Exxonmobil Upstream Research Company

Exxon Production Research Company

L Donald Maus

Mark E Ehrhardt

Jerry M Speers

James D Howell

George G Binder, Jr

Torney M Van Acker

A method and apparatus for controlling the riser base pressure and detecting well control problems, such as kicks or lost circulation, during drilling of an offshore well using a gas-lifted riser. The pressure control apparatus preferably includes two separate control elements, one to adjust the pressure at the surface (p ) and the mass flow rate out of the top of the riser ({dot over (m)} ) to compensate for changes in riser base pressure (p ) and the other to adjust either or both of the boost mud flow rate (q ) and lift gas flow rate (q ) to maintain a constant or nearly constant mass flow rate entering the base of the riser ({dot over (m)} ). According to the method of the present invention, the well return flow rate (q ) is preferably determined by directly measuring various other parameters and then computing q from the measured parameters. The computed value of q may be compared to the drill string flow rate (q ) to detect well control problems, such as kicks or lost circulation.

Method and apparatus for controlling pressure and detecting well control problems during drilling of an offshore well using a gas-lifted riser

Gas storage is provided for a subsea gas-lifted riser during offshore drilling and/or production operations. One or more gas storage chambers positioned along and about the subsea riser are connected to a gas conduit. Each chamber has at least one valve for controlling passage of gas out of the chamber and into the gas conduit. The valves serve to allow the gas from the storage chambers to be injected as lift gas as needed.

Method and system for storing gas for use in offshore drilling and production operations

A method is disclosed for controlling pressure in a wellbore during drilling. The method includes operating a drilling system to have a first fluid pressure gradient inside a drillstring extending from the earth's surface to a drill bit at the bottom of the wellbore. The drilling system has a second fluid pressure gradient lower than the first fluid pressure gradient in an annular space between the drillstring and the wellbore from a selected depth in the wellbore to the earth's surface. Introduction of drilling fluid to the inside of the drillstring is stopped, and fluid flow in the annular space from a point below the selected depth to a point above the selected depth is selectively controlled to cause a substantially constant fluid pressure at a predetermined depth in the wellbore.

Method for controlling bottom-hole pressure during dual-gradient drilling

A method for controlling the pressure at the base of a gas-lifted riser during casing installation is disclosed. Prior to casing installation, drilling fluid is displaced from the riser and the riser is filled with seawater. During casing installation, the riser base pressure is monitored, and the height of seawater in the riser is adjusted to compensate for increases in the riser base pressure. The riser base pressure is thereby maintained substantially equal to the seawater pressure at the base of the drilling riser throughout installation of the casing.

Method for installing a well casing into a subsea well being drilled with a dual density drilling system

A method and apparatus is disclosed for determining the flow rate of drilling fluid flowing from a subaqueous well. The invention may also be used to determine the presence of an abnormal drilling condition during heaving motion of an offshore vessel from which the drilling operation is conducted. The invention measures the volume of fluid passing predetermined locations in the drilling system at particular points in time so as to eliminate the influence that the expansion and contraction of a telescoping section has on the total volume of drilling fluid within the system.

Method and apparatus for compensating well control instrumentation for

A method and apparatus for determining the gel strength of drilling mud by the repetitive steps of: flowing mud through a conduit positioned in a nonhorizontal attitude at a flow rate where the shear rate of the mud is in the range of greater than zero to about 20 sec..sup.-1, interrupting the flow of mud to provide a static column of mud in the conduit, and measuring the differential pressure of the mud between vertically spaced points during both the flow and static intervals.

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Houston, TX, United States of America

L Donald Maus