Steam flooding

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

Domestic petroleum, natural gas, and natural gas Hquids production has declined at a rate commensurate with the decrease in reserves (see Table 2). Consequently, the reserves/production ratio, expressed in years, remained relatively constant from about 1970 through 1992, at 9—11 years (16). Much of the production in the early 1990s is the result of enhanced oil recovery techniques water flooding, steam flooding, CO2 injection, and natural gas reinjection. 

The injection of large volumes of steam, steam flooding, is used to mobilize oil which is produced at offset production wells. Smaller volumes of steam are injected in the cycHc steam stimulation or huff n puff process (Eig. 2). Many wells are placed on several cycles of steam stimulation and then used as injection or production wells in steam flood projects. 

Gravity override of low density steam leads to poor volumetric sweep efficiency and low oil recovery in steam floods. Nonchemical methods of improving steam volumetric sweep efficiency include completing the injection well so steam is only injected in the lower part of the oil-bearing zone (181), alternating the injection of water and steam (182), and horizontal steam injection wells (183,184). Surfactants frequently are used as steam mobihty control agents to reduce gravity override (185). Field-proven surfactants include alpha-olefin sulfonates (AOS), alkyltoluene sulfonates, and neutralized... 

Thermally stable foam additives, such as alkylaryl sulfonates and C -C g alpha-olefin sulfonates, are being used in EOR steam flooding for heavy od production. The foam is used to increase reservoir sweep efficiency (178,179). Foaming agents are under evaluation in chemical CO2 EOR flooding to reduce CO2 channeling and thus increase sweep efficiency (180). 

Results described in the literature have resulted in several patents, such as one for the improvement of the transport of viscous crude oil by microemulsions based on ether carboxylates [195], or combination with ether sulfate and nonionics [196], or several anionics, amphoterics, and nonionics [197] increased oil recovery with ether carboxylates and ethersulfonates [198] increased inversion temperature of the emulsion above the reservoir temperature by ether carboxylates [199], or systems based on ether carboxylate and sulfonate [200] or polyglucosylsorbitol fatty acid ester [201] and eventually cosolvents which are not susceptible for temperature changes. Ether carboxylates also show an improvement when used in a C02 drive process [202] or at recovery by steam flooding [203]. 

FIGURE 6.4 Steam flooding is one of two principal thermal methods for oil recovery and has been commercially applied since the early 1960s. A mixture of steam and hot water is continuously injected into the oil-bearing formation to displace mobilized oil to adjacent production wells. Reprinted with permission from Enhanced Oil Recovery. Copyright 1984 by the National Petroleum Council. 

Polyalkylene polyamine salts are prepared by contacting polyamines with organic or inorganic acids. The polyamines have a molecular weight of at least 1000 Dalton and ranging up to the limits of water solubility [1185]. In a process of demulsification of the aqueous phase of the broken bitumen emulsions, the pH is adjusted to deactivate the demulsifier so that the water may be used in subsequent in situ hot water or steam floods of the tar sand formation. 

G. G. Hoffmann and I. Steinfatt. Thermochemical sulfate reduction at steam flooding processes— chemical approach. In ACS Petrol Chem Div Preprints, volume 38, pages 181-184. 205th ACS Nat Mtg Enhanced Oil Recovery Symp (Denver, CO, 3/28-4/2), February 1993. 

Steam flooding (397,499,500) can greatly increase the recovery of high viscosity crude oils through heat thinning processes. As noted previously, surfactants can be used to reduce the mobility of... 

When this pressure drops, it can be built-up again by water flooding. Unfortunately, after these primary and secondary processes, there still remains up to 70% of the oil adsorbed on the porous clays. Consequently, in recent years, there have been tremendous efforts made to develop tertiary oil recovery processes, namely carbon dioxide injection, steam flooding, surfactant flooding and the use of microemulsions. In this latter technique, illustrated in Fig. 1, the aim is to dissolve the oil into the microemulsion, then to displace this slug with a polymer solution, used for mobility control, and finally to recover the oil by water injection ( 1). 

OIL SAND - FIRE /STEAM FLOOD COAL-IN SITU GASIFICATION SHALE - IN SITU RETORT... 

Augments advanced remediation technologies such as soil heating and steam flooding. 

Steam contains the extra heat energy that is requited and it has been widely used by the petroleum industry since the mid-1960s to stimulate the production of thick oils. Two techniques, steam stimulation and steam flooding, aie cuttently used. 

Steam flooding is more sophisticated and difficult than steam stimulation. This technique uses separate injection and production wells to improve both rate and amount of production. 

By improving "sweep" and "mobility control," surfactant-based methods offer the most promising ways to alleviate these problems. This use of surfactants appears to be just on the verge of commercialization for steam flooding. Because miscible CO2 flooding has been commercialized more recently, the use of surfactants to improve gas-flood EOR has not yet been commercialized. Conceivably, however, the long-term viability of gas flooding could prove to be dependent on the success of current research efforts in the use of surfactants to alleviate "bypass" problems. 

The use of surfactants to create dispersions that improve flow behavior in EOR is currently associated quite closely with CO2 and with steam flooding. However, for two decades research on dispersion-based flow control focused on the development of low-pressure, low-temperature foams for other applications, such as improving water floods and reducing the losses of natural gas from underground storage. Direct applications to CO2 flooding did not appear until 1978 (48,49). 

Many enhanced oil recovery processes use gas drives to displace trapped oil, ie. steam floods and CO2 floods. The sweep efficiency of these methods is often low because of the unfavorable mobility ratio of gas to oil. (The mobility of gas is much greater than the mobility of oil.) Therefore, gas tends to overide or finger through oil. 

In recent years there has been considerable interest in the use of foams in chemical steam flood, CO2, and low tension processes. To date, principal applications have been as diverting agents where the foam has been used to block high permeability, low oil saturation zones and hence force drive fluids through lower permeability, higher oil saturation zones. The utility of foams in more general mobility control roles has not been extensively... 

Decker and Flock (74) investigated the application of emulsion injection for steam-flooding processes. In laboratory models, emulsions containing 5 vol% crude oil were effective in blocking channels created by steam injection during subsequent steam-injection cycles. Oil droplets in the emulsion were predominantly in the 1-2- xm range, but droplets as large as 10 fxm were observed. 

The two main thermal recovery processes are steam injection and in situ combustion. In the steam injection process, steam of 80% quality is injected into the reservoir to displace oil. The steam can be injected continuously (called steam drive ) or intermittently (called cyclic steam injection ). In the steam drive process, steam is injected in several injection wells and the oil is produced in several production well. In cyclic injection process, steam is injected in several (previously producing) wells for 2-6 weeks, soaked for 3-7 days, and produced back for a few weeks or months. This cycle can be repeated several times. Often, the steam flood is preceded by cyclic injection. Steam injection has been used commercially for several decades. In fire flooding or in situ combustion process, air is injected and ignited inside the reservoir. A combustion front... 

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