Coalbed Methane Water Research Articles

Pressurized upflow reactor system for the bioconversion of coal to methane: Investigation of the coal/sand interface effect

Microbial generation of coal bed methane (CBM) represents a significant source of natural gas on Earth. While biostimulation has been demonstrated in batch cultures, environmental parameters such as overburden pressure and formation water flow need to be tested at the laboratory scale to understand in situ potential. We designed and constructed a high-pressure (HP) flow-through reactor system that simulates in situ conditions of underground coal seams. Two stainless-steel columns contained coal from the Powder River Basin (PRB), USA, or a coal/sand mixture to represent the interface of coal seams with sandstone layers, which are hypothesized to exhibit higher methanogenesis rates in situ. The system was filled with CBM formation water, inoculated with a methanogenic enrichment from PRB coal beds, and stimulated with algal biomass as a nutrient. The reactors were incubated under pressure (5.4 atm) and flow of CBM water (0.01 mL/min), and control batch cultures were incubated at ambient pressure and without flow (± amendment). Dissolved and headspace methane concentrations were analyzed over time by gas chromatography for 75 days. The pressurized reactors exhibited longer latency periods than ambient pressure controls, but methane production did not reach a plateau phase, which might reflect the impact of scale on the inoculum. The coal/sand reactor exhibited higher methane production than the coal-only reactor, a pattern also observed in the corresponding controls, suggesting an interface effect on methanogenesis. This study indicates that the HP flow test system we designed is well suited for the study of methanogenesis and provides a successful demonstration of CBM generation from the PRB in field-relevant laboratory conditions as a precursor to meso‑scale demonstrations.

Fluorescence Characteristics of Coalbed Methane Produced Water and Its Influence on Freshwater Bacteria in the South Qinshui Basin, China

Production of coalbed methane (CBM) resources commonly requires using hydraulic fracturing and chemical production well additives. Concern exists for the existence of chemical compounds in CBM produced water, due to the risk of environmental receptor contamination. In this study, parallel factor method analysis (PARAFAC), fluorescence index, and the fluorescence area integral methods were used to analyse the properties of CBM produced water sampled from Shizhuang Block (one of the most active CBM-producing regions in the Qinshui Basin). A culture experiment was designed to determine the effect of discharged CBM produced water on microorganisms in freshwater. Water quality analysis shows the hydrochemistry of most water samples as Na-HCO3 type produced water of CBM appears as a generally weak alkaline (pH 8.69 ± 0.185) with high salinity, high alkalinity, and a high chemical oxygen demand (COD) value. Three individual components were identified by using parallel factor method analysis as humic-like components (C1), fulvic-like components (C2), and amino acid-like substances (C3). The fluorescence characteristic index comprehensively explains that the fluorescent substances in CBM produced water has the characteristics of a low degree of humification and a high recent self-generating source. The region integration results of characteristic peaks show that tyrosine-like and tryptophan-like materials account for more than 67% of fluorescent substances in CBM produced water. The addition of produced water from coalbed methane promotes the growth of freshwater bacteria, and this process is accompanied by the decrease of the proportion of fulvic acid, humic acid, and the increase of the proportion of soluble microbial metabolites. This paper proposes a convenient method for organic matter identification of CBM produced water and provides some theoretical support and reference for the improvement of CBM water treatment and utilization.

Gypsum and Coal-bed Methane Water Modify Growth Media Properties, Nutrient Uptake, and Essential Oil Profile of Lemongrass and Palmarosa

Coal-bed methane (CBM), an important energy source, coproduces a vast amount of saline-sodic wastewater, CBM water (CBMW), with environmental and economic disposal issues. This research evaluated under a greenhouse production system the influence of gypsum (CaSO4·2H2O) and CBMW on yields, essential oil (EO) content and composition in lemongrass (Cymbopogon flexuosus) and palmarosa (C. martinii), and on growth medium pH and available nutrients. CBMW treatments had higher pH than tap water treatment. Gypsum reduced pH in all CBMW treatments but did not affect pH in tap water treatment. While CBMW may increase the available Cu and Fe in growth medium, the application of gypsum may negate this effect. CBMW significantly increased growth medium Na. Gypsum increased growth medium S, and CBMW increased S in the high gypsum treatments. Palmarosa height, fresh weight, geranyl acetate, and isoneral in lemongrass EO were reduced, while geraniol in palmarosa EO increased with CBMW relative to tap water. In distillation waste plant tissue, CBMW increased Na in lemongrass and palmarosa by almost eight times; increased total P, S, and Mn in palmarosa; and reduced total N, S, Ca, and Mg in lemongrass and Ca in palmarosa, relative to tap water. This study demonstrated that CBMW may be used for greenhouse production of high-value crops, but it may affect the yields and oil content of some crops and growth medium characteristics.

