Study on High Temperature Block Removing Fluids Used on Dina-2 Ges Field

Severe sand production and blocking of production string have been encountered in Dina-2 Gas field, seriously affecting the safe and steady production of the well. An efficient high temperature chelating block removing agent has been developed to deal with the problems above mentioned. Based on the study on the characteristics of the rocks found in the Dina gas field, a high temperature organophosphorus acid chelant that can efficiently chelate calcium, aluminum and iron ions was selected through complexometric titration. The chelant was then mixed with hydrofluoric acid and weak organic acids in different ratios to form many base block removing fluids. The blocking removing fluids were then tested through dissolution and corrosion of rock powders for their dissolving rate, high temperature resistance and corrosion inhibitive capacity. Two formulations with better performance were chosen through the tests. The dissolving ability of the two block removing fluids was verified by reacting them with the blockage found in a well. It was found that the block removing fluids were able to function properly at 160℃. The dissolving rate of the block removing fluids was increasing with time, with a maximum of 75%. Compared with mud acid, the new block removing fluids have these advantages such as low acidity, weak corrosiveness, high dissolving capacity, and ability to effectively prevent secondary sedimentation. Analyses of the mineral components and solution of the blockage reacted with the block removing fluids have shown that the block removing fluid are able to quickly dissolve most of the blockage and slowly dissolve quartz and feldspar etc., and metallic ions such as calcium, magnesium, aluminum and iron ions can be effectively dissolved into the solutions, demonstrating the block removing fluids of their superior high temperature performance.