Lake Rainbow Research Articles

Wolverine density, survival, and population trends in the Canadian boreal forest

AbstractThere is limited information available on wolverine (Gulo gulo) population density and trends in the boreal forest of North America. We estimated wolverine density using spatial capture‐recapture methods across 2 boreal forest study areas in Red Lake, Ontario (26,568 km2) and Rainbow Lake, Alberta (19,084 km2), Canada. We also used radio‐telemetry data to estimate annual survival of adult and sub‐adult wolverines and evaluated population trends with a stage‐based matrix model. We used an array of run poles and live traps to detect wolverines. In Red Lake over 3 winter field seasons (2019–2022), we detected 56 individual wolverines (17 females, 32 males, and 7 unknown sex), and in Rainbow Lake over 2 field seasons (2014–2016), we detected 48 individuals (19 females, 18 males, and 11 of unknown sex). Average densities in Red Lake and Rainbow Lake were 3.64 and 6.74 wolverines/1,000 km2, respectively. Adults and sub‐adults occurred at equal abundance. Spring snow cover, roads, and industrial developments were not associated with spatial patterns of wolverine density. Most deaths occurred near roads; wolverines were killed in fur traps set along roads, by wolves using roads to travel, and by vehicles. The largest source of death was from incidental (n = 6 in Red Lake) or licensed fur trapping (n = 8 in Rainbow Lake) and we report 8 injuries from fur trapping sets. Red Lake survival estimates for adults (0.87) and sub‐adults (0.86) contributed to a stable population trend. Rainbow Lake survival estimates for adults (0.66) and sub‐adults (0.50) contributed to a declining population trend based on a relatively low sample of radio‐days. Red Lake and Rainbow Lake combined survival estimates for adults (0.77) and sub‐adults (0.73) also contributed to a declining population trend. Our survival and population modeling suggests that human‐caused mortality is a significant risk to these populations. Our results can be applied to wolverine status assessments and used as benchmarks for future monitoring. Wolverine population stability or growth might be achieved by reducing incidental trapping deaths or injury and hindering human access to wolverine habitats through decommissioning or limiting development of industrial roads or other anthropogenic linear features.

Predicting distribution, production, recreational fishing demand, and conservation concern of Indigenous rainbow trout populations based on landscape characteristics

Landscape ecology has mainly been integrated in aquatic science to describe patterns and processes in stream networks, but many lakes are connected through their tributaries and are also impacted by their position and connectivity within the watershed. This information on lake characteristics can be used by inland fisheries managers that oversee large landscapes comprising many waterbodies to predict (i) species composition; (ii) population dynamics and productivity; (iii) recreational fishing pressure; and (iv) overall conservation concern. We developed a methodology to assess these four items for the rainbow trout (Oncorhynchus mykiss) fishery of British Columbia by presenting a case study focused on the Clearwater and North Thompson watersheds using the following: the connectivity of lakes within the stream network to predict rainbow trout presence, stream order and lake area to estimate habitat availability and predict population dynamics and productivity (supply), and travel time from population centres to predict recreational fishing pressure (demand). By incorporating connectivity and environmental proxies of habitat, we explore patterns in population dynamics that can be used by fisheries managers to identify populations sensitive to overfishing or disturbance.

Beaver (Castor canadensis) use of borrow pits in an industrial landscape in northwestern Alberta

Borrow pits, dug by industry to provide substrate for infrastructure such as roads and well sites, are prevalent throughout the boreal forest of western Canada yet little is known about their use by wildlife. During field surveys in Rainbow Lake, Alberta, we found that beavers (Castor canadensis) used inundated borrow pits extensively for foraging and over wintering, suggesting that borrow pits increase beaver populations above their natural carrying capacity in industrial landscapes. We visited a random sample of 90 borrow pits in the field and categorized them as having active beaver lodges with caches (n = 16), inactive lodges (n = 13), cutting (n = 29), no activity (n = 13), or as not inundated or not a borrow pit (n = 19). We then used this sample to model where beavers established lodges versus where they were inactive or were only cutting. We found that borrow pits with active lodges had unique characteristics from other pits in our sample and were closer to streams, marshes, and swamps and had greater vegetation concealment from roads. These models can be used by managers to develop methods for increasing or decreasing the abundance of beavers living at borrow pits. Wildlife managers might want to use borrow pits to increase beaver abundance because of the positive effects beavers can have on ecosystems and because beavers are an important source of food for boreal carnivores. For example, we found that wolverines (Gulo gulo) used borrow pits as hunting grounds for beavers and one wolverine denned within a beaver lodge at a borrow pit. Conversely, managers might want to reduce beaver populations living at borrow pits because of the damage that beavers can cause to infrastructure and because subsidized beaver populations might alter predator-prey dynamics. To accomplish this, we suggest reducing available vegetation around borrow pits, isolating new borrow pits from natural beaver habitats, digging borrow pits where there is less chance of having surface water, filling in borrow pits with substrate, or not creating borrow pits and using a centralized gravel pit or mine for substrate.

