Showing papers on "Natural gas published in 1982"

Methanol from coal and natural gas

Abstract: The present invention is directed to a process which uses the methanol synthesis gas from steam reforming in a first methanol plant and effectively integrates a second methanol plant which uses as the methanol synthesis gas (a) the purge gas from the first methanol plant and (b) the clean syn-gas produced by partial oxidation.

Role of Diffusion in Primary Migration of Hydrocarbons

Abstract: The following effective diffusion coefficients D(cm2/sec) were determined for the diffusion of light hydrocarbons through the water-saturated pore space of shales: methane (2.12 × 10-6), ethane (1.11 × 10-6), propane (5.55 × 10-7), iso-butane (3.75 × 10-7), n-butane (3.01 × 10-7), n-pentane (1.57 × 10-7), n-hexane (8.20 × 10-8), n-heptane (4.31 × 10-8), and n-decane (6.08 × 10-9). On the basis of these new data, a deterministic, dynamic model was set up to simulate the diffusive transport of light hydrocarbons (C1 to C10) from source rocks. For eight documented source-rock units, representing a wid range of geologic conditions (maturities of 0.40 to 1.35% mean vitrinite reflectance; oil- to gas-prone kerogens), the cumulative amounts of hydrocarbons escaping with time were calculated. Thus, it was shown that diffusion represents an effective process for primary migration of gas but not for oil. The rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial-size gas fields. For example, a cumulative amount of 109 kg of methane (1.5 × 109 std m3 or 5.3 × 1010 scf) has escaped by diffusion in 540,000 years from a certain volume (1,000 km2 by 200 m thick) of a high-mature gas-prone Mesozoic source rock in western Canada. The origin of hydrocarbon accumulations with high gas-to-oil ratios in low-mature sediments in geologically young basins ("early gases and condensates") can be explained by an early phase of primary migration predominantly based on diffusion. During the initial stages of the accumulation history of those fields (extending up to millions of years under certain conditions), the reservoir gas changes with geologic time from a methane-rich to a wet-gas composition. At low-maturity levels (below about 0.6% Rm), even oil-prone source rocks yield methane-rich light-hydrocarbon mixtures by migration through diffusion. Compositional trends among reservoir gases of several multiple-pay gas fields in Louisiana represent evidence for diffusive transport of hydrocarbons. The variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites. In the shallow pay zones, compounds of high diffusivity are enriched. For example, in the Sligo gas field of Louisiana, the methane/ethane and the iso-butane/n-butane ratios increase from 10.2 to 36.0 and from 0.86 to 1.13, respectively, from the deepest to the shallowest of the five productive reservoir sands, which are spread over a a depth interval of 5,500 ft (1,676 m). Diffusion of light hydrocarbons in the subsurface can also have economically adverse effects. For example, existing gas accumulations can be destroyed by dissipation. The rate of this destruction was calculated for the Harlingen gas field, Holland. By diffusive loss through 400 m of shale cap rock, the initial amount of methane in place of 1.93 × 109 std m3 (6.8 × 1010 scf) is reduced by one half over a period of 4.5 million years. This leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady-state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock.

Role of Naturally Occurring Gas Hydrates in Sediment Transport

Abstract: Naturally occurring gas hydrates have the potential to store enormous volumes of both gas and water in semi-solid form in ocean-bottom sediments and then to release that gas and water when the hydrate's equilibrium conditions are disturbed. Therefore, hydrates provide a potential mechanism for transporting large volumes of sediments. Under the combined low bottom-water temperatures and moderate hydrostatic pressures that exist over most of the continental slopes and all of the continental rises and abyssal plains, hydrocarbon gases at or near saturation in the interstitial waters of the near-bottom sediments will form hydrates. The gas can either be autochthonous, microbially produced gas, or allochthonous, catagenic gas from deeper sediments. Equilibrium conditions that stabilize hydrated sediments may be disturbed, for example, by continued sedimentation or by lowering of sea level. In either case, some of the solid gas-water matrix decomposes. Released gas and water volume exceeds the volume occupied by the hydrate, so the internal pressure rises--drastically if large volumes of hydrate are decomposed. Part of the once rigid sediment is converted to a gas- and water-rich, relatively low density mud. When the internal pressure, due to the presence of the compressed gas or to buoyancy, is sufficiently high, the overlying sediment may be lifted and/or breached, and the less dense, gas-cut mud may break through. Such hydrate-related phenomena can cause mud diapirs, mud volcanos, mud slides, or turbidite flows, depending on s diment configuration and bottom topography.

