Abstract: Disclosed embodiments include systems and methods for improving the accuracy of bottom hole pressure control. One example embodiment includes a torque and drag model that calculates the elasticity of the drill string, which is included in a managed pressure drilling control system. The addition of the torque and drag calculations provide more accurate surge/swab effect calculations based on pipe movement corrected for elasticity effects. The results of these calculations will be used in a real-time hydraulics model to determine a setpoint pressure which will be utilized by a MPD choke system. Further, the real-time torque and drag models are calibrated to actual hole conditions in real-time using survey, temperature, pressure and downhole tool data to calculate friction factors in a wellbore.

Abstract: Clay-based retarders may be useful in delaying the gel time of a gellable treatment fluid and, consequently, subterranean operations. For example, a method may involve providing a gellable treatment fluid comprising: an aqueous base fluid; a base polymer comprising an acrylamide monomer unit; a polymeric organic crosslinking agent comprising a crosslinkable polymer selected from the group consisting of polyethyleneimine, polyvinylamine, chitosan, any derivative thereof, any salt thereof, and any combination thereof; and a clay-based gel retarder; introducing the gellable treatment fluid into a wellbore penetrating a subterranean formation; and forming a gel with the gellable treatment fluid in at least a portion of the wellbore, at least a portion of the subterranean formation, or both. In some instances, producing the gellable treatment fluid may involve not pre-hydrating the clay-based gel retarder.

Abstract: A tubing retrievable surface controlled subsurface safety valve 106 is adapted to be positioned in a well tubing string 102 to control the flow through the tubing string. The safety valve includes an annular housing or body 200 defining a fluid passageway through which fluids and/or gasses may flow to the surface. The safety valve is equipped with a valve closure member such as flapper 252, positioned in the fluid passageway which is moveable between an open and closed position. The valve closure member is engaged and actuated by a longitudinally extending operator 242 that engages the valve closure member 252. In one embodiment, the longitudinally extending operator 242 may be a tubular member longitudinally moveable within the valve body. The longitudinally extending member 242 is operatively coupled to a spring guide 226. A biasing spring 222 is positioned in a spring chamber 120 defined by a spring housing 228 and the spring guide 226. A spring 256 biases the closure member 252 in the closed position.