Paleohydraulic reconstruction of the largest Glacial Lake Missoula draining(s)

Glacial Lake Missoula (GLM) was the source of Earth’s largest known peak flood discharges onto the Channeled Scabland, northwestern United States. The original studies of GLM were based on geomorphological mapping of lake sediments and shorelines. More recently, studies have emphasized the computational fluid dynamics of downstream megaflood routing and characteristics in the Channeled Scabland and adjacent areas. However, actual details of the lake-draining processes GLM have received little scientific attention. In this paper, we employ two-dimensional hydraulic modelling to understand the paleoflow conditions for different scenarios of draining GLM at its highest stands. Values are calculated for three GLM drainage hydrographs (2.6; 13; 17 × 10 6 m 3 s −1) that previous studies had estimated for outlet flows. Consistent with regional mapping and with the original interpretation of fluvial geomorphology by other studies, the modelling shows that lake silt sequences in the gorges of GLM must postdate the most highly energetic outburst events from the lake. This is because the flows generated in the lake by megaflood outflows are sufficiently energetic to erode any accumulated silt deposits. In contrast, the gravels underlying the silts in these zones include boulder-sized clasts, large-scale cross stratification, and 70–100 m-high bars forms, all of which indicate very high-energy flood flow conditions. The modelling also shows that the paleohydraulic conditions which developed in the lake basin during the largest megaflood outflows would be capable of accounting for the observed bedrock scour at Rainbow Lake Pass, various “high eddy deposits” (eddy bars of flood gravel) in gorges, and the “giant ripple marks” (subaqueous gravel dunes) that were classically described in the 1940s. Previous studies interpreted the glacial lake silt/rhythmites and related deposits, such as the Ninemile Section, as evidence for numerous fillings and drainings of GLM. Our modelling suggests that these inferred events must have been relatively low in energy and magnitude relative to the earlier outburst(s) that emplaced the flood gravels, subaqueous gravel dunes, and scabland-like erosion surfaces.

Monitoring fluid injection in a carbonate pool using time-lapse analysis: Rainbow Lake case study

Time-lapse analysis is not commonly done for carbonate pools because the dry bulk modulus of the carbonate matrix is very high. The high dry bulk modulus dominates the rock strength and the low modulus of the fluids within the pore space and, therefore, the high bulk modulus masks the effects of fluid changes. Thus, the fluid effects seen in seismic data after gas injection are small and difficult to detect in carbonate reservoirs.

19th Century Eutrophication of a Remote Boreal Lake: A Consequence of Climate Warming?

To investigate the response of a remote boreal lake to recent climate warming, a ∼200-year varved sediment record from Rainbow Lake A (RLA), located in the northern boreal forest of Wood Buffalo National Park, straddling northern Alberta and the Northwest Territories (Canada), was investigated using diatom assemblages and biogenic silica concentrations. Diatom community composition, trends in diatom-inferred total phosphorus (TP) and biogenic silica levels all showed significant changes beginning between circa 1830 and 1840, coincident with the onset of increasingly warm June/July temperatures in northern Canada. We evaluated several hypotheses which may have caused these nutrient changes, including local anthropogenic disturbances, forest fires, increased atmospheric deposition of nutrients or pollen, and internal sources of nutrient regeneration. We concluded that TP is likely increasing as a result of enhanced internal cycling of phosphorus due to either increased thermal stratification in response to warmer summer temperatures and/or decreased meromictic stability. The results presented here, in combination with other recent paleolimnological research in northern latitude regions, suggest widespread aquatic response to increasing temperatures beginning in the 19th century.

Records of geomagnetic secular variation since 1200 AD and the potential for chronological control of lake sediments in northern Alberta

We assess whether absolutely aged declination changes can be used to date recent, massive lake sediments at the sub-century scale. Three issues limiting such studies are addressed: recovery of undisturbed recent lake sediments, assessment of the reliability of the geomagnetic record, and the comparison of lake-sediment records with historic records. A 793-year long geomagnetic chronology was obtained from the annually laminated sediment of Rainbow Lake A. Sediment disturbance was minimized by freezing the sediment in situ and maintaining this state for geomagnetic analyses. Geomagnetic chronologies ca. 600 years long from the massive sediments of Fariya Lake and Ninisith Lake were collected in removable plastic tubes using a piston-corer. Sediment disturbance was minimized by ex situ draining of water from the plastic tubes. The reliability of the geomagnetic record was assessed using a measure of internal coherence with an absolute cutoff of 15°. By further separating the samples at coherence values of 5° and 7.5°, it was possible to identify zones of disturbance and reduced compaction. The most reliable samples had a high magnetic intensity due to high inputs of magnetic minerals, sediment compression, and inputs of stable magnetic minerals. Neither freezing nor dewatering of the sediments appeared to decrease reliability of the geomagnetic record. The declination chronology from the annually laminated sediments was significantly correlated with a 230-year long historical record from Churchill, Manitoba, and with the massive lake sediment chronology from Fariya Lake. Geomagnetic dating was not possible, however, because of the large amplitude in the annually laminated sediment declination record, the large number of years of sediment in many specimens, and the lack of reliability for samples that contain few years of sediment per specimen.