CO2 Removal from high CO2 content hydrocarbon containing streams

Abstract: Carbon dioxide is removed from CO 2 and hydrocarbon containing gaseous streams. In the instance where the hydrocarbons and CO 2 are such that hydrocarbons would condense out during CO 2 removal, the gas stream is treated in one or more stages to accomplish hydrocarbon composition control.

Process for separating carbon dioxide and acid gases from a carbonaceous off-gas

Abstract: A process is described for the separation of carbon dioxide and sulfide gases from oil shale retorting off-gases, coal gasification off-gases, oxygen fireflooding off-gases or carbon dioxide miscible flood enhanced oil recovery off-gases for recycle to a retort, gasifier, petroleum reservoir or to further sulfide processing prior to export. The process separates the off-gases into an essentially sulfur-free light BTU fuel gas, a heavy hydrocarbon stream and a carbon dioxide acid gas stream wherein the off-gas is compressed if necessary and cooled to separate the various streams. The carbon dioxide acid gas stream is expanded in an auto-refrigeration step to provide the necessary process refrigeration. In the oil shale retort and coal gasification applications the sulfur constituents are sorbed on spent oil shale particles or coal ash.

A Thermodynamic Evaluation of Thermal Recovery of Gas From Hydrates in the Earth (includes associated papers 11863 and 11924 )

Abstract: An examination is made of the potential for recovering gas from naturally occurring hydrates. Factors to be considered in such a study are (1) location of the hydrate fields, (2) purity of hydrates in the reservoir, (3) types of media in which hydrates form, (4) thermodynamic conditions of temperature, pressure, and composition, and (5) thermal properties of the reservoir. Based on these considerations, calculations were made to determine the energy needed to dissociate hydrates and the amount of gas recovered per g mol of hydrate dissociated. 14 refs.

Carbon dioxide fracturing process and apparatus

Abstract: There is described a new and improved method of fracturing an underground stratigraphic formation penetrated by a well bore including the steps of pumping a stream of liquified gas into the formation to cause the fracturing thereof and then introducing proppants directly into the stream of liquified gas for injection of the proppants into the fractures. Prior to introducing the proppants into the liquid gas stream, they are cooled and pressurized to the storage temperature and pressure of the liquified gas.

Process for recovery of natural gas liquids from a sweetened natural gas stream

Abstract: A sweet natural gas stream is stripped of water and hydrocarbon components heavier than methane to substantially any selected degree by countercurrent extraction with polyethylene glycol dimethyl ether while at pipeline pressures The stripped natural gas meets pipeline specifications The rich polyethylene glycol dimethyl ether is let down in pressure through selected successive stages which respectively isolate fractions that are rich in ethane, propane, butanes, and hydrocarbons heavier than butane Lastly, waste water is removed from the solvent to regenerate the polyethylene glycol dimethyl ether The separated gas streams of ethane, propane, butanes, and hydrocarbons heavier than butanes are individually compressed, combined, condensed and cooled to form a natural gas liquid stream, suitable for pipeline shipment A sour natural gas stream may also be treated in the same equipment if adequate solvent quantities are employed to remove water and acidic components from the sour gas and if a sweetening unit is added to remove the acidic components from the combined liquid hydrocarbon stream

Gas hydrates in ocean bottom sediments

Abstract: Gas hydrates belong to a special category of chemical substances known as inclusion compounds. An inclusion compound is a physical combination of molecules in which one component becomes trapped inside the other. In gas hydrates, gas molecules are physically trapped inside an expanded lattice of water molecules. The pressures and temperatures beneath Arctic water depths greater than 1,100 ft (335 m) and subtropical water depths greater than 2,000 ft (610 m) are suitable for the formation of methane hydrate. Theoretical depths to the base of a gas hydrate layer in ocean bottom sediments are determined by assuming: (1) a constant hydrostatic pressure gradient, (2) two typical hydrothermal gradients, (3) variable geothermal gradients, and (4) pure methane hydrated with conna e seawater. In addition to pressure and geothermal gradient, other variables affecting the stability of gas hydrate are examined. These variables are hydrothermal gradient, sediment thermal conductivity, heat flow, hydrate velocity, gas composition, and connate water salinity. If these variables are constant in a lateral direction and the above assumptions are valid, a local geothermal gradient can be determined if the depth to the base of a gas hydrate is known. The base of the gas hydrate layer is seen on seismic profiles as an anomalous reflection nearly parallel to the ocean bottom, cross-cutting geologic bedding plane reflections, and generally increasing in sub-ocean bottom time with increasing water depth. The acoustic impedance is a result of the relatively fast velocity hydrate layer overlying slower velocity sediments. In addition, free gas may be trapped beneath the hydrate, thereby enhancing the reflection.

