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Площадь: 23446.7 км²
Khmer basin
Cambodia has just achieved its first oil production stage since twice attempts failed. On December 28, 2020, the Prime Minister announced officially the first drop of Cambodian crude oil was pumped successfully from its exclusive seawater by KrisEnergy. It is about fifty years to become an oil-producing country since many international companies have explored hydrocarbon resources through different political regimes.
The first oil was produced from Cambodia Block A (CBA) which covers most of the Khmer basin, in the Gulf of Thailand (GoT). KrisEnergy, the operator of CBA, planned to develop first the most advanced exploration trend, namely the Apsara area, which is situated in the northeastern section of the CBA concession. This Apsara oil trend is one of the seven geological trends where there are potential for oil and gas to be trapped in CBA [3] and has been formally declared the commercial quantities of oil in 2010 by Chevron Texaco [4].The original Petroleum Permit Application (PPA) of Chevron Texaco was designed in 2010 for a phase field development plan in which the initial phase 1A comprised one production mini platform with twenty-two production wells and was estimated to produce the oil at the peak 7500 bopd out of the recoverable oil of 8.6 mmbbl from this Area. In subsequent circumstances, KrisEnergy became the operator of CBA in 2014 and adjusted the original PPA for dealing with the government in order to move forward to the production stage. Mini Phase 1A was finally adopted for the flow of Cambodian first drop as soon as the new PPA of KrisEnergy was approved in 2017 by the government of Cambodia. The Mini Phase 1A in the current PPA was simplified to an unman mini platform that accommodated the mini facilities with a maximum of six production wells.
The expectations of both Chevron Texaco and KrisEnergy were to commence the first Phase to evaluate whether the reservoir performance would be appropriate with the exploratory estimation in the Apsara oil field. According to the reassessing drilling wells by Chevron Texaco in 2007, it was concluded that the oil accumulation in CBA was much less than the previous estimation lead to initiate a lower risk method of three phases (1A, 1B, and 1C) for oil field develop ment in CBA. In addition, KrisEnergy which was a marginal field development company deployed the lowest risk Mini Phase 1A due to the awareness of high-level uncertainty surrounding the oil reserves and did not expect to produce economically within this phase on its own.
Since the beginning of the offshore activity in the 1970s, it took forty years to identify the Khmer Basin within seven prospective trends and about another ten years to discover the first economical petroleum reservoir, the Apsara area. In the early 1970s, a French oil company, Elf-Erap, shot the first seismic survey and achieved the study drill of three wells in the early acreages (Figure 1(a)). After the collapse of Khmer Rouge regime, the Cambodian government divided the offshore licenses into seven blocks (block I-VII) where 2D, 3D seismic, and nine explorational drills were conducted by Enterprise, Campex, and Premiere in their block licenses (Figure 1(b)). These companies decided to give up at the end when world oil price slumped down and left these block licenses to be free. In 2002 Chevron Texaco came and signed the production sharing agreement with the government to explore and extract the hydrocarbon resources in CBA.
Figure 1. Block license modifications based on the continental shelf claims, geological discoveries, and hydrocarbon potential during 1972-2002. (a) Cambodia-Cambodian Shelf Concessions in 1975; (b) The seven offshore blocks after Cambodia-Russia geologists studied the geological and geophysical information to identify the basins entire the country in 1987 and (c) The offshore blocks were revised and divided into 6 blocks in 2002.
The geological formation of the Khmer Basin, consisting of the CBA, in the GoT is reported many similarities to other Thai, Malaysian and Vietnamese Basins which lie to the west, south and east respectively [8]. However, the degree of success of first oil involved many challenges of operatorship and the diverse geological factors that affect the petroleum formation and hydrocarbon accumulation. By knowing the complexities and uncertainties of the particular geological characteristics including age and type of source rock, age and type of reservoir rocks, structural trapping styles and the hydrocarbon reservoirs in the offshore Cambodia through exploration programs, time and huge budget were necessarily needed in order to reduce risks and conclude the oil more confident.
Few sources of technical report can be accessed through the purposes of academic research and knowledge sharing to review for this paper. The General Department of Petroleum (GDP) of the Ministry of Mines and Energy (MME) is a primary channel for knowledge sharing and the informative references. In addition, the technical reports of operators, consultants, and academic researchers are also resourceful for the reviews even if some critical information is partially disclosed regarding to the restrictions of subsurface geology of Cambodia, especially the results of oil and gas exploration.
This paper reviews comprehensively the relevant research articles related to oil and gas in the GoT, and the exploration activities in Cambodian water from the 1970s to 2022s through many exploration programs including seismic surveys, drilling wells, and the interpretation in the paucity of both published information and exploration data availability. There have been reports of the formation of the Khmer Basin with the earlier assumptions, then, followed by reassessments and detailed studies to figure out a more certain geological formation, petroleum system, chemical and physical properties of the rock, and the circumstance of choosing the method to flow the first oil.
Geology of the Khmer Basin
The tectonic setting of the Asia and SE Asia lead to the origin of the GoT. The period from Late Cretaceous to Eocene time, the Indo-Australian plate separated from Gondwanaland moving northward to collide with the Eurasian plate (Figure 2(a)). As the Indian subcontinent continued pushing north, SE Asia was slowly rotated clockwise, changing the angle of subduction from perpendicular orientation to increasingly oblique. This new angle formed a major thrust fault in the region which is responsible for the development of N-S extensional zones and formed the numerous N-S trending basins currently. In addition to the lateral right extension, the plate collision causes either the Indo-Australian oceanic crust subducts under the Sundaland. This subduction opened the Gulf of Thailand 50 Ma with back-arc extension transpression/transtension associated with right-lateral strike-slip faulting. Looking closer at the formation of the GoT, all basins are N-S extensional faults formation in the Cenozoic, which link up with the NNW trending Three Pagoda Transfer Fault, as shown in the Figure 2(b).
Figure 2. Plate tectonic movements reform the continental and oceanic crust structures in the Cenozoic era in South East Asia: (a) The movement of Indo-Australia plate to hit with Eurasian plate causing major local thrust slip faults and uplifts which influence gradually the changes in geological distribution, and (b) The eleven N-S elongate pull-apart basins in the GoT associated with Eocene/Oligocene oblique slip. Modified from Fyhn et al., (2010) and Pakdeesirote et al., (1997).
The Khmer Basin is one of eleven N-S elongate pull-apart basins in the GoT associated with Eocene/Oligocene oblique slip. The Western and Eastern Gulf of Thailand sub-segments are separated from one another by the Ko Kra Ridge with nine basins in the west and three basins in the east: the Pattani and Malay Basins and the smaller Khmer Basin.
Source of information: The Milestone of Cambodian First Oil Production in the Khmer Basin, Gulf of Thailand, Kimhak Neak, Kakda Kret, Tola Sreu, Sirisokha Seang, Chanmoly Or. Open Journal of Yangtze Gas and Oil, 2023, 8, 19-42.
Следующий Бассейн: Shuangfeng