Ian. 2009. Petroleum geology (oil geology) of the south of England. http://www.soton.ac.uk/~imw/Oil-South-of-England.htm. Version: 9th April, 2009.
Ian West, Romsey, Hampshire
and:
School of Ocean and Earth Science ,
National Oceanography Centre, Southampton
Southampton University,
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Wytch Farm is Europe's largest onshore oilfield. It has reserves of 467 million bbl - 74 million cubic metres. There are three reservoirs: the Frome Formation (Middle Jurassic), a relatively minor reservoir, at about 800m; the Bridport Sands (Upper Lias, Lower Jurassic) at about 900m; and the Sherwood Sandstone (Triassic) the most important reservoir at about 1600m. The oil field is situated on the south side of Poole Harbour, in the northern part of the Isle of Purbeck, with extension seaward, to the east, into Poole Bay. The original and main site is on a branch road from Norden (near Corfe Castle). The oil field is well-concealed in the Purbeck Forest and most of it is in private land inaccessible to the public. Very little of it can be seen without special arrangements. The huge Goathorn drilling rig projects well above the trees and can be seen from the South Haven Peninsula, and from Brownsea Island and Sandbanks. The public cannot get close to this. Some pumps, successfully concealed from environmental impact, are on Furzey Island in Poole Harbour. There is also a gathering station, a rail terminal and a pipeline to Southampton Water. All this is very well-known, but it is hardly seen at all by the public because of a prize-winning environmental policy by the operators - BP.
The Bridport Sands reservoir was in production since 1979. The Sherwood Sandstone reservoir is extensive and continues eastward under Poole Bay to near Bournemouth Pier. An early plan to obtain oil from the relatively shallow water of Poole Bay was to construct an offshore island, Hook Island. This scheme was rejected and difficult to implement in a such an environmentally sensitive and valuable residential and holiday region. Later there was much success with Extended Reach drilling from the Goathorn Peninsula, northwest of Studland village. This type of drilling accelerated production by three years and continues very successfully.
The Bridport Sands are well known as the Upper Reservoir of the Wytch Farm Oilfield, Dorset. As a marine Jurassic sandstone, with good porosity and permeability, they form a good, conveniently accessible example of a Jurassic reservoir, and are not greatly different from North Sea sandstones, such as the Brent Sandstone. They have been much studied (and further information will be added).
Hoe No.1, Hoe Lane, North Baddesley, near Southampton and Romsey
(If interested, compare to - drilling in the 1920s.)
Humbley Grove Oilfield, Hampshire
.
The Singleton Oilfield (map ref. SU 884154) is inconspicuously situated in Singleton Forest about 10km. north of Chichester, Sussex. It is within the picturesque Chalk hills and forests of the South Downs. It is near the A286, the Midhurst road, north of Chichester, and about 2km. north of the village of Singleton. You cannot drive to the well site but it is not far from a public footpath in the woods. The site is fairly small, well-fenced and guarded and effectively hidden in the woods. Little can be seen from the outside.
The beam pumps are painted a dull, vegetation colour. There is control over noise to a limit of 33 decibels; the trees help reduce noise, particularly when they are in leaf. It is, thus, relatively inoccuous from an environmental point of view and has hardly any visual impact; many walkers may go past on the nearby footpath without being aware that it is there. Obviously, if it was greatly expanded or there were long phases of active drilling it would be much more conspicuous.
The oilfield is one of several in the West Weald, that is the West Sussex and East Hampshire region. It is within onshore licence PL 240 and is largely owned by Providence and it is operated by Star Energy Group PLC (STAR). The field has been producing since 1986. Estimates of STOIIP [oil in place] in the Great Oolite reservoir are approximately 70 MMSTB [million barrels]. Produced oil ia at 37° API. It is trucked to the Holybourne Rail terminal for sale (Providence Oil Company, October, 2007 - Singleton Oil Field Acquisition Effective).
