Well drilling systems and methods with pump drawing fluid from annulus

Abstract

A well pressure control method can include regulating pressure in a wellbore by operating a suction pump which draws fluid from an annulus formed between a drill string and the wellbore, the fluid entering the suction pump proximate the earth's surface. Another well pressure control method can include regulating pressure in a wellbore by operating a suction pump which applies suction pressure to an annulus formed between a drill string and the wellbore. A well drilling system can include a suction pump positioned proximate the earth's surface. The suction pump can receive fluid which exits an annulus formed between a drill string and a wellbore.

What is claimed is: 
     
         1 . A well pressure control method, comprising:
 regulating pressure in a wellbore by operating a suction pump which receives fluid that exits an annulus formed between a drill string and the wellbore, the fluid entering the suction pump proximate the earth's surface.   
     
     
         2 . The method of  claim 1 , wherein operating the suction pump comprises increasing a rate of the fluid drawn from the annulus by the suction pump, thereby reducing the wellbore pressure. 
     
     
         3 . The method of  claim 1 , wherein operating the suction pump comprises decreasing a rate of the fluid drawn from the annulus by the suction pump, thereby increasing the wellbore pressure. 
     
     
         4 . The method of  claim 1 , wherein regulating pressure further comprises maintaining an annulus pressure set point. 
     
     
         5 . The method of  claim 1 , wherein regulating pressure further comprises maintaining a wellbore pressure set point. 
     
     
         6 . The method of  claim 1 , wherein regulating pressure further comprises maintaining a standpipe pressure set point. 
     
     
         7 . The method of  claim 1 , wherein operating the suction pump comprises varying a flow rate of the suction pump relative to a flow rate of a rig pump which injects the fluid into the drill string. 
     
     
         8 . The method of  claim 1 , further comprising detecting an event based on sensing at least one suction pump parameter. 
     
     
         9 . The method of  claim 8 , wherein the suction pump parameter comprises at least one of a group including pump horsepower, suction pressure, pressure differential across the pump, flow rate, and revolutions per minute. 
     
     
         10 . The method of  claim 8 , wherein the event comprises an undesired influx from a formation into the wellbore. 
     
     
         11 . The method of  claim 8 , wherein the event comprises an undesired loss from the wellbore into a formation. 
     
     
         12 . The method of  claim 11 , wherein the suction pump parameter comprises a lack of the fluid entering the suction pump. 
     
     
         13 . The method of  claim 1 , further comprising determining a property of the fluid based on a sensed suction pump parameter. 
     
     
         14 . The method of  claim 13 , wherein the fluid property comprises at least one of a group including viscosity, density, temperature, and gas content. 
     
     
         15 . The method of  claim 1 , wherein operating the suction pump further comprises a control system causing the suction pump to change the wellbore pressure in response to detection of an event. 
     
     
         16 . The method of  claim 15 , wherein the event comprises an undesired influx into the wellbore, and wherein the control system causes the suction pump to increase the wellbore pressure in response to the detection of the undesired influx. 
     
     
         17 . The method of  claim 15 , wherein the event comprises an undesired loss from the wellbore, and wherein the control system causes the suction pump to reduce the wellbore pressure in response to the detection of the undesired loss. 
     
     
         18 . The method of  claim 15 , wherein the control system automatically causes the suction pump to change the wellbore pressure in response to the detection of the event. 
     
     
         19 . The method of  claim 15 , wherein the control system causes the suction pump to change the wellbore pressure by a predetermined amount in response to the detection of the event. 
     
     
         20 . The method of  claim 1 , wherein operating the suction pump comprises varying a fluid level in a reservoir, thereby varying hydrostatic pressure in the wellbore. 
     
     
         21 . The method of  claim 20 , wherein varying the fluid level in the reservoir further comprises increasing the fluid level while flow of the fluid through the drill string is substantially ceased. 
     
     
         22 . The method of  claim 1 , wherein regulating the wellbore pressure further comprises maintaining a desired fluid level in a reservoir, thereby maintaining a desired hydrostatic pressure in the wellbore. 
     
     
         23 . The method of  claim 1 , wherein operating the suction pump comprises varying a suction pressure applied to the annulus by the suction pump. 
     
     
         24 . The method of  claim 1 , wherein regulating the wellbore pressure further comprises maintaining a desired suction pressure applied to the annulus proximate the earth's surface. 
     
     
         25 . The method of  claim 24 , wherein the suction pressure comprises less than atmospheric pressure. 
     
     
         26 . The method of  claim 1 , wherein operating the suction pump is performed while flow of the fluid through the drill string is substantially ceased. 
     
     
         27 . The method of  claim 1 , wherein operating the suction pump is performed while making a connection in the drill string. 
     
