Coalbed

Coalbed Methane

The potential in British Columbia Tertiary coal deposits.

Emphasis: New Deposits.

By

George S. Green, B.A. Geol.

(© 2010 George S. Green)

 

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Forward

This paper was originally written in 1992. It was re-written in 2010 so that it could be run through a word processor. Some editing simplified the text and condensed the information used to support the premise of this work.

There are two geological maps that should be used in conjunction with the reading of this paper. I leave it up to the reader to secure those maps through the respective departments of government that produced them. They are Geological Survey of Canada publications;

Fraser River Map 1386-A and Parsnip River Map 1424-A.

What I look for are the Eocene sedimentary strata that occur within the map areas. It is my opinion, that these sedimentary strata may contain more coal than has heretofore been discovered. The details underlying this observation are outlined in this paper.

 

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Preface

Please consider for a moment that all coal deposits currently identified in British Columbia have only been located because of one thing common to all; that thing being 'outcrop'. In the history of coal exploration in B.C., especially for thermal coal, coal has only been discovered in the locations where it outcrops. From outcrop, it was followed underground but only locally. If it did not outcrop, its location elsewhere was not considered. At this time in British Columbia, late 1800's to mid 1900's exploration geologists and mining engineers were after low cost strip coal, and they prospected for it using (mainly) Geological Survey of Canada reports and maps identifying outcrop.

In addition to this, no one was going to drill 3,000-foot exploration holes looking for coal just to find out if the geologist was right or wrong. Let alone put down another 300 holes to delineate a new deposit. Add to this the cost of sinking a 3,000 foot shaft and the overall cost was simply too much. Therefore, for economic reasons, no one set out to look for coal beyond that which did not outcrop.

Now (1992) (which is when this was first written) and along comes 'coalbed methane' and all you need to do is drill a few holes to make it work. Now any coal deposit down to 5,000 feet under the right geological circumstances becomes of value.

I have looked at the geology of some of the Eocene coal deposits of central British Columbia and I am of the opinion that new, yet undiscovered coal deposits remain to be discovered. Principally in down dropped fault blocks that do not outcrop, and which may or may not be covered by Miocene lava flows.

This research began with an area of interest that extended from Prince George and Vanderhoof in the north, to Tulameen and Princeton in the south. It was perhaps the most difficult of the areas identified (overall) but it was based upon my experience at Hat Creek and an intention to find coal near to the natural gas pipelines that service the lower mainland of B.C.

 

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Introduction

In 1975, B.C. Hydro drilled into its Hat Creek (lignite) coal deposit. That deposit turned out to be in excess of 600 meters thick. Reserves approached one billion (metric) tons. The lower most identifiable seam (alone) measured some 120 meters in true thickness! All of it solid, clean coal.

Since this author's participation in B.C. Hydro's 1977-78 exploration program on the Hat Creek property, this author has maintained an interest in B.C. Tertiary coal deposits and their related geology. By 1982, this geologist felt that there existed a possibility that another Hat Creek sized deposit might be found elsewhere in the region.

Several efforts were undertaken to find interested parties able to fund further research. This, mainly for the large coal tonnage possible in making such a discovery. However, because of poor market conditions and the extreme depth involved, as well as the quality of the coal, there was little interest shown. The effort then turned in 1992 towards coalbed methane.

There are two things about B.C. Tertiary coal deposits that are of interest for this study. One, is that these deposits occur throughout most of south-central British Columbia, from Prince George in the north to Princeton in the south. The larger deposits found to date being the Similkameen deposit near Princeton, the Merritt deposit near the town of Merritt, the Hat Creek deposit west of the town of Cache Creek and the Bowron River deposit east of Prince George.

In addition to this, coal outcrops occur all along the Fraser River as it flows south from Prince George to Lytton, B.C. Very few of these coal outcrops have ever been drilled to any depth sufficient enough to determine if their thickness might approach that of the Hat Creek deposit. Even the Hat Creek deposit; first located because of outcrop, was not looked at in detail until 1975.

