Investigation of Changing Pore Topology and Porosity during Matrix Acidizing using Different Chelating Agents

Core flooding acidizing experiments on sandstone/carbonate formation are usually performed in the laboratory to observe different physical phenomena and to design acidizing stimulation jobs for the field. During the tests, some key parameters are analyzed such as pore volume required for breakthrough as well as pressure. Hydrochloric acid (HCl) is commonly used in the carbonate matrix acidizing while Mud acid (HF: HCl) is usually applied during the sandstone acidizing to remove damage around the well bore. However, many problems are associated with the application of these acids, such as fast reaction, corrosion and incompatibility of HCl with some minerals (illite). To overcome these problems, chelating agents (HEDTA, EDTA and GLDA) were used in this research. Colton tight sandstone and Guelph Dolomite core samples were used in this study. The experiments usually are defined in terms of porosity, permeability, dissolution and pore topology. Effluent samples were analyzed to determine dissolved iron, sodium, potassium, calcium and other positive ions using Inductively Coupled Plasma (ICP). Meanwhile Nuclear Magnetic Resonance (NMR) was employed to determine porosity and pore structure of the core sample. Core flood experiments on Berea sandstone cores and dolomite samples with dimensions of 1.5 in × 3 in were conducted at a flow rate of 1 cc/min under 150oF temperature. NMR and porosity analysis concluded that applied chemicals are effective in creating fresh pore spaces. ICP analysis concluded that HEDTA showed good ability to chelate calcium, sodium, magnesium, potassium and iron. It can be established from the analysis that HEDTA can increase more amount of permeability as compared to other chelates

Metabolic regulation of feed intake in monogastric mammals

Nutrients and their metabolites control short and long term feed intake through direct or indirect endocrine secretions that interact with local and central neural processes. Carbohydrates, fats, proteins and products from both mammalian and microbial enzymic digestion directly affect the release of hormones from the gastrointestinal tract and pancreas. The quantitative and temporal release of these hormones depends on nutrient composition, site of digestion, and products released within the gastrointestinal tract. The hormones act collectively to control meal size with many suppressing intake through the jejunal, ileal and/or colonic brakes, which reduce gastric emptying, propulsive contractions along the intestine, and gastrointestinal tract secretions. However, many of these nutrient-stimulated hormones also act through the vagal nervous system or directly on specific regions of the brain to have longer-term effects on feed intake. The main metabolic control of long-term feed intake, energy metabolism, body composition and body weight is via two opposing energy monitoring systems, adenosine monophosphateactivated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), which act both peripherally and centrally within the hypothalamus. AMPK is activated when cells are depleted of adenosine triphosphate (ATP) by monitoring the adenosine monophosphate (AMP)/ATP ratio. AMPK inhibits ATP-consuming pathways and stimulates ATP-producing pathways through the regulation of enzymes involved in lipid, carbohydrate and protein metabolism. AMPK regulates the concentration of a key intake-controlling metabolite, malonyl-CoA, within the hypothalamus. Low energy status and high AMPK activation leads to inactivation of mTOR, which contrary to AMPK, reflects high energy status of an animal. Activation of mTOR within the hypothalamus is also controlled by insulin and leptin. Basal insulin and leptin concentrations increase with animal adiposity status. Low energy or adiposity status results in low concentrations of malonyl-CoA and low activation of mTOR, stimulating the expression of melanocortin system orexigenic peptides, neuropeptide tyrosine and agouti-related peptide, and reducing the expression of anorexigenic peptides, pro-opiomelanocortin, α-melanocyte-stimulating hormone and cocaineand amphetamine-related transcript, thereby increasing intake and reducing energy expenditure. By converse mechanisms, perceived high energy status reduces feed intake, while increasing energy expenditure. The concepts described can help explain how many dietary and non-dietary situations affect feed intake in animals