Reverse Combustion Instabilities in Tar Sands and Coal

1980 ◽  
Vol 20 (04) ◽  
pp. 267-277 ◽  
Author(s):  
Robert D. Gunn ◽  
William B. Krantz
Keyword(s):  
Reaction Zone ◽  
Combustion Front ◽  
Stability Theory ◽  
Coal Gasification ◽  
Gas Production ◽  
Volatile Components ◽  
In Situ Combustion ◽  
Tar Sands ◽  
Vertical Well

Abstract A linear stability analysis shows that reverse combustion in coal and tar sands is only conditionally stable for mobility ratios less than one. However, high air-flow rates and gas generation at the combustion front can be stabilizing influences. For unstable operation, an estimate of the size of the reverse combustion channel may be obtained from the curve for the most highly amplified wave length. This provides a method for calculating the air flux, combustion front velocity, and rate of progress of the burn front. Recently the U.S. DOE Laramie Energy Technology Center (LETC) and Sandia Laboratories obtained experimental data about reverse combustion from a field test of in-situ coal gasification at Hanna, WY. These data show that 9.7 days were required for the development of a reverse combustion path 68 to 70 ft in length. The stability theory developed in this work predicts a length of 64 ft for this same 9.7-day period. In addition to quantitative predictions, stability theory provides an explanation of certain puzzling qualitative observations concerning reverse combustion. Introduction In-situ combustion is a potentially useful method for recovering fossil fuels from underground deposits. A number of in-situ combustion field tests have been conducted in oil reservoirs, tar sands, oil shale deposits, and coal seams. In-situ combustion can be classified into two broad categories: reverse combustion, in which the reaction front travels countercurrent to the flow of air, and forward combustion, in which the reaction zone travels in the same direction as the flow of air. Reverse combustion is especially important for coal and tar sands. During forward combustion, tars vaporized at the flame front in either coal or tar sands travel by convection into cooler regions ahead of the reaction zone where they condense and subsequently reduce the natural permeability of the fuel bed. In reverse combustion, vaporized tars or other high-molecular-weight compounds generated in the reaction zone travel toward the production well through a heated area already contacted by the high temperatures of the combustion front. As an added advantage, reverse combustion in tar sands substantially increases the relative permeability to gas. In lignite and subbituminous coal, drying and partial combustion typically increase the effective permeability to gas by four orders of magnitude. However, bituminous coal frequently swells on heating, and the net effect of reverse combustion on the permeability of swelling coals has not been investigated thoroughly. In coal and tar sands, reverse combustion is primarily a coking or carbonization process - i.e., the volatile components of the tar or coal are partially combusted while most of the carbon or coke is left unburned. For these reasons, reverse combustion represents an important part of some in-situ combustion methods currently being investigated for tar sands and coal. In the linked vertical well process for in-situ coal gasification, reverse combustion is used first to develop a high-permeability path between the production and air injection wells, while in the second stage of the process forward gasification or combustion is used as the major gas production method. Both industrial companies and government laboratories have investigated the linked vertical well process. For tar sands, the LETC is considering the use of reverse combustion as a preparatory mechanism similar to that used in coal.

In Situ Combustion Away From Thin, Horizontal Gas channels

1968 ◽  
Vol 8 (01) ◽  
pp. 18-32 ◽  
Author(s):  
M. Prats ◽  
R.F. Jones ◽  
N.E. Truitt
Keyword(s):  
Combustion Front ◽  
Combustion Process ◽  
Field Tests ◽  
Combustion Surface ◽  
Gas Production ◽  
In Situ Combustion ◽  
Secondary Combustion ◽  
Field Evidence ◽  
Production Wells

