Thailand has been producing domestic petroleum from both onshore and offshore areas as shown on the concession map (Figure 1) since 1981 and its proved petroleum reserves by the end of 2023 consisting of 111.99 MMbbl of crude oil, 4,585.78 Bcf of natural gas and 127.89 MMbbl of condensate, or a total of 1,027.31 MMBOE (Table 1).

or a total of 1,027.31 MMBOE (Table 1). In 2023, the country supplied approximately 0.563 MMBOED from indigenous resources, comprising 12.48% crude oil, 75.33% natural gas (MTJA included) and 12.19% condensate. However, these indigenous petroleum supplies account for only 28% of the country’s total daily consumption. The remaining 72% of demand is acquired from abroad in order to meet the country’s energy demand. To enhance national energy security and reduce reliance on energy importation, the Department of Mineral Fuels, Ministry of Energy, has continually promoted and accelerated exploration and development of indigenous resources. The effort involves studying the petroleum potential in the present non-concessioned areas which had been explored and relinquished by previous concessionaires. The studies have revealed that some areas still have promising petroleum potential with a high chance of success for future commercial discoveries.

Table 1 Summation of Total Domestic Petroleum Reserves (By the end of 2023)
Source: Annual Report 2023, Department of Mineral Fuels (page 95).

Therefore, the Ministry of Energy would like to announce a new bidding round, the 25^th bidding round, to promote both the continuity of petroleum production and the new discovery of resources. This bidding round encompasses nine exploration blocks in the Northeast and Central Regions of Thailand, namely L1/66, L2/66, L3/66, L4/66, L5/66, L6/66, L7/66, L8/66, and L9/66 (Figure 2). These nine onshore blocks cover a total area of 33,444.64 sq.km. Notably, four out of nine blocks L1/66, L3/66, L6/66, and L9/66 cover the previously approved and subsequently relinquished production areas. These blocks are surrounded by numerous existing production fields, for example Sin Phu Horm, Dong Mun, SW1, L33/43, L44/43, L53/43, L54/43, L53/48.

The nine onshore exploration blocks, L1/66, L2/66, L3/66, L4/66, L5/66, L6/66, L7/66, L8/66, and L9/66 are located in the Northeast and Central Regions of Thailand. Detailed descriptions of these blocks are shown as follows:

1. Block L1/66 has an area of approximately 3,223.51 sq.km. containing relinquished L15/43 production area and is surrounded by Sin Phu Horm production field.

2. Block L2/66 has an area of approximately 3,917.03 sq.km.

3. Block L3/66 has an area of approximately 3,918.22 sq.km. and is surrounded by Dong Mun production field.

4. Block L4/66 has an area of approximately 3,656.65 sq.km.

5. Block L5/66 has an area of approximately 3,436.01 sq.km.

6. Block L6/66 has an area of approximately 3,966.86 sq.km. and is surrounded by SW1, L33/43, and L44/43 production fields.

7. Block L7/66 has an area of approximately 3,483.51 sq.km.

8. Block L8/66 has an area of approximately 3,957.41 sq.km. and is surrounded by L53/43, L54/43, and L53/48 production fields.

9. Block L9/66 has an area of approximately 3,885.44 sq.km.

1. Northeast Region

The petroleum exploration in this region began in 1962. Up until now, the whole area is mostly covered by 2D seismic data (~30,000 km) and small portions by 3D seismic (~4,000 sq.km.). 64 petroleum wells have been drilled in the area with significant discoveries in eight gas accumulation structures, namely Nam Phong, Sin Phu Horm, Dong Mun, Si That, Phu Khieo, Chonnabot, Kalasin, and Nong Khaman. Only two gas fields, Nam Phong and Sin Phu Horm, have successfully produced gas from the Permian carbonate reservoirs. The rest of gas discovery structures together with the high potential That Phanom, Si That, Kalasin, and Nong Khaman structure have undergone comprehensive studies by several current concessionaires, with the hope to provide high amount of natural gas to the region in the near future.

The commercial Nam Phong gas field was the only natural gas supply for the Nam Phong Power Plant during 1990-2023. After the Sin Phu Horm gas field started producing at the end of 2023, its natural gas has been transported by 65 km. southward pipeline to the flow station located nearby the Nam Phong gas field and not only used as gas feed for power plant but also for NGV fuel stations in this region.