Method of treating carbon-dioxide-containing natural gas

Abstract: A cryogenic separation process for rejecting carbon dioxide from a carbon-dioxide-containing natural gas mixture. The invention is specifically designed for treating a natural gas mixture recovered from a petroleum well employing the enhanced recovery technique of carbon dioxide flooding. The carbon-dioxide-containing natural gas mixture is treated using a particular arrangement of fractional condensation, partial vaporization and rectification unit operations to produce an enriched-methane gas stream and carbon dioxide product streams at various pressures. The invention is well suited for the bulk separation of large quantities of carbon dioxide from carbon-dioxide-containing natural gas mixtures, as a preparatory step for the subsequent purification of the enriched-methane product by conventional absorption techniques.

Process for the reduction of the sulfur content in a gaseous stream

Abstract: A process for extracting sulfur from a gas containing hydrogen sulfide comprises the step of oxidizing the gas over a catalyst containing titanium dioxide as an active ingredient.

Process for liquefying methane

Abstract: A process for liquefying natural gas in which heavier hydrocarbons are separated in a scrub column from the natural gas prior to liquefaction. The feed to the scrub column is intercooled against the methane-rich overhead from said column and isentropically expanded before being introduced to the column and separated from the heavier hydrocarbons. The methane-rich overhead stream is compressed utilizing the mechanical energy of expansion and liquefied in a refrigerated heat exchanger.

3He/4He ratios of methane-rich natural gases in Japan

Abstract: Measurements of 3He/4He and 20Ne/4He ratios in 12 CH4-rich natural gas samples were made with a magnetic deflection mass spectrometer equipped with a metallic high-vacuum purification line. In order to check the resolving power, sensitivity and stability of the mass spectrometer, atmospheric air in Tokyo was measured repeatedly. The mean 3He/4He ratio in Tokyo air was (1.43 ± 0.03) × 10-6. CH4-rich gases with significantly high 3He/4He ratios were first observed in this study. The 3He/4He ratios for 5 natural gas samples collected from hot springs and mineral springs in inland basins were as high as (1.7–7.3) × 10-6, probably due to the large contribution of the upper mantle-derived He. In comparison, the 3He/4He ratios for 2 samples from water wells distributed in coastal areas facing the Pacific Ocean and 5 samples from gas fields in the southern Kanto district were as low as ∼10-7. Most of the He in these gases is inferred to be radiogenic and of crustal origin.

Process to separate nitrogen from natural gas

Abstract: A process to separate by rectification low concentration nitrogen from natural gases having a gradually increasing nitrogen concentration which employs a nitrogen heat pump cycle to generate necessary liquid reflux for a fractionation column and is compatible with both single column and double column process arrangements.

Interpretation of Subsurface Hydrocarbon Shows

Abstract: Hydrocarbons occur in the subsurface in four modes: (1) continuous phase oil or gas, (2) isolated droplets of oil or gas, (3) dissolved hydrocarbons, and (4) associated with kerogenous rocks. All of these modes of occurrence can result in what is described as a subsurface hydrocarbon "show." Each show type has markedly different implications to exploration and must be differentiated as the first step in show interpretation. Only continuous phase occurrences of oil and gas indicate that a trapped and potentially producible accumulation of hydrocarbons has been discovered. Free oil or gas recovery from the formation or subsurface hydrocarbon saturations of greater than 55% indicates a continuous phase occurrence. Continuous phase shows can be interpreted quantitatively. The static hydrocarbon column downdip from a continuous phase occurrence can be calculated from one well bore if the subsurface oil or gas saturation, capillary properties, hydrocarbon-water interfacial tension, oil density, and water density of the reservoir are known. Producing wells are by definition continuous phase oil or gas, and estimates of oil-water or gas-water contacts from normally available exploration data are practical and reasonably accurate based on a documented field study. Continuous phase oil or gas can extend either updip or downdip from a commercial reservoir. These continuous phase shows can also be interpreted quantitatively to determine how large an oil or gas column is required downdip to explain the show. By this method it can be determined whether an exploratory well penetrated the updip waste zone or downdip transition zone of an oil or gas field. Field studies illustrate that quantitative show interpretation of noncommercial shows can provide reliable estimates of the downdip hydrocarbon column. This type of data can be used in a systematic manner to explore for subtle stratigraphic and combination traps.