The site, has at present six wells, including five beam pumps or pumpjacks (nodding donkeys) and a jet pump well. A few years ago the site was producing about 450 barrels of oil per day Anonymous (2008), but the figure is now higher and at about 600BOPD (Providence Oil Company). Planned expansion will increase production to between 850 to 1,000 barrels per day. Providence Energy will be increasing the one-hectare site by 0.3 hectares and installing four new jet pumps. Singleton Oilfield has been in operation since 1990 and has expanded several times over the past 18 years. It has planning permission to drill for oil until 2016. For more information on ownership see Providence (2007). It should be noted that Star Energy Group PLC (STAR) are also involved with Providence in Natural Gas production at the Singleton Oilfield.
The main reservoir rock at Singleton, as in adjacent areas of the Western Weald (Sussex-Hampshire border) is the Great Oolite, although the limestones of the Forest Marble and Cornbrash above are also in use. The field consists of two east west trending elongate horst blocks divided by a narrow graben (Providence Oil Company, October, 2007 - Singleton Oil Field Acquisition Effective). The wells produce from the Great Oolite formation, consisting predominantly of oolitic lime grainstones deposited during transgressive/regressive episodes and has been sub-divided into three members. Note that there can on occasions be some problems with terminology, in that the Great Oolite Limestone Formation was considered by Sellwood et al. (1985) to be part of a larger Great Oolite Group which also includes the Forest Marble. It seems here that from the reference to three members, the scheme of Sellwood et al is being used, and that the members are the Humbly Grove Member (at the base), the Hoddington Member and Herriard Member. The Forest Marble lies above the Herriard Member, and consists, in the region, of skeletal oolitic packstones and grainstones with interbedded claystones (mudstones). It tends to be more skeletal than the Great Oolite Formation beneath, and has a typical Forest Marble fauna, including crinoidal debris.
An isopach (thickness) map of the Great Oolite Limestone Formation (i.e. Great Oolite sensu stricto) has been provided by Sellwood et al. (1985). He gave the Great Oolite Limestone Formation as between 60 and 75m. thick in the area of Singleton and Horndean. The Singleton X-9 well was drilled in this main Great Oolite reservoir in the southwest flank of the field. However the Singleton X-8x well is situated on the northern flank of the field and a 2,000 foot (609m.) horizontal section was drilled and completed in the Cornbrash and Forest Marble sequences. Wells in the area have similar oil water contacts within the Great Oolite reservoir, indicating that the prospects may be connected Providence (October, 2007) have provided a map of the oilfield showing that the wells are greatly deviated to the south, the southwest and to the southeast for two or three kilometres. Some of these pass close to the village of Singleton, which is south of the well site. The map suggests that the location for the facilities could have been at the village, or on open fields south of its present site, but an environmentally concealed place in woodland was probably preferable.
In the long term future the oilfield could be used for gas storage (Providence, October, 2007). This means that it is not a temporary operation but it likely to be an almost permanent feature, at least in some form.
Hasley Hill, New Forest - Fordingbridge No.1 Petroleum Exploration Borehole
An exploratory borehole for oil, Fordingbridge No.1, was put down by BP (The British Petroleum Company Limiited) at the western end of Hasley Hill (map reference near SU192118), near Ogdens, in 1959. The location is at 229 feet or 69.7 metres above OD. It was a major borehole, especially for that time, extending down to 1368 metres, and penetrating the Mercia Mudstone. There must have been a large drilling rig on Hasley Hill.
Fordingbridge No.1 is the only borehole for petroleum exploration within the New Forest and was drilled at a time when planning and environmental regulations were less strict. However, there was an application for a borehole at Denny Lodge by Shell in 1982. That application was rejected. An important deep borehole for geothermal exploration at Marchwood was drilled at the former Marchwood Power Station. This also provided useful information to the oil industry.
There follows an extract from Falcon and Kent (1960), pp. 48-49, giving summary information on the well at Hasley Hill. Norman Leslie Falcon was the Chief Geologist of BP. and Dr. Percy Edward Kent (well-known as Peter Kent, F.R.S.), Geological Advisor of BP Exploration (Canada).
"MORE RECENT BORINGS IN SOUTHERN ENGLAND
...
(c) Fordingbridge, Hampshire
Lat. 500 54' 17.7"; long. 010 43' 59.6"; elevation 229 feet O.D. [69.8m.] [Mr A.P. Terris was Resident Geologist at the borehole]
The section of Fordingbridge No 1, drilled on a gravity and seismic high at Ogdens (Hasley Hill), near Fordingbridge, is still being worked out, but the following brief account may be given.