1.1 Structural and General Geology

At the present day the so-called Khorat Plateau is a relatively flat, mountain-rimmed plain, typically ranging from 150 to 200 meters above sea level. Its sole external drainage is via Mekong River to the southeast. It covers an area of some 200,000 sq.km., occupying most of Northeast Thailand and extending into parts of Laos (Booth and Sattayarak, 2011). Isan area encompasses the portion of the Khorat Plateau within Thailand only.

Figure 3 Map Showing the Isan and North-Central Regions of Thailand
Source: JOHN BOOTH & NARES SATTAYARAK, 2011

The surface data indicate that the Mesozoic sequence (Khorat Group) covers the largest area. The Khorat Group is a thicker unit which also encompasses the fluvial-alluvial, subkha, and eolian sediments. The Triassic pre-Khorat rocks are defined as fluvio-lacustrine sediments deposited in the Triassic half-graben. The Permo-Carboniferous rocks comprise of sediments of shallow to deep marine depositional environments during the Late Carboniferous to Permian. However, several petroleum exploration wells and seismic data show that the Triassic pre-Khorat rocks and Permo-Carboniferous rocks predominantly underlie the Khorat Group in the main area. The Triassic pre-Khorat rocks were deposited in the half-graben or graben which occurred locally but not related to the present structure. The Permo-Carboniferous rocks deposited in this area probably comprise of the sediments of platform, restricted-platform, interior-outer platform-basin, and margin-basin plain depositional environments during the Late Carboniferous to Permian as illustrated in the figure of Carbonate facies and fracture distribution in Isan area (Thailand Basin Study Report Northeast Thailand (Isan Area), DMF & PTTEP, 2021).

Figure 4 Carbonate Facies and Fracture Distribution in Isan Area
Source: DMF and PTTEP, 2021

The stratigraphic succession of the Khorat Plateau can be divided by major unconformities into three intervals the Khorat Group (Late Jurassic to Late Cretaceous), the Kuchinarai Group (fluvial-alluvial red bed and lacustrine late Triassic sediments), and the Saraburi Group (Late Carboniferous to Late Permian: extensive marine carbonate and siliciclastics).The primary target for hydrocarbon exploration in the Northeast provinces is the Late Carboniferous to Late Permian interval (Pha Nok Khao and siliciclastic Hua Na Kham Formations). The secondary target is the Late Triassic Kuchinarai Group and Carboniferous Si That carbonate (Figure 5).

Figure 5 Stratigraphic Section of Khorat Plateau, Northeast Thailand, Showing the Petroleum System and Interpreted Key Geological Events

Petroleum potential: After the collision between Indochina block and South China block, the Upper Carboniferous to Upper Permian lacustrine - shallow marine sediments were deposited. These sediments have TOC values of 0.3 to 1.6% and contain Type II and III kerogens. Then, an extensional phase commenced during the Lower Permian to Upper Permian and produced horst and graben geometry. The structural high area such as horst block was the place for Permian carbonate of the Saraburi Group (reservoir) deposition. At the same time, the structural low or basinal area was the place for shale (Nam Duk Formation) deposition. For the Permian carbonate reservoir, it is in fact a tight formation with the matrix porosity of 2%. However, dolomitization, fracturing, and hydrothermal leaching have enhanced the reservoir quality with up to 15% porosity (Chinoroje and Cole, 1995 and Booth and Sattayarak, 2011).

During the Upper Permian to Upper Triassic, inversion and local thin-skinned thrusts developed. These tectonic events may be induced by the collision between Sibumasu block (or Shan Thai block) and Indochina block. The depositional environment had changed to fluvio-lacustrine due to uplifting and led to the lacustrine shale of the Huai Hin Lat or Kuchinarai Group deposition. This group is also considered a source rock. Numerous discoveries demonstrated that gas in the Permian carbonate reservoir was sourced from the Triassic Kuchinarai Group, originating from structural low areas. Hydrocarbon likely migrated vertically along the extensional fault that developed during the Triassic extension into Permian carbonate on the hanging wall blocks. Mudstone in the Kuchinarai Group acts as a regional seal. Hydrocarbon is trapped by angular unconformity to the base of the Khorat Group (Booth and Sattayarak, 2011).

