SERVICE CONTRACT 6-A ( OCTON AREA )
Service Contract 6 - Block A (also called the Octon Block) is located in the northern half of what is known as the Northwest Palawan Oil Province. This block covers an area of approximately 108,150 hectares in water depths generally less than 600 feet (Figure 1). The Northwest Palawan Oil Province remains to be the country’s most productive basin and is host to a number of significant oil and gas discoveries in both carbonate and clastic reservoirs.
Eight (8) wells have been drilled within the SC 6A. The area is amply covered by both 2D and 3D seismic data. A minor discovery, Octon Field, yielded oil, gas, and condensate during tests of the Middle Miocene-age Galoc Clastic Unit turbidite sandstones. Geologically, the Octon discovery has close semblance to the nearby producing Galoc Field in SC 14C-1 operated by Galoc Production Company.
Current play concepts for the SC 6A Block center around the development and distribution of hydrocarbon-charged clastic units. The most recent evaluation of the block has identified several prospective drilling targets, mostly fault-induced blocks.
Brief Exploration Overview: Octon Block
Following the discovery of Cadlao Field in 1977, Amoco Philippines drilled several wells over the extensive Service Contract No. 6 prior to converting to the present production retention areas. Philodrill assumed operatorship of Service Contract 6A from Alcorn Petroleum in 1988, drilling two wells in the same year. Well Esperanza -1 flowed dry gas at 7.1 million cubic feet per day from Pagasa sands at a depth of 1,700 feet. Well Saddle Rock -1 was drilled along the north plunge of the large Malajon structure to test shallow Lower Miocene Galoc Clastic Unit (GCU) sands encountered in Amoco’s Malajon well twelve kilometers to the south. Though the Saddle Rock well encountered 80 net feet of sand with live oil shows from 550 to 850 feet, the well was untested due to mechanical and safety conditions.
A more significant discovery was made in 1990 with the drilling of well Octon-1, testing 12,500 MCFG and 1,050 barrels of condensate per day. A step out well (Octon-2) was drilled down dip, establishing an oil leg testing 1,800 BOPD. A second appraisal well (Octon -3) located two and one-half kilometers east of the discovery drilled hydrocarbon saturated sands. All tests on the third well, however, recovered water. Subsequent studies of the drilling, casing and cementing programs including whole core analysis and detailed petrophysics suggest the Octon -3 test results to be invalid due to a poor cementing job.
The entire contract area has extensive 2D seismic coverage acquired by Phillips Petroleum, Amoco and Cities Service during the 70’s. Philodrill acquired a total of 1,285 line-kilometers and limited 3D coverage of the Octon area during the early 1990s. Various depositional, reservoir and hydrocarbon modeling studies have been undertaken around the Octon area by British consulting firms.
In 1998, Geco-Prakla completed a block-wide 3D seismic survey for the Octon Block Consortium, acquiring more than 1,400 square kilometers of seamless data over the whole SC 6A block and adjoining areas (Figure 2). The initial processed data indicated a much improved overall structural picture of the entire block. Interpretation of the acquired data was contracted out to the UK-based Robertson Research. The Robertson work also delved on the Galoc discovery and associated leads and prospects to evaluate the potential of a joint Galoc/Octon development project.
In 2002, Rock Oil International (ROII) farmed-in into the North Sector of SC6A, in mostly shallow waters (less than 200 meters depth). Their evaluation of the area generated a portfolio of eight (8) drillable prospects in a variety of play types. These prospects, as well as the other structures of interest within the whole block, are discussed in another section of this report.
From the ROII work, the Octon Field volumetrics have been updated and reevaluated. Reserves estimates suggest that at P50 level of confidence, estimates of oil and gas in place in the northern part of the Octon Field are 16.8 to 23.0 BSCF gas and 9.3 to 12.0 MMSTB oil. These estimates can be increased by the additional potential volume of the southern Octon Field area. A latter work by another farminee to the block, Vitol GPC Investment SA (Vitol GPC), confirmed and validated those prospects that ROII have identified.
Vitol GPC’s studies extensively evaluated the available options for developing the Octon Field, which were generally tied to the planned Phase 2 Galoc development program to take advantage of the synergy offered by the various activities on the Galoc Field. Unfortunately, the Galoc Phase 2 program suffered protracted delays at the time, rendering Vitol GPC unable to meet its SC 6A farmin commitments. Vitol GPC finally decided to withdraw from the consortium in late 2010.
In fulfillment of its farmin work commitment to the consortium, Pitkin Petroleum Plc acquired a total of 508 sq km of full fold 3D and 48.5 line-km of 2D data during the last quarter of 2013 (Figure 2). Processing of this data set was completed in mid-2014. In August this year, Pitkin manifested their withdrawal from the Octon Block by end-December 2014 due internal funding issues.
Discovery and Prospects
Past and recent reviews of the SC6A-Octon Block resulted in the delineation and validation of several prospects, some of which have been drilled and tested with generally favorable results. As previously mentioned, the wells Octon -1, Octon -2, and Esperanza -1 have either flowed or had significant hydrocarbon shows. Had the wells Saddle Rock-1 and Octon-3 been tested or drilled without mechanical problems, these could have had the same good results. Also within the block are the Malajon- 1 and Nalaut-1 wells which had minor oil shows. Only the Calamian-1 well drilled in 1971 did not encounter hydrocarbons but this was drilled without the benefit of good seismic support.
