Drilling system and flow control apparatus for downhole drilling motors

An apparatus for controlling a flow of fluid through a downhole drilling motor which includes a first flow passage and a second flow passage communicating with the first flow passage and extending through an unsealed bearing section of the downhole drilling motor, said apparatus comprising:

• variable flow channel means for providing a variable flow channel, having a selectable effective cross-sectional area, in communication with the first flow passage of the downhole drilling motor, and including a valve, comprising a valve seat body having an opening defined therethrough, and a valve member disposed in said valve seat bodies so that said valve member is movable between a first position relative to said opening wherein said flow channel is defined with a first effective cross-sectional area and a second position relative to said opening wherein said flow channel is defined with a second effective cross-sectional area;
• and
• control means for controlling said variable flow channel means so that said variable flow channel has a selected effective cross-sectional area characterized to cause at least a predetermined minimum flow of the fluid to occur through the second flow passage, including biasing means for biasing said valve member towards said first position and a return spring disposed between said valve seat body and said valve member, and locking ball and spring means for releasably retaining said valve member in said first position.

An apparatus for controlling a flow of fluid through a downhole drilling motor which includes a first flow passage and a second flow passage communicating with the first flow passage and extending through an unsealed bearing section of the downhole drilling motor, said apparatus comprising:

• variable flow channel means for providing a variable flow channel, having a selectable effective cross-sectional area, in communication with the first flow passage of the downhole drilling motor, and wherein said variable flow channel means is adapted for disposition in a drill bit having defined therein a cavity and fluid outlets extending from said cavity and includes a valve seat disposed in said cavity;
• an a valve member slidably disposed in said cavity in operative association with said fluid outlets and said valve seat so that said fluid outlets and said valve seats are unblocked by said valve member in response to said valve member in a first position and further so that said fluid outlets are unblocked but said valve seat is blocked by said valve member in response to said valve member in a second position and still further so that said fluid outlets are blocked but said valve seat is unblocked by said valve member in response to said valve member in a third position;
• and
• control means for controlling said variable flow channel means so that said variable flow channel has a selected effective cross-sectional area characterized to cause at least a predetermined minimum flow of the fluid to occur through the second flow passage.