The commercial discoveries in these Northeast provinces are the Nam Phong and the Sin Phu Horm gas fields. Both fields have the same petroleum system and have the approximated proven recoverable resources of 1.7 Tcf. The gas contains mostly 95% methane, 1 to 3 % CO2 (Racey, 2011).

Figure 6 Play Type Identifaction Summary in Isan Area
Source: DMF and PTTEP, 2021

Figure 6 aims to establish the Permian marine facies distribution and environment in the Khorat Plateau based on the seismic data which cover the whole area together with well data. Several isolated platforms have been identified such as Nam Phong, Phu Horm, Si That, Dong Mun, Kalasin, Dao Rung & Kaset Sombun, Chonnabot, and Nong Khaman.

2. North - Central Region

In terms of petroleum system, North - Central Thailand is a well-known region for completed habitat of oil accumulation in Tertiary basins. Producing oil fields are located within these Tertiary basins, including Fang, Phitsanulok, Phetchabun, Kamphaeng Saen, and the Suphan Buri Basins (Figure 7 & Figure 9). The main oil reservoirs in the area are Oligocene/Miocene fluvio-lacustrine sandstone and Miocene intrusive igneous rocks. Trap types in the basins include antithetic and synthetic faults, rollover, faulted anticline, tilted fault blocks, stratigraphic pinch-out, and pre-Tertiary buried hill. The 25th bidding round offers two onshore petroleum exploration blocks in the North-Central area for applicants who would like to seek opportunities in the lower risked area which lies alongside active producing petroleum oil fields. The L6/66 block covers the Wichian Buri oil field and L8/66 block covers the Kamphaeng Saen and Suphan Buri oil fields. (Figure 2)

2.1 Structural and General Geology

2.1.1 Phetchabun Basin (Wichian Buri Sub-basin)

This basin covers an area of 3,300 sq.km. and is situated in North-Central Thailand, east of the Phitsanulok Basin and on the western edge of the Khorat Plateau. The basin comprises two main sub-basin, the north Phetchabun in the north and the Wichian Buri in the south with three much smaller intervening grabens. It has a total Tertiary sediment thickness of at least 2,500 meters in the Wichian Buri Sub-basin and 1,100 meters in the North Phetchabun Sub-basin (William et al., 1995).

Figure 7 Section across Wichian Buri Sub-basin and Phetchabun Basin
(from Carnarvon Petroleum website, www.carnarvonpetroleum.com)

A cross-section through the Wichian Buri part of the basin is shown in Figure 7. The basin comprises a steeply faulted north-south trending half-graben, with an east-dipping fault bounding the graben in the south and a west-dipping fault bounding the half-graben in the north. The Wichian Buri and Bo-Rang discoveries are located along a NE-SW trending strike-slip accommodation zone between these two half-grabens, while the Si Thep discovery is located on a tilted fault block in the southernmost part of the sub-basin (William et al., 1995). A series of gravity lows and intervening saddles oriented NNE-SSW to NNW-SSE occurs along the length of the basin. Oligo-Miocene fluvial and lacustrine sediments fill the basin and are overlaid by Quaternary volcanic rocks and sediments.

The succession comprises an unnamed basal Tertiary interval comprising of around 400 meters of syn-rift fluvial sediments and rift volcanics. Overlaying this interval is the 1,850-meter-thick lacustrine shales, interbedded with thin fluvial sandstones and occasional coals which together are assigned to the Wichian Buri Group. An unconformity separates the Wichian Buri Group from a younger 350-meter-thick sequence of lacustrine mudstones, sandstones, and coals of the Chaliang Lab Formation. The sequence is capped by a few hundred meters of Plio-Pleistocene fluvial sediments (Remus et al., 1993).

Figure 8 Phetchabun Basin Stratigraphy, Petroleum System, and Sedimentary Environments
(Adapted from Remus et al., 1993 and William et al., 1995)

Petroleum potential: Oil-prone shales with average TOCs of around 4% occur in the Upper Mioceneto to Pliocene Chaliang Lab Formation, interbedded with potential reservoir sandstones. Williams et al. (1995) recorded TOC values of 0.5–9.0% with HI values of 50–900 mg/g and Tmax values of 420–440oC, indicating that most of their analyzed samples were immature, but had excellent source potential and were dominated by Type I and Type II kerogens, signifying that they were oil prone. Geothermal gradients in this basin are 4.6oC/100 meters. Igneous intrusions occur throughout the Wichian Buri Sub-basin and have provided sufficient heat to cause local hydrocarbon generation from lacustrine source rocks which elsewhere are immature.