Abstract In most published discussions and theories of in situ combustion, the combustion fronts are assumed to be vertical. However, evidence from field tests leaves no doubt that combustion fronts often advance more rapidly along the top than near the bottom of a formation as a result of difference in density between injected air and formation liquids. The approximation proposed in this paper to determine the movement of the resultant tilted combustion surfaces states that the vertical rate of movement of combustion surfaces is proportional to the horizontal oxygen flux. Where self-ignition is possible, the proposed method demands that a secondary combustion surface exist around production wells which produce some oxygen. These secondary combustion surfaces may be formed long before the primary combustion surface can advance from injection to production wells. Heat liberated near production wells at these secondary combustion surfaces can contribute to an early increase in production rate. Results indicate that significant oil recoveries cannot be obtained from the usual flood patterns (five-spots, seven-spots, etc.) without producing large volumes of unused oxygen. Ideally, to increase oxygen-consumption efficiency, well patterns should allow oil production from a first line of production wells and gas production from more distant lines of producers. However, it may be desirable to produce some gas at all wells to support (and benefit from) active secondary combustion surfaces. Results indicate that the well spacing through which combustion can be advanced is larger than that predicted by other methods. A large number of production wells may still be desirable to take quick advantage of gravity drainage. From a comparison with results at South Belridge field, California, it appears that this method adequately describes oxygen concentration and temperature histories and combustion-front shapes. However, this method does not accurately locate the most advanced point of the combustion surface. There is some field evidence to substantiate the actual presence of secondary combustion surfaces at South Belridge. Use of the proposed method appears warranted at this time when lay-over of the combustion surface can be anticipated. Introduction The assumption of vertical combustion fronts has been embodied in all previous publications which use the movement of combustion fronts away from injection wells to determine the temperature and fluid distributions in the reservoir. The only paper concerned with a mathematical model of the combustion process in which a nonvertical combustion front is used was written by Gottfried. Actually, nonvertical combustion fronts have been observed in most in situ combustion field tests for which adequate data are available. In practice, the typical vertical extent of the burned zone decreases with distance from the injection well, and this burned zone is at or near the top of the sand body. In some cases, such as at South Belridge field near Taft, Calif., the combustion surface is almost horizontal over a very large area. Thus, for some years an obvious and serious gap has existed between theory (vertical fronts) and practice (tilted fronts). This is indicated in Fig. 1. Tilted combustion fronts such as observed at South Belridge sometimes result from the natural tendency of injected gases to rise to the top of an oil sand. SPEJ P. 18ˆ

Fuel Formation and Conversion During In-Situ Combustion of Crude Oil

SPE Journal ◽  
2013 ◽  
Vol 18 (06) ◽  
pp. 1217-1228 ◽  
Author(s):  
Hascakir Berna ◽  
Cynthia M. Ross ◽  
Louis M. Castanier ◽  
Anthony R. Kovscek
Keyword(s):  
Oil Recovery ◽  
Photoelectron Spectroscopy ◽  
Combustion Front ◽  
Combustion Products ◽  
Combustion Tube ◽  
Cross Sectional ◽  
In Situ Combustion ◽  
X Ray ◽  
Study Results

Summary In-situ combustion (ISC) is a successful method with great potential for thermal enhanced oil recovery. Field applications of ISC are limited, however, because the process is complex and not well-understood. A significant open question for ISC is the formation of coke or "fuel" in correct quantities that is sufficiently reactive to sustain combustion. We study ISC from a laboratory perspective in 1 m long combustion tubes that allow the monitoring of the progress of the combustion front by use of X-ray computed tomography (CT) and temperature profiles. Two crude oils—12°API (986 kg/m3) and 9°API (1007 kg/m3)—are studied. Cross-sectional images of oil movement and banking in situ are obtained through the appropriate analysis of the spatially and temporally varying CT numbers. Combustion-tube runs are quenched before front breakthrough at the production end, thereby permitting a post-mortem analysis of combustion products and, in particular, the fuel (coke and coke-like residues) just downstream of the combustion front. Fuel is analyzed with both scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). XPS and SEM results are used to identify the shape, texture, and elemental composition of fuel in the X-ray CT images. The SEM and XPS results aid efforts to differentiate among combustion-tube results with significant and negligible amounts of clay minerals. Initial results indicate that clays increase the surface area of fuel deposits formed, and this aids combustion. In addition, comparisons are made of coke-like residues formed during experiments under an inert nitrogen atmosphere and from in-situ combustion. Study results contribute to an improved mechanistic understanding of ISC, fuel formation, and the role of mineral substrates in either aiding or impeding combustion. CT imaging permits inference of the width and movement of the fuel zone in situ.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

