Last checked at 21 Mar 2016 08:00
Stellar Resources plc
("Stellar Resources" or the "Company")
Horse Hill-1 Oil Discovery, Weald Basin, UK
Aggregate Flow Rate Likely the Highest of any UK Onshore New Field Discovery Well
Stellar Resources (AIM: STG, ISDX: STG) announces that Horse Hill Developments Ltd has informed the Company that the final Horse Hill 1 ('HH-1') Portland test flowed at a stable dry oil rate of 323 barrels of oil per day ('bopd'), double the previously reported rate. The final total aggregate stable dry oil flow rate from two Kimmeridge limestones plus the overlying Portland sandstone stands at 1688 bopd. Over the 30-90 hour flow periods from each of the 3 zones, no clear indication of any reservoir pressure depletion was observed. Further analysis of data is ongoing and will be reported shortly.
Flow Test Highlights
· The final Portland test of 323 bopd, over an 8.5-hour, period is the highest stable dry oil flow rate from any onshore UK Portland well. On further testing, with a larger pump, the rate doubled from the previously reported stable dry oil rate of 168 bopd. The Portland was produced at maximum pump capacity and showed no clear indication of depletion. It is likely that the rate can be further increased using a higher capacity downhole pump during the next planned test.
· Proof that the Kimmeridge limestones contain significant volumes of moveable light oil that can be flowed to surface at commercial rates
· As previously reported, the stable, natural dry-oil flow rate of 464 bopd from the Lower Kimmeridge Limestone is the first ever flow from this rock unit in the Weald Basin and onshore UK
· Based on the analysis of published reports from all significant UK onshore discovery wells, the Company concludes that the well's 1688 bopd is likely the highest aggregate stable dry-oil flow from any onshore UK new field wildcat discovery well
· Based on the analysis of published reports from all significant UK onshore discovery wells, the Company concludes that the 901 bopd from the Upper Kimmeridge zone is likely the highest stable natural dry oil flow rate from a single reservoir in any UK onshore new field wildcat discovery well
· High quality Brent Crude produced: light, sweet oil (40 degrees API in Kimmeridge, 35-37 degrees API in Portland) 1,940 barrels delivered to the Esso Fawley refinery
· Preliminary analysis confirms that the Lower and Upper Kimmeridge Limestone units are naturally fractured reservoirs with high deliverability
· Strong possibility for further optimisation and increased flow rates from all 3 zones in future development and production wells, particularly through the use of horizontal wells
Summary Table of Test Results
Zone | Maximum Instantaneous Oil Rate | Stabilised Dry Oil Rate | Perforated Interval | Stabilised Flow Period | Depth Below Surface |
bopd | bopd | ft | hours | ft | |
U. Portland * | 360 | 323 | 103 | 8.5 | 2000 |
U. Kimmeridge ** | 1008 | 901 | 88 | 4.0 | 2800 |
L. Kimmeridge ** | 700 | 464 | 80 | 7.5 | 2950 |
Total | 2068 | 1688 | 271 | 20 | |
Note: * flow rate limited by pump stroke rate capacity ** natural flow | |||||
Final Portland Flow Test
As previously reported, the first Portland test period gave a stable dry oil rate of 168 bopd over 9 hours. Further periods of flow using the same pump, re-seated immediately above the perforated zone, resulted in a similar stable dry oil flow over a two-day period. It was apparent that the rate was limited by the 7-ft stroke capacity of the pump. A larger 26-ft stroke pump was installed resulting in a maximum rate in excess of 360 bopd and an average stable rate of 323 bopd over 8.5 hours. This flow rate was still limited by pump capacity. During pumping, annulus fluid levels did not drop appreciably, implying little pressure depletion.
HH-1 Overview and Recap
The HH-1 discovery well, completed in November 2014, was the first modern well since the 1980s to test the entire Jurassic and Triassic section of the Weald Basin, reaching Palaeozoic basement at circa 8500 feet. The well was drilled with oil-based mud to ensure good electric log data collection. A comprehensive suite of modern Schlumberger log data, including magnetic resonance data, was acquired. Geological samples were collected at 10 ft intervals throughout the well specifically for geochemical analysis.
The analysis of thermal maturity data (vitrinite reflectance) from geological samples, by a leading analyst in Switzerland, showed that the Kimmeridge section of the well was within the peak oil generative window. Previous researchers had stated that the Kimmeridge was thermally immature, and whilst recognised to be the time equivalent of the North Sea's main oil source rock, had likely only generated either early stage immoveable bitumen or minor quantities of moveable oil, as seen in the Upper Kimmeridge Limestone in Balcombe-1, 15 km to the south of HH-1.
As previously announced, geochemical analysis of samples throughout the c. 1300 ft thick Kimmeridge shale section of HH-1, showed that the shales comprised a world class oil source rock. Analysis of 277 samples showed 780 ft of drilled section exceeding 2% total organic carbon ("TOC") by weight, with an average of 4.1% TOC. The richest section, and possible sweet-spot, lay between the Upper and Lower Kimmeridge Limestones with an average of 5% TOC and a high of 9.4% TOC. The organic shales demonstrated high oil generative potentials ranging from an average of 35 kg/tonne to a high of 103 kg/tonne and with high Hydrogen Indices ("HI") averaging 754. Further significant potential source rock sections were identified in the Middle Jurassic and Lias sections of the well.
Both Nutech and Schlumberger, leaders in the field of electric log analysis in rocks with low permeabilities, were then engaged to investigate the presence of oil in the HH-1 well. The Company reported the results during 2015, which indicated that a mean estimated total of between 9.97 and 10.99 billion barrels of OIP, or oil in the ground, existed under the HH-1 licence area, contained in shales and limestones of the Kimmeridge, Oxford Clay and Lias.
