06 at approximately 29–37 m, 14–24 m and 87–96 m respectively. The source describes a variable 3–10 m seam with clay bands or partings about 2–8 cm thick beneath a mudstone–shale roof.
The A1–A2 interburden is described as fine, locally tuffaceous sandstone with subordinate finer beds. Volcanic input may aid recognition, but a tuffaceous appearance is not automatically an isochron unless petrography or geochemistry demonstrates a correlatable event bed.
The thesis panel tests the core pick for Seam D against wireline response in two boreholes. A relatively low gamma trace and boxcar-to-cylindrical geometry support recognition of a low-clastic interval; brief departures from that motif are evaluated against partings seen in core.
The thesis panel tests the core pick for Seam C against wireline response in five boreholes. A relatively low gamma trace and boxcar-to-cylindrical geometry support recognition of a low-clastic interval; brief departures from that motif are evaluated against partings seen in core.
In the thesis correlation, the C–D is bounded by coal markers already identified in core.
The thesis panel tests the core pick for Seam B2 against wireline response in three boreholes. A relatively low gamma trace and boxcar-to-cylindrical geometry support recognition of a low-clastic interval; brief departures from that motif are evaluated against partings seen in core.
In the thesis correlation, the B2–C is bounded by coal markers already identified in core. The irregular gamma motif is consistent with the observed alternation—the b2–c interburden is dominated by very fine sandstone and siltstone—but the curve is an averaged petrophysical response rather than a facies name.
The thesis panel tests the core pick for Seam B1 against wireline response in three boreholes. A relatively low gamma trace and boxcar-to-cylindrical geometry support recognition of a low-clastic interval; brief departures from that motif are evaluated against partings seen in core.
In the thesis correlation, the B1–B2 is bounded by coal markers already identified in core. The irregular gamma motif is consistent with the observed alternation—between b1 and b2, the source describes pale grey claystone and siltstone with fine heterolithic layering—but the curve is an averaged petrophysical response rather than a facies name.
The thesis panel tests the core pick for Seam A2 against wireline response in three boreholes. A relatively low gamma trace and boxcar-to-cylindrical geometry support recognition of a low-clastic interval; brief departures from that motif are evaluated against partings seen in core.
In the thesis correlation, the A2–B1 is bounded by coal markers already identified in core. The irregular gamma motif is consistent with the observed alternation—the a2–b1 package contains heterolithic fine-grained clastics and the suban marker used in the source correlation—but the curve is an averaged petrophysical response rather than a facies name.
The thesis panel tests the core pick for Seam A1 against wireline response in three boreholes. Here the diagnostic target is the coal-top boundary: the upward change into a finer, generally higher-gamma roof is more important than the shape of the coal trace in isolation.
The thesis panel tests the core pick for Seam A1 against wireline response in three boreholes. Here the diagnostic target is the seam body, including short departures from the low-gamma motif that can be tested against the documented internal partings.
In the thesis correlation, the A1–A2 is bounded by coal markers already identified in core. The irregular gamma motif is consistent with the observed alternation—the a1–a2 interburden is described as fine, locally tuffaceous sandstone with subordinate finer beds—but the curve is an averaged petrophysical response rather than a facies name.
The five-well panel is the central correlation test because it places lithofacies, seam picks and interpreted stratigraphic packages side by side. A correlation is credible where marker order, core character and log response remain coherent without implausible thickness jumps; it weakens where picks depend on one motif or cross long uncontrolled distances.
The topographic model spans source-reported elevations of roughly 69–99 m and carries the borehole collars used to construct the seam surfaces. Its job is geometric control: collars must sit on the correct surface, elevations must share one datum and no seam should cross above terrain.
The A1 structure-contour and surface pair is built from three boreholes, an interpreted thickness range of about 3–10 m, and a source-reported attitude of N310°E/18° NE. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The A2 structure-contour and surface pair is built from three boreholes, an interpreted thickness range of about 12–15 m, and a source-reported attitude of N306°E/25°. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The B1 structure-contour and surface pair is built from three boreholes, an interpreted thickness range of about 9–14 m, and a source-reported attitude of N287°E/33°. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The B2 structure-contour and surface pair is built from three boreholes, an interpreted thickness of about 4–5 m, and a source-reported attitude of N291°E/24°. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The C structure-contour and surface pair is built from five boreholes, an interpreted thickness range of about 8–14 m, and a source-reported attitude of N299°E/28°. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The D structure-contour and surface pair is built from two boreholes, an interpreted thickness of about 4 m, and a source-reported attitude of N291°E/30°. Contours summarize the interpolated roof or floor elevation; they are not additional measurements between boreholes.
The stacked three-dimensional view assembles all principal seam surfaces into one geometric hypothesis. Correct superposition and broadly coherent dip are encouraging, but they are necessary rather than sufficient tests: independently interpolated surfaces can look orderly while carrying the same biased picks.
This section converts the three-dimensional seam stack back into a two-dimensional geological test. Vertical spacing, local thickness and surface continuity can be compared directly with borehole intersections, making the section more diagnostic than an oblique 3D view.
The strike-oriented section should display comparatively small apparent dip if its orientation is genuinely close to strike. Departures from that expectation may record seam undulation, structural complexity, changing strike or simply a section that is oblique to the local surface.
The dip-oriented section is the clearest view of down-dip seam separation and the cumulative geometry of the coal-bearing stack. Source-reported dips range from about 18° to 33° among the seams, so exact parallelism should not be assumed.