Abstract: An electropositive and water-based production well treating fluid system exhibits electropositivity by using a cationic viscosifier meanwhile matched with a cationic fluid loss additive and, optionally, contains a mud-building agent, an electrical stabilizing agent, a colloid-stabilizing agent, lubricant, an oil layer protective agent and/or a weighting agent. The electropositive production well treating fluid can beffer solve the contradiction of technical requirements between “treating fluid stability” and “bore hole stability”, and features a strong ability to inhibit the dispersion of clay, a good effect of protecting oil-gas reservoirs, fast drilling speeds, regular shape of bore holes and good resistance to salt.

Abstract: This invention provides an automatic control system and method for bottom hole pressure (BHP) in the underbalanced drilling. It relates to a computer automatic control technology. The automatic control system according to the invention includes a processing module for the BHP based on the mechanisms of hydraulics. The BHP in the underbalanced drilling is calculated from the acquired standpipe pressure (SPP), the calculated circulating pressure loss in the drilling tools, drill bit pressure drop and the fluid colunm pressure in the drill string. The resulting BHP is then compared with the set pressure value of the system. In case that the BHP is higher or lower than the set pressure, an instruction to regulate throttle valve opening will be issued in order to bring the BHP back to the set pressure range and complete BHP monitoring and control.

Abstract: This invention provides an automatic control system and method for bottom hole pressure (BHP) in the underbalance drilling. It relates to a computer automatic control technology. The automatic control system according to the invention includes a processing module for the BHP based on the mechanisms of hydraulics. The BHP in the underbalance drilling is calculated from the acquired standpipe pressure (SPP), the calculated circulating pressure loss in the drilling tools, drill bit pressure drop and the fluid column pressure in the drill string. The resulting BHP is then compared with the set pressure value of the system. In case that the BHP is higher or lower than the set pressure, an instruction to regulate throttle valve opening will be issued in order to bring the BHP back to the set pressure range and complete BHP monitoring and control.

Abstract: The present invention provides an electropositive and water-based production well treating fluid system. The production well treating fluid system can be made to exhibit electropositivity by using a cationic viscosifier meanwhile matched with a cationic fluid loss additive and optionally matched with a mud-building agent, electrical stabilizing agent, colloid-stabilizing agent, lubricant, oil layer protective agent and/or weighting agent. Such kind of electropositive production well treating fluid can solve better the contradiction between “treating fluid stability” and “bore hole stability”, and has features in strong ability of inhibiting the dispersion of clay, good effect of protecting oil-gas reservoir, fast drilling speed, regular shape of bore hole and good resistance to salt. The present invention relates further to a method of preparing said production well treating fluid system and use of the drilling fluid and well completion fluid in petroleum drilling and well completion.