The Si Thep discovery (Figure 7) was drilled to a total depth of 1,300 meters in Permo-Triassic volcanic rocks and encountered oil in Miocene thin sands between 660–670 meters and 734–739 meters, lithologically similar to those in Wichian Buri. Reservoir quality is generally poor due to a combination of low sand shale ratios, lack of coarser grained material due to the smallness of the graben depositional system, and lack of a quartz-rich provenance area.

The Na Sanun East Field adjacent to the south of Bo Rang-1 (Figure 7) has exhibited gross reserves of 20 MMbbls of oil in three separate fault compartments and is also reservoired in fractured Tertiary volcanic rocks, having flow rates of 150–4,000 bopd.

2.1.2 Suphan Buri and Kamphaeng Saen Basins

These two small basins in the Southern Central Plains are located to the south of the Phitsanulok Basin between the Mae Ping and Three Pagodas fault zones. Small oil discoveries have been made in the Miocene fluvial sandstones.

The Suphan Buri Basin (Figure 8) covers an area of 970 sq.km. and is the Tertiary sedimentary basin which is characterized by a series of narrow, elongate, northwest-southeast/north-south fault trending. The Tertiary basins were formed as a result of extensional tectonics believed to have been initiated during an Eocene oblique slip extensional structural event. Non-marine, mainly fluviolacustrine is the depositional environment. Miocene Shale appears to be the main Tertiary seal. The basin is dominated by flood plain and marginal marine Shale.

Figure 9 Cross-sections through Suphan Buri Basin and Kamphaeng Saen Basin, modified from Bidston & Daniels (1992)

Petroleum potential: The Suphan Buri Basin contains Upper Oligocene–Lower Miocene mainly lacustrine source rocks and Middle–Upper Miocene alluvial/fluvial sandstone reservoirs bounded by faults (Ronghe & Surarat, 2002). The geothermal gradient in the Suphan Buri Basin is estimated at between 4.2 and 6.2oC/100 meters (Petersen et al., 2006 and Petersen & Mathiesen, 2007) with a reservoir temperature of 77oC at 1,300 meters. The Sawang Field (also called the U Thong Field) was discovered on the west flank of the basin by BP in the 1980s and produced 300 bpd of 328 API oil.

The Neung Field (later called the Kamphaeng Saen Field) was discovered by BP in the Kamphaeng Saen Basin (Figure 8) and has reportedly produced oil at 100 bpd. Reservoirs in the Sawang (U Thong) Field comprise mainly Miocene conglomerates and sandstones (alluvial fans and fan deltas) deposited at the base of the main basin-bounding fault and sourced from lacustrine shales located deeper in the basin. In the Neung Field, the reservoirs are in Miocene fan-delta channels within a dominantly mudstone-rich lacustrine interval.

Nine blocks are offered for the 25^th bidding round. All blocks cover a total area of 33,444.64 sq.km. The blocks are divided by the region into two regions as follows:

L1/66

Figure 10 Seismic Profile of Udon Prospect

Location : L1/66 is located in Udon Thani, Nong Bua Lam Phu, and Khon Kaen Provinces.

Area : It covers an area of 3,223.51 sq.km.

Description of the block : L1/66 block is located around Sin Phu Horm Field which is the area with highest gas production in onshore Thailand. The four prospects are Kok Sathon, Phu Khao, Nong Sang, and Udon (Figure 9).

The play of Udon prospect is Permian carbonate reservoir of the Pha Nok Khao Formation sourced by the Late Carboniferous Si That Formation in the deeper part. The structural trap in this prospect is a thrusted anticline, supported by the success of the Phu Horm Field and Nam Phong Field, which are established gas production areas in onshore Thailand. This thrusted anticline is overlaid by the Triassic Kuchinarai Group which also can be a source rock for the Pha Nok Khao Formation. This prospect is sealed by the Nam Phong Formation.

The play of Kok Sathon prospect shows apparent reef feature of the Pha Nok Khao Formation which is expected to be a porous reservoir sourced and sealed by the Late Carboniferous Si That and Nam Phong Formations respectively.

Phu Kao-1 well proves existence of hydrocarbon in the Triassic Kuchinarai Group which is also a potential play for the Phu Khao and Nong Sang prospects.

