Summary At elevated temperatures in aqueous solution, partially hydrolyzed polyacrylamides (HPAMs) experience hydrolysis of amide side groups. However, in the absence of dissolved oxygen and divalent cations, the polymer backbone can remain stable so that HPAM solutions were projected to maintain at least half their original viscosity for more than 8 years at 100°C and for approximately 2 years at 120°C. Within our experimental error, HPAM stability was the same with and without oil (decane). An acrylamide-AMPS copolymer [with 25% 2-acrylamido-2-methylpropane sulphonic acid (AMPS)] showed similar stability to that for HPAM. Stability results were similar in brines with 0.3% NaCl, 3% NaCl, or 0.2% NaCl plus 0.1% NaHCO3. At temperatures of 160°C and greater, the polymers were more stable in brine with 2% NaCl plus 1% NaHCO3 than in the other brines. Even though no chemical oxygen scavengers or antioxidants were used in our study, we observed the highest level of thermal stability reported to date for these polymers. Our results provide considerable hope for the use of HPAM polymers in enhanced oil recovery (EOR) at temperatures up to 120°C if contact with dissolved oxygen and divalent cations can be minimized. Calculations performed considering oxygen reaction with oil and pyrite revealed that dissolved oxygen will be removed quickly from injected waters and will not propagate very far into porous reservoir rock. These findings have two positive implications with respect to polymer floods in high-temperature reservoirs. First, dissolved oxygen that entered the reservoir before polymer injection will have been consumed and will not aggravate polymer degradation. Second, if an oxygen leak (in the surface facilities or piping) develops during the course of polymer injection, that oxygen will not compromise the stability of the polymer that was injected before the leak developed or the polymer that is injected after the leak is fixed. Of course, the polymer that is injected while the leak is active will be susceptible to oxidative degradation. Maintaining dissolved oxygen at undetectable levels is necessary to maximize polymer stability. This can be accomplished readily without the use of chemical oxygen scavengers or antioxidants.

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Stability of Partially Hydrolyzed Polyacrylamides at Elevated Temperatures in the Absence of Divalent Cations

Apparatuses, devices, systems and methods for detecting access disconnection are provided. The present invention includes electrical contacts in fluid and electrical communication with a fluid passing between a patient and a medical system during therapy. In this regard, the present invention can use a direct-contact measurement to detect access disconnection, such as dislodgment of an access device from the patient through which fluid can flow during therapy including, for example, medication delivery, dialysis therapy and the like.

Access disconnection systems and methods

Permeability of a highly permeable zone in a subterranean formation is reduced by injecting into the formation a polymerizable material which expands on polymerization, and thereafter effecting such polymerization.

Reducing the permeability of a rock formation

A review of pyrolysis, aquathermolysis, and oxidation of Athabasca bitumen

Enhanced oil recovery (EOR) refers to the technologies developed to increase extraction of crude oil from reservoirs after primary production. In situ combustion (ISC) is one of the methods developed for EOR. This review examines studies done by researchers worldwide to improve our understanding of the mechanism of oil cracking kinetics, which is one of the fundamental mechanisms of in situ combustion. Good agreement between the laboratory and field results has encouraged further research in this field. Extensive research at the laboratory scale to understand the pyrolysis and oxidation behavior of coke formed from medium and light oil and also to propose more realistic models to mimic the true behavior of in situ combustion has been undertaken in recent years. Apart from the classical Arrhenius model, researchers have come up with other models (two-step oxidation model) based on the type of combustion activity observed from their samples, thus modeling the process more accurately. Research work showing o...

In situ combustion in enhanced oil recovery (eor): a review

After general remarks on the oxidation reactions of hydrocarbons involved in in situ combustion, the heat releases are estimated and a formula is derived for computing the heat of combustion in the high temperature zone. Then a theoretical discussion of reaction kinetics in porous media is presented and applied to the in situ combustion processes. It is observed that there is some similarity between the kinetics of reverse and wet forward combustion processes. Furthermore, the influence of rock matrix properties on crude oil oxidation is illustrated by differential thermal analysis experiments. This observation is of great importance for practical applications. Some information concerning the use of low temperature oxidation data and the value of the reaction order with respect to oxygen partial pressure is derived from the interpretation of reverse combustion experiments using a numerical model. (16 refs.)

Chemical Aspects of In-Situ Combustion - Heat of Combustion and Kinetics

Spontaneous Ignition in Oil Reservoirs

The Institut Francais du Petrole carried out laboratory studies to simulate the in-situ combustion of crude oil by use of a 20 cm dia, 210 cm long combustion tube packed with sand. Following a series of dry combustion tests with oil and air, wet combustion tests were run by injecting water after the dry combustion had attained a steady-state velocity. A minimum water-air ratio of 0.001 cu m/std cu m was sufficient to overcome sand saturation and bring steam to the combustion front; a maximum water-air ratio of 0.004-0.006 cu m/std cu m caused extinction of the high-temperature zone. There was no coke deposit behind the combustion front as long as wet combustion took place with a high-temperature zone. Water injection led to more efficient heat utilization and to a higher combustion-front velocity.

Laboratory research on wet combustion

This process comprises injecting into the formations a liquid organic mixture containing at least one polymerizable chemical compound and a catalyst. The organic mixture reacts with a limited amount of injected oxidizing gas to produce a solid compound which consolidates the formations without substantially reducing their permeability. The process is characterized by the combined use of a polyethylenic hydrocarbon and of a catalyst which comprises at least one element of the group consisting of zirconium, cerium, lanthanum and lanthanides and at least one element selected from the group formed by vanadium, manganese, cobalt and zinc.

Process for consolidating geological formations

The purpose of this project was to study the influence of experimental conditions on wet combustion, especially the water/air ratio in the injected fluids. A series of laboratory tests was conducted under pressure in a horizontal adiabatic cell, with water/air ratios between 0.001 and 0.006 cu m/scm. The results are compared with those of dry combustion. No coke deposit was observed behind the combustion front as long as a high temperature zone existed. In some cases, extinction of the combustion front occurred. At the highest water/air ratio investigated, a steady-state normal wet combustion front could be obtained. In addition, even at the lowest water/air ratio considered, the combustion front velocity was higher than in dry combustion; this velocity increased continually with the water/air ratio. More efficient heat utilization was substantiated by the fact that, in spite of the higher combustion front velocity, the peak temperature remained nearly unchanged and the length of the steam plateau increased throughout the test. (14 refs.)

Jacques Burger

Papers

Chemical Aspects of In-Situ Combustion - Heat of Combustion and Kinetics

Spontaneous Ignition in Oil Reservoirs

Laboratory research on wet combustion

Process for consolidating geological formations

Laboratory research on wet combustion