Acid Clathrates for Well Stimulation

The paper presents the results of laboratory and field researches of the developed in Russia solid acid reagent - netrol. <br>From chemical viewpoint netrol is a solid compound of carbamide clathrate and a mixture of inorganic acids. The main part of acid mixture is constituted by nitric acid, which intensifies the effect of acid treatment due to oxidizing ability. Carbamide is a clathrate former and in the netrol solution it provides low interfacial tension, increased detergency and effective penetration, as well as compatibility with water of high salinity. Netrol also includes phosphoric and borohydrofluoric acids, providing stability of a solid netrol form, prolonged effect of acid treatment of the netrol solution and its ability to dissolve silica minerals of rock matrix. <br>As compared with well-known hydrochloric acid the netrol solution has more effective penetration, especially in mudded carbonate and terrigenous reservoirs with viscous, highly paraffinic and highly resinous oil. It is also compatible with formation waters of high salinity. The netrol solution is easily producible and safe to handle. <br>In 2004-2005 bottomhole zones of the production and injection wells in carbonate and terrigenous low-permeable reservoirs in Russia and Kazakhstan oilfields were successfully treated with netrol solutions. <br>