Geothermal Exploration Well Mol-GT-01(-S1) Final Wellsite Geological Report
5 Geology and Lithostratigraphy
5.1 Introduction
The mudlogging services were provided by GeoService GmbH. Lithological descriptions commenced from the start of the 24” section at 34m with the first sample taken at 40m. Hydrocarbon indications are presented in chapter 6 of this report. The cuttings descriptions made by the Wellsite Geologist are presented in appendix B. The presence of the Wellsite Geologist was however mainly limited to picking casing and coring points. For the remainder of the sample descriptions refer to the daily mudlogging reports by GeoService. Some samples were also collected by Smet during drilling of the conductor to 34m.
All formation boundaries are referenced to ground level (mMDBGL).
Final formation tops were picked based on the wireline Gamma Ray from run A2, B1, D1 and E1. Only in the 12¼” section tops were based on the memory LWD Gamma Ray data as there was a depth stretch error in wireline run C1 recorded by BLM. During drilling real-time LWD-GR was used for correlation in all sections. For the Tertiary formations down to the Chalk Group, the Mol-1 well was used for reference and for the deeper sections, the well was correlated with the Merksplas and Poederlee wells.
The stratigraphic scheme utilised in this report follows the Lithostratigraphic scale of Belgium, Geologica Belgica, Vol. 4 (2001), Nr. 1-2 with additional reference from the National Stratigraphic Commission Belgium ( http://natstratcommbelgium.drupalgardens.com/ ). Also the 2 papers on Belgian stratigraphy by B. Laenen (2002) were used as reference.
5.2 Ungrouped Pliocene and Miocene formations 0.0 to 190.8m (+25.0 to -165.8m/TAW)
This upper interval can be sub-divided in 5 formations, comprising the Mol, Kasterlee, Diest, Berchem and Voort Formation.
Mol Formation Late Pliocene 0.0 to 25m (+25 to 0m/TAW)
The top of this formation is taken at ground level. The transition to the underlying Kasterlee Formation is ambiguous and based on expected isopach only. The formation comprises white, pure, coarse and medium fine sand, sometimes lignitic and with some lenses of micaceous clay. The lower part is very slightly glauconitic.
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Kasterlee Formation Zanclean to (early?) Piacenzian 25 to 35m (0 to -10m/TAW)
The top and the base of the Kasterlee formation are not clearly identifiable and are based on the expected isopach. The formation comprises grey fine micaceous sand, without fossils, slightly glauconitic, with lenses of micaceous clay at the base micaceous fine sand, often very glauconitic, burrowed and mottled at some places, a basal GRAVEL: of flints and rare silicified fossils is present.
Diest Formation Tortonian to early Messinian 35 to 151.5m (-10 to -126.5m/TAW)
The top of the formation is based on the expected isopachs of the above lying formations. The base is taken at an increase with depth in Gamma ray and density and correlating with Mol-1. No background gas is recorded in the formation.
The formation consists mainly of unconsolidated SAND with some beds of GRAVEL: The sand is grey green to brownish with colourless, milky, rarely reddish quartz grains, fine to medium grained, locally medium to coarse grained, moderately sorted, sub-angular to rounded, locally argillaceous, glauconitic, with ochre brown limonite pebbles. At 90m rare SHELL FRAGMENTS occur. The GRAVEL: is milky, yellowish, rarely reddish, rounded to well rounded.
Dessel Member 135.0 to 151.5m (-110.0 to -126.5m/TAW)
This member occurs locally in the Campine Basin at the base of the Diest Formation and could be identified in MOL-GT-01 as well based on correlation with Mol-1. The top is taken at a decrease in GR and density and an overall increase in resistivity. The member consists of fine sand with at the base GRAVEL: milky, yellowish, rarely reddish, rounded to well-rounded with rare shark teeth.
Berchem Formation Late Aquitanian to Serravallian 151.5 to 181.0m (-126.5 to -156.0m/TAW)
The top of the formation is marked by a sharp increase in Gamma Ray readings, coinciding with an increase in density. These increased levels correspond to the high glauconite content of the sand. Up to 80% of glauconite grains have been observed in the samples. The formation consists entirely of dark green SAND(STONE), predominantly fine, occasionally medium, very glauconitic, slightly argillaceous, rare silica cement and with abundant shell fragments (oysters). The transition to the underlying Voort Formation is somewhat gradual.
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Voort Formation Chattian 181.0 to 190.8m (-156.0 to -165.8m/TAW)
The transition from the above lying Berchem Formation is gradational and is taken at a Gamma Ray reading of 70 API. The formation consists of dark green SANDSTONE: friable, fine, well sorted, angular, with an argillaceous matrix, moderately glauconitic, pyritic and it has good visible porosity.
5.3 Rupel Group 190.8 to 314.3m (-165.8 to -289.3m/TAW)
The Rupel Group comprises the Eigenbilzen and Boom formations. The pick of the top of the group is ambiguous.