2021 ◽  
pp. 1-13
Author(s):  
Melek Deniz Paker ◽  
Murat Cinar
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Combustion Front ◽  
Fractured Reservoirs ◽  
Front Propagation ◽  
High Permeability ◽  
Vertical Orientation ◽  
In Situ Combustion ◽  
Horizontal Orientation

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (/SC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of /SC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied /SC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several /SC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to airflow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil AP/ gravity was higher. Based on the experimental results a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

Kinetics of Wet In-Situ Combustion: A Review of Kinetic Models

2014 ◽  
Author(s):  
E. A. Cavanzo ◽  
S. F. Muñoz ◽  
A.. Ordoñez ◽  
H.. Bottia
Keyword(s):  
Kinetic Model ◽  
Crude Oil ◽  
Kinetic Models ◽  
Combustion Front ◽  
Chemical Interaction ◽  
Combustion Process ◽  
Oxidation Reactions ◽  
In Situ Combustion ◽  
Temperature Oxidation

Abstract In Situ Combustion is an enhanced oil recovery method which consists on injecting air to the reservoir, generating a series of oxidation reactions at different temperature ranges by chemical interaction between oil and oxygen, the high temperature oxidation reactions are highly exothermic; the oxygen reacts with a coke like material formed by thermal cracking, they are responsible of generating the heat necessary to sustain and propagate the combustion front, sweeping the heavy oil and upgrading it due to the high temperatures. Wet in situ combustion is variant of the process, in which water is injected simultaneously or alternated with air, taking advantage of its high heat capacity, so the steam can transport heat more efficiently forward the combustion front due to the latent heat of vaporization. A representative model of the in situ combustion process is constituted by a static model, a dynamic model and a kinetic model. The kinetic model represents the oxidative behavior and the compositional changes of the crude oil; it is integrated by the most representative reactions of the process and the corresponding kinetic parameters of each reaction. Frequently, the kinetic model for a dry combustion process has Low Temperature Oxidation reactions (LTO), thermal cracking reactions and the combustion reaction. For the case of wet combustion, additional aquathermolysis reactions take place. This article presents a full review of the kinetic models of the wet in situ combustion process taking into account aquathermolysis reactions. These are hydrogen addition reactions due to the chemical interaction between crude oil and steam. The mechanism begins with desulphurization reactions and subsequent decarboxylation reactions, which are responsible of carbon monoxide production, which reacts with steam producing carbon dioxide and hydrogen; this is the water and gas shift reaction. Finally, during hydrocracking and hydrodesulphurization reactions, hydrogen sulfide is generated and the crude oil is upgraded. An additional upgrading mechanism during the wet in situ combustion process can be explained by the aquathermolysis theory, also hydrogen sulphide and hydrogen production can be estimated by a suitable kinetic model that takes into account the most representative reactions involved during the combustion process.

Predictability of Crude Oil In-Situ Combustion by the Isoconversional Kinetic Approach

SPE Journal ◽  
2011 ◽  
Vol 16 (03) ◽  
pp. 537-547 ◽  
Author(s):  
Murat Cinar ◽  
Berna Hasçakir ◽  
Louis M. Castanier ◽  
Anthony R. Kovscek
Keyword(s):  
Crude Oil ◽  
Combustion Front ◽  
Front Propagation ◽  
Combustion Tube ◽  
Complex Nature ◽  
Oil Viscosity ◽  
In Situ Combustion ◽  
Temperature Oxidation ◽  
Isoconversional Analysis

Summary One method to access unconventional heavy-crude-oil resources as well as residual oil after conventional recovery operations is to apply in-situ combustion (ISC) enhanced oil recovery. ISC oxidizes in place a small fraction of the hydrocarbon, thereby providing heat to reduce oil viscosity and increase reservoir pressure. Both effects serve to enhance recovery. The complex nature of petroleum as a multicomponent mixture and the multistep character of combustion reactions substantially complicate analysis of crude-oil oxidation and the identification of settings where ISC could be successful. In this study, isoconversional analysis of ramped temperature-oxidation (RTO) kinetic data was applied to eight different crude-oil samples. In addition, combustion-tube runs that explore ignition and combustion-front propagation were carried out. By using experimentally determined combustion kinetics of eight crude-oil samples along with combustion-tube results, we show that isoconversional analysis of RTO data is useful to predict combustion-front propagation. Isoconversional analysis also provides new insight into the nature of the reactions occurring during ISC. Additionally, five of the 10 crude-oil/rock systems studied employed a carbonate rock. No system displayed excessive oxygen consumption resulting from carbonate decomposition at combustion temperatures. This result is encouraging as it contributes to widening of the applicability of ISC.