 

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The second thing of interest is that much of the region where these Tertiary coal deposits are located, is covered by Miocene lava and/or basalt flows. In some localities, these plateau basalts and lava flows cover Tertiary sedimentary strata containing coal. The inference is that additional coal, that does not outcrop, might yet be located beneath these basalt and lava flows.

These volcanic flows also provide confinement pressure, and it is confinement pressure that packs the coalbed methane into the pore spaces of the coal. In general, the greater the confinement pressure the greater the amount of coalbed methane that can be packed into that coal. For these reasons, plus industry interest in coalbed methane, these areas are going to become of interest for exploration purposes.

 

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Location, access and topography.

The principle area in question is situated between the towns of Prince George in the north and Cache Creek in the south. This involves several thousand square miles of land..

The area, by a large measure, is accessible by way of a number of primary and secondary roads. Highway 97 for example, runs the full length of the area of interest.

The topography is characterized by low to moderately high relief mountain ranges with low rolling foothills, some of which are located atop a broad expanse of volcanic plateaus, cut by deeply incised river valleys. The Fraser River being the most notable example.

The land is covered with sagebrush in the south and pine, poplar and fur trees in the north. Cattle ranching, mining and timber harvesting are the principle industries in the region.

 

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Geology.

This paper will use the geology of the Hat Creek property as a reference or type locality around which further discussions will take place. The sedimentary strata containing the coal and the formations immediately above and below these strata at Hat Creek are of particular interest. These formations were identified and designated formations during the 75-78 exploration work conducted on the Hat Creek property by B. C. Hydro and its consultants.

The lower most formation identified at Hat Creek is the Coldwater Formation, an assemblage of sandstone, siltstone, claystone, conglomerate and minor coal. It is approximately 1,372 meters thick. Its lower contact was never penetrated at Hat Creek.

The formation immediately above the Coldwater Formation is the Hat Creek Formation. It rests conformably upon the Coldwater and consists mainly of coal with numerous interbeds of siltstone, claystone, sandstone and pebble conglomerate. It is approximately 550 meters thick and is divisible into six identifiable members.

Above, and in a conformable contact with the Hat Creek Formation, there sits the Medicine Creek Formation. It consists mainly of siltstone and claystone; semi to unconsolidated in nature which causes it to break down rapidly upon weathering. An upper contact for the Medicine Creek Formation has yet to be located. Drilling data indicates that the formation itself exceeds 200 meters in thickness. Some estimates place its thickness at around 500 meters.

The coal seams within the Hat Creek Formation are Eocene in age and are contemporaneous with those of the Merritt and Princeton- Similkameen coalfields.

The environment of deposition for the coal at Hat Creek was relatively stable and increasingly so in a northeasterly direction. The source area for the sediments contained within the rock members of the Hat Creek Formation existed to the southwest of the deposit. Sediment flooded into the basin from this direction.

Recommended reading: A Tectonic History of The Hat Creek Coal Deposit, copyright 1992 by George S. Green, B.A. Geol. This paper will discuss the geology of the Hat Creek property in detail and is useful for its bibliography.

 

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Structural Geology.

The structural geology of the Hat Creek deposit is characterized by a high incidence of high angle reverse faulting; left and right lateral strike slip components to this faulting; and bedding plane and low angle thrust faulting. This structural setting is indicative of the presence of strong compressive forces impinging upon the deposit most likely (and relatively speaking) from the north.

The deposit is flanked on three sides by mid-sized mountain ranges. To the east are the Trachyte and Cornwall Hills mountain ranges; to the west are the Mount Martly Stock and the Clear Range Mountains; and to the north are the Pavillion Mountains.

From the stratigraphic and structural evidence, it appears that the Pavillion Mountains, which may not have been present at the time of the deposition of the coal, rose up, on a wedge shaped fault plane and more or less plowed into the Hat Creek coal deposit at the north end of the Hat Creek valley. This activity appears to have caused the folding and faulting now evident throughout deposit.