Eigenbilzen Formation Late Rupelian 190.8 to 211.7m (-165.8 to -186.7m/TAW)
The boundary with the above lying Voort Formation is hardly distinguishable and not very well defined in the area. Here it is taken at a drop in resistivity readings to values staying below 20 ohm.m and correlation with Mol-1. The formation is composed of SANDSTONE: dark green, colourless/clear to milky, yellowish and reddish quartz grains, friable, fine to coarse, moderately sorted, angular to rounded, with an argillaceous matrix, very glauconitic, pyritic and with good visible porosity.
Boom Formation Early to Middle Rupelian 211.7 to 314.3m (-186.7 to -289.3m/TAW)
Based on correlation, the Boom Formation can be sub-divided in 4 members, from top to bottom: the Boeretang, Putte, Terhagen en Belsele-Waas Member. The top of the Boom Formation is taken at an increase in Gamma ray readings and an associated drop in resistivity readings at the start of a cyclic interval.
Boeretang Member 211.7 to 230.4m (-186.7 to -205.4m/TAW)
This Member is characterised by a cyclic response of the resistivity, showing the rhythmic change in silt content. The Member comprises light grey to beige CLAYSTONE: firm and silty, alternating with grey argillaceous SILTSTONE.
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Putte Member 230.4 to 284.2m (-205.4 to -259.2m/TAW)
The Putte Member is a rather homogeneous unit entirely consisting of light grey to beige CLAYSTONE: firm, silty, sandy, glauconitic, very pyritic and ferruginous with abundant foraminifera and rarely ostracods. In the deeper part the claystone becomes light to medium grey, in places brownish, plastic, silty, fine sandy, micaceous and contains foraminifera.
Terhagen Member 284.2 to 302.7m (-259.2 to -277.7m/TAW)
The top of the Member is taken at the base of a high Gamma Ray bed. This peak is less pronounced than in Mol-1. The Member comprises the same lithology as the lower part of the above lying Putte Member: light to medium grey CLAYSTONE: in places brownish, plastic, silty, fine sandy, micaceous and it contains foraminifera. A thin bed of LIMESTONE is present at 299m which is micro-crystalline, light grey, beige, hard and without visual porosity.
Belsele-Waas Member 302.7 to 314.3m (-277.7 to -289.3m/TAW)
The top of this Member is taken at the start of an interval with overall lower Gamma Ray readings and higher resistivity readings. The Member comprises light to medium grey CLAYSTONE: in places brownish, plastic, silty, fine sandy, micaceous and it contains foraminifera, similar to the above lying Terhagen Member, but the silt and sand content is higher and increases towards the base.
5.4 Tongeren Group 314.3 to 326.8m (-289.3 to -301.8m/TAW)
The Tongeren Group only comprises the Zelzate Formation which at its turn is only represented by the Ruisbroek Member.
Zelzate Formation Early Priabonian to Early Oligocene 314.3 to 326.8m (-289.3 to -301.8m/TAW
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Ruisbroek Member 314.3 to 326.8m (-289.3 to -301.8m/TAW)
The Zelzate formation is mainly composed of SAND(STONE) with some interbeds of SILT/CLAYSTONE. The top of the formation / Member is taken at a further drop in Gamma ray readings and an increase in resistivity associated with the appearance of sand in the cuttings. The sand is green grey, predominately seen as loose quartz, medium, well sorted, sub-rounded, micaceous with abundant glauconite. The unconsolidated nature of the sand is also indicated by the large wash-out seen on the caliper log. The silt/claystone is beige brown, plastic to firm, sandy and it contains Nummulites and shell debris.
5.5 Maldegem Formation 326.8 to 358.7m (-301.8 to -333.7m/TAW) Late Lutetian to Bartonian
This formation is not part of a group and can be sub-divided in 4 Members based on log response and lithology, from top to bottom: Zomergem, Onderdale, Asse and Wemmel Member.
Zomergem Member 326.8 to 328.8 (-301.8 to -303.8m/TAW)
This thin unit is identified based on correlation with Mol-1 and comprises claystone. It stands out on the caliper log as an interval with much less washout than the above and under lying sand units.
Onderdale Member 328.8 to 339.2m (-303.8 to -314.2m/TAW)
The top of the Onderdale Member is taken at a drop in Gamma Ray readings and the unit clearly stands out on the caliper log as highly washed out zone. The Member consists of grey SAND(STONE), poorly consolidated, fine grained, well sorted, glauconitic and micaceous.
Asse Member 339.2 to 351.1m (-314.2 to -326.1m/TAW)
The top is taken on the GR log at an increase in Gamma Ray readings. The unit is also much less sensitive to washing out as indicated by the caliper log. The Member consists entirely of CLAYSTONE: greenish to bluish grey, plastic, silty and slightly glauconitic.
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Wemmel Member 351.1 to 358.7m (-326.1 to -333.7m/TAW)
The top of the Member is picked at a distinct increase in resistivity readings, corresponding to a drop in Gamma ray readings and the presence of sandstone in the cuttings. The Member is composed of beige grey SANDSTONE: friable, argillaceous, silty and glauconitic. In the lower part of the unit a sandy CLAYSTONE/SILTSTONE bed is intercalated.