Quantification of water and exposed lined areas of coal-bed methane water ponds using regular true-color images by developing a novel uniformness based multi-component algorithm

The Powder River Basin in Montana and Wyoming supplies about 40 percent of coal in the United States. In recent decades, coalbed methane (CBM) extracted from coal beds has become an important source of energy in the United States and other countries. CBM water is the produced water brought to the surface as a byproduct of gas extraction. The use of CBM water from the Powder River Basin for irrigation is limited by its relatively high sodium adsorption ratio so the water has to be maintained in lined retention ponds. The liners can be detached from the pond bed, breached through normal weathering or from extreme weather events, and can wear out with time. Water level changes due to constant and dynamic evaporation and precipitation of rainfalls and snowfalls and refilling by gas companies. The objectives of this study are: (1) to develop and validate a novel uniformness based multi-component algorithm to quantify the areas of water and exposed (not submerged in water) liners of the retention ponds from regular red-green-blue (RGB) images, and (2) to quantify the areas of water and liners of the CBM retention ponds in the Powder River Basin using high-resolution true-color images such as free Google Earth imagery. The multi-component algorithm is composed of a sequence of processes: georeferencing, denoising, RGB to L * a * b* color space transformation, K-mean clustering analysis, intelligent identification of connected component in each class, extraction of water body based on maximum uniformness, extraction of exposed lined zones based on uniformness or least root-mean-square value of RGB, and eventually calculation of water area and exposed line area. Application of the multi-component algorithm to the CBM retention ponds in the Powder River Basin using high-resolution true-color images shows that the algorithm can extract accurately water area and the exposed area of liners from these images of high spatial resolution (0.20 ∼ 0.34 m), providing a useful tool to use regular RGB images as a resource for monitoring reservoirs, lakes or artificial small ponds.

Influence of humic acid on the long-term performance of direct contact membrane distillation

In this study, the influence of humic acid on the treatment of coalbed methane water by direct contact membrane distillation was examined with bench-scale test unit. During short-term distillation (1000 min), high level of humic acid above 50 ppm resulted in significant decrease in permeate flux, while low level of humic acid (∼2 ppm) had little influence on the flux. For the long-term distillation (5000 min), the flux decline began at 3400 min in the presence of 5 ppm humic acid and 5 mM Ca2+, and decreased to ∼40% of initial flux at 5000 min. The spectroscopic analysis of the membrane used revealed that the surface was covered by hydrophilic layers mainly composed of calcite. The membrane fouling effect of humic acid became more significant in the presence of Ca2+ due to more facile calcite formation on the membrane surface. It was demonstrated that humic acid enhanced CaCO3 deposition on the membrane surfaces, thereby expediting the scaling phenomenon.

Coal-Bed Methane Water: Effects on Soil Properties and Camelina Productivity.

Every year, the production of coal-bed natural gas in the Powder River Basin results in the discharge of large amounts of coal-bed methane water (CBMW) in Wyoming; however, no sustainable disposal methods for CBMW are currently available. A greenhouse study was conducted to evaluate the potential to use CBMW as a source of irrigation water for camelina [ (L.) Crantz]. We assessed the effects of three CBMW concentrations (0% [1:0], 50% [1:1], and 100% [0:1] tap water to CBMW) on selected soil properties, growth, seed oil, and fatty acid composition of three camelina cultivars: Blaine Creek, Ligena, and Pronghorn. The 100% CBMW reduced seed and estimated biofuel yields by 24 and 23%, respectively, but increased the oil content by 3%, relative to the control. Additionally, the 100% CBMW visibly affected soil through formation of surface crust due to elevated levels of sodium (653 mg Na kg). The 50% CBMW had no significant effects on the seed yield, estimated biofuel yield, and oil content, but the soil Na levels were still high (464 mg kg), which could pose a long-term impact on soil structure. The CBMW tended to reduce the total saturated fatty acid, but it had no significant effects on the total monounsaturated or polyunsaturated fatty acids of camelina seeds. Overall, CBMW diluted with an equal amount of good-quality water could be used to irrigate camelina in the short term. Afterward, only good-quality water would have to be used until the accumulated dissolved solids are flushed out.

