Phosphonic acid / hydrofluoric acid: fracture stimulation bend remedy recipe

Phosphonic acid / hydrofluoric acid: fracture stimulation bend remedy recipe

Hydraulic fracturing pressure to open and remain open to rely on pressure. Transmitted by the pumped fluid pressure, so as to increase the pump displacement, the pressure also increases. In this process, the pressure is transmitted to the rock around the wellbore. If the pump displacement continues to increase, the pressure will increase. Will eventually reach a pressure limit, the limit at this point, the rock due to withstand the pressure applied thereon the split.
Perforating the long sections or deviated well, as long as the fluid pressure generated gradient exceeds a fracture gradient, will lead to a new generation of cracks or to re-open the natural fractures, as cracks may occur anywhere. In general, the rock at its weakest point break, so there will be cracks generated. However, if the pressure continues to increase, will be due to changes in near-wellbore pressure to produce more cracks. After the formation of stress cracks will be based on the direction of its natural direction Yan Shen. Emitted by each of the holes are likely to be the location of the crack opening. There are a number of small cracks, but some large enough to carry a large portion of the working fluid.
Although the manual is generated around the wellbore stress environment, but often only produce a small number of  hydraulic fracturing  several large cracks. Because increasing fracture surface pressure around the various small cracks generally difficult to come together. Stresses around the crack surface structure makes cracks between mutually exclusive. However, because there are holes around the shaft and combined stress, cracks may be combined at some point, they are connected through a narrow path, sometimes toward the major cracks in corners. Therefore, the treatment solution must contain many tiny cracks in the area, and then flows into an area with a few large cracks. In the process of flowing through this channel, the fluid must pass a tortuous, narrow cracks (tortuous path). The twists and turns will produce a lot of pressure loss, the pressure causes cracks to open a smaller scale than anticipated, or lead to early sand plug. This may be due to tortuous sand blocking a direct result, because the channel is not wide enough rock,  Proppant  pass and come together and put up a bridge to further prevent subsequent proppant pass.
Traditional treatment methods tortuosity can change perforating programs to reduce the length of perforating, changing its distribution, positioning and phasing, or by gathering perforation and eased. Other techniques include the use of viscous fluid, improve pump displacement to open the crack; using abrasive perforating, pumped  Proppant  slug (in the main action of the analysis phase) and pumped into hydrochloric acid (HCl)) or an organic acid preflush . Each one of these technologies may have a degree of success or success probability problems, however, in most cases, in the application of one or more of the above remedies, the bending problem still exists. In northeastern Brazil, a case, all of the above mentioned methods are available for the attempt, but still does not solve the bending problem. Finally the application of sandstone formations acid-free pre-wash or rinse step after acidification technologies.
Ammonium phosphonates and hydrogen fluoride (SAS) Overview
Phosphonic acid and ammonium hydrogen fluoride to produce a mixture of ammonium phosphonates and hydrogen fluoride, hereinafter referred to as SAS acids. This acid has five hydrogen atoms in different stoichiometric conditions, they will travel to the left. Ph SAS acid value is higher, at about 2, with a number of other beneficial properties. Without the use of an acidic solution or with an acid pre-rinse. In the presence of an acid, carbonate minerals will dissolve and release of calcium, calcium ions in turn react with fluorine to produce insoluble calcium fluoride, this substance can quickly precipitate is caused by damage to a reservoir potential source. Therefore, the use of acid soil on sandstone bedrock reservoir for processing, we need first to use pre-pre-rinse liquid to dissolve carbonates, pad fluid is generally hydrochloric acid or other non-fluorine. Will be a sufficient number of pre-pumped into the reservoir, in theory, these pre-solution can be 2 to 3 feet away from the wellbore within the scope of all the carbonate removed, in order to reduce the main processing stages of hydrofluoric acid (HF) come into contact with any risk of carbonate minerals.
Very strong activity in the pre-dissolution of the carbonate solution can be the first to open the flow path through the rocks, and may be damaged area around the other. Subsequently, the main hydrofluoric acid treatment process can be carried out according to the same flow path, may not have access to clogging silicate clays and other minerals. These processes are very complex, involving many repetitive pre-rinsing step, mainly hydrofluoric acid treatment stage, rear hydraulic and steering agents, acids can be difficult to ensure that the correct stage to the appropriate area, and offered suitable mineral substances. Therefore, this result may be acid treated uneven regional distribution, injury treatment is poor, even with the rock due to the incompatibility of acid oil produced while the accident and, ultimately resulting in poor yield.
Application of SAS acid is avoided this problem arises and changes acidification technologies. Phosphonic acid component is an effective calcium chelator, which will prevent subsequent precipitation of calcium fluoride formation. In addition, SAS acid is high Ph value of the buffer acid solution, while the other acid Ph value is very low. Due to its high value Ph, SAS acid and calcium carbonate slowly (with traditional methods compared to the applied acid), so that it is more difficult to release the lead to formation of a precipitate of calcium fluoride, calcium ions. This way, using SAS acid, it is possible to eliminate the use of the pad fluid and reservoir rock with a reduced risk of harmful reactions to a minimum level. This approach greatly simplifies the sandstone bedrock acidification step, eliminating the need for carefully arranged according to the order necessary for a variety of liquid pumped.