Deposit # 1 (at the north end of the Hat Creek Valley) is characterized by an asymmetrical syncline (the Hat Creek Syncline) with a north/south axis plunging 17 degrees to the south. The east limb of this syncline terminates in a faulted anticline with an uplifted eastern limb. Several additional faults occur within the deposit, all of which are reverse faults.

All of this structural evidence, together with the stratigraphic evidence indicates that this deposit was deformed as the result of strong compressional forces impinging upon the property, relatively speaking from a northern direction.

 

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Tectonic History

The following geochronological order (sequence of events) is offered here as a conceptual aid to understanding the deformation processes that are believed to have affected the Hat Creek coal deposit.

The coal was deposited sometime during the Eocene epoch and overlain by the Medicine Creek Formation (also Eocene in age). During the following Oligocene epoch, uplift and erosion of the region began and the Hat Creek deposit and its overlying sediments began to erode.

The Hat Creek valley as a whole and the Pavillion Mountains started to rise. However, the Pavillion Mountains were rising at a rate somewhat faster than the rate at which the Hat Creek valley rose. The effect of this differential displacement caused the Pavillion Mountains to impinge upon the coal deposit at the north end of the Hat Creek valley, causing the deposit to compress, fold and rupture.

In the following Miocene epoch, after some period of erosion, further tectonic activity caused basalt and lava flows to spread out and cover the region, including the early, low profile Pavillion Mountains. This was followed by another period of uplift and erosion (late Miocene to early Pliocene) and the Hat Creek deposit was faulted as the Pavillion Mountains were driven upward towards there present degree of exposure.

It is anticipated, that in some areas in the surrounding region, down dropped fault blocks containing coal may yet be found, lying beneath overriding lava and/or basalt flows. These are the areas of interest for this study.

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Additional Coal Deposits

The Medicine Creek and Hat creek formations were identified and designated to be formations as a result of the 74-78 exploration programs.

On Fraser River Map 1386-A, these sediments (at Hat creek) are designated "Coldwater Beds" and in the literature this is the normal designation assigned to these particular sediments. This designation occurred before the advent of the 74-78 exploration work at Hat Creek. This designation is also applied to the coal bearing sediments in the area around Kamloops, Merritt and Cache Creek. Therefore any "Coldwater Beds" sediments could contain coal that may be equivalent to the coal contained within the Hat Creek Formation.

In 1977-78, the Medicine Creek and Hat Creek formations were considered to sit conformably on top of the Coldwater Beds sediments. This was the local view of things owing to the sub-crop positioning of the "D" coal seam at the bottom of the Hat Creek Formation near 'Trench-B'; and as well owing to the drilling data generated after the "D" coal seam was penetrated. The sediments beneath the 'D' coal seam appear to correlate with description of the Coldwater Beds generally. It seemed reasonable to conclude that the Hat Creek Formation sat on top of the Coldwater. However, no one did any regional work beyond Hat Creek to confirm this.

Given the fact that the coal at Quilchena and Merritt, identified as occurring in Coldwater Beds, correlates in terms of age with the coal at Hat Creek, consideration must be given to the Coldwater regionally being contemporaneous with the Medicine Creek and Hat Creek formations. If this is the case, then Coldwater Beds generally may contain coal wherever they are identified. No one (in the literature it seems) has bothered to do any correlation work with respect to the pre 1975 Coldwater and its contained coal (relative to the Hat Creek coal) other than to designate that coal as occurring within the Coldwater and applying that name. So, any sediments identified as "Coldwater Beds" occurring to the northeast of Hat Creek and/or to the south of Clinton for example, may contain coal equivalent to that of the coal occurring at Hat Creek.

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No one has bothered to look closely at the Merritt coal, with an eye to correlating it to the Hat Creek coal, especially in terms of its depositional positioning. Just where in the Hat Creek section does the Merritt coal fit? Alternatively, does it fit there at all?