Drilling began in the Tertiary beds of the Hampshire basin; the Chalk was reached at 678 feet and. the Upper Greensand and Gault penetrated from 1997 to 2251 feet. Beneath the Gault the well passed directly into Kimmeridge Clay, shown by a core 20 feet below the top to be Lower Kimmeridge (with Aulacostephanus, etc.). Only 210 feet of Kimmeridge Clay remained beneath the Gault. The unconformity eliminates the Lower Greensand, Wealden, Purbeck, Portland and Upper Kimmeridge, measuring approximately 4000 feet in eastern Dorset (the nearest outcrops) and some 2700 feet at Portsdown on the other side of the same Tertiary basin. This represents a very considerable pre-Albian uplift.
Beneath the Kimmeridge the boring proved a normal sequence of Corallian (about 170 feet), Oxford Clay (about 430 feet), Cornbrash (35 feet) and Great Oolite Series (404 feet). The last-named was mainly limestone, with only a minor development of argillaceous beds which could be ascribed to the Fuller's Earth, in marked contrast to recent borings nearer the Dorset coast (see the account of the Radipole borings). Below, 118 feet of sandy and ferruginous limestones and ironstones are ascribed to the Inferior Oolite, and beneath this the well proved an Upper Lias development of Bridport Sands type, 250 feet thick. The remainder of the Lias was normal, except that the Middle and Lower subdivisions totalled only about 450 feet and rested upon 60 feet of beds ascribed on fossil evidence to the Rhaetic. The well was completed at 4487 feet, 106 feet into the Keuper [Mercia Mudstone]."
Borehole Succession in Listed Format:
Rotary Table (?) - 229ft. - 69.8m. ht. above O.D.
Tertiary - middle of Bracklesham Group downwards
(678ft - 206.7m. thickness)
Base of Tertiary and top of Chalk - 678ft. - 206.7m. depth.
Chalk (1319ft. - 402m. thickness)
Base of Chalk and top of UGS - 1997ft. - 608.6m. depth.
Upper Greensand & Gault
Unconformity - 2251ft. - 686m. depth.
Lower Kimmeridge Clay (210ft. - 64m. thickness)
Base of KC and top of Corallian - 2461ft. - 750m depth. depth.
Corallian (about 170ft. - 51.8m. thickness)
Base of Corallian and top of Oxford Clay - 2631ft. - 801.9m. depth.
Oxford Clay - (about 430ft. - 131m. thickness)
Base of Oxford Clay and top of Cornbrash - 3061ft. - -932.9m. depth.
Cornbrash - (35ft. - 10.7m. thickness)
Base of Cornbrash and top of Great Oolite - 3096ft. - 943.7m. depth.
Great Oolite - (mostly lst. but with some Fullers Earth) (404ft. - 123.1m. thickness)
Base of Great Oolite and top of Inferior Oolite - 3500ft. - 1066.8m. depth.
Inferior Oolite - sandy and ferruginous limestones and ironstones - (118ft. - 36m. thickness)
Base of Inferior Oolite and top of Bridport Sands 3618ft - 1102m. depth.
Upper Lias - Bridport Sands - (250ft. - 76.2m. thickness)
Base of Bridport Sands and top of Liassic Clays - 3868ft. - 1179m. depth.
Middle & Lower Liassic Clays - (450ft. - 137m. thickness)
Base of Middle & Lower Liassic Clays and top of Penarth Group (Rhaetic) - 4318ft. - 1316m. depth.
Penarth Group (Rhaetic) - (60ft. - 18.3m. thickness)
Base of Penarth Group and top of Mercia Mudstone (Keuper) - 4378ft. - 1334.4m. depth.
Mercia Mudstone (Keuper) penetrated - (60 feet - 18.3m.)
TD = actual - 4487ft - 1367.6m. (4438ft. - 1352.7m. - calculated on above figures).