5.6 Zenne Group 358.7 to 383.0m (-333.7 to -358.0m/TAW)
The Zenne Group comprises two formations, from top to bottom, the Lede and Brussel Formation. The top of the group is taken at a further decrease in Gamma Ray readings to values below 45 API.
Lede Formation Middle Lutetian 358.7 to 372.5m (-333.7 to -347.5m/TAW)
This formation consists of SANDSTONE: beige grey, friable, with colourless/clear quartz, fine to medium, poorly sorted, sub-angular, glauconitic with common Nummulites, calcareous cement and it has good visible porosity in places. Two distinct beds with higher density are visible on the log, probably consisting of sandy limestone or calcareous sandstone.
Brussel Formation Early Lutetian 372.5 to 383.0m (-347.5 to -358.0m/TAW)
This formation is very similar to the above lying Lede Formation. The top is picked at a decrease of the Gamma Ray readings below 30 API with corresponding increase in resistivity. The formation consists of SANDSTONE: beige grey, friable, with colourless/clear quartz, fine to medium, poorly sorted, sub-angular, argillaceous in places, glauconitic with common Nummulites, calcareous cement and it has good visible porosity in places. One distinct bed with higher density is visible on the log, probably consisting of sandy limestone or calcareous sandstone.
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5.7 Ieper Group 383.0 to 480.3m (-358.0 to -455.3m/TAW)
The Ieper Group comprises two formations, from top to bottom the Tielt and Kortrijk formations. The top of the group is taken at an increase in Gamma Ray readings, coinciding with a drop in resistivity.
Tielt Formation Middle to Late Ypresian 383.0 to 401.2m (-358.0 to -376.2m/TAW)
The Tielt Formation comprises 2 Members, from top to bottom the Egem and Kortemark Members.
Egem Member 383.0 to 392.3m (-358.0 to -367.3m/TAW)
This unit consist of sandy SILTSTONE and towards the top fine SANDSTONE: glauconitic and containing foraminifera.
Kortemark Member 392.3 to 401.2m (-367.3 to -376.2m/TAW)
The top of this Member is taken at a slight increase in resistivity, together with a drop in density. The Member consist of SILTSTONE: greenish grey, glauconitic with shell fragments at the base.
Kortrijk Formation Early and Middle Ypresian 401.2 to 480.3m (-376.2 to -455.3m/TAW)
The Kortrijk Formation comprises 3 Members based on correlation with Mol-1, from top to bottom the Aalbeke, Mons-en-Pévèle and Orchies Member. The top of the formation is taken at an increase in Gamma ray readings and a drop in resistivity.
Aalbeke Member 401.2 to 408.9m (-376.2 to -383.9m/TAW)
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This unit comprises entirely light grey CLAYSTONE: in places brownish, plastic, becoming silty towards the top, fine sandy, micaceous, glauconitic. It contains foraminifera and echinoid spines.
Mons-en-Pévèle Member 408.9 to 446.0m (-383.9 to -421.0m/TAW)
The top of the Member is marked by a distinct drop in Gamma Ray readings, together with an increase in resistivity. The Member comprises light greenish grey, locally brownish grey SILTSTONE: firm, sandy, argillaceous, micaceous, glauconitic and it contains foraminifera and echinoid spines. The siltstone is interbedded with and grading to argillaceous SANDSTONE and sandy CLAYSTONE: in general the sequence is coarsening upwards.
Orchies Member 446.0 to 480.3m (-421.0 to -455.3m/TAW)
The top of the Member is marked by an increase in Gamma ray and density readings, associated with a drop in resistivity. The unit consists of light greenish grey SILTSTONE and sandy CLAYSTONE in the upper part, firm to moderately hard, slightly glauconitic, locally calcareous and silty CLAYSTONE in the lower part.
5.8 Landen Group 480.3 to 596.7m (-455.3 to -571.7m/TAW)
The Landen Group just comprises the Hannut Formation. The top of the group is taken at a distinct drop in Gamma Ray readings to values below 45 API.
Hannut Formation Early to Middle Thanetian 480.3 to 596.7m (-455.3 to -571.7m/TAW)
The Hannut Formation can be sub-divided in 3 Members based on correlation, from top to bottom the Grandglise, Halen and Waterschei Member.
Grandglise Member 480.3 to 507.8m (-455.3 to -482.8m/TAW)
This Member is composed of SANDSTONE: light greenish grey, friable, fine, well sorted, glauconitic to very glauconitic. The upper part between 480 and 496m is strongly washed out to more than 40 inch according to the PPC caliper readings. The lower part of the unit is somewhat silty and argillaceous and is only washed out in the coarser grained beds.
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Halen Member 507.8 to 568.6m (-482.8 to -543.6m/TAW)
The top of this unit is picked at the depth where the Gamma Ray increases above 45 API. This rather uniform Member comprises predominantly SILTSTONE: grading to SANDSTONE: light greenish grey, friable to moderately hard, silt, very fine to fine, rare medium, sub-angular, moderately sorted, argillaceous, glauconitic, occasionally pyritic and micaceous and is non to locally moderately calcareous.