Oxidative condensation of natural gas or methane into gasoline range hydrocarbons

Abstract: This invention relates to a new process for the direct conversion of natural gas or methane into gasoline range hydrocarbons (i.e., synthetic transportation fuels or lower olefins) via catalytic condensation using superacid catalysts.

Natural gas hydrates in Canada

Abstract: The presence of hydrate in at least 20 northern Canadian wells onand off-shore has been inferred by the nature of gas release from formations and from geophysical well-log interpretations. In addition, hydrates have been identified in gas fields in Siberia and on the north slope of Alaska. There are extensive data on temperature pressure relationships for different hydrate compositions. Relating such curves to depth within the earth and superimposing measured geothermal gradients provides a means of predicting the depth zones of occurrence. Maximum thicknesses probably do not exceed 1800 m. In water depths greater than 200 to 300 m, gas-hydrates may be found in sediments at, or close to, the sea-floor. The destruction of the hydrate by changing the thermal regime may lead to problems similar to those associated with bottom-founded structures or pipelines in permafrost terrain. Decomposition of gas-hydrates may occur naturally in areas such as the Beaufort shelf. The resulting large volumes of natural gas may weaken the sediments leading to instability with respect to natural or induced loads such as earthquakes. The Soviets estimate that as much as 10%3 (525 Tcf) of gas hydrate may underlie the on-shore areas of the northern Soviet Union. In addition, as much as lO%d of gas hydratemay underlie the earth's oceans. A rough calculation based on known gas-hydrate horizons in the northern Mackenzie Delta suggest the presence of sufficient additional gas to increase reserves by 15 per cent. Dissociation of hydrates either by heat absorbed from drilling mud or from the pressure decrease at the drill-bit can be a significant hazard to the safety of drilling operations in the north. The problems which might result by producing conventional hydrocarbons from depths below a hydrate zone have yet to be solved.

Recovery of power from vaporization of liquefied natural gas

Abstract: Power is recovered from the vaporization of liquefied natural gas by warming and vaporizing the liquefied natural gas against a first multicomponent stream which is cooled and liquefied. The liquefied multicomponent stream is pumped to an elevated pressure and is warmed and vaporized against a second multicomponent stream which is cooled and liquefied. The warmed first multicomponent stream is heated, expanded through a generator loaded expander and recycled. The liquefied second multicomponent stream is pumped to an elevated pressure, heated, vaporized and expanded through a second generator loaded expander and recycled.

Method of removing hydrogen sulfide from gases utilizing a zinc oxide sorbent and regenerating the sorbent

Abstract: A spent solid sorbent resulting from the removal of hydrogen sulfide from a fuel gas flow is regenerated with a steam-air mixture. The mixture of steam and air may also include additional nitrogen or carbon dioxide. The gas mixture contacts the spent sorbent containing metal sulfide at a temperature above 500° C. to regenerate the sulfide to metal oxide or carbonate. Various metal species including the period four transition metals and the lanthanides are suitable sorbents that may be regenerated by this method. In addition, the introduction of carbon dioxide gas permits carbonates such as those of strontium, barium and calcium to be regenerated. The steam permits regeneration of spent sorbent without formation of metal sulfate. Moreover, the regeneration will proceed with low oxygen concentrations and will occur without the increase in temperature to minimize the risk of sintering and densification of the sorbent.