Remark : The area that does not overlap with the sensitive area is 2,239.75 sq.km.

L2/66

Figure 11 Seismic Profile of Si That and Chai Wan Prospects

Location : L2/66 is located in Sakon Nakhon, Udon Thani, and Kalasin Provinces.

Area : It covers an area of 3,917.03 sq.km.

Description of the block : L2/66 consists of at least six prospects which are Si That, Kumphawapi, Chai Wan, Phu Kratae, That Phu Wong, and Kham Muang. The seismic profile shows the Si That and Chai Wan structures. Thay have half-graben lips to basement structure characteristic. Seismic data indicate that the Khorat Group rocks are almost horizontal, with minimal folding. This is due to the thrust fault cutting through the underlying Permo-Carboniferous rocks, with several minor faults.

All three formations – the Si That Formation, Carbonate Rocks, and Upper Clastics Rocks – have been identified within these structures. The prospect of this structure is the upper and middle Permian carbonates of the Pha Nok Khao Formation which were the reservoir objectives. From seismic interpretation, the blue line horizon is the top of carbonates play, resulting in the recommendation for petroleum exploration in this area. The source rock is the Upper Carboniferous of the Si That Formation, that deposited in shallow marine. The red line horizon is interpreted as the top of the Si That Formation.

This area has exploration wells such as Si That-A, Si That-1, Si That-2, and Si That-3ST. These wells proved the existence of a reef massif, dolomite, and significant fracture enhanced porosity and permeability within the Pha Nok Khao Formation. Although Si That-2 (Cairn in 1998) tested 1.28 mmscf/d proving the existence of a gas column in the Si That area, it showed that in that location the carbonate was generally tight. However, if this area is to move forward with exploration, the Si That structure is likely to be developed for gas production soon.

Remark : The area that does not overlap with the sensitive area is 2,634.16 sq.km.

L3/66

Figure 12Seismic Profile of Kalasin Prospect

Location : L3/66 is located in Khon Kaen, Maha Sarakham, Udon Thani, and Kalasin Provinces.

Area : It covers an area of 3,918.22 sq.km.

Description of the block : L3/66 covers the Dong Mun production area of block L27/43. The 3D seismic data in the Kalasin prospect show that the strong-parallel reflector is the Si That Formation. The Pha Nok Khao carbonate platform overlies this formation and is proven by two exploration wells drilled in 2010 and 2013, respectively. These wells encountered gas and H2S in the Pha Nok Khao carbonate reservoir. The main risk associated with this prospect is H2S. Therefore, it is a good opportunity for exploration and development. Another promising prospect in this block is the Kranuan prospect. The seismic data indicate that the Si That Formation underlies the carbonate platform, and the overlying clastic rocks exhibit an onlap relationship with the carbonate rocks. The Si That Formation has the potential to serve as source rocks, while the carbonate rocks are considered prospective reservoir rocks. This prospect demonstrates high potential for success.

Remark : The area that does not overlap with the sensitive area is 2,459.95 sq.km.

L4/66

Figure 13Seismic Profile of That Phanom Prospect

Location : L4/66 is located in Nakhon Phanom, Mukdahan, Yasothon, and Amnat Charoen Provinces.

Area : It covers an area of 3,656.65 sq.km.

Description of the block : L4/66 block consists of three prospects which are That Phanom, Mukdahan, and Non Sung. The play of That Phanom prospect is the Permian carbonate reservoir of the Pha Nok Khao Formation sourced by the Late Carboniferous Si That Formation in the deeper part. The Pha Nok Khao Formation is overlaid by the Triassic Kuchinarai Group which can be a source rock or seal for the formation. The seismic profile shows reef-like feature of Pha Nok Khao which is expected to be porous reservoir.

The play of Mukdahan prospect is the Triassic Kuchinarai Group. The Mukdahan-1 well successfully encountered hydrocarbons in the Triassic Kuchinarai Group. Moreover, in deeper part, where the well did not encounter, the Pha Nok Khao Formation may potentially contain hydrocarbons.

The play of Non Sung prospect is the Triassic Kuchinarai Group and the Permian carbonate of the Pha Nok Khao Formation. The Non Sung-1 well presents shale of the Triassic Kuchinarai Group with 1.2% TOC content, indicating potential source rock. In deeper part, the well penetrated the Permian carbonate. The carbonate is tight and extremely fractured but fractures are filled with calcite. However, there is potential for finding good fractured reservoir in nearby areas.