Waterschei Member 568.6 to 596.7m (-543.6 to -571.7m/TAW)
The top of the Member is taken where the Gamma Ray starts rising, coinciding with a gradual drop in resistivity readings and sonic velocity. The unit comprise CLAYSTONE: light greenish grey, also light brownish grey, firm to moderately hard, silty in the upper part, calcareous in the lower part, slightly glauconitic at the top, micaceous in places with rare pyrite and rare foraminifera.
5.9 Heers Formation 596.7 to 611.3m (-571.7 to -586.3m/TAW) Middle to Late Selandian
The Heers Formation is not part of a group and can be clearly sub-divided into 2 Members based on lithology, the Gelinden Member at the top and the Orp Member at the base. The top is taken at a distinct increase in resistivity readings and the appearance of marl in the cuttings.
Gelinden Member 596.7 to 607.5m (-571.7 to -582.5m/TAW)
The Member comprises light grey MARL, firm, with rare foraminifera and sponge spicules. Minor CHALK is present which is off-white, crumbly and fossiliferous, probably re-worked sediment from the Chalk Group.
Orp Member 607.5 to 611.3m (-582.5 to -586.3m/TAW)
The Orp Member consists of fine glauconitic SANDSTONE: which is friable, pyritic and calcareous. It has fair visible porosity in places. The unit is characterised by its relative high Gamma Ray readings and the low sonic velocities.
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5.10 Chalk (Krijt) Group 611.3 to 901.0m (-586.3 to -876.0m/TAW)
Based upon log correlation and lithology, the Chalk Group is sub-divided from top to bottom into the Houthem, Maastricht, Gulpen and Vaals Formation.
Houthem Formation Early and Middle Danian 611.3 to 636.3m (-586.3 to -611.3m/TAW)
The top of the Houthem Formation is picked at a slight decrease in penetration rate and a decrease in GR-readings, along with the occurrence of limestone in the cuttings. The very top of the formation shows high sonic velocities, possibly representing a hardground. The formation is rather uniform and consists of LIMESTONE with a grainstone / rudstone texture, is yellowish light grey to beige, firm, occasionally glauconitic, with abundant fossils and has no to rarely good visible porosity. The lower boundary with the Maastricht Formation is ambiguous.
Maastricht Formation Late Maastrichtian 636.3 to 710.7 (-611.3 to -685.7m/TAW)
The top is taken at a high sonic velocity bed, possibly a hard ground, but it is ambiguous. The calcarenites of the Maastricht Formation are very similar to the calcarenites of the Houthem Formation, but the latter does not contain chert. The Maastricht Formation comprises LIMESTONE (Calcarenite) with grainstone texture, yellowish light grey to beige, firm, with abundant fossils, no to poor visible porosity, with layers of CHERT, brownish grey to greyish brown, hard, splintery. At the base a bed of SANDSTONE is present which is light grey, greenish, medium to coarse, sub-rounded to well-rounded and moderately sorted grains, glauconitic. Due to the high glauconite content of the SANDSTONE: the bed shows a high GR response. The resistivity shows a strongly serrate pattern down to 685m, indicating layering, possibly due to the presence of thin chert bands. Below 685m the amount of chert increases significantly to 20-40% in the samples. It occurs as dispersed nodules in the limestone.
Gulpen Formation Late Campanian to Late Maastrichtian 710.7 to 856.0m (-685.7 to -831.0m/TAW)
The top of the Gulpen Formation is taken at a decrease in Gamma Ray readings, at the start of an interval with rather constant resistivity and sonic values. It corresponds to a negative drilling break. Although various units can be distinguished based on the resistivity and sonic curves, the lithology observed in the cuttings is rather uniform. The formation down to 827m comprises LIMESTONE: microcrystalline, arenitic, beige, hard, glauconitic, without visual
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porosity, and CALCAREOUS MARL, firm, light grey, greenish, silty to fine sandy, with rare glauconite, is fossiliferous and contains rare foraminifera. The basal unit between 827 and 856m is composed of crypto- to microcrystalline, LIMESTONE: white to greyish white, hard, rare glauconitic, without visible porosity.
Vaals Formation Early Campanian to Late Campanian 856.0 to 901.0m (-831.0 to -876.0m/TAW)
The top of the formation is taken at an increase in Gamma Ray to 60 API and a shift to higher resistivity values. The top is marked by a negative drilling break. The formation starts with grey MARL, grey, soft to firm, silty, fossiliferous, with rare glauconite and with increasing beds of SILTSTONE with depth, light grey, firm, glauconitic, marly to calcareous. At the base a SANDSTONE bed is present, light grey, greenish, fine to medium, angular to sub-rounded, well sorted, very glauconitic. Due to the high content of glauconite, the bed shows a relative high Gamma Ray response and it has low sonic velocities.
