Inter-casing pressure control systems and methods

Abstract

An apparatus and method for controlling and/or reducing undesirable and dangerous buildup of formation gases and fluids in the annular space between casing strings in an oil & gas well. The process comprises injecting a brine of cesium formate into a cement annulus between concentric well casings; and monitoring the pressure of the brine within the annulus. Based on the pressure, the flow rate of the brine being injected is controlled to displace or control formation gases and fluids within the annulus.

1 . A process comprising:
 injecting brine comprising cesium formate into a cement annulus between concentric well casings;   monitoring a pressure of the brine within the cement annulus; and   controlling a flow rate of the brine being injected based on the monitored pressure.   
     
     
         2 . (canceled) 
     
     
         3 . The process according to  claim 1 , wherein the flow rate and pressure of the injected brine is controlled using an air pump. 
     
     
         4 . The process according to  claim 1 , wherein the flow rate and pressure of the injected brine is controlled using a pressure intensifier. 
     
     
         5 . (canceled) 
     
     
         6 . The process according to  claim 1 , wherein the process further comprises ramping up the pressure of the brine within the cement annulus to an initial predetermined pressure over a period of time between four hours to five days. 
     
     
         7 . (canceled) 
     
     
         8 . The process according to  claim 1 , wherein the process further comprises cycling between bleeding a fluid from the cement annulus and injecting brine. 
     
     
         9 . The process according to  claim 8 , wherein the process further comprises:
 measuring a density of the fluid being bled from the cement annulus; and stopping the bleeding when the measured density exceeds a predetermined threshold.   
     
     
         10 . The process according to  claim 1 , wherein the process comprises:
 injecting the brine into the cement annulus to reach an initial predetermined pressure using dynamic pressurizing unit, the dynamic pressurizing unit having a pump configured actively to apply pressure to the brine; and   once the initial predetermined pressure is reached, injecting the brine into the cement annulus to maintain a steady-state predetermined pressure using a passive pressurizing unit, the passive pressurizing unit being configured passively to release brine stored under pressure.   
     
     
         11 . The process according to  claim 1 , wherein the injected brine is monovalent. 
     
     
         12 . The process according to  claim 1 , wherein the process further comprises filtering the brine to less than 2 microns prior to injection. 
     
     
         13 . The process according to  claim 1 , wherein the brine is injected at less than 40 litres/hour. 
     
     
         14 . (canceled) 
     
     
         15 . The process according to  claim 1 , wherein the process further comprises, prior to injecting the brine:
 measuring the pressure in the cement annulus;   removing fluid from the cement annulus until a predetermined pressure is reached;   determining a rate of increase of pressure; and   controlling the flow rate of the brine based on the determined rate of increase of pressure.   
     
     
         16 . (canceled) 
     
     
         17 . The process according to  claim 1 , wherein the brine is injected using a treatment line, and the process further comprises monitoring a temperature of the treatment line and heating the treatment line when the temperature of the treatment-line falls below a predetermined threshold. 
     
     
         18 . An apparatus comprising:
 an annulus connector configured to connect to a cement annulus between concentric well casings;   a pressurizing unit configured to inject brine under pressure into the cement annulus between concentric well casings via the annulus connector; and   a pressure monitor configured to monitor the pressure of the brine within the cement annulus; and   a controller configured to control the pressurizing unit to control a flow rate of the brine being injected based on the monitored pressure.   
     
     
         19 . The apparatus of  claim 18 , wherein the pressurizing unit comprises:
 a dynamic pressurizing unit comprising a pump configured to apply pressure to the brine; and   a passive pressurizing unit comprising a compression reservoir configured to hold a volume of brine at an elevated pressure and a passive-pressurizing-unit release valve configured to deliver brine under pressure to the cement annulus between concentric well casings.   
     
     
         20 . The apparatus according to  claim 19 , wherein the dynamic pressurizing unit is configured to elevate the pressure within the compression reservoir. 
     
     
         21 . The apparatus according to  claim 19 , wherein the pump is an air pump. 
     
     
         22 . (canceled) 
     
     
         23 . The apparatus according to  claim 19 , wherein the dynamic pressurizing unit comprises a hydraulic intensifier configured to intensify the pressure applied by the pump on the brine. 
     
     
         24 . (canceled) 
     
     
         25 . The apparatus according to  claim 19 , wherein the dynamic pressurizing unit is releasably attached to the apparatus. 
     
     
         26 - 27 . (canceled) 
     
     
         28 . The apparatus according to  claim 18 , wherein the apparatus is configured to ramp up the pressure of the brine within the cement annulus to a predetermined value and then to maintain that pressure. 
     
     
         29 . The apparatus according to  claim 18 , wherein the apparatus comprises a treatment line between the pressurizing unit and the cement annulus, the treatment line having one or more one-way valves configured to prevent retrograde flow from the cement annulus and one or more pressure regulators. 
     
     
         30 - 35 . (canceled)