Catalytic Activation of Carbon Monoxide on Metal Surfaces

Abstract: Interest in carbon monoxide has increased dramatically during the past decade. This is due primarily to a new interest in energy resources other than natural gas and petroleum resources which include coal, oil shale, and heavy residua. In any process which involves gasification to convert these hydrogen-deficient materials to hydrocarbons or other organic compounds, CO is one of the principal products of the gasification step, and its subsequent hydrogenation to form the required final products is of extreme importance. It is thermodynamically possible to produce methane as SNG, hydrocarbon liquids as fuels, and alcohols and olefins as chemical intermediates — the major problem is the selectiveproduction of the desired product. During the overall conversion process, the reaction between CO and water is important, viathe water gas shift reaction, not only because it is used to adjust the H2/CO ratio in the gas stream between the gasifier and the reactor, but also because H2O is a by-product of the CO hydrogenation reaction and can react with unconsumed CO in the syngas reactor to form CO2.

Safety device for underground storage of liquefied gas

Abstract: A liquefied gas such as propane is stored in underground galleries wherein there is a gaseous phase above a liquid phase and at the bottom, water in a sunk draining trap. The storage is worked, i.e., gas is introduced or extracted through tubes extending into the lower part of the liquefied gas. In case of emergency, failure or damage to the implements, the stored product is isolated. The water level is raised for covering the lower end of the tubes and water is allowed to rise up in the tubes until the pressures are in balance.

Gas well liquid removal system and process

Abstract: A split-stream method and apparatus for preventing the accumulation of liquids, such as water or oil, in subterranean gas wells having low shut-in bottom hole pressures is provided. A compressor whose capacity can be less than the theoretical adiabatic horsepower for full wellhead depletion, is used to remove a two-phase liquid-gas mixture through a secondary fluid transmission conduit. Production of dry gas in larger quantities through a primary production conduit is then possible since liquids cannot accumulate to kill the well. An optional mechanism for initiating production in very low pressure wells and a means of preventing the buildup of paraffin is also described.

Relationship of Methane Content of Coal Rank and Depth: Theoretical vs. Observed

Abstract: Prediction of gas content of coalbeds, and therefore potential producibility, has relied primarily on its observed relationship to coal rank, pressure, and the methane adsorption capacity of a given coal. This relationship has been illustrated by the construction of adsorption isotherms for various coals from experimental data. The value and limitations of these adsorption isotherms are addressed by relating them to observed coalbed methane gas content data. The general conclusion is made that the cause of the pattern of correlation of residual gas to rank is a change in the internal structure of the coal and the moisture content of the coal. 8 refs.

Natural gas adaptor system for automobiles

Abstract: There is provided a natural gas charging system for a vehicle which has an internal combustion engine adapted to run on gasoline or on natural gas, as well as a gasoline tank adapted to feed gasoline through a carburetor to the engine. The gas charging system includes storage means such as tanks which are adapted to store natural gas under a given storage pressure, and delivery means through which natural gas can be delivered from the storage means through an air-mixing means to the carburetor of the vehicle. A compressor is adapted to receive low-pressure natural gas and to compress it up to the storage pressure, and the engine is made to drive the compressor through drive means. Conduit means are provided from the output of the compressor to the storage means.

Gaseous hydrocarbons around an active offshore gas and oil field.

Abstract: Low molecular weight hydrocarbons (LMWHs, C/sub 1/-C/sub 4/) were measured from the water column and sediments around an oil and gas field. No significant differences in mean methane levels were observed between platforms that were and were not discharging brine. However, in the 20-station grid, the relative standard deviations were greater and the highest individual methane and ethane concentrations were found in surface waters near the platform discharging brine. Higher methane values at all depths observed during summer coinciding with decreased ethane/ethene ratios in a near-bottom nepheloid layer provided direct evidence of in situ biological production associated with increases in zooplankton and bacterial biomass in the water column. The sediment LMWHs are predominantly of thermogenic origin probably due to seepage from the subsurface, as evidenced by high levels of methane and elevated ethane/ethene ratios. The LMWH input from brine discharge in the field is estimated at 283 g/day.

A Computer Model for Planning the Development of an Offshore Gas Field

Abstract: A description is given of a gasfield planning model developed and used to select a plan for future development of a partially depleted offshore gas field. The model succeeds in integrating physical constraints of reservoir behavior and gas flow in wells, surface pipes, and compressors with variables that describe possible development activities. This enables a development plan that maximizes the economic worth of the gas resources to be found. The mathematical techniques of mixed integer programming (MIP) are used to find the optimal plan.