5.11 Belgian Coal Measures (Steenkoolterrein) Group 901.0 to 3107.2m (-876.0 to -3080.0m/TAW)
The top of the group is marked by distinct increase in resistivity readings to > 10 ohm.m and a shift to faster sonic velocities.
The Group is subdivided in various sequences, mostly coarsening up (table 3). Based on the occurrences of marine claystone beds was tentatively subdivided in formations and nembers. The marine claystone beds were never as such recognized in the cuttings.
After/during the drilling of well Mol-GT-02, based on GR-correlation between the wells, drilling parameters and cuttings lithology, within the Belgian Coal Measures the following normal faults were recognized in Mol-GT-01 (table 4).
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Mol‐GT‐01‐S1 (Near Vertical Well) Depth interval Fm Mb Sequence Thickness Note (mMDBGL) (mMDBGL) Interbeds without obvious large scale Alternation occurs to be quite at 901.0 1550.0 649.0 Charleroi Fm fining up or coarsening up. random. Coarsening Upward sequence 1550.0 1606.6 56.6
Coarsening Upward sequence 1606.6 1717.0 110.4
Interbeds with no clear pattern 1717.0 1913.0 196.0 Locally up to 40% of coal.
Coarsening Upward sequence 1913.0 1948.0 35.0 No significant coal. Marine claystone bed 1948.0 1954.0 6.0 Marine claystone bed
Significant quantity of coal (50%) General coarsening upward 1954.0 2015.0 61.0 in the very bottom.
Fm Chatelet Finefrau Nebenbank 2015.0 2019.5 4.5 Marine claystone bed. SANDSTONE: w hite to off w hite, hard, predominantly fine to occasionally medium Finefrau Nebenbank Sandstone 2019.5 2042.0 22.5 grained, w ell cemented w ith silica, locally slightly dolomitic, (and not micaceous). Fining upward sequence 2042.0 2080.0 38.0 Coarsening upward sequence 2080.0 2104.5 24.5
Coarsening upward sequence 2104.5 2130.0 25.5 Ransart Mb Ransart Mb Floriffoux Coarsening Upward sequence 2130.0 2240.5 110.5 5% of coal in the top Sarnsbank? 2240.5 2245.5 5.0 Marine claystone bed? Coarsening Upward sequence (about 30m of the sequence is faulted out at 2245.5 2314.0 68.5 No significant coal 2292m) Marine claystone bed 2314.0 2319.5 5.5 Marine claystone bed Coarsening Upward sequence 2319.5 2379.0 59.5 No significant coal Marine claystone bed 2379.0 2387.0 8.0 Marine claystone bed
Coarsening Upward sequence 2387.0 2398.0 11.0 No significant coal Marine claystone bed 2398.0 2402.0 4.0 Marine claystone bed WeakCoarsening Up sequence 2402.0 2461.0 59.0 Marine claystone bed 2461.0 2465.0 4.0 Marine claystone bed Coarsening Upward sequence 2465.0 2524.5 59.5 20% coal in the top. Marine claystone bed 2524.5 2530.5 6.0 Marine claystone bed
Coarsening Upward sequence 2530.5 2550.0 19.5 10% coal in the top. Coarsening Upward sequence 2550.0 2632.5 82.5 No significant coal. Marine claystone bed 2632.5 2634.5 2.0 Marine claystone bed
Fm Andenne Coarsening Upward sequence 2634.5 2667.0 32.5 No significant coal. Coarsening Upward sequence 2667.0 2678.5 11.5 No significant coal. Coarsening Upward sequence 2678.5 2687.5 9.0 2m coal bed at 2678.5-2680.5m
Coarsening Upward sequence 2687.5 2722.0 34.5 Up to 25% coal in the top Interbeds with no clear pattern 2722.0 2740.0 18.0 Coarsening Upward sequence 2740.0 2798.0 58.0 No significant coal in the top Interbeds with no clear pattern 2798.0 2855.0 57.0 Coarsening Upward sequence (about 60m of the sequence 2855.0 2890.5 35.5 No significant coal in the top is faulted out at 2875m) Prominent Sandstone bed. 2890.5 2896.0 5.5 Fining upwards sequence 2896.0 2936.0 40.0
Predominant Clay-Siltstone Sequence 2936.0 3098.5 162.5 Chokier Fm Claystone sequence with very high GR 3098.5 3109.5 11.0 Table 3: Sequence Stratigraphy of the Belgian Coal Measures Group.
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Fault Well Depth Notes Structural information Throw
Not spotted on drilling ~30m Mol-GT-01 2292m parameters. Mudloggers report missing some limestone (calcite)
mudloggers report 10% Mol-GT-01 2861m The fault at 2861 in Mol-GT-01 (calcite) and 2875m in Mol-GT-S1 is the ~60m Very high penetration rate with same fault. Geometrical missing low bit weight between 2874 consideration indicate that the Mol-GT-01-S1 2875m and 2887m; mudloggers report fault dip at least 56° in a NE-ly 10% (calcite) direction. Table 4: Faults in the Belgian Coal Measures Group.