The Board commented:
"This is excellent news and we look forward to future plans to bring these exciting results into production"
Interest in Horse Hill
Stellar Resources owns a 10% direct interest in HHDL. HHDL is a special purpose company that owns a 65% participating interest and operatorship of Licence PEDL137 and the adjacent Licence PEDL246 in the UK Weald Basin.
Qualified Person's Statement:
Stephen Sanderson, who has over 35 years of relevant experience in the oil industry, has approved the information contained in this announcement. Mr Sanderson is a Fellow of the Geological Society of London and is an active member of the American Association of Petroleum Geologists.
For further information please contact:
Stellar Resources plc: +44 (0) 20 7440 0640
Alastair Clayton
Nominated Adviser:
Cairn Financial Advisers LLP +44 (0) 20 7148 7900
James Caithie / Sandy Jamieson
Broker:
Optiva Securities Limited +44 (0) 20 3137 1902
Christian Dennis / Jeremy King
Public Relations:
Square1 Consulting +44 (0) 20 7929 5599
David Bick
Glossary
discovery | a discovery is a petroleum accumulation for which one or several exploratory wells have established through testing, sampling and/or logging the existence of a significant quantity of potentially moveable hydrocarbons |
degree API | a measure of the density of crude oil, as defined by the American Petroleum Institute |
electric logs | tools used within the wellbore to measure the rock and fluid properties of surrounding rock formations |
extended flow test | a flow test, as per the permission granted by the Oil and Gas Authority, with an aggregate flow period duration over all zones of greater than 96 hours and up to 90 days maximum |
flow test | a flow test or well test involves testing a well by flowing hydrocarbons to surface, typically through a test separator. Key measured parameters are oil and gas flow rates, downhole pressure and surface pressure. The overall objective is to identify the well's capacity to produce hydrocarbons at a commercial flow rate |
generative potential (S2) | the amount of hydrocarbons that can be generated from a unit volume of source rock established via the S2 peak from rock-eval pyrolysis, normally expressed in milligrams of hydrocarbon per gram of rock (or kilogram per tonne) |
horizontal wells | wells that during drilling are steered so as to be at or close to 90 degrees from the vertical to follow a particular geological stratum or reservoir unit |
hydrogen index (HI) | the amount of hydrogen relative to the amount of organic carbon in a sample, normally expressed in milligrams of hydrogen per gram of TOC. The higher the amount of hydrogen the more oil prone the source rock when subjected to time temperature and pressure; an initial HI over 450 normally indicates an oil prone source rock |
limestone | a sedimentary rock predominantly composed of calcite (a crystalline mineral form of calcium carbonate) of organic, chemical or detrital origin. Minor amounts of dolomite, chert and clay are common in limestones. Chalk is a form of fine-grained limestone |
magnetic resonance | a phenomenon by which a nucleus absorbs electromagnetic radiation of a specific frequency in the presence of a strong magnetic field; it is used in modern electric logs |
mean | or expected value, is the probability-weighted average of all possible values and is a measure of the central tendency either of a probability distribution or of the random variable characterised by that distribution |
moveable oil | oil that can flow or be pumped to the surface |
naturally fractured reservoirs | fractured reservoirs contain cracks or surface of breakage within rock; fractures can enhance permeability of rocks greatly by connecting pores together; naturally fractured reservoirs have been created over geological time by nature, not man-made via hydraulic fracturing |
organic rich | a rock rich in organic matter which, if subjected to sufficient heat and pressure over geological time, will generate oil or gas. Typical source rocks, usually shale or limestone, contain above an initial 2% organic matter by weight |
P50 | a 50% probability that a stated volume will be equalled or exceeded |
peak oil generative window | a vitrinite reflectance (Ro) measurement of 0.5-0.7%, indicating conditions that are thermally mature to generate moveable oil |
permeability | the capability of a porous rock or sediment to permit the flow of fluids through its pore spaces |
pump stroke capacity | in a rod pump the product of the rod cross-sectional area, maximum distance between the top and bottom of the rod stroke movement and the pump stroking speed |
recoverable volumes | a rock rich in organic matter which, if subjected to sufficient heat and pressure over geological time, will generate oil or gas. Typical source rocks, usually shale or limestone, contain above an initial 1% organic matter by weight |
reservoir deliverability | the fluid production rate that can be achieved from a particular reservoir or reservoir unit |
reservoir pressure depletion | a reduction in reservoir pressure as indicated by downhole pressure gauges positioned in the well close to the zone being tested |
sandstone | a clastic sedimentary rock whose grains are predominantly sand-sized. The term is commonly used to imply consolidated sand or a rock made of predominantly quartz sand |
source rock | a rock rich in organic matter which, if subjected to sufficient heat and pressure over geological time, will generate oil or gas. Typical source rocks, usually shale or limestone, contain above an initial 1% organic matter by weight |
thermal maturity | a term applied to source rocks which have received sufficient temperature and pressure over geological time to generate hydrocarbons |
total organic carbon | the weight percentage of organic carbon within the rock which is a commonly used measure of hydrocarbon source rock richness |
vitrinite reflectance | a measure of the percentage of incident light reflected from the surface of vitrinite particles in a sedimentary rock. It is referred to as % Ro and is a measure of the thermal maturity of a rock. Top of the oil window is dependent on source rock type, but is widely recognised to be at an Ro equivalent of between 0.5-0.7%. |
wildcat | an exploration well in an unproven geological concept, rock unit or area |