Geochemical multiaquifer assessment of the Huntly coalfield, New Zealand, using a novel chloride-bicarbonate-boron ternary diagram

This study investigates the chemical signature of produced water from the Huntly coalfield in New Zealand during coalbed methane (CBM) development using a newly proposed chloride-bicarbonate-boron (Cl-HCO3-B) ternary diagram. This ternary diagram is used to identify the source of fluid in the different aquifers (groundwater, CBM and deep basement) and the potential communication between these aquifers. A comparison study of Huntly with other local and international CBM fields (Maramarua, Powder River Basin, San Juan Basin, Raton, Atlantic Rim, Liulin and Alberta) was also carried out to help characterize and verify the origin of water being abstracted. Results from the ternary diagram showed that produced water samples from Huntly CBM wells shows CBM water characteristics, with high chloride (Cl−) concentrations originating from moderate permeability coal seams. The water samples also indicate that there is some communication with shallower aquifers based on significant bicarbonate (HCO3−) concentration. Water samples from the basement well meanwhile, showed deep basement water characteristics, with high boron (B) concentrations and originated from low permeable formations, far from the recharge area. Water samples from the shallow groundwater well displayed a shallow groundwater signature high in bicarbonate (HCO3−), and showed no significant connection with the coal seam or deeper aquifer. When comparing the Huntly CBM water with water samples from other CBM fields, the former showed similar CBM water chemical signatures and comparable patterns, with minor ion concentration differences. The novel ternary diagram proved to be a reliable tool to identify the possible links between deep and shallow aquifers, qualitative formation permeability and origins of water in one diagram. It therefore enhances our understanding of the natural CBM reservoir setting and could improve field development, wastewater management and water quality monitoring in the future.

Cultivation of a native alga for biomass and biofuel accumulation in coal bed methane production water

Coal bed methane (CBM) production has resulted in thousands of ponds in the Powder River Basin of low-quality water in a water-challenged region. A green alga isolate, PW95, was isolated from a CBM production pond, and analysis of a partial ribosomal gene sequence indicated the isolate belongs to the Chlorococcaceae family. Different combinations of macro- and micronutrients were evaluated for PW95 growth in CBM water compared to a defined medium. A small level of growth was observed in unamended CBM water (0.15g/l), and biomass increased (2-fold) in amended CBM water or defined growth medium. The highest growth rate was observed in CBM water amended with both N and P, and the unamended CBM water displayed the lowest growth rate. The highest lipid content (27%) was observed in CBM water with nitrate, and a significant level of lipid accumulation was not observed in the defined growth medium. Growth analysis indicated that nitrate deprivation coincided with lipid accumulation in CBM production water, and lipid accumulation did not increase with additional phosphorus limitation. The presented results show that CBM production wastewater can be minimally amended and used for the cultivation of a native, lipid-accumulating alga.

Coal-Bed Methane Water Effects on Dill and Its Essential Oils.

Pumping water from coal seams decreases the pressure in the seam and in turn releases trapped methane; this is the most common and economic method of methane extraction. The water that is pumped out is known as "coal-bed methane water" (CBMW), which is high in sodium and other salts. In the past 25 yr, the United States has seen a 16-fold increase in the production of coal bed methane gas, and trillions of cubic meters are yet to be extracted. There is no sustainable disposal method for CBMW, and there are very few studies investigating the effects of this water on plants and their secondary metabolites and on soil properties. This study was conducted to determine the effects of CBMW on soil chemical properties and on the biomass and essential oil yield and composition of dill ( L.). This crop was grown in a greenhouse and was subjected to different levels of CBMW treatment: tap water only; 25% CBMW, 75% tap water; 50% CBMW, 50% tap water; 75% CBMW, 25% tap water; and 100% CBMW. The major dill oil constituents, limonene and α-phellandrene, were not affected by the treatments; however, the concentration of dill ether increased with increasing CBMW levels, whereas the concentration of carvone decreased. In soil, sodium level significantly increased with increasing level of treatment, but pH and cation exchange capacity were not much affected. Coal bed methane water could be used for irrigation of dill for one growing season, but longer-term studies may be needed to clarify the long-term effects on soil and plant.