Charleroi Formation Late Upper Bashkirian; upper Westphalian A to B 901.0 to 1606.6m (-876.0 to -1581.2m/TAW)
The Charleroi Formation consists of an alternation mainly between siltstone, claystone, sandstone and coal. Generally, lithologies tend to grade to each other.
The CLAYSTONE is medium to dark grey to brownish grey, firm to moderately hard, occasionally sub fissile, silty, micro-micaceous, slightly carbonaceous and with fine plant remains and silty locally grading to siltstone.
The SILTSTONE is medium to dark grey to brownish grey, moderately hard to hard, occasionally sub-fissile, micro-micaceous, generally carbonaceous, argillaceous, sandy occasionally grading to sandstone.
The SANDSTONE is light to medium grey to brownish grey, hard, very fine to fine, well sorted, sub-rounded to rounded, argillaceous, slightly calcareous, micaceous, with carbonaceous laminations and locally coal particles, locally silica cemented, poor to fair visible porosity.
The COAL is black, brittle, vitreous lustre and is present in generally thin beds that never exceed 3m of thickness.
In the 17½” hole, based on the GR, sonic log and gas readings, the coal seams were located at 908m, 920m, 952.5-955m, 960m, 969m, 977m, 983m, 1004, 1009m, 1019m, 1028m, 1050m, 1055m, 1091-1093.5m, 1098.5-1100.5m, 1111m, 1120m, 1132m, 1155m, 1164m, 1175m, 1200m, 1202m, 1212m, 1218m, 1227m, 1231m, 1235m, 1281m, 1290m, 1307m, 1315m, 1329m, 1365m, 1401m, 1418m, 1430m, 1454m. In the 12¼” hole section, coal seams are located at 1527m, 1537m and 1541m based on gas readings and GR. The cased hole sonic data does not show any character due the absence of cement behind the casing.
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Some LIMESTONE (up to 15% of cuttings volume) was recorded between 1045 and 1060m. The limestone is light brown, hard and microcrystalline.
A conventional core was cut from 1034 to 1042m, 133m below the top of the formation. See Appendix C for core report.
The base of the Charleroi Formation corresponds to the Wasserfall marine band. The marine band was not seen on the GR-logs or in the cuttings.
Châtelet Formation Early Upper Bashkirian; Lower Westphalian A 1606.6 to 2245.5m (-1581.2 to -2219.9m/TAW)
Based on the occurrence of the Finefrau Nebenbank, a marine band, the Châtelet Formation was subdivided in the Floriffoux Member and the Ransart Member.
Floriffoux Member 1606.6 to 2019.5m (-1581.2 to -1994.0m/TAW)
The sequences are mostly coarsening up and are composed of claystone, siltstone and sandstone grading to each other. Traces to 5% of coal occur throughout, but may locally be in excess of 20%
The CLAYSTONE is dark grey to locally black, firm to hard, locally fissile, occasionally micro-micaceous, locally carbonaceous, silty grading to siltstone.
The SILTSTONE is brownish grey to grey, friable to moderately hard, micro- micaceous, locally carbonaceous, locally sandy, argillaceous, grading to claystone.
The SANDSTONE is off white to light grey to light brownish grey, friable to hard, very fine to fine grained, well sorted, well cemented with silica or dolomitic cement, locally micaceous, sub rounded to rounded, poor visible porosity, silty grading to SILTSTONE: rare pyrite.
The COAL is black, brittle, vitreous lustre. The main coal seams are located at 1722, 1748, 1752, 1835, 1852, 1862, 1872, 1905, 1953 and 2004m.
The base of the Floriffoux Member coincides with the base of the Finefrau Nebenbank (2015 – 2019.5m), a marine claystone bed. The bed could not be distinguished in the cuttings.
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Ransart Member 2019.5 to 2245.5m (-1994.0 to – 2219.9m/TAW)
The interval 2019.5 – 2042.0m is a 22.5m thick sandstone bed, known as the Finefrau Nebenbank sandstone bed. The sandstone is white to off white, hard, predominantly fine to occasionally medium grained, well cemented with silica, locally slightly dolomitic, poor visible porosity, rare pyrite (and not micaceous).
The rest of the Ransart Member comprises mostly coarsening up sequences. As in the Floriffoux Member, the sequences are composed of siltstone and sandstone grading to each other. Traces to 5% of coal occur throughout.
The CLAYSTONE is medium to dark grey to brownish grey, friable to firm occasionally moderately hard, micro-micaceous, locally carbonaceous and mostly silty.
The SILTSTONE is medium to dark grey to brownish grey, firm to hard, micro- micaceous, locally very fine sandy, argillaceous and locally carbonaceous.
The SANDSTONE is white to off white to beige, hard, predominantly fine occasionally medium grained, sub rounded to rounded, well cemented with silica, locally slightly dolomitic, poor visible porosity, micro-micaceous, fine carbonaceous matter, silty.
The COAL is black, brittle, with a vitreous lustre. No significant coal seams are present within the Ransart Member.
