Countries’ Teamwork Brings Survey Success

Contributors: Michael McWalter
Graphic courtesy of 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.

Comments (0)

 

Regions and Sections

Regions and Sections Column - Carol McGowen
Carol Cain McGowen is the development manager for AAPG's Regions and Sections. She may be contacted via email , or telephone at 1-918-560-9403.

Regions and Sections Column - Michael McWalter

AAPG member Michael McWalter is a petroleum geologist who works as an industry regulatory and institutional specialist for various governments. Based in Port Moresby, Papua New Guinea, he is resident adviser to the Department of Petroleum and Energy of the Government of Papua New Guinea, and a visiting adviser to the Cambodian National Petroleum Authority and the newly established Petroleum Commission in Ghana. He also is a director of both the Circum-Pacific Council for Energy and Mineral Resources and the Board of the Transparency International – Papua New Guinea.

Regions and Sections Column

Regions and Sections is a regular column in the EXPLORER offering news for and about AAPG's six international Regions and six U.S. Sections. News items, press releases and other information should be submitted via email or to: EXPLORER - Regions and Sections, P.O. Box 979, Tulsa, OK 74101. 

View column archives

See Also: Book

Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 4168 Book

See Also: Bulletin Article

Although the linkages among surface sediments, geomorphic forms, and hydrodynamics in Holocene ooid tidal sand shoals have been evaluated recently, how these factors are reflected in the geomorphic evolution and stratigraphic record of shoals is less constrained. Yet, such understanding is essential to developing meaningful predictive conceptual models of three-dimensional architecture of ancient reservoir analogs. Integrating remote-sensing imagery, high-frequency seismic data, and core characterization from Lily Bank, a modern tidally dominated Bahamian ooid shoal in which sedimentologic processes are well documented, reveals the stratigraphic record of geomorphic change. An irregular, gently dipping rocky surface (interpreted as the top Pleistocene) with no pronounced topographic high underlies the Holocene oolitic succession. A 6-m (20-ft)–thick poorly sorted, gravelly muddy sand with few ooids overlies this basal surface. This lower interval is overlain by sand with an upward increase in proportion of ooids, sorting, and grain size. The uppermost unit, present only under active bar forms, is well-sorted oolitic medium sand with accretionary foresets. Sediments vary stratigraphically and geomorphically; the lower unit is finer and less well sorted than the upper units, and in the oolitic upper unit, sediment size and sorting on bar crests are distinct from bar flanks. Collectively, these results suggest that a marked antecedent bump is not necessary for occurrence of ooid shoals and that the stratigraphic record of analogous ooid shoal systems may preserve clues of geomorphic position, as well as geobody size and orientation.
Desktop /Portals/0/PackFlashItemImages/WebReady/Relations-between-geomorphic-form-and.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3563 Bulletin Article

The Upper Jurassic Arab Formation in the Arabian Peninsula, the most prolific oil-bearing interval of the world, is a succession of interbedded thick carbonates and evaporites that are defined stratigraphically upsection as the Arab-D, Arab-C, Arab-B, and Arab-A. The Arab-D reservoir is the main reservoir in Khurais field, one of the largest onshore oil fields of the Kingdom of Saudi Arabia.

In Khurais field, the Arab-D reservoir is composed of the overlying evaporitic Arab-D Member of the Arab Formation and the underlying upper part of the Jubaila Formation. It contains 11 lithofacies, listed from deepest to shallowest: (1) hardground-capped skeletal wackestone and lime mudstone; (2) intraclast floatstone and rudstone; (3) pelletal wackestone and packstone; (4) stromatoporoid wackestone, packstone, and floatstone; (5) Cladocoropsis wackestone, packstone, and floatstone; (6) Clypeina and Thaumatoporella wackestone and packstone; (7) peloidal packstone and grainstone; (8) ooid grainstone; (9) crypt-microbial laminites; (10) evaporites; and (11) stratigraphically reoccurring dolomite.

The Arab-D reservoir lithofacies succession represents shallowing-upward deposition, which, from deepest to shallowest, reflects the following depositional environments: offshore submarine turbidity fans (lithofacies 1 and 2); lower shoreface settings (lithofacies 3); stromatoporoid reef (lithofacies 4); lagoon (lithofacies 5 and 6); shallow subtidal settings (lithofacies 7 and 8); peritidal settings (lithofacies 9); and sabkhas and salinas (lithofacies 10). The depositional succession of the reservoir represents a prograding, shallow-marine, reef-rimmed carbonate shelf that was subjected to common storm abrasion, which triggered turbidites.

Desktop /Portals/0/PackFlashItemImages/WebReady/arabian-carbonate-reservoirs-a-depositional-model.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 3771 Bulletin Article

See Also: CD DVD

Desktop /Portals/0/images/_site/AAPG-newlogo-vertical-morepadding.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 4053 CD-DVD

See Also: Energy Policy Blog

Crude oil and natural gas infrastructure problems, from pipeline oil spills to train derailments and fires, have been in the news recently. Though these problems are not new, public concern is growing. Think tanks and government agencies have been considering the problems and potential solutions for some time and are now reporting the results of their studies. Here are reports of one oil and one natural gas infrastructure study.
Desktop /Portals/0/PackFlashItemImages/WebReady/Oil-and-natural-gas-infrastructure-challenges-03mar-17-2015-hero.jpg?width=50&h=50&mode=crop&anchor=middlecenter&quality=90amp;encoder=freeimage&progressive=true 16886 Energy Policy Blog