Coalbed methane-produced water quality and its management options in Raniganj Basin, West Bengal, India

Coalbed methane (CBM) recovery is associated with production of large quantity of groundwater. The coal seams are depressurized by pumping of water for regular and consistent gas production. Usually, CBM operators need to pump >10 m3 of water per day from one well, which depends on the aquifer characteristics, drainage and recharge pattern. In India, 32 CBM blocks have been awarded for exploration and production, out of which six blocks are commercially producing methane gas at 0.5 million metric standard cubic feet per day. Large amount of water is being produced from CBM producing blocks, but no specific information or data are available for geochemical properties of CBM-produced water and its suitable disposal or utilization options for better management. CBM operators are in infancy and searching for the suitable solutions for optimal management of produced water. CBM- and mine-produced water needs to be handled considering its physical and geochemical assessment, because it may have environmental as well as long-term impact on aquifer. Investigations were carried out to evaluate geochemical and hydrogeological conditions of CBM blocks in Raniganj Basin. Totally, 15 water samples from CBM well head and nine water samples from mine disposal head were collected from Raniganj Basin. The chemical signature of produced water reveals high sodium and bicarbonate concentrations with low calcium and magnesium, and very low sulphate in CBM water. It is comprehend that CBM water is mainly of Na–HCO3 type and coal mine water is of Ca–Mg–SO4 and HCO3–Cl–SO4 type. The comparative studies are also carried out for CBM- and mine-produced water considering the geochemical properties, aquifer type, depth of occurrence and lithological formations. Suitable options like impounding, reverse osmosis, irrigation and industrial use after prerequisite treatments are suggested. However, use of this huge volume of CBM- and mine-produced water for irrigation or other beneficial purposes may require careful management based on water pH, EC, TDS, alkalinity, bicarbonate, sodium, fluoride, metals content and SAR values.

Winter discharge of coalbed methane water in the Powder River Basin, Wyoming

ABSTRACTThe heat transported with coalbed methane (CBM) water is shown to influence the thermal, flow, and ice characteristics of the Powder River, the principal river draining the Powder River Basin, Wyoming, during winter. The writers suggest how management of CBM water discharge from numerous tributary streams will minimize potential adverse influences on river channel stability and ecology. Their study, conducted over two winters (2009–2010 and 2010–2011), indicates that besides augmenting the river's natural flow, a substantial winter influence of CBM water discharge was the formation of open-water leads typically extending up to several kilometres along the river. The leads result from warm coherent plumes of CBM water discharge that gradually cool and dissipate when exposed to frigid air. Lead formation alters flow thalweg alignment, concentrating flow along the lead, and plays a potentially significant role for biota along the river. The leads were observed to attract fish, birds, and other wildlife during winter.

The effect of coal-bed methane water on spearmint and peppermint.

Coal bed methane is extracted from underground coal seams that are flooded with water. To reduce the pressure and to release the methane, the water needs to be pumped out. The resulting waste water is known as coal bed methane water (CBMW). Major concerns with the use of CBMW are its high concentrations of S, Na, dissolved Ca, Mg, SO, and bicarbonate (HCO). Irrigation water is a scarce resource in most of the western states. The objective of this study was to evaluate the effect of various amounts of CBMW on the growth, essential oil content, composition, and antioxidant activity of spearmint ( L.) and peppermint ( L.) crops that were irrigated with the water. These two crops are grown in some western states and are potential specialty crops to Wyoming farmers. The irrigation treatments were 0% CBMW (tap water only), 25% CBMW (25% CBMW plus 75% tap water), 50% CBMW (50% CBMW and 50% tap water), 75% CBMW (75% CBMW plus 25% tap water), and 100% CBMW. Analyses of the data revealed that the CBMW treatments did not affect the antioxidant capacity of spearmint or peppermint oil (242 and 377 μmol L Trolox g, respectively) or their major oil constituents (carvone or menthol). Coal bed methane water at 100% increased total phenols and total flavonoids in spearmint but not in peppermint. Coal bed methane water also affected oil content in peppermint but not in spearmint. Spearmint and peppermint could be watered with CBMW at 50% without suppression of fresh herbage yields. However, CBMW at 75 and 100% reduced fresh herbage yields of both crops and oil yields of peppermint relative to the control.