Andenne Formation latest Serpukhovian to early Bashkirian (Chokierian or Alportian to Yeadonian, based on goniatite zonation) or Namurian B-C Mol-GT-01: 2245.5 to 3096.1m (-2219.9 to -3069.0m/TAW) Mol-GT-01-S1: 2245.5 to 3098.5m (-2219.9 to -3071.8m/TAW)
As in the overlying other intervals of the Belgian Coal Measures Group, the sequences are composed of claystone, siltstone and sandstone grading to each other. Most sequences are coarsening upwards. Traces of coal occur throughout, but locally some higher percentages were observed in the top (sandy) part of some of the sequences. The lithologies are equal to those of the overlying Châtelet Formation. Only few coal seams were observed: 2470, 2550, 2678, 2699, 2899 and 3013m. Below 2936m, both sandstone and coal have mostly disappeared from the cuttings.
A core was cut from 2926 to 2931.2m in the Andenne Formation in the original hole. For core chip descriptions see Appendix C.
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At the time of drilling well Mol-GT-01, the Beringen reverse fault was believed to be intersected at 2400m within the Andenne Formation, bringing about a 145m repeat. However GR-correlation while drilling well Mol-GT-02 revealed GR to correlate fairly well beween the wells Mol-GT-01 and Mol-GT-02 and therefore no reverse fault is believed to be present in well Mol-GT-01.
Chokier Formation Alportian to Arnsbergian Mol-GT-01: 3096.1 to 3107.2m (-3066.9 to -3080.0m/TAW) Mol-GT-01-S1: 3098.5 to 3109.5m (-3071.8 to -3082.8m/TAW)
The top of the Chokier Formation in marked by a gradual, but distinct increase in GR- readings. GR readings in the Chokier Formation are generally above 150 API. The Spectral Gamma Ray log reveals that the increase in GR is due to the increase in concentration of Uranium.
The formation comprises claystone similar to that of the overlying formations, but is slightly darker.
5.12 Souvré Formation Pendleian to Asbian Mol-GT-01: 3107.2 to TD at 3148.0m (-3080.0 to TD at -3120.6m/TAW) Mol-GT-01-S1: 3109.5 to 3175.5m (-3082.8 to -3148.7m/TAW)
This formation is not part of a group and represents the transition from the clastic Belgian Coal Measures Group to the Dinantian limestones.
The top of the formation is picked on GR-correlation with wells Merksplas, Poederlee and Halen at a distinct drop from GR-reading above 165 API to GR-readings of 90-100 API. Generally GR readings are highly variable between 90 and 220 API.
The formation comprises mainly CLAYSTONE: dark grey to dark brownish grey, moderately hard to hard, fissile, micro-micaceous, locally micro-pyritic also lumps of pyrite, slightly to locally moderately calcareous, locally siliceous.
A few thin limestone bed occurs. In well Mol-GT-01 the first limestone bed occurs at 3141.5m (34.3m below the top) and was recognized with 30% in the cuttings sample between 3140 and 3142.5m. The limestone bed was marked by a slightly higher pump pressure while drilling. In well Mol-GT-01-S1 the same limestone bed occurs at 3147.5m (38.0m below the top)
The LIMESTONE is a very fine grained packstone (calcarenite), medium grey, firm to moderately hard, slightly argillaceous, with very fine carbonaceous matter.
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Other than the claystone and limestone, up to 5% of CALCITE is present. The Spectral Gamma Ray readings show high Uranium concentrations of 20-30ppm in the upper part. Below 3160m the Uranium concentrations drop as the formation is becoming more calcareous with depth.
The formation tops for the Chokier and Souvré were intersected both in the original hole and the side-track. The apparent dip for these formation tops were calculated as well as the true dip for an assumed dip direction of 30°.
True dip azimuth Formation top Easting X Northing Y Depth m/TAW 30 (assumed dip direction)
Chokier Fm in OH 201782.85 212942.46 -3069.0 Chokier Fm in ST 201785.85 212971.42 -3071.8 Distance 29.11 On azimuth5.91 True dip with 30° dip azimuth 6.04 Apparent dip on azimuth 5.52
True dip azimuth Formation top Easting X Northing Y Depth m/TAW 30 (assumed dip direction)
Souvré Fm in OH 201781.82 212942.17 -3080.0 Souvré Fm in ST 201785.54 212971.31 -3082.8 Distance 29.37 On azimuth7.27 True dip with 30° dip azimuth 5.82 Apparent dip on azimuth 5.37
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5.13 Carboniferous Limestone (Kolenkalk) Group 3175.5 to Total Depth at 3610.0 (-3148.7 to TD at -3582.9m/TAW)
The Kolenkalk Group could be subdivided in the Goeree and Loenhout formations based on log correlation. The transition from the Souvré to the Goeree Formation is transitional in areas of lower slope deposits. The top of group is taken at the top of a 9m thick interval with significantly lower Gamma Ray readings than the overlying beds coinciding with a significant increase in limestone in the cuttings. The overall density and sonic velocity values increase in the Kolenkalk Group compared to the overlying Souvré Formation.
