In situ combustion

Keywords production decline, economic decline, infill drilling, bypassed oil, attic/cellar oil, production potential, coiled tubing, formation damage, cross-flow, side-track, enhanced oil recovery (EOR), steam injection, in-situ combustion, water alternating gas (WAG), debottlenecking, produced water treatment, well intervention, intermittent production, satellite development, host facility, extended reach development, extended reach drilling. 

Like steam injection, in-situ combustion is a thermal process designed to reduce oil viscosity and hence improve flow performance. Combustion of the lighter fractions of the oil in the reservoir is sustained by continuous air injection. Though there have been some economic successes claimed using this method, it has not been widely employed. Under the right conditions, combustion can be initiated spontaneously by injecting air into an oil reservoir. However a number of projects have also experienced explosions in surface compressors and injection wells. 

Energy in the form of injected water or CO2 may be suppHed to increase the rate of production of light cmde oils. AppHcation of heat to the reservoirs, eg, using hot water, steam, heated CO2, fireflood, or in situ combustion, however, is generally associated with the production of heavier, viscid cmdes. 

The in situ combustion method of enhanced oil recovery through air injection (28,273,274) is a chemically complex process. There are three types of in situ combustion dry, reverse, and wet. In the first, air injection results in ignition of cmde oil and continued air injection moves the combustion front toward production wells. Temperatures can reach 300—650°C. Ahead of the combustion front is a 90—180°C steam 2one, the temperature of which depends on pressure in the oil reservoir. Zones of hot water, hydrocarbon gases, and finally oil propagate ahead of the steam 2one to the production well. 

A service well is a well drilled or completed for the purpose of supporting production in an existing field. Wells of this class are drilled for the following specific purposes gas injection (natural gas, propane, hutane, or flue gas), water injection, steam injection, air injection, salt water disposal, water supply for injection, observation, injection for in-situ combustion. 

Development Development well OO Development well OO Exploration well O Auxiliary well O Production well O - oil - gas Injection well O - water - gas - in-situ combustion Appraisal well OO Development well O... 

Thermal recovery methods involve the use of steam and in-situ combustion. Thermal EOR processes add heat to the reservoir to reduce the viscosity of the oil or to vaporize it. In addition, these processes use steam or oil combustion... 

Front-tracking model for in situ combustion oil recovery [1515]... 

P. S. Rocha, M. A. Miller, and K. Sepehmoori. A succession-of-states front-tracking model for the in-situ combustion recovery process. In Situ, 21(1) 65-100, February 1997. 

Preliminary work showed that first order reaction models are adequate for the description of these phenomena even though the actual reaction mechanisms are extremely complex and hence difficult to determine. This simplification is a desired feature of the models since such simple models are to be used in numerical simulators of in situ combustion processes. The bitumen is divided into five major pseudo-components coke (COK), asphaltene (ASP), heavy oil (HO), light oil (LO) and gas (GAS). These pseudo-components were lumped together as needed to produce two, three and four component models. Two, three and four-component models were considered to describe these complicated reactions (Hanson and Ka-logerakis, 1984). 

Four component models were found very difficult or impossible to converge. Models K, M and O are more complicated and have more reaction paths compared to models 1 or N. Whenever the parameter with the highest variance was eliminated in any of these three models, it would revert back to the simpler ones Model I or N. Model N was the only four pseudo-component model that converged. This model also provides an estimate of the HO/LO split. This model together with model 1 were recommended for use in situ combustion simulators (Hanson and Kalogerakis, 1984). Typical results are presented next for model I. 

Fig. 5.3.7 Experimental set-up ofthe in situ combustion hp-Xe129 NMR experiment. Adapted from Ref. [2],...

The in situ monitoring of high temperature reactions by hpl29Xe magnetic resonance is still in its infancy. Although the previous work on gas phase dynamics in porous media has shown the feasibility of dynamic microscopy and M RI and the first in situ combustion NMR spectra have been collected, much more development remains to be done. To date, hpl29Xe NMR and MRI are currently the only techniques available to study gas dynamics in porous and opaque systems. 

The in situ combustion method of enhanced oil recovery through air injection (397,503,504) is an exceeding complex process chemically. However, because little work has been done on the effect of chemical additives to oil recovery efficiency, this process will not be discussed herein. 

Poulson, R.E. Frost, C.M. Jensen, H.B. Characteristics of Synthetic Crude from Crude Shale Oil Produced by In-situ Combustion Retorting, In Shale Oil, Tar Sands, and Related Fuel Sources Yen, T.F., Ed ACS Adv. Chem. Ser. No. 151, 1976, 1. 

Modifications in the Composition of Crude Oils During In Situ Combustion... 

During enhanced oil recovery by in-situ combustion, a crude oil undergoes chemical changes (pyrolysis reactions) and physical changes (dilution by the cracking products, vaporization and condensation of some fractions). Both phenomena are important for oil production ... 

The objective of this work is to study the possible influence of the crude oil composition on the amount of coke deposit and on its ability to undergo in-situ combustion. Thus, the results would provide valuable information not only for numerical simulation of in-situ combustion but also to define better its field of application. With this aim, five crude oils with different compositions were used in specific laboratory tests that were carried out to characterize the evolution of the crude oil composition. During tests carried out in a porous medium representative of a reservoir rock, air injection was stopped to interrupt the reactions. A preliminary investigation has been described previously (8). 

This experimental work gives data that help us to understand the mechanisms of coke formation during in-situ combustion. 

Kinetics of fuel formation for in-situ combustion", Fith Soc Petroleum Engrs Middle East Show, SPE paper No 15736" (March... 

Audibert, A., Roucache, J., "Evolution of the Composition of a Crude Oil During In-situ Combustion", Characterization of Heavy Crude Oils and Petroleum Residues. Ed. Technip, Paris, p 135-139, (1984). 

Bojes, J.M., Wright, G.B., "Application of Fluid Analyses to the Operation of an in-situ Combustion Pilot". Annu. Technical Meeting of Petroleum Soc. of CIM, Paper No 86-37-61, (June 1986). 

Kinetics and Energetics of Oxidation of Bitumen in Relation to In Situ Combustion Processes... 

Other experimental methods have been proven technologically feasible but are still commercially unviable. These include in-situ combustion, electromagnetic charging, and similar methods. 

In situ air stripping, in soil and ground water treatment, 25 844 In situ bioremediation, in soil and ground water treatment, 25 836-842 In situ combustion enhanced oil recovery method, 18 630-631 In situ composites, 13 503 In situ diagnostics, for MOCVD, 22 155-156... 

Characteristics of Synthetic Crude from Crude Shale Oil Produced by in Situ Combustion Retorting... 

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