An 840-Year Record of Fire and Vegetation in a Boreal White Spruce Forest

Boreal forest fire and vegetation history was examined using an 840-yr fossil pollen and charcoal record from a site dominated by Picea glauca in Alberta, Canada. The record was created using contiguous 5-yr samples of annually laminated sediments from a 2.7-ha lake (Rainbow Lake A in Wood Buffalo National Park). Following a peak in the microscopic charcoal accumulation rate (CHAR), there is a sequence of peaks in sediment thickness and in 14 of the 21 common pollen and spore taxa. The general pollen sequence is an initial peak in herbs, then shrubs, then deciduous trees, and finally conifers and Sphagnum. The peak value for each taxon differs following individual fires, suggesting that a site does not undergo the same postfire vegetation sequence following all fires. Based on the CHAR, pollen, and sediment thickness records, at least 12 large, local fires are apparent. The average time interval between the 12 fires is 69 yr. Significant periodicities in CHAR and in 11 of the pollen taxa range between 95 and 185 yr. These estimates of the mean fire interval are broadly similar to the 71–142 yr fire cycle for Picea glauca forests, estimated by dendrochronological analysis of regional forests. The pollen taxa also exhibit long-term changes in relative abundance. An initial dominance by Picea cf. glauca is terminated by a fire around AD 1185 and is replaced by Populus dominance between AD 1250 and 1550; the fire is followed by an 800-yr period of increasing abundance of Picea cf. glauca. Herbs and shrubs generally exhibit a peak in abundance between AD 1350 and 1750. These long-term patterns may reflect climatic change, response to fires with different characteristics, or rearrangement of the forest patches around Rainbow Lake A.

AN 840-YEAR RECORD OF FIRE AND VEGETATION IN A BOREAL WHITE SPRUCE FOREST

Boreal forest fire and vegetation history was examined using an 840-yr fossil pollen and charcoal record from a site dominated by Picea glauca in Alberta, Canada. The record was created using contiguous 5-yr samples of annually laminated sediments from a 2.7-ha lake (Rainbow Lake A in Wood Buffalo National Park). Following a peak in the microscopic charcoal accumulation rate (CHAR), there is a sequence of peaks in sediment thickness and in 14 of the 21 common pollen and spore taxa. The general pollen sequence is an initial peak in herbs, then shrubs, then deciduous trees, and finally conifers and Sphagnum. The peak value for each taxon differs following individual fires, suggesting that a site does not undergo the same postfire vegetation sequence following all fires. Based on the CHAR, pollen, and sediment thickness records, at least 12 large, local fires are apparent. The average time interval between the 12 fires is 69 yr. Significant periodicities in CHAR and in 11 of the pollen taxa range between 95 ...

An Application of Chemical Tracers In Monitoring Injection In Vertical Hydrocarbon Miscible Floods

Abstract Chemical tracers have been utilized to effectively monitor injected fluid movement in two vertical hydrocarbon miscible floods in the Rainbow Field, Alberta. By placing small slugs of chemical tracers, consisting of sulphur hexafluoride (SF6) and chlorinated fluorocarbons (CFC) or halocarbons within the injectants, the spreading and development of chase gas and solvent banks were monitored, and in some cases, reservoir flow channels identified. In addition, geological units were confirmed and well workover planning improved, resulting in increased cost effectiveness in operating the miscible floods. The chemical tracer program commenced with the first field application conducted in the Rainbow Keg River "A" (R.K.R.A.) Pool secondary miscible flood on January 31, 1991, where chase gas injection into two wells was traced. Subsequently a program of tracing chase gas and solvent was initiated at one well location in November, 1991 in the Rainbow 1 Keg River "B" (R.K.R.B.) Pool tertiary miscible flood, and later at six additional chase gas and solvent co-injection wells. This paper presents the design of the tracer programs, the significance to the operation of the miscible oil recovery schemes and alternative tracers considered for the future. Introduction Husky Oil operates seven mature secondary and three tertiary miscible flood enhanced oil recovery projects in the Rainbow Field of northwest Alberta (Figure 1). Cost effective operation of these floods requires that solvent and chase gas sweep a significant extent of the reservoir without being produced at high rates. If miscible solvent bypasses large portions of the reservoir due to channeling, recovery efficiency will be lower than expected. Maintaining cost effective operation of hydrocarbon miscible flooding has required the development of extensive tracer programs designed to track and optimize solvent distribution in the reservoir as well as detect breakthrough at the very early stages. Previously, Husky had used radioactive tracers to monitor solvent bank placement in the R.K.R.B. Pool(1). Following the successful conclusion of this program and others in Rainbow Lake, other tracers were researched with the expectation that more of the analysis could be conducted on site and with reduced cost. More recently, Husky has used several Freon" haIocarbons and SF6 as chemical tracers to monitor chase gas and solvent injection in both the R.K.R.A and B Pools. FIGURE 1: Field location map. Illustrations available in full paper. Tracing injected chase gas and miscible solvent is used to identify the distribution of these fluids, both regionally and vertically, in the miscible floods. This enabled identification of the source of early solvent and chase gas breakthrough due to reservoir channeling, and allowed for early remedial action. Tracers less expensive than radioactive tracers, both from an initial cost and a per sample analysis cost basis were sought. They had to be detectable and accurately measurable at extremely low concentrations in the field lab and be readily handled by the field operations group. Finally, they could not be native to the oil reservoirs or have adverse rock or fluid adsorption or partitioning characteristics.

