Method and control system for allocating steam to multiple wells in steam assisted gravity drainage (sagd) resource production

Abstract

A system includes a steam distributor configured to distribute steam received from a steam generator to multiple injection wells in a well pad for steam assisted gravity drainage (SAGD) resource production. The system also includes one or more processors configured to control the steam distributor to distribute the steam to the injection wells according to a resultant scheme including values representing multiple parameters for the SAGD resource production. The parameters include the allocated quantities of steam, pressures within multiple production wells associated with the injection wells, and time periods that the steam is directed into the injection wells. The one or more processors are configured to determine the resultant scheme by performing multiple iterations of a surrogate evaluation process until a stop criterion is met, and identifying the resultant scheme as the sample scheme of a final iteration prior to the stop criterion being met.

What is claimed is: 
     
         1 . A system comprising:
 a steam distributor configured to distribute steam received from a steam generator to multiple injection wells in a well pad for steam assisted gravity drainage (SAGD) resource production; and   one or more processors configured to control the steam distributor to distribute the steam to the injection wells according to allocated quantities of steam designated in a resultant scheme, the resultant scheme including values representing multiple parameters for the SAGD resource production, the parameters including the allocated quantities of steam to the injection wells, pressures within the injection wells and within multiple production wells associated with the injection wells, and time periods that the steam is directed into the injection wells, the one or more processors configured to determine the resultant scheme by performing multiple iterations of a surrogate evaluation process until a stop criterion is met,   wherein the one or more processors perform a first iteration of the surrogate evaluation process by designing a first sample scheme and then evaluating the first sample scheme using a reservoir simulation model to provide a predicted resource output associated with the first sample scheme, the one or more processors configured to sequentially repeat the surrogate evaluation process for one or more additional iterations using sample schemes having different values of the parameters than preceding sample schemes previously evaluated in the reservoir simulation model, the values of the parameters in the sample scheme of each of the additional iterations selected based on the predicted resource outputs associated with the preceding sample schemes, the one or more processors configured to identify the resultant scheme as the sample scheme of a final iteration prior to the stop criterion being met.   
     
     
         2 . The system of  claim 1 , wherein the stop criterion is based on at least one of a number of iterations, expiration of a designated time period, or a measured variance in the predicted resource outputs associated with the sample schemes in a group of recent iterations being less than a designated threshold value. 
     
     
         3 . The system of  claim 2 , wherein the stop criterion is met responsive to the measured variance in the predicted resource outputs associated with the sample schemes in the group of recent iterations being less than the designated threshold value, the group including the sample schemes from a previous three iterations before the stop criterion is met, the designated threshold value being no greater than 5%. 
     
     
         4 . The system of  claim 1 , wherein the one or more processors are configured to design the sample schemes of the additional iterations such that all of the designated quantities of steam allocated to the injection wells in one sample scheme are different than all of the designated quantities of steam allocated to the injection wells in the preceding sample schemes. 
     
     
         5 . The system of  claim 1 , wherein the one or more processors are configured to control the steam distributor to vary the quantities of steam allocated to the injection wells over time according to the resultant scheme. 
     
     
         6 . The system of  claim 1 , wherein a predicted resource output associated with the resultant scheme that is provided by the reservoir simulation model is greater than the predicted resource outputs associated with the preceding sample schemes. 
     
     
         7 . The system of  claim 1 , wherein the one or more processors are configured to use the reservoir simulation model to provide the predicted resource output and at least one of a predicted steam input or a predicted steam-to-resource ratio associated with the first sample scheme, the one or more processors configured to select the values of the parameters in the sample scheme of each of the additional iterations based on the predicted resource outputs and the at least one of the predicted steam input or the predicted steam-to-resource ratio associated with the preceding sample schemes. 
     
     
         8 . The system of  claim 1 , wherein the one or more processors are configured to design the sample schemes of the additional iterations such that the allocated quantities of steam to the injection wells in the well pad do not exceed a designated steam capacity and the pressures in the injection wells and the production wells are maintained within respective operating pressure ranges. 
     
     
         9 . The system of  claim 1 , wherein the multiple parameters for SAGD resource production in each sample scheme further include one or more of number of injection wells, relative distances between the injection wells, relative spacing between each injection well and each associated production well, locations of the injection wells and the production wells, steam injection rates into the injection wells, steam quality provided by the steam generator, steam temperature provided by the steam generator, degree of sub-cool in the production wells, porosity of a subterranean reservoir, and permeability of the subterranean reservoir. 
     
     
         10 . The system of  claim 1 , wherein the injection wells and the production wells define multiple well pairs in the well pad, each well pair including one injection well and one production well, the well pad including between two and ten well pairs, wherein the multiple parameters for SAGD resource production in each sample scheme further include a number of well pairs in the well pad. 
     
     
         11 . The system of  claim 1 , further comprising pumps disposed within the production wells, the one or more processors configured to control operation of the pumps such that the pressures within the production wells approximately match the pressures designated in the resultant scheme. 
     