Philodrill discovered the Octon Field in 1990. The Octon structure is a large north-south trending fault-bounded anticlinal anomaly. The first drilled well, Octon -1, flowed oil and condensate from the target Galoc Clastic Unit during tests. An appraisal step-out well, Octon -2 drilled in 1991, established an oil leg within the same sandstone reservoir. Estimated in-place reserves for the Octon Field are in the order of 16-23 BSCF and 9 – 12 MMBO.
The most exciting prospect of the recently developed prospects is the West Malajon Prospect located in a water depth of 73 meters. It is a three-way dip upthrown fault closure with two very prominent seismic bright spots corresponding to the two major turbidite sandstone intervals of the Early Miocene Galoc Clastic Unit (Figure 3). These bright spots conform to certain structural closure levels making them legitimate direct hydrocarbon indicators (DHIs). Initial AVO analysis of these bright spots indicates that they are positive hydrocarbon indicators. The areal extent of the closure with the DHI is 20.0 square kilometers. However, the mapped structural closure extends downdip of the DHI depth and the area of the lowest closing contour is 81.0 square kilometers. At the deeper closure level, the West Malajon Prospect becomes a part of the larger Malajon anticlinorium, an amalgamation of three major fault compartments that includes the compartment drilled by the Malajon-1 well and the compartment that was drilled by the Saddle Rock-1 well. A recent petrophysical analysis indicates that both wells have oil pays in the Galoc sandstones. The Malajon anticlinorium is essentially an inverted Paleogene synrift graben, very similar to the petroleum-prolific Sunda folds of the Sundaland basins.
The West Malajon Prospect has an estimated mean unrisked reserves of 84.0 MMBO with an upside of up to 531 MMBO. The probability of geological success (POGS) of this prospect is 46%. Based on a minimum economic reserve threshold of 25.0 MMBO, the probability of commercial success (POCS) of this prospect is 37%. Proposed total depth for the first well in the West Malajon Prospect is 610 meters. The reservoir objectives are anticipated to be between the depths of 242 to 562 meters.
The Barselisa Prospect is a three-way dip downthrown fault closure that straddles shallow and deep waters (Figure 4). The primary Galoc turbidite sandstone reservoir objective has a closure of 150.0 square kilometers. The prospect has mean unrisked reserves of 178.0 MMBO with an upside of up to 1,243.0 MMBO. A 2,000-meter well is sufficient to evaluate the potential of this prospect. There are several Sundaland commercial fields that are analogous to this particular prospect.
The Malajon Syn-Rift is a three-way dip upthrust fault closure on the Eocene sands, which were already drilled by the Malajon-1 well and which exhibited relatively good, wet gas shows. The closure of this prospect measures 62.5 square kilometers with an estimated unrisked mean gas reserves of 281 BCF and an upside of 1,714 BCF (Figure 5). Syn-rift hydrocarbon production analogues can be found in many fields of the southern Sundaland basins. The Sampaguita wells, located on the Reed Bank just to the west of the area, tested gas and condensate from Eocene sandstones.
This is a tilted fault block closure, a relatively new play in the basin, with the Pre-Tertiary as the primary reservoir objective. Its closure is 41.0 square kilometers. The estimated unrisked mean and upside reserves of this prospect are 183 BCFG and 1,195 BCFG respectively (Figure 6). One of the most prolific oil-producing fields in Southeast Asia is the Bach Ho Field (>700 MMBO) located in the Cuu Long Basin offshore southern Vietnam, which produces from Pre-Tertiary fractured granite. Other Pre-Tertiary producers in similar rift-sag basins to the Northwest Palawan Area are found in the Bohai Gulf and northern China.
The East Barselisa represents the three-way dip wrench fault closure play in the portfolio. It has the Galoc turbidite sandstones as the main objective with the younger Batas turbidite sandstones as the secondary objective (Figure 7). For the Galoc reservoirs alone, the unrisked mean reserves of the prospect are 39.0 MMBO with an upside of 168.0 MMBO.
Capare is a closure similar to the Malajon Syn-Rift Prospect, but with older Eocene reservoir objectives (Figure 8). Its areal extent of this prospect is 55.0 square kilometers with potential mean unrisked reserves of 282 BCFG and an upside of 1,731 BCFG.
The San Vicente is another Pre-Tertiary tilted fault block play similar and to the west of the Santa Rita Prospect (Figure 9). It has a closure of 45.0 square kilometers and its estimated unrisked mean reserve potential is 224.0 BCFG with an upside of 1,363 BCFG.
The Concepcion Prospect is a shallow unconformity truncation play, which is new in the Northwest Palawan Area. Its closure is 14.5 square kilometers, which is relatively small compared to the rest of the prospects in the portfolio, but, this could open up a new exploration frontier as numerous, similar plays are known to exist all over the eastern part of the Northwest Palawan Area. The mean unrisked reserves of this prospect are 9.0 MMBO with an upside of up to 53.0 MMBO (Figure 10). Similar very shallow unconformity traps have been proven to produce in very shallow depths at the East Champion/Champion Ultra-Shallow Field (EUR of 100-200 MMBO) offshore Brunei.