Method and Apparatus for Maintaining Pressure In Well Cementing During Curing

Abstract

Method and apparatus are provided for cementing wells and preventing fluid entry into the wellbore before the cement cures and increasing radial stress in the cement. Impacts or vibrations are applied to the casing during the time that the cement is curing. The sources of the impacts or vibration are placed in the casing during displacement of the cement slurry and are mechanically coupled to the inside wall of the easing. The sources are later withdrawn from the casing.

1 . A method for cementing a casing in a well, comprising:
 during placement of cement in an annulus outside the casing, pumping down with a displacement fluid inside the casing an apparatus for applying an impulse or vibration to the casing and mechanically coupling the apparatus to the casing;   after placement of the cement, activating the apparatus; and   retrieving the apparatus from the casing.   
     
     
         2 . The method of  claim 1  wherein the apparatus is a jar, the jar is energized by change of pressure in the casing and is activated when pressure outside the jar is increased. 
     
     
         3 . The method of  claim 1  wherein the apparatus is a vibrator connected to an accumulator wherein the accumulator receives fluid flowing through the vibrator and is energized by a change of pressure in the casing. 
     
     
         4 . The method of  claim 3  wherein the vibrator is activated when pressure inside the casing is increased to a selected value. 
     
     
         5 . The method of  claim 1  wherein the apparatus is repeatedly energized or activated by increasing and decreasing pressure in the casing. 
     
     
         6 . The method of  claim 1  further comprising applying a fluid pressure above the cement in the annulus while activating the apparatus in the casing. 
     
     
         7 . The method of  claim 6  further comprising monitoring fluid pressure in the fluid while activating the apparatus in the casing. 
     
     
         8 . The method of  claim 1  further comprising applying an impulse or vibration to the casing at a proximate end of the casing. 
     
     
         9 . A method for cementing a casing in a well, comprising:
 during placement of cement in an annulus outside the casing, pumping down with a displacement fluid inside the casing a plurality of apparatuses for applying an impulse or vibration to the casing and mechanically coupling the apparatuses to the casing at spaced apart locations;   after placement of the cement, activating the apparatuses near simultaneously; and   retrieving the apparatuses from the casing.   
     
     
         10 . The method of  claim 9  wherein the apparatuses are adjusted to activate near simultaneously when pressure in the casing is increased. 
     
     
         11 . The method of  claim 9  wherein the apparatuses are mechanically coupled to the casing by spring-loaded members that extend into a groove in the casing. 
     
     
         12 . The method of  claim 9  wherein the apparatuses are mechanically coupled to the casing by slips pressed against the casing. 
     
     
         13 . A method for cementing a casing string in a wellbore, comprising:
 placing the casing string in the wellbore, the casing string having a recessed groove at a selected location inside the casing string;   pumping cement into the casing and an annulus outside the casing;   displacing the cement from the casing by a displacement fluid and placing an impulse or vibration source in the casing while displacing the cement such that the impulse or vibration source locks in the recessed groove; and   after the cement is displaced from the casing, applying pressure in the casing to activate the impulse or vibration source.   
     
     
         14 . The method of  claim 13  wherein the casing further includes a plurality of recessed grooves at selected locations in the casing string and a plurality of impulse or vibration sources are placed in the casing while displacing the cement, each of the impulse or vibration sources being adapted to lock into a selected recessed groove and to bypass any recessed grooves above the selected recessed groove. 
     
     
         15 . The method of  claim 14  wherein the impulse or vibration sources are set to activate near simultaneously as pressure in the casing is increased. 
     
     
         16 . The method of  claim 13  wherein the impulse source is a jar. 
     
     
         17 . The method of  claim 13  wherein the vibration source is a vibrator activated by fluid flow through the vibrator, the fluid being received by an accumulator. 
     
     
         18 . A method for cementing a casing string in a wellbore, comprising:
 placing the casing string in the wellbore;   placing a marker inside the casing;   pumping cement into the casing and an annulus outside the casing;   displacing the cement from the casing by a displacement fluid and placing an impulse or vibration source in the casing while displacing the cement, the source being joined to a locking mechanism that activates when the locking mechanism senses the marker; and   after the cement is displaced from the casing, applying pressure in the casing to activate the impulse or vibration source.   
     
     
         19 . The method of  claim 18  wherein a plurality of markers are placed inside the casing and a plurality of impulse or vibration sources are placed in the casing while displacing the cement, each of the impulse or vibration sources being joined to a locking mechanism that activates when the locking mechanism senses a selected marker. 
     
     
         20 . The method of  claim 19  wherein the impulse or vibration sources are set to activate near simultaneously as pressure in the casing is increased. 
     
     
         21 . The method of  claim 18  wherein the impulse source is a jar. 
     
     
         22 . The method of  claim 18  wherein the vibration source is a vibrator activated by fluid flow through the vibrator. 
     
     
         23 . A device for supplying an impulse or vibration to a casing during cementing of the casing, comprising:
 a placement section, the placement section having a member adapted for sliding inside the casing and a diaphragm that may be opened under a pressure differential to allow fluid by-pass of the sliding member;   a locking section, the locking section having locking dogs adapted for sliding inside the casing and locking into a recessed groove; and   an impulse or vibration source connected to the placement section and the locking section.   
     
     
         24 . The device of  claim 23  further comprising a fishing neck, the fishing neck being mechanically connected to the locking dogs to remove the locking dogs from the recessed groove when an upward force is applied to the fishing neck. 
     
     
         25 . The device of  claim 23  wherein the impulse or vibration source is a jar. 
     
     
         26 . The device of  claim 23  wherein the vibration source is a vibrator activated by fluid flow through the vibrator. 
     
     
         27 . A device for supplying vibration to a casing during cementing of the casing, comprising:
 a placement section, the placement section having a member adapted for sliding inside the casing and a diaphragm that may be opened under a pressure differential to allow fluid by-pass of the sliding member;   a locking section, the locking section having locking dogs adapted for sliding inside the casing and locking into a recessed groove;   a fluid-driven hammer; and   an accumulator for receiving fluid after the fluid passes through the hammer.   
     
     
         28 . A device for supplying vibration to a casing during cementing of the casing, comprising:
 a placement section, the placement section having a member adapted for sliding inside the casing and a diaphragm that may be opened under a pressure differential to allow fluid by-pass of the sliding member; and   a locking section, the locking section being battery-powered and having slips that may be extended outward to mechanically couple the device to the casing; and   an impulse or vibration source connected to the placement section and the locking section.   
     
     
         29 . The device of  claim 28  further comprising a fishing neck, the fishing neck being mechanically connected to the locking dogs to remove the locking dogs from the recessed groove when an upward force is applied to the fishing neck. 
     
     
         30 . The device of  claim 28  wherein the impulse or vibration source is a jar. 
     
     
         31 . The device of  claim 28  wherein the vibration source is a vibrator activated by fluid flow through the vibrator. 
     
     
         32 . A method for selecting method and apparatus to cement a casing in a well and controlling fluid entry into a cement column in an annulus outside the casing after pumping of a cement slurry, comprising:
 predicting the amplitude of casing movement as a function of axial distance along the casing from an impact or vibration source to be placed in the well;   predicting the effect of the predicted casing movement on gel strength of the cement slurry in the annulus;   predicting the pressure along the cement column considering gel strength affected by and not affected by an impact or vibration source, cement properties and an applied pressure at the surface;   comparing the pressure along the cement column to expected pore pressures in the well; and   selecting an impact or vibration source and method of use to maintain pressure in the cement column above pore pressures in the well for a selected time after pumping of the cement.