6 research outputs found
Sandstone matrix acidizing knowledge and future development
To meet rising global demands for energy, the oil and gas industry continuously strives to develop innovative oilfield technologies. With the development of new enhanced oil recovery techniques, sandstone acidizing has been significantly developed to contribute to the petroleum industry. Different acid combinations have been applied to the formation, which result in minimizing the near wellbore damage and improving the well productivity. A combination of hydrofluoric acid and hydrochloric acid (HF:HCl) known as mud acid has gained attractiveness in improving the porosity and permeability of the reservoir formation. However, high-temperature matrix acidizing is now growing since most of the wells nowadays become deeper and hotter temperature reservoirs, with a temperature higher than 200 °F. As a result, mud acid becomes corrosive, forms precipitates and reacts rapidly, which causes early consumption of acid, hence becoming less efficient due to high pH value. However, different acids have been developed to combat these problems where studies on retarded mud acids, organic-HF acids, emulsified acids, chelating agents have shown their effectiveness at different conditions. These acids proved to be alternative to mud acid in sandstone acidizing, but the reaction mechanism and experimental analysis have not yet been investigated. The paper critically reviews the sandstone acidizing mechanism with different acids, problems occurred during the application of different acids and explores the reasons when matrix stimulation is successful over fracturing. This paper also explores the future developing requirement for matrix acidizing treatments and new experimental techniques that can be useful for further development, particularly in developing new acids and acidizing techniques, which would provide better results and information of topology, morphology and mineral dissolution and the challenges associated with implementing these “new” technologies
Ring-Exchange Interaction Effects on Magnons in Dirac Magnet CoTiO
In magnetically ordered materials with localized electrons, the fundamental
magnetic interactions are due to exchange of electrons [1-3]. Typically, only
the interaction between pairs of electrons' spins is considered to explain the
nature of the ground state and its excitations, whereas three-, four-, and
six-spin interactions are ignored. When these higher order processes occur in a
loop they are called cyclic or ring exchange. The ring-exchange interaction is
required to explain low temperature behavior in bulk and thin films of solid
He [4-8]. It also plays a crucial role in the quantum magnet LaCuO
[9,10]. Here, we use a combination of time domain THz (TDTS) and magneto-Raman
spectroscopies to measure the low energy magnetic excitations in CoTiO, a
proposed Dirac topological magnon material [11,12] where the origin of the
energy gap in the magnon spectrum at the Brillouin zone center remains unclear.
We measured the magnetic field dependence of the energies of the two lowest
energy magnons and determine that the gap opens due to the ring-exchange
interaction between the six spins in a hexagon. This interaction also explains
the selection rules of the THz magnon absorption. Finally, we clarify that
topological surface magnons are not expected in CoTiO. Our study
demonstrates the power of combining TDTS and Raman spectroscopies with theory
to identify the microscopic origins of the magnetic excitations in quantum
magnets.Comment: 7 pages, 4 figures in main text, 26 pages and 11 figures in
supplemen