On The Characterization Of Rock Fluid And Fluid Fluid Interactions In Carbonate Rocks Using The Ultracentrifuge

Abstract The ultracentrifuge provides an easy and fast way of estimating the physical properties of reservoir rock/reservoir fluid systems such as wettability information, capillary pressure and relative permeability curves. The ultracentrifuge has been utilized both in routine core analysis and at the research level. In this work, an extensive experimental program was conducted for the characterization of core from the Rainbow Lake Reefs. Numerous plugs were tested for wettability and capillary pressure characteristics. During the experimental procedure, it was found that the conventional use of the centrifuge data introduces uncertainties that may compromise the quality of the results. As a result, a series of improvements was designed and implemented to allow for the collection of more accurate and consistent data using Charged Couple Devices (CCD). Moreover, a series of experiments was performed aiming at producing recovery data for both water imbibition and EOR experiments. A number of interesting and often neglected issues were addressed. The capillary pressure data often showed hysteresis that did not reflect the hysteresis observed in porous plate measurements. This paper summarizes the work completed to date, provides information on the wettability and capillary pressure characterization of the Rainbow Lake Reefs, and presents the results of gravity assisted immiscible gas injection of water flooded plugs. The hysteresis phenomenon observed between primary and secondary drainage is not consistent. The fluid propagation in a three-phase system varies from sample to sample at low Bond Numbers. Amott indices do not change significantly with temperature for strongly water-wet media. There cannot be a consistent correlation among wettability indices and other physical properties for the reef cores. USBM indices on raw centrifuge data are different than the same, indices calculated on fitted curve data but not enough to alter the overall wettability classification. Introduction Literature Survey The measurement of reservoir wettability and the assessment of its importance for the recovery of crude oil have been the topic of numerous research papers in the past fifty years. Several reviews have been published that address the methods and options that a researcher has available when measuring wettability. Although simple contact angle measurements are still thought to be the most universal measure of wettability(l), other methods have emerged through the years that take advantage of the changes in capillary phenomena as they are affected by changes in wettability(2). The Amott test(3) and the USBM test(4) and their various combinations have been widely applied in the literature for the determination of the wettability characteristics of given reservoir/crude oil combinations. The initial single wettability characterizations (i.e., oilwet, water-wet, and neutral) were later complemented by new terms such as mixed(5), fractional, etc. In real systems, the distinction between different types of wettability became more and more vague. One of the tools that has gained considerable popularity in the past decades is the centrifuge and its variations. Starting from the original paper of Hassler and Brunner(6), much effort has been spent on both the experimental part and the interpretation part of centrifuge technology.

Optimization of Vertical Miscible Flood Performance Through Cyclic Pressure Pulsing

Abstract The concept of improving the performance of vertical hydrocarbon miscible floods is addressed. Improvement is attempted through cyclic pressure pulsing. The idea is to force recovery from dendritic structures or other unswept areas through pressure pulsing of the solvent and gas phases. A series of vertical miscible floods was performed on a-core from the Rainbow Keg River area. Methane (solvent) displaced n-pentane (oil) under a variety of rate and pressure scenarios. All runs were performed at rates significantly higher than the critical rate for the specific system. Through the experiments it was established that at the core level, the rate of displacement has a considerably larger effect on oil recovery than the pressure pulse. However, even if the solvent has broken through, reduction of frontal advance rates can provide significant incremental oil recovery. Introduction Vertical hydrocarbon miscible floods are frequently used in the Rainbow Lake reefs of northern Alberta. Oil is displaced downward by a less viscous solvent. Viscous fingering, which is in part triggered by local heterogeneities is blamed for reduced sweep efficiencies and oil recoveries which are less than what was expected in the design stage. In most cases, the solvent is chased by another gas. When both solvent and chase gas break through, the gas to oil ratio (GOR) increases dramatically with a comparable decrease in oil production. The standard approach in controlling excessive gas or solvent production is workovers in which the current perforations are cement squeezed and new perforations are made lower in the reef. This procedure is costly and is not always successful. Husky proposed another procedure in optimizing the displacement strategy which can improve the vertically directed miscible floods, by applying a cyclic flow interruption consisting of periodical shut-in(1). Field observations lead to the formulation of the concept(2,3). Conceptually, periodic shut-in and pressure pulses cause reduction and even reversal in the advancement rate of the solvent/oil flood front. These changes would allow not only the cones and fingers of solvent to heal back, but also the healing process would increase the length of the mixing zone. Longer mixing zones reduce the tendency for fingers to form. Also, these changes would change the pathways of dispersion and diffusion, potentially accessing bypassed oil. The problem with the cyclic flow interruptions is that production is discontinued. The question was raised whether a similar effect could be observed through a continuous process. It was proposed that cyclic pressure pulsing under restricted flow could provide increased mass transfer between solvent and oil and also allow for the solvent to access previously inaccessible oil through lateral spread. It was decided to test the proposed ideas in the experimental system previously used to test the applicability of the shut-in concept(2.3). FIGURE 1: Schematic of the experimental apparatus. (Available in full paper) Experimental The demonstration experiments were conducted in core from Rainbow Keg River "B" pool. The properties of the different pieces used in this study are shown in Table 1. Methane was used as the solvent and n-pentane as the oil.