Furthermore, if the Hat Creek coal deposit extended further to the north/northeast, as its stratigraphy suggests, any Coldwater Beds identified to the northeast of Hat Creek would appear to be an extension of the Hat Creek geology and should otherwise be drill tested for coal. If for no other reason than to establish the positioning of these Coldwater sediments relative to the stratigraphy of the Hat Creek deposit itself and the general geology of the region.

Additionally, Coldwater Beds in the area would seem to indicate that an environment of deposition, perhaps suitable for the formation of coal, could have existed further to the north and northeast of Hat Creek, perhaps to and beyond the town of Clinton. The occurrence of Coldwater Beds to the south of the town of Clinton, indicates that a waterway with a possible direction of flow to the north, may have existed at the time of the deposition of the Hat Creek coal deposit. This direction of flow may have terminated at Clinton creating an embayment suitable for the formation of coal.

Certainly, it seems that a topographic low of some kind existed in this area. It is now covered by a thick series of Miocene lava and basalt flows. Might coal have formed in this topographic low during the Eocene? Might this coal now be located beneath some of these lava flows?

Since it is confinement pressure that drives coalbed methane into the pore spaces of the coal, this may be a good place to look for new coal deposits that may generate and retain coalbed methane.

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Property selection for consideration

Apart from the fact that no one seems to have bothered to look beneath any of these lava and/or basalt flows for the presence of another large-scale coal deposit; no one has bothered to drill test any of the outcrops of coal that happen to be located along the Fraser River and some of its tributaries.

Churn Creek for example. Churn Creek is located some 60 miles northwest of Hat Creek. In this same area, the Fraser River cuts through a massive landslide, which at one time must have blocked the Fraser River. Located in the bank of the river are, what seem to be, several highly contorted coal seams; which may or may not correlate with those of the Hat Creek Formation. I have not found any reference to these seams in the literature. There does not seem to have been any drilling in the area to test the depth of the sedimentary strata beneath this slide at Churn Creek.

(These "coal seams" that I am speaking of, were sighted in the bank of the Fraser River from a road half a mile away and to the east of the river. They may be argillite or black lava beds. I was not able to get any closer. This needs to be checked out before proceeding further with this particular hypothesis, at this location.)

To the northeast of the Hat Creek property, the Bonaparte area may be of some interest. There are some sedimentary strata in this area that may be contemporaneous with that of the Coldwater and the coal at Hat Creek. This is another area to check for the presence of coal bearing strata.

To the northwest of Hat Creek, there occurs an outcrop of coal located near Big Bar Creek. It is located on the east side of the Fraser River canyon, half way between Big Bar and Churn Creek. These coal seams are exposed and visible from the air. They may correlate with the coal seams of the upper portions of the Hat Creek Formation. Additional coal might be found at depth if such a correlation proves correct.

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In the Quesnel area, there are a number of Eocene coal seams reported to outcrop along the Fraser River and some of its tributaries. Ministry of Mines Bulletin #11 refers to a number of these sightings. This indicates that an environment of deposition for these Eocene coal deposits extended from Hat Creek northward for some distance.

The general premise in the literature is that they were formed as the result of the periodic damming of the Fraser River. This may indeed have happened as the region was subjected to several periods of uplift and erosion throughout the ages. The question becomes one of thickness.

The Vanderhoof area may also be of interest for this study. The bedrock geology there is made up of Pliocene basalt flows. In a neighboring area identified as the Hulatt-Finmoore area, much of the bedrock geology is made up of Paleocene - Eocene strata. Might these basalt flows be covering sedimentary strata containing coal? (See the Parsnip River Map 1424-A and the "PEs" strata identified there).

Prince George north and south has showings of "MPs" strata containing Paleocene-Eocene "lignite". No drilling seems to have been done to test the depth or thickness of any of these outcrops. (See Parsnip River Map 1424-A)

Also, on the Fraser River near Alexandria "MPs" and "Its" strata occur in this area and may contain coal.