Respuesta del agua subterránea somera y de la química del suelo a 3 años de riego subsuperficial por goteo usando agua extraída para el gas metano de mantos de carbón

Disposal of produced waters, pumped to the surface as part of coalbed methane (CBM) development, is a significant environmental issue in the Wyoming portion of the Powder River Basin, USA. High sodium adsorption ratios (SAR) of the waters could degrade agricultural land, especially if directly applied to the soil surface. One method of disposing of CBM water, while deriving beneficial use, is subsurface drip irrigation (SDI), where acidified CBM waters are applied to alfalfa fields year-round via tubing buried 0.92 m deep. Effects of the method were studied on an alluvial terrace with a relatively shallow depth to water table (∼3 m). Excess irrigation water caused the water table to rise, even temporarily reaching the depth of drip tubing. The rise corresponded to increased salinity in some monitoring wells. Three factors appeared to drive increased groundwater salinity: (1) CBM solutes, concentrated by evapotranspiration; (2) gypsum dissolution, apparently enhanced by cation exchange; and (3) dissolution of native Na–Mg–SO4 salts more soluble than gypsum. Irrigation with high SAR (∼24) water has increased soil saturated paste SAR up to 15 near the drip tubing. Importantly though, little change in SAR has occurred at the surface.

Characteristics of produced water during coalbed methane (CBM) development and its feasibility as irrigation water in Jincheng, China

Water resources are scarce in Jincheng. Huge quantities of water are pumped out in the dewatering course, and the disposal of CBM water is one of the most important problems during the extracting of CBM. Based on the data of CBM water production, chemical characteristics, the irrigational conditions for major crops, and China irrigation water standard, the feasibility of CBM water as irrigation water is discussed. The result shows the CBM water quality doesn’t fully meet irrigation water quality standards in Jincheng, its high salinity and sodium adsorption ratio (SAR) in CBM water might affect crops growth and lead to yield loss, and can’t be used as irrigation water directly, but with the treatment of the reverse osmosis (RO) to lower the salinity and SAR of CBM water, the CBM water can be used as irrigation water.

Deep subsurface drip irrigation using coal-bed sodic water: Part I. Water and solute movement

Water co-produced with coal-bed methane (CBM) in the semi-arid Powder River Basin of Wyoming and Montana commonly has relatively low salinity and high sodium adsorption ratios that can degrade soil permeability where used for irrigation. Nevertheless, a desire to derive beneficial use from the water and a need to dispose of large volumes of it have motivated the design of a deep subsurface drip irrigation (SDI) system capable of utilizing that water. Drip tubing is buried 92cm deep and irrigates at a relatively constant rate year-round, while evapotranspiration by the alfalfa and grass crops grown is seasonal. We use field data from two sites and computer simulations of unsaturated flow to understand water and solute movements in the SDI fields. Combined irrigation and precipitation exceed potential evapotranspiration by 300–480mm annually. Initially, excess water contributes to increased storage in the unsaturated zone, and then drainage causes cyclical rises in the water table beneath the fields. Native chloride and nitrate below 200cm depth are leached by the drainage. Some CBM water moves upward from the drip tubing, drawn by drier conditions above. Chloride from CBM water accumulates there as root uptake removes the water. Year over year accumulations indicated by computer simulations illustrate that infiltration of precipitation water from the surface only partially leaches such accumulations away. Field data show that 7% and 27% of added chloride has accumulated above the drip tubing in an alfalfa and grass field, respectively, following 6 years of irrigation. Maximum chloride concentrations in the alfalfa field are around 45cm depth but reach the surface in parts of the grass field, illustrating differences driven by crop physiology. Deep SDI offers a means of utilizing marginal quality irrigation waters and managing the accumulation of their associated solutes in the crop rooting zone.

