In September 2011, APEX was awarded a 100% working interest and the operatorship of Block 36 in the Sultanate of Oman, a large exploration block in the southern part of the prolific Rub al Khali petroleum basin of the Saudi Arabian peninsula, with an area of 18,500 km2 (4.6 million acres or 199 townships).
Block 36 is highly underexplored with only one shallow and two deep wells (Al Hashman and Burkanah) prior to APEX acquiring the Block. Each deep well had hydrocarbon shows with over 40 meters of Silurian source rock. The Silurian is one of the main source rocks that generated oil for the giant fields in Saudi Arabia, such as Ghawar. There are several potential reservoir units in the Paleozoic, below and above the source rock. Geochemical modelling indicates that much of the Block is in the oil window for hydrocarbon maturity of the Silurian source.
Wells Drilled in Block 36:
Fasad-1 (Cities Service, 1959)
- Dead oil in U. Jurassic Lekhwair and extractable oil in L. Cretaceous Natih
Al Hashman-1 (PDO, 1990)
- Oil show and completion attempt in Silurian Sahmah
Burkanah-1 (Phillips, 2000)
- Oil/gas shows
Hayah-1 (DNO, 2016)
- Strat test, minor gas shows
In addition to the Silurian, a Mesozoic petroleum system is present over much of the Block, as evidenced by a surface oil seep, in the form of a conical sand mound, which was found by an APEX seismic crew near the centre of the Block. The hydrocarbons present at the seep have been typed by CGG Robertson as late Jurassic/early Cretaceous.
The Silurian Sahmah source rock is one of the major sources for the giant Saudi fields and has been modelled to be in the oil window over a significant portion of Block 36. The sandstone member within the Sahmah has 15 meters and 5 meters of net hydrocarbon pay respectively, in the Burkanah and Al Hashman wells of Block 36.
Block 36, situated on the southeastern flank of the Rub Al Khali Basin, inherits its structural style from both Saudi Arabia to the North and the South Oman Salt Basin to the South-East. In eastern Saudi Arabia a complex strike-slip environment is described whereas the Western Deformation Front of the South Oman Salt Basin is also structurally complex with transpressional character. Northeast to southwest trending strike-slip faulting has created numerous structural features interrupting the northward regional dip to form potential hydrocarbon traps. Reservoirs identified in the three deep wells drilled on the Block are the same as those documented onshore Saudi Arabia and Qatar.
Exploration Work Since Block 36 Acquired
In September 2013, APEX concluded a farm-out agreement with the Norwegian company, DNO International.
DNO acquired 1,000 km of new high-resolution 2D seismic and reprocessed another 4000 km of legacy 2D seismic. On the basis of the reprocessed and newly acquired seismic, APEX and its partner identified a number of structural prospects and numerous exploration leads. The reserve size of the prospects and leads ranges from 50 to 300 million barrels.
The first exploration well under the farm-out, Hayah-1, was drilled by DNO in May 2016 as a stratigraphic test in the previously undrilled western portion of the Block, reaching a total depth of 3010m. DNO subsequently decided to withdraw, having invested more than $US 30 million in exploration costs, returning 100% of the Block to APEX, effective in early 2017.
Based on the important geological insights provided by the Hayah well, APEX developed a new and promising structural model of the prospectivity of the Block, firming up the potential of certain of the leads and identifying several promising new plays. One of these is a stratigraphic play with large resource potential in the Mesozoic, where Jurassic and Cretaceous reservoirs pinch out in the north-centre of the Block.
Extensive geochemistry work has been completed by APEX, both on subsurface samples as well as through a new surface geochemical study. The latter indicated areas of anomalous hydrocarbon microseeps at surface, many of which coincide with leads and prospects identified from seismic interpretation.
In addition, a regional resource play has been identified on the Block, in the Rhuddanian sandstone horizon trapped within the prolific Silurian Sahmah source rock, based on a discovery in a nearby Block made in late 2017 and currently under development. This light-tight oil play has potential areal extent in the Block which APEX has estimated to be in excess of 4000 km2.