Horizontal Drilling In the Keg River Carbonate Reefs

Abstract This paper describes techniques and drilling practices optimized through drilling six medium radius horizontal wells, in carbonate reefs, under vertical miscible flood in the Rainbow Lake area of N.W. Alberta, Canada. Horizontal drilling technology was utilized to alleviate gas/solvent coning through reduced drawdown. This will accelerate and increase oil recovery beyond that achievable with vertical producers. Drilling techniques were optimized by a continuous process of technique evaluation and improvement. Several monitoring methods were developed, permitting real time evaluation of drill-string drag, which proved to be effective in monitoring hole cleaning and the onset of wellbore solids coating. Well design, reef penetration procedures, bottom-hole assembly choice, drilling fluids and coring techniques have been optimized over the six well program, such that each successive well met its technical and economic objectives. Average production of the horizontal wells was 2.8 times that of vertical wells with lower drawdowns. Through the optimization process, well costs were reduced from 25 times that of a vertical well to 1.7 times. Introduction The Rainbow Basin is located in a remote area of northwestern Alberta, Canada at 58 °N latitude and 114 ° W longitude, with an areal extent or approximately 30 square kilometres (Figure 1). The surface topography is muskeg and stunted coniferous forest. Temperature varies from -50 ° C in winter to +30 ° C in summer months. Oil field activity is seasonal due to restricted access, hence most drilling activity commences upon freeze-up in October and continues until spring thaw in early April. Because of the random nature of pinnacle reef structures, concentrated development efforts further complicate access with busy roads and pipeline networks. Husky Oil operates 250 of the 700 wells drilled in the Rainbow Basin. The field was discovered in 1965, with secondary recovery techniques starting in the early 1970's. The primary oil objective is the Devonian Keg River pinnacle reef structures. Husky Oil operates seven vertical miscible floods in the Rainbow Lake area. As these miscible floods reach maturity, gas/solvent coning in the vertical producers has become a major problem. FIGURE I: Rainbow basin - major Keg River pools. (Available in full paper) The objectives of horizontal well technology in Rainbow are to alleviate gas and solvent coning by reducing drawdown and to increase the recoverable oil by producing a higher percentage of the oil sandwiched between the gas and water zones (Reference 1, Figure 2). Geological and Reservoir Characteristics Since all pools have similar characteristic, the "A" Pool structure will be discussed for the purposes of this paper. The "A" Pool structure is a large pinnacle reef with an area extent of 467 hectares, extending approximately 2,200 m in diameter at the original oil/water contact, 750 m in diameter at the reef top and 220 m thick. The reef consists of an inner reef core and reef fore-slope comprised of 100% dolomite. The inner reef core has vugular and inter-crystalline porosity with high permeability of 12% and 100 md respectively. Lost circulation problems are common when drilling into this section of the reef, due to large vugs and possible fractures.