The Marchwood No.1 Geothermal Borehole, 1979-1980
The Marchwood No. 1 Geothermal Borehole was commenced on the 8th November 1979 and completed on the 27th February 1980. It preceded the other geothermal well of the area, which was Southampton No.1 Borehole. That was started on the 26th September 1981, and the well head is located in central Southampton north of the West Quay centre and is in now in the car park of the children toy store - Toys-R-Us.
Thus the Marchwood well was the first geothermal experiment in the region and a drilling rig was put in place so as to be capable of drilling to the Total Depth (T.D.) of 8580 feet (2615m.). The Marchwood and Southampton area is part of a region of high heat flow through the underlying strata. At Southampton the rate is 59 milliwatts per square metre compared to 40mW/m 2 for more northerly parts of Hampshire (Edwards and Freshney (1987). This is almost a 50% increase, and seemed worth exploiting. I was at the Geology Department of Southampton University at the time and followed, to some extent, the progress of both wells. The initial hope was that the Sherwood Sandstone reservoir, a porous red, Triassic sandstone exposed in the Sidmouth to Budleigh Salterton area, would contain hot water at about 100 degrees Centigrade. The usual geothermal gradient is about 30 degrees per kilometre, so that without considering the details, a temperature like this would be expected at round about 3 kilometres. Thus, if the Sherwood Sandstone had been near the total depth of the well, about 2600m, water with a temperature near that of boiling water might have been obtained, and this could have been useful. It was intended to use the heat produced to supplement the energy supply for the Marchwood, coal-fired Power Station, to which the well was adjacent.
However, the Marchwood Borehole, did not produce hot water at this temperature. We shall consider, below, why the temperature was lower than expected. A further complication was that a year or so after the drilling, and for other reasons, the Marchwood Power Station was demolished. Thus, there was no real use nearby for the warm water. However, in spite of the lack of commercial success with regard to geothermal energy, the borehole was certainly a successful research venture. It provided much information on potential oil reservoirs in the area, and particularly helped the understanding of the Bridport Sands, the Upper Reservoir of the Wytch Farm Oil Field.
The Sherwood Sandstone of the Trias was the selected target for hot water. This is because it was the deepest formation in the area that was expected to be sufficiently porous and permeable. This was proved to be the case. An older sandstone, the Devonian Old Red Sandstone lies lower in the borehole sequence, but it is tight, that is, non-porous and non-permeable from a practical point of view. The Sherwood Sandstone can transmit water from a considerable distance and is recharged up-dip in Devon. It should be appreciated, though, that the water is saturated brine. This is because the Trias contains substantial salt deposits in places and some evaporites were proven in the Marchwood Borehole. Even if hot water is pumped from a well it cannot be used directly but has to be directed through stainless steel heat exchangers with the aid of downhole, stainless steel pumps. The brine may also contain heavy metals in solution, and has to be discharged somewhere. The ideal is to have two adjacent boreholes, a production borehole for producing hot water and an injection borehole for disposing of used brine. There was no second borehole at Marchwood. At Southampton Geothermal Well there is only one borehole but the used brine and any associated trace element content is discharged into Southampton Water (already a polluted estuary). Thus the matter is not necessarily simple.
The British Government department, BERR, have commented that the geothermal aquifer resource within the Wessex Basin, under the Bournemouth area, appears to be the most attractive for possible future exploitation, but the commercial risks of speculative drilling remain high. At 3.5p/kWh or more, the cost of heat from the aquifer resource is still significantly higher than that from conventional industrial boilers (approximately 1.44p/kWh). See also Rollin, for more information on low temperature geothermal energy in the UK, including the Wessex Basin.
