Contributors: Michael McWalter
Graphic courtesy of Michael McWalter
I have just returned from Kompong Thom town, the capital of Kompong Thom Province, some 200 kilometers north of Phnom Penh, the capital of Cambodia.
In my capacity as adviser to the Cambodian National Petroleum Authority (CNPA), I had been invited to attend the kick-off meeting for the country’s largest-ever onshore seismic program.
Finally, serious investment is being made in the exploration of Cambodia’s onshore sedimentary basins. It is foreign investment, but regional in nature.
PetroVietnam Exploration and Production Overseas Ltd. (PVEP) was awarded Block XV by the Royal Government of Cambodia on Dec. 12, 2009, for a period of seven years over an area of some 6,500 square kilometers to the north and east of the Tonle Sap Lake.
After reviewing the results of prior exploration work, comprised principally of aeromagnetic and airborne gravity surveys conducted by the Japanese National Oil Co. in 1996 and some road-based vibroseis seismic data acquired by PGS a few years ago, PVEP has elected to enter into the next phase of its approved work program with the acquisition of 600 line-kilometers of 2-D reflection seismic data.
Exploration of Cambodia’s onshore basins is at a fundamental level involving the definition of the basic structure and architecture of the basins. Based on the earlier surveys, the Tonle Sap basin is believed to comprise two depocentres, which are thought to hold sediments up to five kilometers in depth – but as yet, no drilling has taken place to elucidate the stratigraphy.
The kick-off meeting in the small provincial capital of Kompong Thom included:
- The CNPA, as petroleum sector manager and regulator of Cambodia.
- PVEP, the petroleum contractor.
- Seismic contractor BGP, the geophysics service company of the Chinese National Petroleum Corp.
- Provincial officials and officials of other national government ministries and agencies.
The seismic acquisition program was reviewed, and then the assembled group adjourned to the field survey site to the west of the capital to witness the start of the survey and the conduct of initial check shots.
The Tonle Sap Lake, which lies in the middle of Cambodia, is an expansive body of freshwater, alternately filled up by the Mekong River during the rainy season and then discharging its waters back into the Mekong in the dry season. It provides vast food supplies to the people of Cambodia and has a pristine and very large catchment area.
Therefore, environmental and social sensitivities toward exploration there are high – however, the two identified sedimentary basins are offset at depth from the current surface depression that gives rise to the lake, so it is unlikely that drilling will ever need to take place in the lake itself (although the footprint of exploration is clearly within the lake’s overall catchment area).
Not only are there environmental and social impact risks, but there are significant safety risks attached to the survey, due to the presence of large amountsº of unexploded ordinance (UXOs) arising from the darker days of Cambodia’s modern history and large scale aerial bombing and extensive mining of the area.
This requires highly specialised UXO clearance teams to survey the corridors of the seismic lines most carefully before any entry may be made for petroleum operations.
Housed in a dried-up rice field under a decorative Khmer awning, the assembled visitors eagerly awaited the boom of the first check shot. For many of them, particularly the National and local officials, this was their first experience of onshore seismic acquisition.
In a carefully choreographed demonstration, the first charge was set off and the thud of the source reached the visitors, followed by an appropriately visible small blow out from the shot hole, a safe distance in front of them.
“We do this many thousands of times and listen to the seismic reflections from the strata through a 10-kilometer chain of geophones spread out along the line,” explained the Chinese BGP crew chief in English to one of the Cambodian officials.
Few of the Cambodians speak Vietnamese or Chinese and vice versa, so English becomes the lingua franca – but there are no Texan tones here!
After two more check shots, using different source parameters, and a review of the seismic acquisition records that showed reflecting sediments were clearly present down to four seconds, a happy and contented audience journeyed back to town, to banquet at a local restaurant on delicacies that satisfied the appetites of Cambodian, Vietnamese and Chinese alike (and me, too!).
The end result: This survey, in a very good example of Asian collaboration and cooperation, brought together Cambodia, Vietnam and China respectively in the guise of CNPA, an upcoming national petroleum regulator; PetroVietnam, an expanding national petroleum company; and BGP, the large and globally deployed seismic contacting arm of the CNPC.