Identification of Gas Channeling and Construction of a Gel-Enhanced Foam Plugging System for Oxygen-Reduced Air Flooding in the Changqing Oilfield

Abstract

The accurate identification of gas channeling channels during foam-assisted oxygen-reduced air flooding (FAORAF) and the analysis of the main controlling factors are essential to propose reasonable and effective countermeasures to enhance oil recovery (EOR). However, there are few comprehensive studies on identifying gas channeling channels, the influencing factors, and the corresponding plugging EOR systems in FAORAF. The channeling channels of the injection and production wells of the Changqing Oilfield, China, under varying development schemes are identified utilizing fuzzy membership function theory in this work to obtain their primary distribution. The characteristics and influence factors of gas channeling channels are analyzed by numerical simulation using CMG. The recovery performance of each foam blocking system is evaluated by twin-tube sand pack models. As well, based on the features of reservoir fractures, a new gel-enhanced foam plugging system is developed. The results show that channeling channels chiefly develop along NE 60–70° and that foam could reduce gas channeling. Natural and artificial fractures are the principal factors causing gas channeling, followed by the injection method and gas injection rate. Under the premise of the injection and migration efficiency, the optimal gel system is a 0.1% HPAM + 0.1% organic chromium crosslinking agent. The addition of gel increases the viscosity of the liquid phase and strengthens the mechanical strength of the foam liquid film. At a permeability ratio of 12, the recovery factors of the binary plugging systems composed of microspheres, PEG, and gel combined with foam are 40.89%, 45.85%, and 53.33%, respectively. The movable gel foam system has a short breaking time (only 18 days) and a recovery factor of about 40% at a permeability ratio of 20. To be suitable for oil reservoirs with microfractures, an improved ternary gel foam system—0.1% HPAM + 0.1% chromium crosslinking agent + 0.05–0.1% nano-SiO2—is developed. Compared with the binary gel foam system, the recovery rate of the new nano-SiO2 gel foam system after 15 days of ageing using the core splitting test is 25.24% during the FAORAF process, increasing by 12.38%.

Experimental Evaluation of Anticorrosion of a Standard 20# Gathering Pipeline by Injecting Oxygen-Reduced Air into Simulated In-Service Wells

“…The equation for calculating the uniform corrosion rate of hanging pieces is as follows: Among them, r corr is the uniform corrosion rate of the hanging piece surface, mm/a; M is the mass of the hanging piece before the experiment, g; M′ is the quality of the hanging piece after the experiment, g; S is the surface area of the hanging piece, cm 2 ; T is the experimental time, h; and ρ is the density of the hanging piece, g/cm 3 .…”

“…Reserves of low- and ultralow-permeability reservoirs are increasing annually in the world. Among the commonly used gas flooding methods (CO 2 flooding, N 2 flooding, flue gas flooding, natural gas flooding, and air flooding) for low-permeability reservoirs, oxygen-reduced air flooding (ORAF), as a production method with the advantages of abundant gas sources, environmental protection, energy conservation, and low investment cost, has been gradually popularized at home and abroad. − ORAF is used to treat air to achieve a safe oxygen content range (oxygen concentration ≤ 10%) and inject it into the formation. The low-temperature oxidation reaction between crude oil and O 2 in the formation generates a large amount of heat and CO, CO 2 , and CH 4 gases, which form the flue gas drive in the reservoir and have a certain mixed phase.…”

The Enhanced Oil Recovery Effect of Nitrogen-Assisted Gravity Drainage in Karst Reservoirs with Different Genesis: A Case Study of the Tahe Oilfield

“…The gas channeling and lower oil recovery can be observed with the greater the amount of gas injection. The gas channeling occurs at the high structural location of the gas-producing outlet; therefore, the gas channeling should be controlled and plugged in time to improve the utilization ratio of injected gas [21][22][23][24].…”

Temperature- and Salt-Tolerant 2-Acrylamide-2-methylpropanesulfonic Acid/AM@SiO2 Microgel Particles: Synthesis and Enhanced Oil Recovery Performance Evaluation

“…In addition, the heterogeneity of reservoirs always accelerates the water channeling process through high permeability, which leads to early water breakthrough and high water-cut. Therefore, to increase and stabilize production in high water-cut reservoirs, it is necessary to take practical measures to enhance oil recovery (EOR). , The technology of profile control treatment can effectively plug high permeable channels, modify the injection profile, and control the water channeling of injected water and edge/bottom water, therefore considerably improving water flooding recovery. – …”