     
         28 . The method of  claim 1 , wherein operating the suction pump is performed while substantially no injection of the fluid into the drill string is occurring. 
     
     
         29 . The method of  claim 1 , wherein operating the suction pump comprises the suction pump drawing the fluid through the drill string and annulus, without any rig pump injecting the fluid into the drill string. 
     
     
         30 . The method of  claim 1 , wherein the fluid exits the annulus below an annular blowout preventer. 
     
     
         31 . The method of  claim 1 , wherein the fluid exits the annulus between an annular seal and an annular blowout preventer. 
     
     
         32 . The method of  claim 1 , wherein the fluid exits the annulus between two annular blowout preventers. 
     
     
         33 . A well pressure control method, comprising:
 regulating pressure in a wellbore by operating a suction pump which applies suction pressure to an annulus formed between a drill string and the wellbore.   
     
     
         34 . The method of  claim 33 , wherein the suction pressure comprises less than atmospheric pressure. 
     
     
         35 . The method of  claim 33 , wherein fluid enters the suction pump proximate the earth's surface. 
     
     
         36 . The method of  claim 33 , wherein operating the suction pump comprises increasing a rate of fluid drawn from the annulus by the suction pump, thereby reducing the wellbore pressure. 
     
     
         37 . The method of  claim 33 , wherein operating the suction pump comprises decreasing a rate of fluid drawn from the annulus by the suction pump, thereby increasing the wellbore pressure. 
     
     
         38 . The method of  claim 33 , wherein regulating pressure further comprises maintaining an annulus pressure set point. 
     
     
         39 . The method of  claim 33 , wherein regulating pressure further comprises maintaining a wellbore pressure set point. 
     
     
         40 . The method of  claim 33 , wherein regulating pressure further comprises maintaining a standpipe pressure set point. 
     
     
         41 . The method of  claim 33 , wherein operating the suction pump comprises varying a flow rate of the suction pump relative to a flow rate of a rig pump which injects the fluid into the drill string. 
     
     
         42 . The method of  claim 33 , further comprising detecting an event based on sensing at least one suction pump parameter. 
     
     
         43 . The method of  claim 42 , wherein the suction pump parameter comprises at least one of a group including pump horsepower, suction pressure, pressure differential across the pump, flow rate, and revolutions per minute. 
     
     
         44 . The method of  claim 43 , wherein the event comprises an undesired influx from a formation into the wellbore. 
     
     
         45 . The method of  claim 43 , wherein the event comprises an undesired loss from the wellbore into a formation. 
     
     
         46 . The method of  claim 45 , wherein the suction pump parameter comprises a lack of the fluid entering the suction pump. 
     
     
         47 . The method of  claim 33 , further comprising determining a property of the fluid based on a sensed suction pump parameter. 
     
     
         48 . The method of  claim 47 , wherein the fluid property comprises at least one of a group including viscosity, density, temperature, and gas content. 
     
     
         49 . The method of  claim 33 , wherein operating the suction pump further comprises a control system causing the suction pump to change the wellbore pressure in response to detection of an event. 
     
     
         50 . The method of  claim 49 , wherein the control system also operates a choke to change the wellbore pressure in response to detection of the event. 
     
     
         51 . The method of  claim 49 , wherein the event comprises an undesired influx into the wellbore, and wherein the control system causes the suction pump to increase the wellbore pressure in response to the detection of the undesired influx. 
     
     
         52 . The method of  claim 49 , wherein the event comprises an undesired loss from the wellbore, and wherein the control system causes the suction pump to reduce the wellbore pressure in response to the detection of the undesired loss. 
     
     
         53 . The method of  claim 49 , wherein the control system automatically causes the suction pump to change the wellbore pressure in response to the detection of the event. 
     
     
         54 . The method of  claim 49 , wherein the control system causes the suction pump to change the wellbore pressure by a predetermined amount in response to the detection of the event. 
     
     
         55 . The method of  claim 33 , wherein operating the suction pump comprises varying the suction pressure applied to the annulus by the suction pump. 
     
     
         56 . The method of  claim 33 , wherein the suction pump applies the suction pressure to the annulus proximate the earth's surface. 
     
     
         57 . The method of  claim 33 , wherein operating the suction pump is performed while flow through the drill string is substantially ceased. 
     
     
         58 . The method of  claim 33 , wherein operating the suction pump is performed while making a connection in the drill string. 
     
     
         59 . The method of  claim 33 , wherein operating the suction pump is performed while substantially no injection of fluid into the drill string is occurring. 
     
     
         60 . The method of  claim 33 , wherein operating the suction pump comprises the suction pump drawing fluid through the drill string and annulus, without any rig pump injecting fluid into the drill string. 
     