Tracking solutes and water from subsurface drip irrigation application of coalbed methane–produced waters, Powder River Basin, Wyoming

One method to beneficially use water produced from coalbed methane (CBM) extraction is subsurface drip irrigation (SDI) of croplands. In SDI systems, treated CBM water (injectate) is supplied to the soil at depth, with the purpose of preventing the buildup of detrimental salts near the surface. The technology is expanding within the Powder River Basin, but little research has been published on its environmental impacts. This article reports on initial results from tracking water and solutes from the injected CBM-produced waters at an SDI system in Johnson County, Wyoming. In the first year of SDI operation, soil moisture significantly increased in the SDI areas, but well water levels increased only modestly, suggesting that most of the water added was stored in the vadose zone or lost to evapotranspiration. The injectate has lower concentrations of most inorganic constituents relative to ambient groundwater at the site but exhibits a high sodium adsorption ratio. Changes in groundwater chemistry during the same period of SDI operation were small; the increase in groundwater-specific conductance relative to pre-SDI conditions was observed in a single well. Conversely, groundwater samples collected beneath another SDI field showed decreased concentrations of several constituents since the SDI operation. Groundwater-specific conductance at the 12 other wells showed no significant changes. Major controls on and compositional variability of groundwater, surface water, and soil water chemistry are discussed in detail. Findings from this research provide an understanding of water and salt dynamics associated with SDI systems using CBM-produced water.

Produced-Water-Volume Estimates and Management Practices

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 125999, ’Produced Water Volume Estimates and Management Practices,’ by J.A. Veil, SPE, and C.E. Clark, Argonne National Laboratory, originally prepared for the 2010 SPE International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Rio de Janeiro, 12-14 April. The paper has not been peer reviewed. Produced water is the largest byproduct associated with oil-and-gas production. Within the USA, nearly one million oil or gas wells are producing hydrocarbons with various volumes of produced water. In the past, several estimates of the annual volume of produced water have been made, but none were highly accurate, nor are they current. The full-length paper describes a study conducted for the US Department of Energy (DOE) to develop accurate estimates of produced-water volumes for 2007. Introduction Produced-water-volume generation and management in the USA are not well characterized at a national level. The DOE asked Argonne National Laboratory to compile data on produced water associated with oil-and-gas production. Produced water is water from underground formations that is brought to the surface during oil-or-gas production. Because the water has been in contact with hydrocarbon-bearing formations, it contains some of the chemicals from the formations and hydrocarbons. It may include water from the reservoir, water previously injected into the formation, and any chemicals added during the production processes. Characteristics of Produced Water The physical and chemical properties of produced water vary considerably, depending on the geographic location of the field, the geologic formation from which the water was produced, and the type of hydrocarbon product being produced. Produced-water properties and volume also vary throughout the lifetime of a reservoir. For those sites where waterflooding is conducted, the properties and volumes of the produced water may vary dramatically because of injection of additional water into the formation to increase hydrocarbon production. The major constituents of concern are salt content, oil and grease (various organic compounds associated with hydrocarbons in the formation), inorganic and organic compounds introduced as chemical additives to improve drilling and production operations, and naturally occurring radioactive material. Produced water from gas production has characteristics that differ from those of produced water from oil production. In addition to formation water, water produced from gas production will contain condensed water, which is water that was in the vapor phase while in the reservoir but condenses into a liquid state in the production/separation system. Produced water from coalbed-methane (CBM) production differs from produced water from both oil and gas production. Oil and grease are less of a concern with CBM water than with other produced waters. To recover the methane in CBM reservoirs, the hydrostatic pressure that caused the adsorption of methane to the coal-bed is reduced through the removal of water from the reservoir through CBM wells. Characteristics of CBM water that may affect reuse are salinity, sodicity, and (to a lesser extent) iron, manganese, and boron.