Remark : The area that does not overlap with the sensitive area is 1,972.13 sq.km.

L5/66

Figure 14Seismic Profile of Chonnabot Prospect

Location : L5/66 is located in Khon Kaen, Chaiyaphum, and Nakhon Ratchasima provinces.

Area : It covers an area of 3,436.01 sq.km.

Description of the block : L5/66 consists of three prospects which are Phu Khiao, Kaeng Khlo, and Chonnabot. The Chonnabot prospect is a NE-SW trending, elongate anticline which was formed during the Tertiary Himalayan Orogeny. This prospect is Permian carbonate associated with inverted horst structural high, followed by stratigraphic combination trap. Source rocks are from the Late Carboniferous Si That Formation (Red line). In addition, the Triassic Pre-Khorat sediment (Kuchinarai Group) below the Khorat Group can be the source rock for Permian carbonate in the high area.

Structurally, this prospect was formed by thin-skinned fault propagation fold. Based on the interpretation from 2D seismic, Permian carbonate Pha Nok Khao was thrusted resulting in thrust faults. These thrust faults are overlaid by the Triassic Pre-Khorat Sediment across the structure, with onlapping reflection geometries. The Nam Phong Formation (Yellow line) is considered to have a regional top seal. Moreover, the Chonnabot-1 and Rattana-1(ST) were drilled in 1982 and 2010, respectively. These wells encountered gas shows in shallow depths, indicating the presence of hydrocarbons.

Remark : The area that does not overlap with the sensitive area is 2,439 sq.km.

L6/66

Figure 15Seismic Profile of Phetchabun Basin

Location : L6/66 is located in Phetchabun, Chaiyaphum, and Lop Buri Provinces.

Area : It covers an area of 3,966.86 sq.km.

Description of the block : The hydrocarbon-bearing reservoir in the L6/66 block is unusual that it is hosted within naturally fractured intrusive igneous bodies (sills). The source rock for the Phetchabun Basin Field comprises the Tertiary lacustrine mudstones which surround igneous reservoir units. They have a TOC content of up to 10.2% and are dominated by Type I and Type II kerogens. Although the lowermost of these strata are currently deep enough to have entered the oil window through burial alone, both burial history modeling and geochemical analysis of well samples suggest that the heat pulse generated by the intrusion of the igneous strata significantly enhanced hydrocarbon maturation. Seismic profiles reveal that these igneous bodies are characterised by a strong top reflector. The red, yellow, and blue seismic horizons interpretation identified three distinct igneous bodies. This geological setting suggests a potential for a good source rock, reservoir, and seal.

Remark : The majority of the L6/66 survey area overlaps with the historical park including the buffer zone and the wider area of the Si-Thep Historical Park. Note that new oil drilling projects are strictly prohibited in the Si-Thep Historical Park and its buffer zones, and in the wider setting, particularly the area that lies between the buffer zones.

The area that does not overlap with the sensitive area is 1,640.76 sq.km.

L7/66

Figure 16Seismic profile of Nong Khaman and Phut Thai Song Prospects

Location : L7/66 is located in Nakhon Ratchasima, Buriram, Maha Sarakham, and Roi Et Provinces.

Area : It covers an area of 3,483.51 sq.km.

Description of the block : L7/66 consists of at least four prospects which are Talat Sai, Phut Thai Song, Phayakkhaphum Phisai, and Nong Khaman. The seismic profile shows the structures of Nong Khaman and Phut Thai Song. The seismic data indicate that the Khorat Group is almost horizontal, with minimal folding. This is due to the thrust fault cutting through the underlying Permo-Carboniferous Rocks, with several minor faults. All three formations – the Si That Formation, Carbonate Rocks, and Upper Clastics Rocks – have been identified within these structures. According to regional geology data, seismic data, and drilling information analysis, the Paleozoic Lower Permian Hua Na Kham and Pha Nok Khao Formations are marine transition facies carbonate deposition belonging to the clastic rock.