     
         12 . The system of  claim 1 , wherein each injection well is associated with a corresponding production well to define a well pair, the injection and production wells in each well pair extending relatively horizontal and parallel to each other along a length through a subterranean reservoir, the injection well disposed vertically between the production well and a ground surface above the subterranean reservoir, the injection well configured to receive the steam from the steam distributor and inject the steam into the subterranean reservoir, the production well configured to collect an oil-based resource from the subterranean reservoir that is heated by the steam. 
     
     
         13 . A method comprising:
 evaluating plural schemes for allocating steam to well pairs in a well pad for steam assisted gravity drainage (SAGD) resource production, the plural schemes comprising an initial set of schemes, the schemes evaluated using a reservoir simulation model, each scheme including values representing multiple parameters for the SAGD resource production, the parameters including one or more of quantities of steam allocated to the well pairs, pressures within the well pairs, and time periods that the steam is directed into the well pairs, wherein evaluation of each of the schemes using the reservoir simulation model provides a predicted resource output associated with the corresponding scheme;   performing a surrogate evaluation process for a first iteration, the surrogate evaluation process including designing a first sample scheme that has different values of the parameters for SAGD resource production than the schemes in the initial set, the values of the parameters in the first sample scheme being selected based on the predicted resource outputs associated with the schemes in the initial set, the surrogate evaluation process including evaluating the first sample scheme using the reservoir simulation model to provide a predicted resource output associated with the first sample scheme;   sequentially repeating the surrogate evaluation process for one or more additional iterations using sample schemes having different values of the parameters than preceding schemes that include the first sample scheme and the schemes in the initial set, the values of the parameters in the sample scheme of each of the additional iterations selected based on the predicted resource outputs associated with the preceding schemes, wherein the surrogate evaluation process is sequentially repeated until a stop criterion is met; and   identifying a resultant scheme for controlling the SAGD resource production according to the values of the parameters contained in the resultant scheme, the resultant scheme identified as the sample scheme of a final iteration prior to the stop criterion being met.   
     
     
         14 . The method of  claim 13 , further comprising controlling an allocation of steam to the well pairs based on the designated quantities of steam allocated to the well pairs described in the resultant scheme. 
     
     
         15 . The method of  claim 13 , wherein the values of the parameters of the sample schemes in the one or more additional iterations are selected based on the predicted resource outputs associated with the preceding schemes to increase the predicted resource output of the sample schemes relative to the predicted resource outputs in the preceding schemes. 
     
     
         16 . The method of  claim 13 , wherein the predicted resource output for each scheme indicates an amount of oil-based resource that is cumulatively produced by the well pairs of the well pad responsive to injecting steam into the well pairs of the well pad according to the values of the parameters designated in the corresponding scheme. 
     
     
         17 . The method of  claim 13 , wherein the values of the parameters in the first sample scheme and the sample schemes in the additional iterations are selected using a Gaussian regression. 
     
     
         18 . The method of  claim 13 , wherein the values of the parameters in the first sample scheme and the sample schemes in the additional iterations are selected based on areas of relatively high variance and areas where the predicted resource outputs of the preceding schemes are relatively high. 
     
     
         19 . The method of  claim 13 , wherein the multiple parameters for SAGD resource production further include one or more of number of the well pairs, relative distances between the well pairs, locations of the well pairs, steam injection rates into the well pairs, steam quality, steam temperature, degree of sub-cool in the well pairs, porosity of a subterranean reservoir, and permeability of the subterranean reservoir. 
     
     
         20 . The method of  claim 13 , wherein each well pair includes an injection well and a production well extending relatively horizontal and parallel to each other along a length through a subterranean reservoir, the injection well disposed vertically between the production well and a ground surface above the subterranean reservoir, the injection well configured to receive steam and inject the steam into the subterranean reservoir, the production well configured to collect an oil-based resource from the subterranean reservoir that is heated by the steam. 
     
     
         21 . The method of  claim 13 , wherein the stop criterion is based on at least one of a number of iterations, expiration of a designated time period, or a measured variance in the predicted resource outputs associated with the sample schemes in a group of recent iterations being less than a designated threshold value. 
     
     
         22 . The method of  claim 21 , wherein the stop criterion is met responsive to the measured variance in the predicted resource outputs associated with the sample schemes in the group of recent iterations being less than the designated threshold value, the group including the sample schemes from a previous three iterations before the stop criterion is met, the designated threshold value being no greater than 5%. 
     
     
         23 . A system comprising:
 a controller configured to evaluate different parameters for allocating steam to well pairs in a well pad for steam assisted gravity drainage (SAGD) resource production, the controller configured to determine expected resource outputs from the well pad based on one or more steam introduction parameters, the steam introduction parameters including one or more of different quantities of steam directed into the well pairs, different pressures controlled within the well pairs, or different time periods that the steam is directed into the well pairs,   wherein the controller is also configured to control introduction of the steam into the well pairs using at least one of the steam introduction parameters based on the expected resource outputs.