Stable isotope and water quality analysis of coal bed methane production waters and gases from the Bowen Basin, Australia

Abstract Coal bed methane (CBM) is a significant growing industry in Queensland's energy sector. It is, however, a relatively new industry with little local water quality data and stable isotope compositions of production waters and gases available in the public domain. This study aims to determine whether water quality and stable isotope data can be correlated with gas and groundwater production and flow pathways, and identify zones of recharge and water mixing. Stable isotope analysis and accessory water quality tests were conducted on CBM production gas and water samples collected from two CBM producing bituminous coal seams within a single field in the Bowen Basin. In the production field, the reservoir seams are gently folded with eastwardly dipping fold axes, and compartmentalised by an ENE normal fault on the flank of a broad central anticline that contains minor faults. For one seam, splitting and a change in coal quality parallels the fault and fold axes. Although virgin reservoir conditions were similar, differing production performance north and south of the main fault suggests it acts as a barrier to water and gas flow along strike. The stable isotope analysis on the production water showed that waters with more positive δD and δ18O compositions were associated with areas of higher water production and shallower depths, whereas more negative δD and δ18O compositions were associated with lower water production and high gas production. The gas isotope analysis showed that production gases had both biogenic and thermogenic origins and that secondary biogenic gas generated through CO2 reduction comprises a significant portion of the CBM produced from this field. More negative CH4 δ13C values characterize the zones of meteoric recharge in shallow, up-dip areas. Gas production data and CO2 δ13C values suggest that this may result from 13CH4 stripping by the recharge waters and/or increased biogenic activity in this area. Smaller CO2–CH4 carbon isotopic fractionation values characterized zones of meteoric recharge, whereas higher isotopic fractionation values characterized the high gas production domain.

Hydraulic fracturing and wellbore completion of coalbed methane wells in the Powder River Basin, Wyoming: Implications for water and gas production

Excessive water production (more than 7000 bbl/month per well) from many coalbed methane (CBM) wells in the Powder River Basin of Wyoming is also associated with significant delays in the time it takes for gas production to begin. Analysis of about 550 water-enhancement activities carried out during well completion demonstrates that such activities result in hydraulic fracturing of the coal. Water-enhancement activities, as the operators in the basin call this procedure, consists of pumping 60 bbl of water/min into the coal seam during approximately 15 min. This is done to clean the wellbore and to enhance CBM production. Hydraulic fracturing is of concern because vertical hydraulic fracture growth could extend into adjacent formations and potentially result in excess CBM water production and inefficient depressurization of coals. Analysis of the pressure-time records of the water-enhancement tests enabled us to determine the magnitude of the least principal stress (S3) in the coal seams of 372 wells. These data reveal that because S3 switches between the minimum horizontal stress and the overburden at different locations, both vertical and horizontal hydraulic fracture growth is inferred to occur in the basin, depending on the exact location and coal layer. Relatively low water production is observed for wells with inferred horizontal fractures, whereas all of the wells associated with excessive water production are characterized by inferred vertical hydraulic fractures. The reason wells with exceptionally high water production show delays in gas production appears to be inefficient depressurization of the coal caused by water production from the formations outside the coal. To minimize CBM water production, we recommend that in areas of known vertical fracture propagation, the injection rate during the water-enhancement tests should be reduced to prevent the propagation of induced fractures into adjacent water-bearing formations. In areas where S3 is unknown, a minifrac should be done to determine the magnitude of S3 (to know whether fracture propagation will be vertical or horizontal), so the water-enhancement activities at the time of well completion are done to minimize water production and optimize gas production.

Feasibility of Using Natural Zeolites to Remove Sodium from Coal Bed Methane-Produced Water

Coal bed methane (CBM) is naturally occurring methane, contained in coal seams saturated with water. In order to extract the CBM, large quantities of water must be pumped from the coal seams. CBM water, produced in some areas of New Mexico, contains low total dissolved solids, which can potentially be used for rangeland irrigation. The water, however, has a high sodium adsorption ratio, which can result in severe deterioration of soil permeability with repeated irrigation. The St. Cloud zeolites exhibit a low selectivity of Na+ over Ca2+ (Vanselow selectivity coefficients of 0.26 and usable Na+ exchange capacity of 0.1 meq∕g ) at the ionic strength of Na+ -laden CBM waters (0.035 M) . Nevertheless, given the availability and low cost of natural zeolites, ion exchange experiments were conducted using packed columns to estimate a treatment cost. The operation and maintenance cost of the zeolite system was estimated to be about $3 per barrel (one barrel =159 liters) compared with $0.75–$4∕bbl for deep well i...