Drilling system and method

Abstract

A closed-loop drilling system and method of drilling oil, gas, or geothermal wells is described, whereby through the control of the flow rates in and out of the wellbore, and by adjusting the pressure inside the wellbore by a pressure/flow control device installed on the return line, surface pressure being increased or decreased as required, this in turn decreasing or increasing downhole pressure, occurrence of kicks and fluid losses may be greatly minimized and quickly controlled. Through the method of the invention the elimination of the kick tolerance and tripping margin on the design of the well is made possible, since the pore and fracture pressure will be determined in real-time while drilling the well, and, therefore, nearly no safety margin is necessary when designing the well, reducing significantly the number of casing strings necessary. The inventive method can be called intelligent safe drilling since the response to influx or fluid loss is nearly immediate and so smoothly done that the drilling can go on without any break in the normal course of action. The new method is applicable to the whole wellbore from the first casing string with a BOP connection, and it can be implemented and adopted to any rig or drilling installation that uses the conventional method with very few exceptions and limitations. The new method is applicable to all types of wells, onshore, offshore, deepwater and ultra-deepwater, with huge safety improvement in difficult drilling scenarios.

I claim:  
     
         1 . A system for drilling a well while injecting a drilling fluid through an injection line of said well and recovering through a return line of said well where the well being drilled is closed at all times comprises a pressure containment device and pressure/flow control device to a wellbore to establish/maintain a back pressure on the well, means to monitor the fluid flow in and out, means to monitor flow of any other material in and out, means to monitor parameters affecting the monitored flow value and means to predict a calculated value of flow out at any given time and to obtain real time information on discrepancy between predicted and monitored flow out and converting to a value for adjusting the pressure/flow control device and restoring the predicted flow value.  
     
     
         2 . A system of drilling a well while being drilled with a drill string having a drilling fluid circulated therethrough, while the well is kept closed at all times, wherein the system comprises: 
 a) a pressure containment device;    b) a pressure/flow control device on the outlet stream;    c) means for measuring mass or volumetric flow and flow rate on the inlet and outlet streams to obtain real time mass or volumetric flow signals;    d) means for measuring mass or volumetric flow and flow rate of any other materials in and out;    e) means for directing all the flow, pressure and temperature signals so obtained to a central data acquisition and control system; and    f) a central data acquisition and control system programmed with a software that can determine a real time predicted out flow and compare it to the actual out flow estimated from the mass and volumetric flow rate values and other relevant parameters.    
     
     
         3 . A system of drilling a well while being drilled with a drill string having a drilling fluid circulated therethrough, while the well is kept closed at all times, wherein said system comprises: 
 a) a pressure containment device;    b) a pressure/flow control device on the outlet stream;    c) means for measuring mass flow rate on the inlet and outlet streams;    d) means for measuring volumetric flow rate on the inlet and outlet streams;    e) at least one pressure sensor to obtain pressure data;    f) at least one temperature sensor to obtain temperature data;    g) a central data acquisition and control system that sets a value for an expected out flow and compares it to the actual out flow estimated from data gathered by the mass and volumetric flow rate meters as well as from pressure and temperature data, and in case of a discrepancy between the expected and actual flow values, adjusting the said pressure/flow control device to restore the outflow to the expected value.    
     
     
         4 . A system according to  claim 1  wherein the well is a gas, oil or geothermal well.  
     
     
         5 . A system according to  claim 3  wherein the at least one pressure sensor is located at the wellhead.  
     
     
         6 . A system according to  claim 3  wherein the system comprises two pressure sensors.  
     
     
         7 . A system according to  claim 6 , wherein one pressure sensor is at the wellhead and the other one at the bottomhole.  
     
     
         8 . A system according to  claim 1  wherein the said central data acquisition and control system is provided with a time-based software to allow for lag time between in and out flux.  
     
     
         9 . A system according to claims  1  or  8  wherein said software is provided with detection filters and/or processing filters to eliminate/reduce false indications on the received mass and fluid flow data, and any other measured or detected parameters.  
     
     
         10 . A system according to  claim 1  which comprises three safety barriers, the drilling fluid, the blow-out preventer equipment and the pressure containment device.  
     
     
         11 . Method comprising, in relation to the system according to  claim 1 , the following steps of injecting drilling fluid through said injection line through which said fluid is made to contact said means for monitoring flow and recovering drilling fluid through said return line; collecting any other material at the surface; measuring the flow in and out of the well and collecting flow and flow rate signals; measuring parameters affecting the monitored flow value and means; directing all the collected flow, correction and flow rate signals to the said central data acquisition and control system; monitoring parameters affecting the monitored flow value and means to predict a calculated value of flow out at any given time and to obtain real time information on discrepancy between predicted and monitored flow out and converting to a value for adjusting the pressure/flow control device and restoring the predicted flow value.  
     
     
         12 . A method of drilling a well while being drilled with a drill string having a drilling fluid circulated therethrough, while the well is kept closed at all times, said method comprising the steps of: 
 a) providing a pressure containment device to the wellbore;    b) providing a pressure/flow control device to control the flow out of the well and to keep a back pressure on the well;    c) providing a central data acquisition and control system and related software;    d) providing mass flow meters in both injection and return lines;    e) providing flow rate meters in both injection and return lines;    f) providing at least one pressure sensor;    g) providing at least one temperature sensor;    h) injecting drilling fluid through an injection line through which said fluid is made to contact said mass flow meters, said fluid flow meters, and said pressure and temperature sensors, and recovering drilling fluid through a return line;    i) collecting drill cuttings at the surface;    j) measuring the mass flow in and out of the well and collecting mass flow signals;    k) measuring the fluid flow rates in and out of the well and collecting fluid flow signals;    l) measuring pressure and temperature of fluid and collecting pressure and temperature signals;    m) directing all the collected flow, pressure and temperature signals to the said central data acquisition and control system;    n) the software of the central data acquisition and control system considering, at each time, the predicted flow out of the well;    o) having the actual and predicted out flows compared and checked for any discrepancy;    p) in case of a discrepancy, having a signal sent by the central data acquisition and control system to adjust the pressure/flow control device and restore the predicted out flow rate, without interruption of the drilling operation.    
     
