Well De-Liquefying System and Method

Abstract

De-liquefying a well includes a steady state de-liquefying cycle which includes an initial step of pressurising the gas with a compressor. In an example embodiment, gas is delivered into the well down an outer tube. The gas displaces liquid within the well by pushing the liquid within tubes up another tube, as a liquid slug, to the surface. A sensor operates to sense the arrival of the liquid. A controller interrogates the sensor to determine whether a slug of liquid has arrived. If not, gas is continued to be delivered into the well. When the controller determines via the sensor that a slug of liquid has arrived, the controller operates to shut the delivery of gas to the well. This may be done either immediately upon detection of the slug or at some predetermined delay thereafter. To shut down the delivery of gas to the well, the controller opens a valve (in the event it was shut) to allow the compressor to discharge to a sales line. The controller also closes a valve and opens another valve to relieve pressure within the outer tube to the separator pressure. The controller then idles for a prescribed time delay before recommencing the cycle.

The claims defining the invention are as follows: 
     
         1 . A method of deliquefying a gas well provided with a well casing in fluid communication with a separator into which gas from the well flows, the method comprising:
 pressurising the gas from the separator;   delivering pressurised gas from the separator back into the well to lift a liquid slug in the well together with the gas used in lifting the liquid from the well to the separator, wherein the gas from the separator which is delivered into the well is pressurised to a pressure sufficient to achieve a gas flow rate up the well of at least 3 m (10 feet) per second while carrying a slug of liquid.   
     
     
         2 . The method according to  claim 1 , further comprising:
 sensing when the liquid slug lifted from the well reaches a location outside of the well; and   ceasing delivery of the gas from the separator back into the well at a selectable time after sensing the liquid reaching the location.   
     
     
         3 . The method according to  claim 2 , further comprising:
 upon expiration of the selectable time period, relieving pressure of the gas to the separator pressure.   
     
     
         4 . The method according to  claim 3 , further comprising:
 performing a deliquefying cycle comprising delivering gas from the separator into the well;   ceasing delivery of gas at the selected time after sensing the liquid reaching the location; and   relieving pressure of the gas to separator pressure.   
     
     
         5 . The method according to  claim 4 , further comprising:
 measuring a time period between delivery of gas back into the well from the separator and the liquid reaching the location; and   using an adaptive algorithm to control a cycle rate of the deliquefying cycle on the basis of historical data relating to the measured time period.   
     
     
         6 . The method according  claim 5 , further comprising:
 performing a start up procedure on initial use of the method, the start up procedure comprising forming a closed gas circuit between the well casing and the separator, and continuously circulating gas from the well to the well separator and back to the well for a selectable minimum time period.   
     
     
         7 . The method according to  claim 6 , wherein the minimum time period is between 5 minutes to 30 minutes. 
     
     
         8 . The method according to  claim 7 , further comprising:
 after performing the start up procedure, operating the method in a start up mode wherein during an initial number of deliquefying cycles after the start up procedure pressure of gas being delivered from the compressor to the well is not relieved to seperator pressure.   
     
     
         9 . The method according to  claim 8 , wherein the initial number of cycles is between 5 to 15 cycles. 
     
     
         10 . The method according to  claim 6 , further comprising:
 providing a return path for the delivered gas into and out of the well, wherein the return path is isolated from a production gas flow path from the well casing to the separator, the return path being arranged to allow one way flow of liquid residing in the well into the return path, wherein providing the return path comprises:   installing an outer tube in the well casing;   installing an inner tube in the outer tube to create a first leg of the return flow path between the inner tube and the outer tube, wherein an inside of the inner tube forms a second leg of the return path; and   providing a one way valve allowing flow of liquid in a direction from the well casing into the outer tube.   
     
     
         11 . The method according to  claim 10 , further comprising:
 providing a valved pressure relief path between the separator and the outer tube, wherein the valved pressure relief path, when opened, enables pressure relief of the gas being delivered from the compressor to the well to be relieved to separator pressure.   
     
     
         12 . A method of de-liquefying a gas well provided with a well casing in fluid communication with a separator into which gas from the well flows, the method comprising:
 installing an outer tube in the well casing;   installing an inner tube in the outer tube to create a first flow path between the inner tube and the outer tube and wherein fluid in the first flow path can flow into the inner tube;   enabling the inner tube to be in fluid communication with a fluid collector at a location outside of the well;   providing a one way valve allowing flow of liquid in a direction from the well casing into the outer tube; and   pressurising gas sourced from the well and delivering the pressurised gas back to the well through the outer tube.   
     
     
         13 . The method according to  claim 12 , wherein enabling the inner tube to be in fluid communication with a fluid collector at a location outside of the well comprises:
 arranging the inner tube to be in fluid communication with the separator wherein liquid and gas flowing through the inner tube is directed to flow into the separator.   
     
     
         14 . The method according to  claim 13 , further comprising:
 ceasing delivery of the pressurised gas upon in response to detecting presence of the liquid at a know location in the inner tube.   
     
     
         15 . The method according to  14 , further comprising:
 venting the outer tube and the inner tube to the separator subsequent to detecting the presence of the liquid.   
     
     
         16 . The method according to  claim 15 , further comprising:
 designating the steps of delivering gas from the separator into the well, ceasing delivery of gas, and relieving pressure of the gas to separator pressure, as a de-liquefying cycle;   measuring a time period between delivery of gas back into the well from the separator and the liquid reaching the location; and   using an adaptive algorithm to control a cycle rate of the de-liquefying cycle on the basis of historical data relating to the measured time period.   
     
     
         17 . A de-liquefying system for a gas well having a well casing in fluid communication with a separator, the system comprising:
 a fluid flow path extending from the separator down the well casing, up the well and to a location outside of the gas well; and   a one way valve in the fluid flow path capable of allowing fluid flow only in a direction from the well casing into the fluid flow path, wherein pressurised gas from the separator is delivered to the well and is capable of displacing liquid in the well up the fluid flow path to the location.   
     
     
         18 . The de-liquefying system according to  claim 17 , wherein the fluid flow path comprises:
 an outer tube extending down the well and being in fluid communication with the separator at a well head end and provided with the one way valve at a down hole end; and   an inner tube suspended in the outer tube and having a down hole end above the one way valve and an opposite well head end in fluid communication with the separator;   wherein pressurised gas from the separator flows down the outer tube and displaces liquid in the outer tube and inner tube up the inner tube to the separator.   
     
     
         19 . The de-liquefying system according to  claim 18 , further comprising:
 a controller configured to cyclically control delivery of pressurised gas to the fluid flow path.   
     
     
         20 . The de-liquefying system according to  claim 19 , wherein the controller operates an adaptive algorithm to vary a rate of cyclically delivering pressurised gas on a basis of a plurality of measured times between delivery of pressurised gas and liquid displaced by the gas reaching the location.