To the northeast of Prince George, there are two large coal deposits. The Bowron River deposit and the Willow River deposit. Both of these coal deposits occur in the Sustut Group of sedimentary strata. Both are Eocene age coal deposits and are of similar grade to that of the Hat Creek deposit.

Further north near the community of McLeod Lake, there is a small outcrop of Sustut Group strata. It too, might be drill tested for coal.

About 125 kilometers to the southwest of Quesnel, Skeena Group strata have been identified. The Skeena Group strata carry coal. There are local lava flows in the area that may cover the coal bearing strata of the Skeena Group. Further work here may be warranted.

Strata of the Skeena Group and the Red Rose Formation should be considered candidates for exploration elsewhere within the Parsnip River map area.

 

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Some currently identified Tertiary coal deposits in the region.

In the Quilchena Basin, there is a 300-meter section, with a partial basalt cap. There are reported to be 4 coal seams; the thickest of which is 4.2 meters thick. overall thickness is measured at 6.7 meters.

In the Merritt Basin, there is a 255-meter section with a partial basalt cap. There are reported to be seven seams ranging in thickness from 1.8 to 8 meters thick (22.25 meters overall).

In the Princeton Basin, there is a 140-meter section with a partial basalt cap. There are reported to be four seams ranging in (aggregate) thickness from 21 to 37 meters. The coal measures are located in the lower 75 meters of the section. Complex folding reportedly affects the deposit.

In the Tulameen Basin, there is an 81-meter section of coal with a partical basalt cap. Aggregate coal measures here, including partings total 21.8 meters. The largest seam measures some 2 to 4 meters thick.

 

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At Chu Chua Creek, on the Thompson River, near Kamloops B.C. there are reported to be three coal zones with an aggregate thickness of 8.1 meters within a section of strata measuring 200 meters. The presence cap rock is un-known. Of the three coal zones; the Upper measures 4.7 meters, the Middle measures 2.3 meters, the Lower measures 1.1 meters and the coal quality comes in as, Sub 'C' to High volatile 'C'. Production of 2,500 tons took place from 1920 to 1923.

South of Quesnel, there occur the Cariboo coal measures. The formation thickness is reported to be 370 meters. There is coal near the surface measuring 1.2 meters and coal at 148 meters measuring some 22 meters in aggregate thickness. Some exploration work was done here on Hudson Creek. The coal quality was reported as being, Sub 'B' to high vol. 'C'. There has been Sporadic exploration in this area since 1920.

Please note that there were three oil and/or gas wells drilled in the area. The Kersley #1 (c86L) and the Kersley # 2 (c84D) NGT, and the Kershaw (d2E). I have yet to locate the geological reports for these wells.

 

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The Sifton Basin- Rapid river Valley is my pick for the best exploration bet. But I have not done very much work there.

The Liard Basin - Coal River Valley Basin is a 5 x 15 kilometer area. There are reported to be a seam or seams 4.6 meters thick. I've no other government information yet for this area.The area is on the Alaska Hwy near where it crosses with the Coal River. No extensive exploration has yet been undertaken there.

In the Tuya River Basin - Dease Lake area there are reports of a 2 meter seam of low sulfur thermal coal referenced in Coal in B.C., Geological Survey of Canada paper 1986-3.

There is the Seaton Coal Basin in the Bulkely Valley area, 24 kilometers South of Hazelton, B.C. Paleocene coal is reported to occur in this area.

There is the Driftwood Canyon Basin but information here is minimal.

There is the Laberge and Tantalus coal basins but information here is minimal as well.

There is the Rapid River Coal Basin, also with minimal information available.

References for all of the above came from; Coal in B.C., An Assessment of Future Prospects by Richard Marshel. Resources Services, Calgary, a Ministry of Mines publication dated; Feb 20, 1992. As well as from; Coal Resources of Canada, a Geological Survey of Canada publication, paper 89-4 by G.G. Smith.

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