     
         61 . The method of  claim 33 , wherein the suction pump receives fluid which exits the annulus below an annular blowout preventer. 
     
     
         62 . The method of  claim 33 , wherein the suction pump receives fluid which exits the annulus between an annular seal and an annular blowout preventer. 
     
     
         63 . The method of  claim 33 , wherein the suction pump receives fluid which exits the annulus between two annular blowout preventers. 
     
     
         64 . A well drilling system, comprising:
 a suction pump positioned proximate the earth's surface, and wherein the suction pump receives fluid which exits an annulus formed between a drill string and a wellbore.   
     
     
         65 . The system of  claim 64 , wherein an increase in a rate of the fluid drawn from the annulus by the suction pump reduces the wellbore pressure. 
     
     
         66 . The system of  claim 64 , wherein a decrease in a rate of the fluid drawn from the annulus by the suction pump increases the wellbore pressure. 
     
     
         67 . The system of  claim 64 , wherein an annulus pressure set point is maintained by flow of the fluid through the suction pump. 
     
     
         68 . The system of  claim 64 , wherein a wellbore pressure set point is maintained by flow of the fluid through the suction pump. 
     
     
         69 . The system of  claim 64 , wherein a standpipe pressure set point is maintained by flow of the fluid through the suction pump. 
     
     
         70 . The system of  claim 64 , wherein a flow rate of the suction pump is varied relative to a flow rate of a rig pump which injects the fluid into the drill string. 
     
     
         71 . The system of  claim 64 , wherein an event is detected based on at least one sensed suction pump parameter. 
     
     
         72 . The system of  claim 71 , wherein the suction pump parameter comprises at least one of a group including pump horsepower, suction pressure, pressure differential across the pump, flow rate, and revolutions per minute. 
     
     
         73 . The system of  claim 71 , wherein the event comprises an undesired influx from a formation into the wellbore. 
     
     
         74 . The system of  claim 71 , wherein the event comprises an undesired loss from the wellbore into a formation. 
     
     
         75 . The system of  claim 74 , wherein the suction pump parameter comprises a lack of the fluid entering the suction pump. 
     
     
         76 . The system of  claim 64 , wherein a property of the fluid is determined based on a sensed suction pump parameter. 
     
     
         77 . The system of  claim 76 , wherein the fluid property comprises at least one of a group including viscosity, density, temperature, and gas content. 
     
     
         78 . The system of  claim 64 , wherein a control system causes the suction pump to change the wellbore pressure in response to detection of an event. 
     
     
         79 . The system of  claim 78 , wherein the control system also operates a choke to change the wellbore pressure in response to detection of the event. 
     
     
         80 . The system of  claim 78 , wherein the event comprises an undesired influx into the wellbore, and wherein the control system causes the suction pump to increase the wellbore pressure in response to the detection of the undesired influx. 
     
     
         81 . The system of  claim 78 , wherein the event comprises an undesired loss from the wellbore, and wherein the control system causes the suction pump to reduce the wellbore pressure in response to the detection of the undesired loss. 
     
     
         82 . The system of  claim 78 , wherein the control system automatically causes the suction pump to change the wellbore pressure in response to the detection of the event. 
     
     
         83 . The system of  claim 78 , wherein the control system causes the suction pump to change the wellbore pressure by a predetermined amount in response to the detection of the event. 
     
     
         84 . The system of  claim 64 , wherein the suction pump varies a fluid level in a reservoir, whereby hydrostatic pressure in the wellbore is varied. 
     
     
         85 . The system of  claim 84 , wherein the suction pump increases the fluid level while flow of the fluid through the drill string is substantially ceased. 
     
     
         86 . The system of  claim 64 , wherein the suction pump varies a suction pressure applied to the annulus by the suction pump. 
     
     
         87 . The system of  claim 86 , wherein the suction pressure comprises less than atmospheric pressure. 
     
     
         88 . The system of  claim 64 , wherein the suction pump receives the fluid while flow of the fluid through the drill string is substantially ceased. 
     
     
         89 . The system of  claim 64 , wherein the suction pump receives the fluid while a connection is made in the drill string. 
     
     
         90 . The system of  claim 64 , wherein the suction pump receives the fluid while there is substantially no injection of the fluid into the drill string. 
     
     
         91 . The system of  claim 64 , wherein the suction pump draws the fluid through the drill string and annulus, while no rig pump injects the fluid into the drill string. 
     
     
         92 . The system of  claim 64 , wherein the fluid exits the annulus  20  below an annular blowout preventer. 
     
     
         93 . The system of  claim 64 , wherein the fluid exits the annulus between an annular seal and an annular blowout preventer. 
     
     
         94 . The system of  claim 64 , wherein the fluid exits the annulus between two annular blowout preventers.