An Overview of Miscible Flooding

Abstract Introduction In most reservoirs, oil recovery can be improved by the implementation of an enhanced oil recovery (EOR) scheme. An EOR scheme can be classified as either a miscible or an immiscible process. In a water flood or an immiscible gas flood, the displacing fluid is not soluble in the displaced oil. The displacement results in a residual oil saturation due to the inter-facial forces between the displacing fluid and the displaced oil. In contrast, miscible fluids are soluble in oil so there will be no inter-facial force between oil and solvent and the theoretical residual oil saturation will be zero. Hydrocarbon miscible floods are the most common tertiary EOR schemes m Western Canada. They can be sub-divided into vertical or horizontal miscible floods. Vertical Miscible Floods Vertical miscible floods are usually implemented in pinnacle reefs or reservoirs with a high relief angle. The majority of Canadian vertical floods have been implemented in the Rainbow Lake, Brazeau River, Pembina/West Pembina, and Wizard Lake areas of Alberta. The solvent is injected as a blanket at the top of the reservoir to take advantage of a gravity stabilized displacement. Subsequent chase gas injection drives the solvent blanket downward. The highest wells in the structure are usually chosen as the injectors to maximize oil displacement and the producing wells are completed in the lowest porous interval above the oil water contract. Production rates are controlled to restrict solvent and water production. Horizontal wells are becoming popular in vertical miscible floods. These wells arc usually drilled as producers near the water/oil contact to reduce water and gas coning problems, and thus increase the production rate and reduce the sandwich loss. Innovative completion techniques such as perforation below or at the oil/water contact have also resulted in reduced sandwich losses. The expected incremental recovery compared to upward waterflood is in the range of 15–40%. The vertical solvent flood process develops a good volumetric sweep efficiency as a result of gravity stabilization of the interface, and is ideal in homogenous reservoirs. In heterogeneous reservoirs with horizontal shale barriers, a substantial reduction in oil recovery improvement can be expected as a result of poor vertical sweep efficiency (e.g. Golden Spike, Alberta). Horizontal Miscible Floods In horizontal miscible floods, solvent and water are injected alternately to mobilize residual oil and push it to the producers. After the injection of solvent and water, chase gas or leaner solvent (which is miscible with the solvent) and water are injected to extend the solvent bank size and complete the displacement process. After injection of 25%–40% hydrocarbon pore volume (HPV) of solvent and chase gas, the process reverts to horizontal water flood to depletion. In other words, in the early stage of the miscible project, oil is replaced by miscible solvent and moved toward producing wells. Later, residual solvent is mobilized by chase gas and moved to where it can contact more residual oil. Through this process, an expensive commodity, residual oil, is replaced by a cheaper commodity, chase gas.

An overview of some of the large scale mechanisms of salt dissolution in western Canada

Well log and seismic data indicate that the bedded rock salts (salts) of the Devonian Age Prairie Formation were widely distributed and uniformly deposited in the Lloydminster area, Western Canada (T45-65, R20W3M-R5W4M); however, as a result of extensive leaching, the distribution of these salts is not now what it once was. The Lloydminster area is now bisected by the north‐south trending main dissolutional edge of the Prairie salt. Thick salt (up to 150 m) is preserved to the west of this edge; to the east the salt is mostly absent. Analyses of remnant salt and patterns of subsurface structural relief suggests that the dissolution of the Prairie salt in the Lloydminster area was triggered and/or accentuated in part by several different large scale mechanisms including: near‐surface exposure, centripetal flow of unsaturated waters, regional faulting/fracturing, glacial loading and/or unloading, dissolution of the underlying salt, and salt creep. These mechanisms are supported by the incorporated seismic and well log control that indicate a direct relationship between the thicknesses of remnant salt and post‐salt strata. Well log and seismic data also indicate that the bedded salts of the Devonian Age Black Creek Member were uniformly deposited within the Black Creek sub‐basin, Rainbow Lake area, western Canada (T105-112, R5-R10W6M); however, as a result of extensive leaching, distribution of these salts is not now what it once was. The Black Creek salts are now preserved only as discontinuous remnants with maximum gross thicknesses on the order of 80 m. Seismic and well log control suggests that the dissolution of the Black Creek salt in the Rainbow Lake study area was triggered and/or accentuated in part by several different large scale mechanisms including: centrifugal flow of unsaturated waters, regional faulting/fracturing and salt creep. Bedded salt is preserved within five other Devonian Age evaporitic units in Alberta, Canada: the Lotsberg Formation, Cold Lake Formation, Beaverhill Lake Group, Leduc Formation, and Wabamun Group. Each of these salts has also been extensively leached in places. In the literature, dissolution is generally attributed to one or more of the previously noted large scale mechanisms. Herein we present an overview of the envisioned principal mechanisms of salt dissolution. In support of these hypothesized mechanisms, we present seismic and geologic control from both the Lloydminster and Rainbow Lake areas of western Canada, which illustrate that the dissolution of subsurface salts is accompanied by the subsidence of post‐salt strata and that the analyses of this information can be used to elucidate the timing and large scale mechanisms of salt dissolution.

Foamed Cement for Squeeze Cementing Low-Pressure, Highly Permeable Reservoirs: Design and Evaluation

Summary Four different cement squeezing techniques have been used on wells producing from the Keg River formation in the Rainbow Lake area of Alberta, Canada. This paper evaluates 151 cement squeeze treatments performed at 96 wellsites and compares the use of foam cement vs. conventional squeeze treatments and techniques. Discussion includes key aspects, such as candidate selection, slurry design, treatment design, economic evaluation, and operational considerations.

