US2012227961A1PendingUtilityA1

Method for automatic pressure control during drilling including correction for drill string movement

37
Individually held — no corporate assignee on recordPriority: Mar 9, 2011Filed: Mar 9, 2012Published: Sep 13, 2012
Est. expiryMar 9, 2031(~4.6 yrs left)· nominal 20-yr term from priority
Inventors:Ossama R. Sehsah
E21B 21/08
37
PatentIndex Score
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Claims

Abstract

A method for determining annulus/wellbore fluid pressure, which is corrected for movement of a pipe string into or out of a wellbore, includes determining an initial annulus fluid pressure in the wellbore. Determining the initial annulus fluid pressure may include measuring a fluid flow rate into the wellbore and/or measuring a fluid pressure in the annulus proximate the surface. A rate of movement of a pipe string into or out of the wellbore is also determined. The initial annulus fluid pressure is adjusted to a corrected annulus fluid pressure by an amount which is a function of the rate of motion of the pipe string, a surface area of the outer wall of the pipe string and a surface area of the inner wall of the wellbore.

Claims

exact text as granted — not AI-modified
1 . A method for determining wellbore fluid pressure, corrected for movement of a pipe string within a wellbore, the method comprising the steps of:
 determining a rate of movement of a pipe string within a wellbore;   determining an initial wellbore fluid pressure at a position within an annular space of the wellbore, the annular space being defined between an outer wall of the pipe string and an inner wall of the wellbore; and   adjusting the initial wellbore fluid pressure to a corrected wellbore fluid pressure by an amount that is at least a function of the rate of movement of the pipe string, a surface area of the outer wall of the pipe string and a surface area of the inner wall of the wellbore.   
     
     
         2 . The method of  claim 1  wherein the step of adjusting the initial wellbore fluid pressure includes the step of:
 determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string. 
 
     
     
         3 . The method of  claim 2  wherein the step of determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string is calculated using a flow rate of fluid flowing from the wellbore, the flow rate measured with a flow meter disposed in a fluid discharge conduit in fluid communication with the annular space of the wellbore. 
     
     
         4 . The method of  claim 2  wherein the step of determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string is a function of fluid displacement of the pipe string in the wellbore, the fluid displacement calculated using volumetric dimensions of the pipe string within the wellbore. 
     
     
         5 . The method of  claim 2  wherein an empirical correction factor is used to correct the determined pressure change, the empirical correction factor being a function of the rate of movement of the pipe string, the surface area of the outer wall of the pipe string and the surface area of the inner wall of the wellbore. 
     
     
         6 . The method of  claim 5  wherein the amount is a function of the determined pressure change and the empirical correction factor. 
     
     
         7 . The method of  claim 1  wherein an empirical correction factor is used to adjust the wellbore fluid pressure to the corrected wellbore fluid pressure, the empirical correction factor being a function of the rate of movement of the pipe string, the surface area of the outer wall of the pipe string and the surface area of the inner wall of the wellbore. 
     
     
         8 . The method of  claim 7  wherein the empirical correction factor is calibrated by measuring pressure proximate a bottom end portion of the pipe string. 
     
     
         9 . The method of  claim 1  further comprising the steps of:
 operating a back pressure system to maintain the corrected wellbore fluid pressure in the annular space of the wellbore near a selected value during any rate of movement of the pipe string within the wellbore, the backpressure system being arranged and designed to apply a back pressure on the annular space of the wellbore. 
 
     
     
         10 . The method of  claim 1  wherein the amount of adjusting corresponds to surge pressure indicative of pipe string movement into the wellbore. 
     
     
         11 . The method of  claim 1  wherein the amount of adjusting corresponds to swab pressure indicative of pipe string movement out of the wellbore. 
     
     
         12 . The method of  claim 1  wherein all of the steps are conducted in real time. 
     
     
         13 . A method for determining wellbore fluid pressure, corrected for movement of a pipe string within a wellbore, the method comprising the steps of:
 determining a rate of movement of a pipe string within a wellbore;   determining an initial wellbore fluid pressure at a position within an annular space of the wellbore, the annular space being defined between an outer wall of the pipe string and an inner wall of the wellbore;   determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string;   determining an empirical correction factor that is at least a function of the rate of movement of the pipe string, a surface area of the outer wall of the pipe string and a surface area of the inner wall of the wellbore; and   adjusting the initial wellbore fluid pressure to a corrected wellbore fluid pressure by an amount that is a function of the determined pressure change and the empirical correction factor.   
     
     
         14 . The method of  claim 13  wherein the step of determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string is calculated using a flow rate of fluid flowing from the wellbore, the flow rate measured with a flow meter disposed in a fluid discharge conduit in fluid communication with the annular space of the wellbore. 
     
     
         15 . The method of  claim 13  wherein the step of determining a pressure change in the annular space of the wellbore resulting from movement of the pipe string is a function of fluid displacement of the pipe string in the wellbore, the fluid displacement calculated using volumetric dimensions of the pipe string within the wellbore. 
     
     
         16 . The method of  claim 13  wherein the empirical correction factor is calibrated by measuring pressure proximate a bottom end portion of the pipe string. 
     
     
         17 . The method of  claim 13  wherein all of the steps are conducted in real time. 
     
     
         18 . A method for determining a pressure change in wellbore fluid pressure due to movement of a pipe string within a wellbore, the method comprising the steps of:
 determining a rate of movement of a pipe string within a wellbore;   determining a pressure change in an annular space of the wellbore resulting from movement of the pipe string; the annular space being defined between an outer wall of the pipe string and an inner wall of the wellbore;   determining an empirical correction factor that is at least a function of the rate of movement of the pipe string, a surface area of the outer wall of the pipe string and a surface area of the inner wall of the wellbore; and   correcting the determined pressure change by an amount that is a function of the empirical correction factor.   
     
     
         19 . The method of  claim 18  wherein the empirical correction factor is calibrated by measuring pressure proximate a bottom end portion of the pipe string. 
     
     
         20 . The method of  claim 18  wherein all of the steps are conducted in real time.

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