Returning to specific matters regarding the Marchwood No. 1 borehole, there was, as mentioned above, a problem regarding depth of the geothermal aquifer. The part of interest is the succession from the Lower Greensand downward. It is well-known that there is usually, in this region, a Pre-Albian unconformity at the base of the Gault, and the Basal Gault Pebble Bed is an indication of this. At the base of the Gault in the Marchwood Borehole (depth - 2240ft. - 682.8m.) , the pebble bed does not seem to have been identified (there was coring in the Gault but without recovery). Under the Gault is a very thin sequence of Lower Greensand. It is from 2240ft. to 2267ft.,only 27ft. or 8.2m (compare to the southwestern Isle of Wight where it is, at Atherfield, about 800ft. or 243m.). There is an unconformity, as is common, at the base of the Lower Greensand. It is lying directly on top of Kimmeridge Clay. The Wealden, which can reach more than 600m in the subsurface, is missing. So too is the Purbeck Formation which reaches about 120m. in Durlston Bay. The Portland Stone and Portland Sand is missing. These units can reach about 70m in total thickness. Thus if about the greatest thicknesses could have present, then the Sherwood Sandstone would have been about 790m. lower, although this would have been the extreme. If you add this to the base of the Sherwood Sandstone in Marchwood No. 1 then you obtain 2515m, just a little less than the total depth of the well. Of course the unconformity present means that some of the Kimmeridge Clay is probably missing, and in any case, the Lower Greensand is abnormally thin. A large drilling rig, shown above, was chosen and the plan for drilling the Marchwood Geothermal Borehole was appropriate to deal, if necessary, with a thick Jurassic-Cretaceous sequence including Wealden, Purbeck and Portland. This was a sensible plan, and a reasonably thick sequence was expected so that the Sherwood Sandstone would prove to be deep and hot. It was therefore a disappointment when the unconformity at the base of the LGS was discovered. It was thus possible to use the spare capacity of the drilling rig to penetrate the Devonian and to gain an understanding of the strata below the economic basement (i.e. below the base of the Permo-Trias). So that is why so much Devonian has been drilled.
Southampton No.1 (Western Esplanade) Geothermal Well, 1981.
Summary Well Data (after Thomas and Holliday, (1982)):
Well Name: Southampton No.1 (Western Esplanade)
Location: Western Esplanade, Southampton
National Grid Reference: SU 41559 12018
Latitude: 50° 54' 24''
Longitude: 1° 24' 33''
Hydrocarbon Exploration Licence: Amoco/Ultramar XL 138
Client and Operator: Department of Energy and Institute of Geological Sciences (now British Geological Survey, BGS)
Drilling Contractor: Kenting Drilling Services Ltd.
Rig: Kenting No. 12.
Spud Date: 26 September 1981
TD Reached: 20 November 1981
KB Elevation: 24.92 ft. AOD
Ground Level: 10.96 ft. AOD
Terminal Depth (TD): 5994 ft. below Kelly Bushing
Hole Diameter (depth below KB)
26 inch to 165 ft.
17.5 inch to 3005 ft.
12.5 inch to 5994 ft.
Casing and completion depths below KB:
20 inch casing to 158 ft.
13 and 3/8 inch casing to 2995 ft.
9 and 5/8 inch liner was hung from 2826 ft. to 5635 ft.
Cores - six cores were taken with total core length of 226 ft. See Thomas and Holliday (1982) for further details of coring.
Wireline logging: Schlumberger Inland Services Inc., Tessel Well Services Ltd.
Mud Logging: Exploration Logging (UK) Ltd.
Drilling Superintendent: Mr. D. McIntyre, Drilcon Ltd.
In addition to the Marchwood Borehole, there is another deep borehole nearby which provides useful information on the geological succession and lithologies. It has provided information relevant to petroleum exploration in addition to its primary purpose in providing geothermal energy and data on geothermal prospects. This well is the Southampton No.1 Geothermal Borehole. It was drilled the year after the Marchwood No.1 Geothermal Well so that this was the second borehole in the area for geothermal energy. The location is Western Esplanade and the well-head is easily seen by parking in the car park of Toys-R-Us and Babies-R-Us, northwest of the West Quay Centre, Southampton.
In many respects Southampton No.1 proved to be similar to Marchwood No.1 and most of the formations are similar and at similar depths. A slight difference is the occurrence of Portland Group beneath the sub-Lower Greensand unconformity. At the time it was hoped that, a sub-Albian fault occurring between the two sites might have led to a significantly deeper level for the Sherwood Sandstone at Southampton, and, consequently, higher temperatures. However, in fact, the situation proved to be similar to that at Marchwood and the downhole brine temperature was at about 76 degrees C. A better figure near 100 degrees might have been obtained had the Cretaceous sequence been without major unconformity and was as thick as on the southern Isle of Wight and at Swanage Bay, Dorset (i.e. if, therefore, the Sherwood Sandstone was about another half kilometre or one kilometre lower). The hot rather than boiling temperature was accepted as satisfactory, and this time, unlike Marchwood, the wellbore was not continued deep into the Devonian (Old Red Sandstone) and merely went into the top part of it before TD'ing.