Development and Application of an In-Situ Combustion Reservoir Simulator

1980 ◽  
Vol 20 (01) ◽  
pp. 39-51 ◽  
Author(s):  
Gary K. Youngren
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Solution Method ◽  
Oil And Gas ◽  
Three Dimensions ◽  
Volatile Components ◽  
In Situ Combustion ◽  
Gas Phases ◽  
Reservoir Simulator

Youngren, Gary K., SPE-AIME, ARCO Oil and Gas Co. Abstract This paper describes a three-dimensional, three-phase in-situ combustion reservoir simulator that rigorously models fluid flow, heat transfer, and vaporization/ condensation. It has five components: water, oxygen, nonvolatile oil, and two arbitrary volatile components. The volatile components partition between the oil and gas phases. The physical mechanisms modeled, the comprehensive mathematical solution method employed, and four applications of the simulator are presented. The applications demonstrate that the simulator can be used to interpret laboratory results and predict the effects of reservoir characteristics and operating strategy on field performance. Introduction Crookston et al. and Farouq Ali thoroughly reviewed previous developments in the mathematical simulation of in-situ combustion processes. Briefly, the earliest studies modeled certain aspects of the process using simple assumptions for the remaining process using simple assumptions for the remaining features in order to make the problem tractable. For example, Chu modeled one-dimensional thermal conduction, convection, and the thermal effects of vaporization and condensation, but multi phase fluid flow effects were simplified by assuming constant fluid saturations. Smith and Farouq Ali simulated conduction, convection, heat losses, and heat generation in two-dimensions, but assumed single-phase flow and constant fuel consumption. Recently, Farouq Ali and Crookston et al. described comprehensive three-phase, two-dimensional simulators that model the most essential features of in-situ combustion; however, results were presented only for hypothetical one- and two-dimensional examples with relatively few grid blocks.The objective of this work was to develop an in-situ combustion simulator that would rigorously model fluid flow, heat transfer, and vaporization/ condensation and still be efficient enough to allow simulation of realistic reservoir problems. Accordingly, the simulator employs a stable, efficient, highly implicit solution method. It is formulated to handle three dimensions, three phases, five components, gravity and capillary forces, heat transfer by convection and conduction within the reservoir and conductive heat loss to adjacent strata. Quantitative data on high-temperature combustion kinetics of crude oils in porous media is inadequate to allow rigorous treatment of reaction kinetics; thus, the combustion reaction is treated simply, yet realistically, by assuming that the combustion rate is limited only by the oxygen flux. This paper first describes the simulator, outlining the physical mechanisms modeled and the numerical solution method employed. It concludes by presenting analysis of real laboratory and field data in one, two, and three dimensions. Simulator Description Physical Properties Physical Properties The most significant features of the simulator are listed in Table l and detailed in Appendix A.The simulator has five components: water, nonvolatile (dead) oil, oxygen, and two arbitrary volatile components that partition between the oil and gas phases. The last four components are considered insoluble in water. The last two components are arbitrary and may be any one of the combinations: nitrogen (N2) and solution gas, N2 and carbon dioxide (CO2), N2 and a distillable hydrocarbon, CO2 and solution gas, or CO2 and a distillable hydrocarbon. SPEJ p. 39

Simulation Study Of The LETC TS-2C In Situ Combustion Test In Utah Tar Sands

1979 ◽  
Author(s):  
Harold L. Hutchinson ◽  
Allan Spivak ◽  
Lyle A. Johnson
Keyword(s):  
Simulation Study ◽  
In Situ Combustion ◽  
Tar Sands

