Malay Basin.
Home waters.
A Cenozoic failed rift / pull-apart basin ~500 km long, ~200 km wide, NW–SE trend. The founder's home waters — 13+ years reading rocks offshore Peninsular Malaysia. Mature gas province with significant oil in Groups H and I. Eight groups (A youngest → M oldest) tell the story of a basin that sagged, filled, inverted, and still leaks today.
01Interactive Basin Map & Spatial Tools
Explore the tectonic envelope of the Malay Basin. Stream real Macrostrat geological tiles, inspect the Western Hinge Fault Zone, review the four founder wildcats, and click anywhere to run live bedrock queries against the Macrostrat API.
02How the basin got here
The Malay Basin is elongate — NW–SE, parallel to the Peninsular Malaysia coastline. It began as a back-arc rift in the Late Eocene, sagged through the Oligocene–Early Miocene, then inverted in the Middle–Late Miocene when regional compression squeezed the older normal faults into anticlinal traps. The post-inversion Pliocene–Recent phase is a quiet regional subsidence — but the basin is still structurally alive.
Group L/M · the basin is born
Extensional rift basin formation. Deposition of continental, lacustrine sediment in half-grabens. Source rocks for the entire petroleum system are laid down here. The crust stretches. The basement drops. The lake forms. Dead plankton begin their slow conversion to oil.
Group K, J, I · sag phase
The rift cools. The basin sags thermally. Fluvial-deltaic systems prograde from the uplifted margins — Group K coarse sandstones at the base, Group J shales, Group I siltstones and coastal-plain sands. This is the first major reservoir package.
Group H, F, E, D · the squeeze
Regional compression inverts the older normal faults. The faults reverse, pushing the hanging wall up. Anticlinal closures form. The Middle Miocene Anticline Play — the proven, highly successful play of the Malay Basin — is born here. Most of the discovered gas and oil is trapped in these Miocene anticlines.
Group A, B, C · the quiet phase
Regional subsidence. Marine transgression. The basin fills with fine-grained marine sediments. The deformation has stopped, but the basin is still settling and still leaking at the edges. The Western Hinge Fault zone — a NE–SW trending basement fault — is the active focus of the 2024–2025 wildcat campaign.
03What's in the section
Eight named groups, ~6–12 km of total section, hydrocarbon-bearing from top to bottom. The Malay Basin uses a letter scheme (Group A through M) rather than named formations — a PETRONAS convention that organises the section by major transgressive cycles.
| GROUP | AGE | LITHOLOGY | ENVIRONMENT | RESERVOIR |
|---|---|---|---|---|
| Group A | Pliocene – Recent | Marine claystone, sandstone | Shallow marine | Poor (cap rock mostly) |
| Group B–C | Late Miocene – Pliocene | Claystone, siltstone, sand | Deltaic to shallow marine | Fair |
| Group D | Late Miocene | Claystone, sandstone, coal | Deltaic to shallow marine | Excellent |
| Group E | Late Miocene | Sandstone, siltstone, shale | Fluvial-deltaic | Excellent (Dulang, Angsi) |
| Group F | Middle Miocene | Sandstone, claystone, coal | Coastal plain to deltaic | Good + regional seal |
| Group H | Early Miocene | Sandstone, shale, coal | Lower coastal plain | Excellent to Good |
| Group I | Early Miocene | Siltstone, sandstone, shale | Coastal plain to shallow marine | Good (Angsi, Sotong) |
| Group J | Early Miocene | Sandstone, shale | Fluvial-deltaic | Fair to Good |
| Group K | Oligocene – E. Miocene | Coarse sandstone, shale | Alluvial plain to lacustrine | Fair (deep play) |
| Group L/M | Oligocene | Siltstone, shale, conglomerate | Lacustrine, alluvial fan | Poor (source rock) |
04Why there is oil here
A working petroleum system needs five elements lined up in space and time. The Malay Basin has them all. The proven play is the Middle Miocene Anticline Play (Group E/F reservoirs in anticlinal closures formed by Miocene inversion). Two emerging plays are still being tested.
Group L/M lacustrine + H/I/J coal
Dual source: Type I/II lacustrine shales (deep kitchens) + Type III/II-III coal and coaly shales (coastal-plain). TOC 1.5–5.0% in coaly shales. Generation onset: Middle Miocene for H/I/J, Early Miocene for L/M.
Groups D, E, F, H, I, J (clastic)
Deltaic to fluvial-deltaic sandstones. Porosity 12–28%, permeability 10–1000 mD. Best fields: Dulang (Group E), Angsi (Groups I/J), Sotong (Groups H/I). Multiple pay zones stacked in single closures.
Intraformational shales + Group F regional
Group F marine shale is a continuous regional seal, 50–150 m thick. Intraformational shales throughout the section provide local seals. Seal-to-reservoir thickness ratio averages 1.5×.