Plays and Prospects
A) Rhuddanian Light Tight Oil/Gas Appraisal Play
The operator of a nearby Block in Oman has recently completed several wells in a tight sand reservoir which APEX has interpreted to be the intra-Sahmah Rhuddanian sand, trapped within the prolific Sahmah hot shale source rock. The wells were deepened below a depleted field producing from the Permian Gharif and Carboniferous Al Khlata formations since the 1980s. The deepened vertical wells each have had between 300 and 600 bpd initial flow rates of light oil (42-47 API) from the Rhuddanian.
The Rhuddanian sands are effectively enclosed and sealed by the Sahmah shale and as a result there is no need for structural closure; the reservoirs are a stratigraphically trapped accumulation. These sands have been the subject of a large-scale drilling effort in Saudi Arabia over the past several years, resulting in several discoveries in the Saudi portion of the Rub Al Khali to the north and east of Block 36.
The Rhuddanian sand is present, and is hydrocarbon-bearing, in both the Burkanah and Al Hashman wells in Block 36. APEX has mapped this formation across the basin in Oman from the recent discovery southwest to Block 36, indicating an areal extent for the play within Block 36 of approximately 4000 km2.
This Rhuddanian play is analogous to the Bakken resource play in the US/Canada. Based on the vertical well production history from the recent nearby discovery, APEX has modeled the performance of horizontal lateral wells in the Rhuddanian, estimating cumulative recoveries of 1.4 MMbbls for each 1000m lateral well. The first such lateral in the nearby Block has tested at more than 3000 bpd (without stimulation) and is being put into production at 1100 bpd.
Stimulated Horizontal Type Well Production Forecast (1000m Lateral)
Based on the APEX modeling, the STOOIP and ROIP (in the oil-bearing area of the play) are estimated to be 9.2 and 1.5 MMbbls per sq. mile respectively.
B) Conventional Exploration Prospects
In addition to the Rhuddanian appraisal play, APEX has a portfolio of high-impact conventional exploration prospects and leads in both the Jurassic and Paleozoic petroleum systems.
The presence of numerous surface hydrocarbon microseep anomalies, many of which overlap mapped prospects and leads provides important corroboration for these seismically-interpreted structures. The composition of the gases encountered at the micro-seeps confirms the presence of an active petroleum system and indicates that these are oil-associated gases.
Ratio of C1/(C2+C3) and C2/(C3+C4) from Acid Extraction Samples
Ratio of C3 to C2 from Acid Extraction Samples
Conventional Exploration Prospects and Leads
- Shallow faulting could trap porous Cretaceous and Jurassic.
- Strong amplitudes at Al Khlata and very strong Sahmah Shale trough suggests thick hot shale source rock.
- Strong “Deep Play” seismic events indicate potential good reservoir at that level (No well tie on Block).
- Area: 30 km2
- Prospective resource: OOIP: 1.06 billion bbls; ROIP: 260 MMbbls
SE Burkanah Prospect
- Fault bounded pop-up feature.
- Closure from Al Khlata to Ghudun.
- Up to 60 km2 closure at Hasirah.
- Amplitudes at Khuff, Al Khlata, Sahmah, Ghudun.
- Area of closure: 28 km2
- Prospective resource:
- STOOIP: 1.1 billion bbls;
- ROIP 267 MMbbls
NE Al Hashman Lead
- Structure is bounded to the South by deep faulting which was mostly truncated by the unconformity at the Gharif level.
- Strong amplitude changes are evident at Gharif and below and are used to define fault throws.
- Surface geochemical anomalies present.
- Area of closure: 20 km2
- Prospective resource:
- OOIP = 725 MMbbls
- ROIP = 177MMbbls
The work completed during the past five years has dramatically de-risked the block, identifying a lower-risk resource play in addition to several high-impact structural prospects where chance of exploration success is highest.
APEX currently plans to drill two wells in late 2019 or early 2020: one appraisal well to test the Rhuddanian resource play, and one exploration well to test a stacked Jurassic/Paleozoic prospect.
APEX is currently undertaking a non-brokered farm-out process to identify a partner to join in this next stage of exploration of Block 36. For further information, please contact: Michael Volcko, CEO at firstname.lastname@example.org or +1-403-708-5231