Evaluation Of Foam Cement Squeeze Treatments For Low-Pressure Highly Permeable Reservoirs

Abstract Squeeze cementing is a well established remedial technique that relies upon controlled slurry placement and pressure as the key to success. Formations with low reservoir pore pressure and high permeability can create severe challenges/or proper cement placement, especially if the high permeability is due to naturally occurring formation vugs and fractures. Recently. a novel technique utilizing low density foam cement has proven to be successful in providing a squeeze cementing method offering a much higher probability of success, as com? pared with more conventional cement systems. This paper will evaluate the use of foam cement vs other conventional squeeze cementing techniques and also the design criteria used for treatment of wells producing from the Keg River formation in the Rainbow Lake area of northwestern Alberta. Seventy-nine individual well case histories involving 129 remedial cementing operations were evaluated to determine their success. Introduction The Keg River reefs in the Rainbow Lake area were, for the most part, discovered during the 19605. There are 19 such reefal structures which are presently on production (Fig. I). For many years, the Keg River formation produced oil with very few production problems. However, it eventually became necessary to implement various secondary and tertiary schemes to improve the recovery factor and maintain production. These recovery schemes required periodic well servicing operations to reduce excess water and gas production. In 1980, the number of well servicing operations increased dramatically. Cement was used in most cases to shut off unwanted production intervals. It was discovered early that normal density Class "G" cement systems would not perform adequately in highly permeable areas of these reefs. The search for a better cementing technology eventually evolved to the use of foam cement to reduce the number of repeat cement squeezes required to achieve hydraulic isolation. This paper evaluates 129 cementing operations in which four different cement systems were applied to the Keg River formation at 79 wells. Geological and Reservoir Overview Langton et al(1,2,3) have described the Rainbow member of the Keg River formation as a generally dolomitized pinnacle or atoll like reefal structure. These reefs are heterogeneous in nature, both horizontally and vertically. Presently, there are five reefs under primary recovery, six under secondary waterflood and eight under miscible production. The reefs, in general, are slightly under pressured with respect to a produced water gradient. Permeability in each of the reefs varies from less than one millidarcy to greater than 10 darcies. The area of reefs which contain many darcies of permeability are characterized by vugs and fractures of all shapes and sizes. It is these reef areas which present the greatest challenge for cement squeezing. Evolution of Cement Squeezing Techniques The primary reason for cement squeezing has been to shut off undesired water or gas production and to ensure hydraulic isolation between multiple perforated intervals. These procedures along with a specialized application of downhole tools (Fig. 2) provide control over how the reef is exploited.

Simulation Of A Directly Miscible Vertical Dlisplacement Hydrocarbon Solvent Flood

Abstract A simulation of the performance of the hydrocarbon miscible flood in the Rainbow Keg River ‘E’ Pool is presented. The reservoir has been under continuous hydrocarbon solvent injection since June 1972. The direct contact miscible flood is being conducted downward in a maximum oil column of172 m. A review of the geology, rock and fluid characteristics is given. The pool was produced on primary depletion from July 1966 to August 1967, and shut-in from August 1967 until the solvent injection commenced in 1972. The black oil model history match of the primary depletion and shut-in is presented. The hydrocarbon solvent flood performance was modeled using J.S. Nolen and Associates' Miscible Vectorized Implicit Program. The simulation study provided an estimate for the efficiency of the hydrocarbon solvent flood of the ‘E’ Pool. Introduction The Rainbow Keg River ‘E’ Pool was discovered in March 1966. The discovery well penetrated a small biohermal pinnacle reef of Middle Devonian age located in the Rainbow Lake Area of Alberta (Fig. 1). The pool began production under primary depletion in June 1966 and was shut-in in August 1967. Due to the initial in-availability of miscible fluid the pool was shut-in for 56 months until May 1972 when injection was commenced. The solvent injection commenced in May 1972. Solvent breakthrough occurred in the two producing wells two to three years later. The third or last well was drilled and completed in ‘E’ Pool in 1978. This well produced solvent immediately even though it was placed in an area of the pool opposite to the two former wells. The field solvent-oil ratio in late 1982 was 650 m3/m3 with a cumulative oil production of approximately 1100 × 103 m3 or 33% of the original oil-in-place (OOIP). This paper discusses the rock and fluid properties. It also describes the reservoir simulation history match of the primary and solvent injection periods. Following the history match the future performance of the reservoir was predicted. History The discovery well of Rainbow Keg River ‘E’ Pool was the 7-18-109-7 W6M well (Fig. 2). It was spudded on 1966-02-22 and drilled to a depth of 2018 m penetrating 172 m of oil-bearing Keg River Reef. The well was completed 89.8 to 83.7 m above the original oil/water contact (AOOWC) in April 1966 (Fig. 3). The pool went on production in July 1966 and continued until August 1967 when it was shut-in. The production data are shown in Figure 4. The pool produced 51 × 103 m3 of oil with no water. The gas to oil ratio (GOR) was very erratic. The initial pool pressure was 17 408 kPa at the mid-point of the perforations (MPP) as shown in Figure 5. There were four pressure surveys during the primary production period. The MPP pressure decreased 3524 kPa to the end of the primary depletion. The pressure was recorded eleven times during the shut-in period. The MPP pressure increased 795 kPa during the shut-in period from September 1967 to March 1972.

