Novel real-time drilling-fluid monitor

Abstract

Drilling-fluid monitoring technology for a drilling rig's drilling-fluid circulation system is disclosed. Pairs of vertically separated pressure sensors are installed at various points in the circulation system, including at the bell nipple, to provide drilling-fluid density information at different points in the circulation system. The bell nipple sensors provide information about the height of the drilling fluid in the bell nipple and the density of the drilling fluid before the cuttings are removed from the fluid. Changes in the bell-nipple drilling-fluid density or height may indicate potentially dangerous borehole conditions. Similarly, comparisons between bell-nipple drilling-fluid density with the density at other points in the circulation system provide information about the status of the circulation system. This information may be used to operate the drilling rig more safely and efficiently during the drilling process.

The invention claimed is: 
     
         1 . A drilling-fluid monitor comprising:
 (a) a pipe configured to be placed in a circulation system of a drilling rig before the drilling-fluid processing system and after the drill bit such that drilling fluid containing cuttings may flow through the pipe;   (b) a first pressure sensor mounted on a first position on the pipe and configured to measure the pressure inside the pipe;   (c) a second pressure sensor mounted on a second position on the pipe and configured to measure the pressure inside the pipe;   (d) wherein the pipe is configured such that when installed in the circulation system of a drilling rig, the first pressure sensor is positioned vertically lower than the second pressure sensor.   
     
     
         2 . The drilling-fluid monitor of  claim 1  wherein the pipe is a bell nipple. 
     
     
         3 . The drilling-fluid monitor of  claim 1  further comprising a viscosity sensor mounted on the pipe and configured to measure the viscosity of drilling fluid within the pipe. 
     
     
         4 . The drilling-fluid monitor of  claim 1  further comprising a temperature sensor mounted on the pipe and configured to measure the temperature of drilling fluid within the pipe. 
     
     
         5 . The drilling-fluid monitor of  claim 1  further comprising:
 (a) a third pressure sensor; and 
 (b) a fourth pressure sensor; 
 (c) wherein the third pressure sensor and the fourth pressure sensor are configured to be placed in a process pit of a circulation system of a drilling rig such that the third pressure sensor is vertically lower than the fourth pressure sensor. 
 
     
     
         6 . The drilling-fluid monitor of  claim 1  further comprising:
 (a) a fifth pressure sensor; and 
 (b) a sixth pressure sensor; 
 (c) wherein the fifth pressure sensor and the sixth pressure sensor are configured to be placed in a suction pit of a circulation system of a drilling rig such that the fifth pressure sensor is vertically lower than the sixth pressure sensor. 
 
     
     
         7 . The drilling-fluid monitor of  claim 5  further comprising:
 (a) a fifth pressure sensor; and 
 (b) a sixth pressure sensor; 
 (c) wherein the fifth pressure sensor and the sixth pressure sensor are configured to be placed in a suction pit of a circulation system of a drilling rig such that the fifth pressure sensor is vertically lower than the sixth pressure sensor. 
 
     
     
         8 . A drilling-fluid circulation system comprising:
 (a) a bell nipple;   (b) a drilling-fluid process pit;   (c) a drilling-fluid suction pit;   (d) a first pair of vertically separated pressure sensors installed at the bell nipple and each configured to measure a pressure of drilling fluid within the bell nipple;   (e) a second pair of vertically separated pressure sensors installed at the drilling-fluid process pit and each configured to measure a pressure of drilling fluid within the drilling-fluid process pit;   (f) a third pair of vertically separated pressure sensors installed at the drilling-fluid suction pit and each configured to measure a pressure of drilling fluid within the drilling-fluid suction pit; and   (g) a controller connected to each of the first pair of vertically separated pressure sensors, the second pair of vertically separated pressure sensors, and the third pair of vertically separated pressure sensors.   
     
     
         9 . The drilling-fluid circulation system of  claim 8  further comprising:
 (a) a first viscosity sensor installed at the bell nipple and configured to measure a viscosity of drilling fluid within the bell nipple; 
 (b) a second viscosity sensor installed at the drilling-fluid process pit and configured to measure a viscosity of drilling fluid within the drilling-fluid process pit; and 
 (c) a third viscosity sensor installed at the drilling-fluid suction pit and configured to measure a viscosity of drilling fluid within the drilling-fluid suction pit; 
 (d) wherein each of the first viscosity sensor, second viscosity sensor, and third viscosity sensor is connected to the controller. 
 
     
     
         10 . The drilling-fluid circulation system of  claim 8  further comprising:
 (a) a first temperature sensor installed at the bell nipple and configured to measure a temperature of drilling fluid within the bell nipple; 
 (b) a second temperature sensor installed at the drilling-fluid process pit and configured to measure a temperature of drilling fluid within the drilling-fluid process pit; and 
 (c) a third temperature sensor installed at the drilling-fluid suction pit and configured to measure a temperature of drilling fluid within the drilling-fluid suction pit; 
 (d) wherein each of the first temperature sensor, second temperature sensor, and third temperature sensor is connected to the controller. 
 
     
     
         11 . The drilling-fluid circulation system of  claim 8  further comprising a blowout preventer actuator connected to the controller. 
     
     
         12 . A method for monitoring a drilling-fluid circulation system, the method comprising:
 (a) collecting pressure information from a first pair of vertically separated pressure sensors installed at a bell nipple and each configured to measure a pressure of drilling fluid within the bell nipple;   (b) processing the pressure information to determine a difference in pressure between the first pressure sensor and the second pressure sensor of the first pair of vertically separated pressure sensors; and   (c) processing the difference in pressure to determine a first measure of the density of the drilling fluid within the bell nipple.   
     
     
         13 . The method of  claim 10  further comprising:
 (a) comparing the first measure of density with a second measure of density previously determined; and 
 (b) providing an indication of a potential underbalanced condition if the difference between the first measure of density and the second measure of density exceed a predetermined value. 
 
     
     
         14 . The method of  claim 11  further comprising controlling a blowout preventer to keep subterranean fluid deposits from exiting the borehole. 
     
     
         15 . The method of  claim 12  wherein the controlling a blowout preventer is one or more of the group consisting of:
 (a) activating an annular preventer; 
 (b) activating pipe rams; 
 (c) activating shear rams; and 
 (d) activating a kill line to inject high density fluid into the annulus between a drill pipe and a borehole wall.