     
         13 . A method of continuous, safe drilling of a well being drilled with a drill string having a drilling fluid circulated therethrough, while the well is kept closed at all times, said method comprising the steps of: 
 a) providing a pressure containment device to the wellbore;    b) providing a pressure/flow control device to control the flow out of the well and to keep a back pressure on the well;    c) providing a central data acquisition and control system and related software;    d) providing mass flow meters in both injection and return lines;    e) providing flow rate meters in both injection and return lines;    f) providing at least one pressure sensor to measure pressure;    g) providing at least one temperature sensor to measure temperature;    h) injecting drilling fluid through an injection line through which said fluid is made to contact said mass flow meters, said fluid flow meters and said pressure and temperature sensors, and recovering drilling fluid through return line;    i) collecting drill cuttings at the surface;    j)measuring the mass flow in and out of the well and collecting mass flow signals;    k) measuring the fluid flow rates in and out of the well and collecting fluid flow signals;    l) measuring pressure and temperature of fluid and collecting pressure and temperature signals;    m) directing all the collected flow, pressure and temperature signals to the said central data acquisition and control system;    n) the software of the central data acquisition and control system considering, at each time, the predicted flow out of the well;    o) having the actual and predicted out flows compared and checked for any discrepancy;    p) in case of a discrepancy, having a signal sent by the central data acquisition and control system to adjust the pressure/flow control device and restore the predicted out flow rate without interruption of the drilling operation.    
     
     
         14 . A method according to claims  12  or  13  wherein the well is a gas, oil or geothermal well.  
     
     
         15 . A method according to claims  12  or  13  wherein the at least one pressure sensor is located at the wellhead.  
     
     
         16 . A method according to claims  12  or  13  wherein the method comprises two pressure sensors.  
     
     
         17 . A method according to  claim 16 , wherein one pressure sensor is at the wellhead and the other one is at the bottomhole.  
     
     
         18 . A method according to claims  12  or  13  wherein the Equivalent Circulating Density of the well being drilled is adjusted by closing or opening the pressure/flow control device.  
     
     
         19 . A method according to claims  12  or  13  wherein the discrepancy between actual and predicted out flows is a fluid loss and the adjustment of the pressure/flow control device comprises opening said device to the extent required to counteract fluid loss and reduce backpressure.  
     
     
         20 . A method according to claims  12  or  13  wherein the discrepancy between actual and predicted out flows is a fluid gain and the adjustment of the pressure/flow control device comprises closing said device to the extent required to counteract fluid gain and increase backpressure.  
     
     
         21 . A method according to claims  12  or  13  wherein the predicted ideal value for the outflow is based on calculations taking into account among others rate of penetration, rock and drilling fluid density, well diameter, in and out flow rates, cuttings return rate, bottomhole and wellhead pressures and temperatures.  
     
     
         22 . A method according to claims  12  or  13  wherein the software provided to the central data acquisition and control system receives as input any early detection parameters to ascertain that an influx/loss has occurred.  
     
     
         23 . A method according to claims  12  or  13  wherein the mass flow metering comprises any subcomponents designed to improve accuracy of the measurement.  
     
     
         24 . A method according to  claim 23 , wherein the subcomponents comprise measuring the mass flux of cuttings being produced at the shakers and mass outflow of gas from the said degasser.  
     
     
         25 . A method according to claims  12  or  13  wherein means are provided to pressurize the well bore through the annulus, independently of the current fluid injection path.  
     
     
         26 . A method according to  claim 23 , wherein the subcomponents comprise measuring the mass flow and fluid flow into the well bore through the annulus, independently of the current fluid injection path.  
     
     
         27 . A method for the real time determination of the fracture pressure of a well being drilled with a drill string and drilling fluid circulated therethrough, while the well is kept closed at all times, said method comprising the steps of: 
 a) providing a pressure sensor at the bottom of the drill string;    b) having fluid and mass flow data generated collected and directed to a central data acquisition and control device that sets an expected value for fluid and mass flow;    c) the said central data acquisition and control device continuously comparing the said expected fluid and mass flow to the actual fluid and mass flow;    d) in case of a discrepancy between the expected and actual value, the said central data acquisition and control device activating a pressure/flow control device;    e) the detected discrepancy being a fluid loss, the value of the fracture pressure being obtained from a direct reading of the bottomhole pressure.    
     
     
         28 . A method for the real-time determination of the pore pressure of a well being drilled with a drill string and drilling fluid circulated therethrough, while the well is kept closed at all times, said method comprising the steps of: 
 a) providing a pressure sensor at the bottom of the drill string;    b) having fluid and mass flow data generated collected and directed to a central data acquisition and control device that sets an expected value for fluid and mass flow;    c) the said central data acquisition and control device continuously comparing the said expected fluid and mass flow to the actual fluid and mass flow;    d) in case of a discrepancy between the expected and actual value, the said central data acquisition and control device activating a pressure/flow control device;    e) the detected discrepancy being an influx, the value of the pore pressure being obtained from a direct reading of the bottomhole pressure provided by the said pressure sensor.