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"(00:00) hello everyone welcome again in engman youtube channel in this quick video we will learn about injection rate and pressure determination for acidizing treatment it's a very interesting topic regarding well stimulation and acidizing operation all right let's go to the topic okay we will start by introduction oxidizing injection rate should be based on the mineral resolution and the depth of the damaged zone determining an optimum injection rate is quite challenging because of at least two reasons the first reason is that the damage zone (00:35) is seldom known with any accuracy all right and also the competing effects of mineral dissolution and the reaction product precipitation all right it's quite classic during acidizing there will always be competition between mineral dissolution and product precipitation in one way your acid will dissolve the mineral and the other way the reaction will produce solid precipitate all right that's one of the challenge for the acidizing and for the injection rate determination we need to know that there is always an upper limit (01:11) on the asset injection rate that is imposed by formation breakdown pressure or formation fracture pressure this is the pressure at which fracture will produce due to injection all right if you increase your injection pressure above this breakdown pressure of course the fracture will propagate it will get larger and it will grow it will propagate and we don't want that all right and acid injection rate can also be limited by surface injection pressure at the pump available during the job okay and how to calculate injection rate (01:49) this is the formula it's quite easy so this is the formula to determine the maximum injection rate of course you don't need to inject your acid above this maximum injection rate so you can keep a safe limit below this maximum injection rate so if you have your data permeability thickness of the base on to be treated all right and if you know the breakdown pressure the result for pressure and delta psf it's a safety margin you can set it at value of 200 through 500 psi all right and this is the viscosity of the acid re is of course (02:32) the drainage radius of your sfor rw velbo radius and this is the skin all right so if you know all this information you can easily calculate your maximum injection rate okay and the actual injection rate can be determined by having a safe margin below this maximum injection rate okay and also what about the injection pressure itself usually only the surface tubing pressure is monitored and recorded only the surface tubing pressure is recorded and it is important to predict the surface injection pressure at the design stage for pumping (03:16) selection okay during your acidizing design stage you need to know or you need to predict the surface injection pressure that can be delivered by your pump and this is the formula so surface injection pressure is flowing bottom hole pressure or flowing injection pressure minus hydrostatic pressure drop plus frictional pressure drop okay so you need to determine your flowing injection pressure and you need to calculate the hydrostatic pressure it's quite easy and also you need to calculate the frictional pressure drop (03:52) which can be calculated using this formula all right it's quite easy also you need to know the density of your fluid the acid mixture and the injection rate the treatment rate and this is the fluid viscosity of the solution or the mixture this is the tubing diameter and this is the tubing length all right using this formula you can then calculate your friction pressure drop all right it's quite easy and that's all thank you so much for watching in the next video we will discuss about the example of injection rate and pressure (04:32) determination thank you"