Temperature distributions at the Paleozoic and Precambrian surfaces and their implications for geothermal energy recovery in Alberta

A large number of bottom-hole temperature (BHT) data from Alberta (55 246 BHT from 28 260 wells) have been used to construct Paleozoic and Precambrian surface-temperature maps. A northward increase of average heat flow in Alberta results in higher subsurface temperatures at the Precambrian basement and at the top of the Paleozoic toward the north and northeast than at the same depths in the south and southeast. However, the temperature distribution at these surfaces is more depth dependent than gradient dependent, and so higher temperature values occur in the western part of the basin. As a result, good geothermal energy potential exists throughout the western half of the province, especially for regions west of the Calgary – Swan Hills – Grande Prairie – Rainbow Lake line. Through the central part of the basin, zones occur where the isotherms and the isopach lines of the Phanerozoic are parallel. These zones probably represent regions where little disturbance to heat transport by vertical water motion occurs. It is suggested that zones in the central part of the basin where such parallelism does not occur may represent areas where conductive transport of heat is perturbed by local, nonlateral fluid flow or zones with nonuniform heat contribution from the crystalline crust or upper mantle. The effect of hydrodynamics in the deeper sediments of the Paleozoic that lie below the BHT observations may also contribute to such zones.

Death and the Good Life by Richard Hugo

Reviews 363 obvious relish for life, an undercurrent of glee. There is a free, unfenceable spirit here. Probably no western writer since Mark Twain has been funny in quite this way. Abbey loves good country, good food, friends, unbossed time — the old, normal, human range. This is behind everything he says, and we recognize it instinctively, genetically. Down the River makes one of the clearest statements of the wilderness corollary to the Turner thesis I have seen. If open land made Americans what they are, then what becomes of them when it’s gone? “Europe was saved,” Abbey writes, “from becoming a permanent prisonhouse by the open­ ing up of America. (And the forcible displacement of America’s original inhabitants.) But suppose we in America surrender our last remnants of wilderness to the demands of industrialism?” For Abbey, a most disturbing rhetorical question. His answer goes far beyond the meliorist accommoda­ tions of such conservationists as René Dubos (the essay containing these thoughts on wilderness is called “Thus I Reply to René Dubos”), into a radical, Abbeyan association of wild country, political freedom, and a full emotional and intellectual life — an ideal state which Abbey says could be called civilization. THOMAS J. LYON, Utah State University Death and the Good Life. By Richard Hugo. (New York: St. Martin’s, 1981. 215 pages, $10.95.) For a first novel by an acclaimed poet, this is a lot of fun. The initial crime is imagined as occurring just after the victim snags two small rainbow trout at Rainbow Lake, in northwest Montana. And the plot, as involved with convolutions as the internal rhymes and rhythms of Hugo at his best poetic form, twists and turns and digresses across the Northwest from Plains (several allusions to Jimmy Carter), Montana to Portland, Oregon. And the hero, A1 “Mush Heart” Barnes, is, every inch of him, a good soul (as well as a good sole). The plot may be a bit bizarre (a frog farm in Albania?) but the characters are good and A1 Barnes is a very likeable hero. There is also a distinct poetic dimension to this detective story, from poetic colorings (“Sedge was receding in the lake now that the surface water was cooling and the big rainbows were coming up”) to poetic surprises (“Sometimes I’ve wondered why women don’t have a skid row. It’s like men reserved destitu­ tion and defeat for their exclusive use.”) to poetic slummings (“ ‘Yes. I wanted to be a poet.’ ‘Really? Cod, there are so many these days. Isn’t that a funny thing for a cop to want to be?’”) and poetic name droppings (“ ‘I see you’re reading William Stafford. . . . Do you like his poems?’”). Are there poet cops in Portland? Do nice men with kindly faces in exclusive clubs really read William Stafford? At least for the purposes of this 364 Western American Literature poet turned detective, the whole world comes together and has a reasonably good time — as good as can be had, with the bodies piling up and the crimes receding into a prehistoric, pre-liberal age of young and brutal cruelty. You just can’t read this detective story in the same way you would read a Christie or a Spillane or Hammett or Sayers—it just won’t work. The reason for the difference is not the poetic colorings nor the plot nor the characters— it’s A1 Barnes himself, who either keeps readers smiling or feel­ ing a somewhat mild disgruntlement. A1 “Mush Heart” Barnes is Sam Spade dug up, patched together, given a love for good cooking and a new eye for the poetic details in characters’ lives and in specific settings, as well as a big soft heart that wants everyone to live a long time and have a good time doing it. He is no hard-nosed, no-nonsense, “gray-mattered” steel-trap mind of indefatigible logic, nor womanizing cynic. “Mush Heart” Barnes’s heart is what leads him on — neither Poirot nor Eliot he. When a rookie cop, Barnes even had trouble getting his bureaucratic quota of speeding tickets. His Seattle superiors therefore gave him — astute superiors! — a police-community relations...