Research of Lifting Technology of Combustion In Situ

2011 ◽  
Vol 347-353 ◽  
pp. 3219-3222
Author(s):  
Xi Shun Zhang ◽  
Xiao Dong Wu ◽  
Shu Qin Ma
Keyword(s):  
Crude Oil ◽  
Oil Recovery ◽  
Heavy Oil ◽  
Gas Production ◽  
Technical Support ◽  
Recovery Ratio ◽  
Heavy Component ◽  
In Situ Combustion ◽  
Dynamic Displacement

In-situ combustion (fire flooding) is one of important methods to improve heavy oil recovery ratio, utilizing the reservoir itself heavy component burning as dynamic displacement of crude oil, improving the crude oil character, flooding efficiency is high, applicability is extensive, and other recover techniques can not match. But the technical support is difficult and broad, and is the key in restricting the effect of in-situ combustion, especially for the effectiveness of development. With the increase of fire flooding development, flowing wells turns to artificial lifting wells, the gas production increases deeply, and the lifting technology faces a lot of new problems. Aiming at the problems of combustion in-situ, the relevant technologies were researched, then some methods and measures suiting to heavy oil fire flooding technology were proposed. And it provided reference for researching of deep heavy oil fire flooding lifting technology in the future.

Evolving Smart Model to Predict the Combustion Front Velocity for In Situ Combustion

2015 ◽  
Vol 3 (2) ◽  
pp. 128-135 ◽  
Author(s):  
Mohammad Ali Ahmadi ◽  
Mohammad Masoumi ◽  
Reza Askarinezhad
Keyword(s):  
Combustion Front ◽  
Front Velocity ◽  
In Situ Combustion

Experimental and Numerical Analysis of In-Situ Combustion in a Fractured Core

SPE Journal ◽  
2011 ◽  
Vol 16 (02) ◽  
pp. 358-373 ◽  
Author(s):  
H.. Fadaei ◽  
L.. Castanier ◽  
A.M.. M. Kamp ◽  
G.. Debenest ◽  
M.. Quintard ◽  
...  
Keyword(s):  
Combustion Front ◽  
Fractured Reservoirs ◽  
Experimental Studies ◽  
Steam Injection ◽  
Combustion Tube ◽  
Fractured Reservoir ◽  
In Situ Combustion ◽  
Matrix Permeability ◽  
The Matrix

Summary Approximately one-third of global heavy-oil resources can be found in fractured reservoirs. In spite of its strategic importance, recovery of heavy crudes from fractured reservoirs has found few applications because of the complexity of such reservoirs. In-situ combustion (ISC) is a candidate process for such reservoirs, especially for those where steam injection is not feasible. Experimental studies reported in the literature on this topic mentioned a cone-shaped combustion front, indicating that the process was governed by diffusion of oxygen into the matrix. The main oil-production mechanisms were found to be thermal expansion of oil and evaporation of light components (Schulte and de Vries 1985; Greaves et al. 1991). In order to confirm these results, we carried out reservoir-simulation studies presented in Fadaei et al. (2010). We have shown that the front has the shape of a cone, and we have performed a combustion/extinction analysis representing the results in a diagram of cumulative production vs. diffusion coefficient and matrix permeability. Before obtaining quantitative and qualitative comparisons, we need to characterize the systems we want to study. Therefore, we also carried out laboratory experiments using kinetic cells and combustion tubes. The kinetic-cell studies showed that the presence of carbonates has a significant effect on combustion kinetics. Our combustion-tube studies confirmed the previously observed coneshaped front. Previous studies reported in literature used heating elements along the combustion tube to regulate the temperature, which may have caused some undue heating of the core. To avoid that, we chose to use efficient insulation to minimize heat losses. Combustion advanced faster in nonconsolidated matrix, in which the permeability was higher than in consolidated matrix. The results showed that the presence of severe heterogeneities may prevent the combustion front from propagating. Several runs were performed for different air-injection rates and pressures and for different permeability contrasts between the matrix and the fracture. The next step of our work is the upscaling of ISC in the fractured reservoir at interwell scale on the basis of knowledge provided by simulation and experimental studies.

Sign in / Sign up

Export Citation Format

Share Document