In spite of the moderate, rather than high temperature, the hot brine could be used at Southampton to provide geothermal energery for central heating. The heat has been used to some extent for local buildings, such as Southampton Civic Centre, West Quay Centre and the Royal South Hants Hospital. The brine is brought to the surface by stainless steel, downhole electric pumps. It is not only saturated for sodium chloride and therefore corrosive, but it also contains very small quantities of undesirable trace elements, heavy metals. The brine is thus not usable directly for central heating but is processed through stainless-steel heat-exchangers before being discharged into Southampton Water (ideally there should be another borehole into which the used brine is discharged downwards, but there is not another borehole at Southampton). Thus, the hot brine can usefully provide geothermal energy, but it is a complex matter and is not cheap or easily. In practice the geothermal energy is used in combination with heat from fossil fuel sources at the power station near the West Quay Centre (note the conspicuously red building).
Pumping is from a downhole turbo pump at about 600m., and at about the level of the Gault and the Lower Greensand. The geothermal aquifer is the Sherwood Sandstone which is much deeper ranging from 1729m. to 1767m. Thus the brine is rising under hydrostatic pressure for about two/thirds of the height, and is pumped up for the last part.
The pumping scheme is explained in basic form in a large colour poster, kindly provided by Utilicom and Southampton Corporation. At the well head, shown above, there is an electrical pump which forces a certain proportion of the brine back down a central pipe so as to provide motive power for the downhole turbo pump. This long, narrow, fluid-driven turbine is fairly deep in the borehole and it pumps the hot brine up an outer concentric pipe to the surface (together with the recycled brine used for the power to drive it). All the equipment has to be stainless steel to avoid corrosion from the brine.
Lyndhurst - A, Formerly-Proposed, Petroleum Exploration Borehole, Denny Inclosure
Oil exploration has taken place in the New Forest and, as noted above, BP has drilled a well at Hasley Hill in 1959 (Fordingbridge No. 1). It proved to be dry, however, and the interest in oil exploration moved to Dorset, particularly Wytch Farm in the 1970s. Shell UK Ltd. acquired the licence blocks for much of the New Forest. Block PL.181 from Lyndhurst eastward was surveyed seismically using the White Lias, the top of the Penarth Group (Rhaetic) as a good reflector. Look at the map above and you will see that the best high area that seems to have closure (no lateral escape) is where the 4400 and 4300ft contours loop round adjacent to south of a fault. This type of half-dome is very promising for trapping upward-moving oil and gas. It is situated exactly where it would not be welcomed - under the Denny Wood Nature Reserve!
Of course, there was controversy regarding an application to drill in Denny Inclosure, even though the Hasley Hill well seems to have gone through without much argument. There was a Public Inquiry and no permission for drilling was granted. A result of the Public Inquiry is that some interesting information of the subsurface became available at the meeting (see above).
Shown above are maps and a cross-section through the strata beneath Denny Inclosure. The proposed trajectory of the Lyndhurst - A Borehole is shown, on the basis of a diagram on a handout sheet provided by Shell UK Ltd at the time of the Public Inquiry. The diagram has been redrawn in colour and labelled with the probable stratal units that are present. The drawing shows the possibility of oil (and gas?) in all the three main reservoirs of the area. However, it is not know whether anything worthwhile is actually present in any or all of the reservoirs, and the matter remains an interesting open question.