Goeree Formation 3175.5 to 3227.5m (-3148.7 to TD at -3200.6m/TAW)
The Goeree Formation consists of limestone interbedded with thin claystone beds and between 3210 and 3225m up to 5% chert was seen in the cuttings.
Two limestone textures were observed in the samples: mudstone and packstone/grainstone. The MUDSTONE is dark grey to black, is hard to very hard, siliceous and is carbonaceous to very carbonaceous. The PACK/GRAINSTONE is medium grey to dark brownish grey to black, hard to very hard, locally siliceous and is possibly recrystallized.
The interbedded CLAYSTONE is dark grey, hard to very hard, splintery to fissile, calcareous, locally slightly silty, siliceous to very siliceous and contains traces of pyrite.
The CHERT in the deeper part is light brown translucent, very hard, has an angular/conchoidal fracture, is carbonaceous/argillaceous and calcareous.
The overall matrix porosity of the Goeree Formation is low with an average of 1.4%, 0.5% median. The formation is intersected by veins, filled with coarse crystalline calcite. At 3221m a larger vug is present as was indicated by the neutron-density X-plot and drilling parameters and confirmed by the image log.
Loenhout Formation Early Brigantian to Holkerian 3227.5 to Total Depth at 3610.0m (-3200.6 to TD at -3582.9 m/TAW)
The top of the formation is taken at the start of an interval with low Gamma Ray readings below 20 API average. No further subdivision has been made, but the deeper part may be contributed to the Velp and Steentje-Turnhout formations.
Due to intermittent total loss of returns beyond 3280m, no cuttings samples are available from 3273m to 3365, from 3487 to 3505m and from 3560 to 3610m.
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The formation down to the karstified limestone at 3280m comprises rather homogeneous limestone. The LIMESTONE has a packstone/grainstone (calcarenite) texture, is light to medium grey to brownish grey, hard to very hard and is locally siliceous. The formation is intersected by abundant veins of CALCITE: white, fine to coarse crystalline.
From 3283m to 3472m the Spectral Gamma Ray log show some thin argillaceous beds, also with higher concentrations of Thorium and Uranium.
Between 3340 and 3360.6m 2 cores were taken with very low recovery (7.8 – 10.4%). Due to the total losses no cutting samples are available for the cored interval. The core chips revealed:
3340-3340.7m: LIMESTONE: packstone to grainstone, medium to dark grey, hard to very hard, carbonaceous, locally pyritic, frequently intersected by thin calcite veins (<0.5 mm), with stylolites (enriched in carbonaceous and argillaceous material), that offset the calcite veining: i.e. thin calcite veining is older than the stylolites.
3349.10m: LIMESTONE: fine grained packstone (fine grained calcarenite), dark grey, hard to very hard, carbonaceous, argillaceous, locally pyritic, no visible porosity, intersected by 7mm thick calcite vein.
3349.2-3350m: irregular wavy interbeds of LIMESTONE: mudstone-fine grained packstone (calcilutite - calcarenite), very dark grey, hard, very carbonaceous, locally pyritic, argillaceous to very argillaceous grading to MARL. Some calcite veins up to 1mm.
Below 3360.5m the formation comprise limestone with thin interbeds of claystone. At 3510m a 5m thick dolomite bed is present (base of Velp Formation?). Below 3472m the formation is less argillaceous / radioactive (U, Th) as was revealed by the SGR log.
The LIMESTONE has a mudstone texture, is dark grey to black, hard, argillaceous, carbonaceous, with veins/fractures filled with translucent to milky white calcite. The interbedded CLAYSTONE is dark grey to black, moderately hard, platy, slightly calcareous, carbonaceous. The DOLOMITE is fine crystalline, beige to dark grey, hard.
Below 3512m the LIMESTONE has a grainstone texture, is fine to medium crystalline, medium to dark grey, hard, carbonaceous, rarely with fractures / veins filled with calcite, with occasionally thin interbeds of CLAYSTONE: black, moderately hard, slightly calcareous, carbonaceous and light grey, firm, platy, pyritic, siliceous. From 3520m onwards 5-10% CHERT is observed: grey brown, translucent, very hard, splintery.
The overall porosity of the formation is low (1.4% average, 0.6% median) and it is clear from the log evaluation that the productivity is coming from intervals with karstified limestones and
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major fractures. The “sweet spot" is the interval 3280.5 - 3284m. This is the zone where total losses occurred. Other fractured zones which may add deliverability are: 3248.5-3249.2m, 3297.8-3298.8m, 3299.7-3300.6m, 3308.0-3309.9m, 3323.9-3325.6m, 3362.9-3364.1m, 3389.0-3390.6m, 3392.9-3393.8m, 3406.3-3407.6m and 3488.2-3488.5m.
5.14 Condroz Group Devonian The Devonian was not reached in well mol-GT-01-S1 as TD was called early in order not to jeopardize the well due to the total losses.
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