Prospect Saskatchewan Natural Gas in Coal Exploring New Energy Sources INTRODUCTION Demand for natural gas is projected to have the highest growth among all fossil fuels. At the same time, conventional gas sources are becoming increasingly ERA PERIOD EPOCH SOUTHERN SASKATCHEWAN difficult to find. As natural gas is an important QUATERNARY GLACIAL DRIFT commodity for Saskatchewan, the province is assessing WOOD MOUNTAIN the economic potential of developing non-conventional NEOGENE gas sources like Natural Gas in Coal (NGC, also known CYPRESS HILLS as Coal Bed Methane). In 2003, Saskatchewan Industry PALEOGENE SWIFT CURRENT TERTIARY Cenozoic RAVENSCRAG and Resources (SIR) initiated a series of preliminary FRENCHMAN assessments focused on mapping the geographic ? BATTLE? WHITEMUD distribution of coals in the Upper Cretaceous Belly River EASTEND Formation and Lower Cretaceous Mannville Group. This issue summarizes geological work done to date. BEARPAW The petrophysical characteristics of the Belly River and Mannville coals in Saskatchewan are, as yet, poorly OLDMAN understood so NGC-production capabilities for FOREMOST BELLY RIVER BELLY RIBSTONE CREEK (JUDITH RIVER) (JUDITH Saskatchewan coals are currently uncertain. The LEA PARK increasing demand and price of natural gas are ALDERSON motivating industry to examine the potential of NGC in MILK RIVER (MILK RIVER) UPPER CRETACEOUS FIRST WHITE SPECKLED SHALE MEDICINE HAT NIOBRARA Saskatchewan’s coal-bearing strata. CRETACEOUS CARLILE Mesozoic SECOND WHITE SPECKS BELLE FOURCHE COALS IN SASKATCHEWAN FISH SCALES WESTGATE COLORADO GROUP VIKING There are three main coal-bearing units in JOLI FOU Saskatchewan: the Tertiary Ravenscrag Formation, the PENSE CANTUAR Upper Cretaceous Belly River Formation, and the Lower LOWER Cretaceous Mannville Group (Figure 1). Both the MANNVILLE CRETACEOUS SUCCESS S2 UPPER Mannville Group and the Belly River Formation in SUCCESS S1 Saskatchewan are successions of sandstones, shales, and JURASSIC coals intercalated with and encased in marine shales. Figure 1 - Stratigraphy of southern Saskatchewan; coal-bearing strata are shown in blue. Each of these intervals contains numerous coal seams having ranks primarily in the sub-bituminous A to BELLY RIVER COALS sub-bituminous C range. The Upper Cretaceous Belly River Formation of Coals of the Ravenscrag Formation are mined at surface southwestern Saskatchewan contains numerous coal in southeastern Saskatchewan and rarely exceed depths seams that have potential for the production of NGC. The of 150 m. The lignite coal in the Ravenscrag is currently Belly River Formation is an eastward-thinning wedge of not considered a viable target for production of NGC. clastics that is present primarily within the western half of the province (McLean, 1971). Initial investigation of the This is the third in a series of informational brochures released by the Petroleum Geology Branch of Saskatchewan Ministry of Energy and Resources. These Belly River Formation in southwest Saskatchewan brochures are intended to highlight prospective areas in the province as identified identified coals in an area south of T15 and west of by staff geologists. It is hoped these will be useful introductions to regions and concepts for explorationists to further develop the oil and natural gas resources of R20W3, with seams mainly concentrated in the upper Saskatchewan. To receive additional copies or new releases, please email Dan part of the formation. Coals in the Belly River are Kohlruss at [email protected]. deepest, at around 550 m, along an east-west trend within T7, 8, and 9 (Figure 2). 19 48 Issue No. 3 October 2005 The net coal isopach map (Figure 4) shows that net Northern limit of T16 coal thicknesses greater than 2 m are largely confined Belly River top T15 below casing to the area south of T15 and west of R20W3. This area lies immediately south of the Hatton Gas Pool, and T14 west of the southwest Saskatchewan oil-field trend. T13 The net coal isopach exhibits a northerly trend, with T12 the thickest net coal interval between R25W3 and T11 27W3. Net coal thicknesses along this trend are Maple Creek around 5 to 9 m, but locally reach 12 m. It should be T10 noted that no data for coal are available in four T9 townships (T11 R23, T9 R24, T9 R23, T8 R24) on the T8 northern part of this trend line so that the actual net T7 coal thickness in these areas is unknown. The apparent thinning of the net coal isopach in the far T6 southwest corner of the study area coincides with a T5 group of wells in which the Belly River top occurs Southern limit of Belly River top below casing T4 above the casing. Thus, the isopach values in this area T3 should be considered as minimum values only. T2 In core, the