The Lower Pha Nok Khao Formation is predicted to be the main hydrocarbon reservoir. The fault nose structure is the main type of structure trap. Numerous layers of claystone and shale are developed in other formations and have proven regional seal, currently observed in the Khorat Plateau as the main type of lithological trap. The Carboniferous-Permian Si That Formation claystone and coal streak have greater hydrocarbon generation potential. According to the seismic interpretation, the Permian carbonates are a recommended play for gas exploration in this area. The wells reached the top of the Pha Nok Khao Formation at 3,000-3,400 meters, which was predominantly tight carbonate with rare claystone in section interpreted as off-shelf debrites.

Remark : The area that does not overlap with the sensitive area is 2,634.16 sq.km.

L8/66

Figure 17Seismic Profile of Kamphaeng Saen Basin

Location : L8/66 is located in Ratchaburi, Nakhon Pathom, Kanchanaburi, and Suphan Buri Provinces.

Area : It covers an area of 3,957.41 sq.km.

Description of the block : The hydrocarbon-bearing reservoirs in Suphan Buri Basin predominantly consist of Miocene conglomerates and sandstones (alluvial fans and fan deltas) deposited at the base of the main basin-bounding fault. These reservoirs are sourced by lacustrine shales located deeper in the basin. In the Kamphaeng Saen basin, the reservoirs are in Miocene fan-delta channels within a dominantly mudstone-rich lacustrine interval. The red, yellow, and blue horizons interpretation identified three distinct sandstone bodies. If the source rocks generate any hydrocarbon, it is likely to migrate upward to accumulate in the reservoirs located in the higher areas.

Remark : The area that does not overlap with the sensitive area is 2,123.98 sq.km.

L9/66

Figure 18Seismic Profile of Don Phrai Prospect

Location : L9/66 is located in Nakhon Ratchasima Province.

Area : It covers an area of 3,885.44 sq.km.

Description of the block : L9/66 consists of at least three prospects which are Sikhio, Lam Phra Phloeng, and Don Phrai. The exploration play of these prospects is the Early to Middle Permian Platform carbonate reservoirs of the Pha Nok Khao Formation, sourced by the Late Carboniferous Si That Formation (deposited in a shallow marine) and the Upper Triassic Kuchinarai Group (deposited in alluvial and lacustrine during the Triassic extension). The seismic profile of Sikhio and Don Phrai prospects illustrate asymmetric half-graben geometries. The package of syn-rift extension between light green and red horizon has been deformed and is interpreted as a Permian Platform carbonate in a shallow marine. The red horizon is interpreted as the top Si that Formation (Carbonate and clastic shallow marine potential source rocks). Currently, the subsurface data in this block is still insufficient, with no 3D seismic or exploration wells available to fully evaluate petroleum system play.

Remark : The area that does not overlap with the sensitive area is 2,123.98 sq.km.

The invitation (25^th Bidding Round) for concession rights has been announced. Interested companies can submit applications for concession rights within ten working days from the 1^st of July 2025 to the 16^th of July 2025.

Open acreage with petroleum deposition potential has already been delineated into nine onshore exploration blocks, located in Northeast and Central regions of Thailand. Data packages are now available to interested companies to study prior to their submission of application.

The Department of Mineral Fuels will evaluate the applications based on the merits of the interested companies. Such companies, whether individual oil companies or joint ventures, must submit evidence showing their corporate profile, financial strength, and petroleum exploration and production capability. These capabilities will be verified before they can be considered for the award of concessions. If the applicant does not possess the specified qualifications, they will be required to submit a Letter of Guarantee from the company with a capital or management relationship with the applicant. This letter must guarantee the provision of necessary support to the applicant to the extent that the applicant is capable of exploring, producing, selling, and disposing of petroleum.

The applicant must also propose a work obligation and expenditure obligation that meet or exceed the minimum requirements specified in the Announcement. An application fee of 50,000 Baht per block and a bid security of 3,000,000 Baht per block must be submitted along with the application.

The bid security will be returned to unsuccessful applicants. For successful applicants, the bid security will be returned and replaced with a bank guarantee as a performance bond.

Qualified companies will be selected based on the merit of their exploration proposals (most suitable for the geological conditions of the exploration block) and proposed development plan.

Qualified companies selected as concessionaires must demonstrate sufficient assets, machinery, and equipment. In addition, qualified companies must have the petroleum expertise to explore, produce, sell, and dispose of petroleum. The successful applicant is required to submit a bank guarantee covering the expenditure amount of the work commitment for the first six-year obligations before signing the concession agreement.

Available Data

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