Fault-bounded anticlines (inversion)
Middle–Late Miocene compression reversed the older normal faults, pushing hanging walls up into anticlinal closures. Seal-dependence: high (SGR-controlled). Stratigraphic pinchouts provide secondary trap type in Group H/I.
Vertical via faults, lateral via carriers
Vertical migration along fault conduits. Lateral migration along deltaic carrier beds from deep kitchens to shallow anticlinal traps. Timing: Miocene to Present (active today).
Western Hinge Fault zone (2024–2025)
LEBAH EMAS-1 (2025) opened a new play fairway along the western hinge fault zone. The hinge zone had been considered high-risk; the wildcat proved the play works. PSC awards via MBR+ (Malaysia Bid Round Plus) Round I continue to focus here.
05See it from the side
A NW–SE transect across the Malay Basin: from the Peninsular Malaysia onshore to the central basin depocentre. The surface is real SRTM; the bodies are real group assignments with reservoir/seal/source labels. The Western Hinge Fault is the structural divide; the basin axis runs through the centre; the founder wells BEKANTAN-1, PUTERI BASEMENT-1, LEBAH EMAS-1, and BUNGA TASBIH-1 are placed at the positions they actually targeted.
06Founder wells (4) — plays the founder signed off
Four PETRONAS Carigali wildcats the founder put his name on. Each one opened something — a play, a fairway, a reservoir concept, or a frontier. Together they sketch the recent evolution of the basin.
BEKANTAN-1
Appraisal and exploration well targeting Group E and H15 clastics near Cendor Graben. Proved the shallowest flowing oil discovery in Malay Basin history, demonstrating that bypassed shallow clastic reservoirs in mature basins hold material commercial pay.
PUTERI BASEMENT-1
Fractured basement play test beneath basin fill. While the crystalline basement tested water-bearing (defining charge/seal risk bounds), the well discovered commercial oil in overlying K-5 sands, de-risking adjacent structural trends and PM318 asset evaluation.
LEBAH EMAS-1
Frontier wildcat that opened a new play fairway along the western hinge fault zone. Logged 11 hydrocarbon-bearing intervals across Groups H, I, and J, confirming an active petroleum system in the margin play.
BUNGA TASBIH-1
Tested syn-rift and post-rift targets on the eastern margin. Primary syn-rift objective proved water-bearing, but the well discovered oil in post-rift Group I and J sands, recalibrating regional syn-rift risk and supporting an MBR+ Round I Small Field Asset PSC award.
07What we don't know
The Malay Basin is mature, but not closed. Four questions are open as of mid-2026. None are blocking, but all of them shape where the next wildcat goes.
○ OPEN QUESTIONS · MALAY BASIN · 2026-07
- Fault seal risk (SGR) is highly sensitive to clay-content estimates in shale gouges. The fault-bounded anticline trap depends on fault-sealing capacity; one bad gouge estimate and the closure leaks. Mitigation: high-resolution GR logs + petrophysical uncertainty ensembles.
- Deep reservoir quality degrades with depth — compaction and diagenesis reduce permeability in Group K/L below 3,000 m. The deep syn-rift play is real but the reservoir quality is the limiting factor. Mitigation: Faust/Gardner parameter checks calibrated vs core.
- Western Hinge Fault zone was just opened by LEBAH EMAS-1 in 2025. The fairway is new; the play concept is new; PSC blocks are being awarded in real time. The next 12–18 months will determine if this becomes the basin's third major play or stays a one-off.
- Source rock distribution at the deep basin axis is poorly imaged. The Group L/M lacustrine shales are the master source, but their lateral continuity and total organic carbon at depths >5 km is uncertain. Seismic + deep wells are the only path to resolution.
Where to next?
Three doors out of the dossier. Pick one — the rest stays out of your way until you ask for it.
Open the cross-section fullscreen.
The SRTM-draped regional section at full width, with the legend, structural symbols, and the four founder wells visible.
OPEN FULLSCREEN ↗ COMPARE BASINSRead the Kinabalu dossier.
Two basins, two stories. Kinabalu Basin is a fold-thrust belt shaped by collision. Malay Basin is an intra-cratonic failed rift. Same country, different tectonics.
↗ KINABALU DOSSIER LAUNCH GEOXOpen the GEOX cockpit.
The prospect-maturation pipeline takes the open questions above, attaches evidence, and returns a falsifiable plan.
OPEN GEOX COCKPIT ↗This page is the reading layer. GEOX is the intelligence layer.
arif-fazil.com/earth is where you read the basin. geox.arif-fazil.com is where you compute it — Kill Matrix K001–K007, evidence ledger (OBS/DER/INT/SPEC), abductive hypothesis, capital bridge. Evidence-first, never adjudicates.