Belly River coal displays a wide spectrum T1 of lithotypes, from carbonaceous shale to R16 R15W3 R23 R22 R21 R20 R19 R18 R17 bright-banded, well-cleated coal (Figure 5). The few R30 R29 R28 R27 R26 R25 R24 cores available have been extensively sampled for Figure 2 - Isopach map of interval from KB to top of uppermost identified Belly River coal; contour interval 50 m (from Frank, 2005). desorption experiments and so a true representation of the lithotypes is unavailable. Measured gas contents In the northwest and southwest corners of the Figure from desorption studies of Belly River coals for Nexen 2 map, it is possible that the shallowest coal seams are hidden behind surface casing and, therefore, cannot be identified. Within the main southwestern T16 coal-bearing area, up to 20 coal seams are present, Hatton Pool T15 ranging in thickness from 0.1 to 3.3 m (Figure 3). The T14 number of seams decreases eastward in conjunction Northern limit of Belly River top T13 with an overall thinning of the Belly River Formation. below casing T12 T11 Maple Creek T10 T9 T8 Oil-field Trend T7 density T6 neutron T5 gamma T4 T3 T2 Southern limit of Belly River top below casing T1 R16 R15W3 R21 R20 R19 R18 R17 R30 R29 R28 R27 R26 R25 R24 R23 R22 Figure 3 - Neutron-density log for Belly Figure 4 - Net coal isopach map (from Frank, 2005); 2 m contour River Renaissance Senate 10-10-2-27W3. interval. In the northwest and southwest corners of the map area, Coal shaded in blue. the Belly River top occurs above surface casing; thus in these areas isopach values represent minimum values only. 2 T78 Battle Creek West 7-2-4-27W3 and Nexen Vidora 77 76 75 6-4-5-25W3 (Coal Gas Technology Ltd., 2004a, 2004b) 74 3 3 73 indicate a mean gas content of 0.97 m of gas per m of coal. 72 71 70 Gas composition tests indicate average methane content of 69 68 67 95%, carbon dioxide from 1 to 5%, and minor amounts of 66 65 64 ethane and propane. Hydrogen sulphide was not detected. 63 62 61 60 59 58 MANNVILLE COALS 57 56 55 In general, the sub-bituminous coals of the Lower 54 53 52 Cretaceous Mannville Group in Saskatchewan form seams 51 50 49 of variable thickness and lateral extent that are spread over 48 47 46 a wide geographical area (Figure 6). Mannville coals range 45 44 43 in depth from near surface in the northeast corner of Figure 42 41 40 6 to 850 m in the west. Within the Mannville, there are two 39 38 37 types of coal occurrence: thin regional paralic coals 36 1 cmcm 35 34 generally less than 2 m thick, and thicker coal bodies within 33 32 paleovalleys and embayments that occur along the margins 31 30 Figure 5 - Core from Nexen 29 of the Unity, Kindersley, and Swift Current paleouplands 28 27 Battle Creek 7-2- 26 (Figure 7). The most significant coals in these areas lie in 25 4-27W3; Belly River coal; 24 23 depth 235.2 to 235.4 m. the lower part of the stratigraphic interval (Figure 8) where 22 21 20 individual coal seams can be more than 5 m thick, such as T19 near Kindersley and the eastern Kerrobert Paleovalley. Some thick coal units may have R29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 R3 resulted from deposition in paleotopographic lows related to subsidence associated Figure 6 - Approximate known geographic location of Mannville T50 Lloydminster coals in western Saskatchewan (from Christopher, 2003; Bend and Prince Albert Frank, 2004). Map covers area T45 Marsden PV from T19 to 78, R3 to 29W3. N. Battleford McGee PV Assiniboia PV Unity PV with dissolution of underlying salt beds. These T40 1 thickened coal beds, more lacustrine than paralic in nature (Christopher, 2003), escaped the Saskatoon T35 Unity Kerrobert PV Unity limitation on thickness imposed by simple Paleoupland 3 fluctuations in sea level. In 1987, Luscar studied 2 Paleoupland T30 four coalfields in the Kerrobert Paleovalley to Emb. Kindersley Emb. Kindersley PV Elbow PV Kindersley Rosetown Kindersley assess the feasibility of mining these Coleville Corridor Plato PV underground coal resources (SIR Assessment 4 File 72N-001). The report estimated coal Elbow tonnage within the four coalfields at 1715 T20 Embayment million tonnes in place. Preliminary studies Chaplin Regina have also identified the Winter-Senlac area and Embayment T15 Moose Jaw Swift Current Chaplin PV the Empress Coal Basin as sites of laterally Eastend PV continuous coal (Bend and Frank, 2004). Swift Current Paleoupland T10 N Coal lithotypes of the Mannville Group are Assiniboia PV (South Branch) T5 similar to Belly River coals in that they range from carbonaceous shale to bright banded coal. Willowbunch Paleoupland Petrographic analyses for coals within the 50 km R30 R25 R20 R15 R10 R5 R30 Legend rd R25 R20 Rosetown Coalfield indicate bright coals are 3 Mer.