Of the reservoirs, the Sherwood Sandstone Reservoir (Trias) is the important reservoir at Wytch Farm and it the reason that the field is one of the largest onshore oil fields in NW Europe (with nearly 500 million barrels reserves). The Sherwood Reservoir, however, requires that special migrations conditions have enabled hydrocarbons to reach the sandstone, and this may or may not have happened in the New Forest area. The Bridport Sands reservoir is the original reservoir of Wytch Farm and is largely operated by water injection to increase the reservoir pressure. The Great Oolite and possibly adjacent Cornbrash reservoirs are those that have proved successful in the eastern Weald area, as at Humbley Grove, Horndean, Singleton etc. It is not known, of course, whether there is any oil or gas in these potential reservoirs at Denny Inclosure. Conditions might have been unfavourable for migration into the area in Cretaceous time (the general migration date for the region was Cretaceous). The extensional fault which provides closure on the north side might not necessarily be sealing (i.e. oil could have escaped upwards in the Cretaceous). The oil industry probably knows much more now about the likelyhood of oil reserves in this New Forest area, although different companies and different geologists may have varying views. Porosity and permeablility of the reservoirs are interesting aspects that students might wish to consider. Fortunately there is much detailed information on Marchwood No.1, the important borehole at Marchwood Power Station. The log of this should be examined in detail, and any information of Fordingbridge No. 1 and Lockerly No. 1 would be useful. Particular aspects to consider would be the marginal facies changes in the Trias towards the southeast, where it thins out, and the improvement in the reservoir characteristics of the Great Oolite in the same direction.
At the time when Lyndhurst - A was planned deviated wells could be drilled but not laterally from any great distance. Now the new Extended Reach Technology, used so successfully at Wytch Farm to obtain oil at the Goathorn Well from the vicinity of Bournemouth Pier means that most of the New Forest can now be drilled from drilling rigs situated beyond its official limits, or from urban areas within the forest region. If it was thought worth-while and cost-effective the Denny Inclosure prospect could now be drilled by extended reach (i.e. obliquely) from a large rig at Lyndhurst, Ashurst or Marchwood.
(This might be a good topic for student discussion and projects on the future of the New Forest National Park in terms of petroleum geology and petroleum industry. The New Forest has been greatly affected by the petroleum industry in various ways, and even the oil from Wytch Farm passes through it by buried pipeline.)
Lymington and New Milton - Petroleum Exploration License - PDL089
Part of the New Forest region near Lymington has been under investigation for petroleum resources by Wessex Exploration Ltd. Details will be found by going to their website at:
Here is a small extract from the start of the webpage to draw attention to their work. Particularly see the good maps. Note the information on the Hurst Castle Prospect.
"Wessex Exploration Limited, bidding on its own in the 9th Landward Bid Round was awarded Petroleum Exploration and Development License (PEDL) 089 on 4 September, 2000. PEDL 089 is located in southern Hampshire near the towns of Lymington and New Milton, on the mainland opposite the western end of the Isle of Wight. The work obligation for the initial term of the PEDL was met when Northern Petroleum drilled the Bouldnor Copse 1 well, and fifty percent of the PEDL was relinquished in September, 2006. The PEDL is now in its second exploration period.
Wessex on 11 September, 2002 made an "Out of Round" application for a Petroleum Production License over the area immediately offshore from and adjacent to PEDL 089. Wessex was awarded License P1153 over this offshore area, effective 3 October, 2003. The primary term of this license expired in October, 2007, but was renewed by DBERR into a second exploration period.
A preliminary structural map of the Hurst Castle Prospect at the Sherwood Sandstone level is shown on the next page. Estimated P10 oil-in-place is of the order of 190 million barrels for the Sherwood reservoir alone, with possible recoverable reserve of 36 million barrels. A separate structural map shows four-way dip closure offshore, with possible P50 recoverable reserves in the 16 million barrel range." ... [continues]
Hurst Castle Prospect
See the details of the Hurst Castle Prospect.
They report that the Hurst Castle Prospect has potential recoverable reserves of the order of 36 million barrels from the Sherwood reservoir, in a Wytch Farm type fault-block feature. The primary reservoir is the Triassic Sherwood Sandstone. The Bridport Sands is a secondary objective as is the Frome Limestone (Great Oolite). In the same region an exploratory well was drilled at Boulder Copse across the West Solent on the Isle of Wight. The results were negative but Wessex Petroleum did not consider that this impacts on the prospectivity of the Hurst Castle objective.
Note that it is of interest regarding the New Forest National Park that the reservoir objectives are the same as those of Shell at Denny Inclosure (Lyndhurst - A).
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