Temporary field storage of gas to optimize field development

Abstract

Methods are provided for managing the production of fluids from a low-permeability subsurface formation in a field. The subsurface formation may be a coalbed formation. The method involves producing formation fluids from a first zone in the subsurface formation for a period of time so as to at least partially dewater the first zone. The formation fluids are separated into a liquid stream that primarily comprises water, and a gas stream that primarily comprises methane gas. The water is sent for disposal, such as into a subsurface formation, while the gas is temporarily stored or flared. A gas processing facility is constructed for the field. In order to manage the outlay of capital for the field development, construction of the gas processing facility is spread out or delayed until the field is ready to produce enough gas to allow the gas processing facility to operate at a substantially greater capacity than would be provided at the beginning of field development.

We claim: 
     
         1 . A method for managing the production of fluids from a low-permeability subsurface formation in a field, the fluids comprising water and gas, and the method comprising:
 completing one or more wells in a first zone within the subsurface formation;   producing formation fluids from the first zone so as to at least partially dewater the first zone;   completing one or more wells in a second zone within the subsurface formation;   producing formation fluids from the second zone so as to at least partially dewater the second zone;   injecting gas from the formation fluids from the second zone into the first zone for temporary storage;   completing one or more wells in a fourth zone within the subsurface formation;   substantially completing a gas processing facility when (i) the gas production rate from the field is able to exceed a designated level, or (ii) at least the first and second zones of the subsurface formation have been dewatered to a designated level;   after substantially completing the gas processing facility, co-producing formation fluids from the first zone, the second zone, and the fourth zone;   substantially separating water in the co-produced formation fluids from the gas in a separator; and   delivering the gas to the substantially completed gas processing facility for processing, the gas comprising greater than about 50 mole percent methane before processing.   
     
     
         2 . The method of  claim 1 , wherein the subsurface formation comprises a coalbed zone, a shale gas zone, or a tight gas zone. 
     
     
         3 . The method of  claim 2 , further comprising:
 completing one or more water injection wells in a subterranean storage zone;   separating water from gas in the formation fluids from the first zone during dewatering; and   injecting water from the formation fluids from the first zone into the subterranean storage zone.   
     
     
         4 . The method of  claim 3 , further comprising:
 flaring a majority of the gas from the formation fluids from the first zone during dewatering of the first zone.   
     
     
         5 . The method of  claim 3 , wherein the subterranean storage zone is an aquifer, a salt cavern, a depleted hydrocarbon reservoir zone, or a coalbed zone that has been previously substantially dewatered. 
     
     
         6 . The method of  claim 3 , wherein the subterranean storage zone is a coalbed zone that is a lateral extension of the subsurface formation that is undergoing dewatering. 
     
     
         7 . The method of  claim 3 , wherein:
 the subsurface formation is a coalbed zone; and   the subterranean storage zone is an extension of the coalbed zone wherein substantial dewatering has previously taken place.   
     
     
         8 . The method of  claim 2 , further comprising:
 separating water from gas in the formation fluids from the first zone during dewatering; and   disposing of the water by releasing it into a surface body of water.   
     
     
         9 . The method of  claim 2 , wherein the designated level for the gas production rate from the field is at least 25 percent of the anticipated maximum weekly production rate from the field. 
     
     
         10 . The method of  claim 2 , wherein the designated level for dewatering the first and second zones of the subsurface formation is a reduction in the average weekly production rate of water in the first and second zones to less than 50 percent relative to the beginning water production for the second zone. 
     
     
         11 . The method of  claim 2 , wherein the designated level for dewatering the first and second zones of the subsurface formation is calculated by:
 establishing a time period;   calculating a weekly average water production rate for the at least one production well in the second zone over the time period;   determining a peak weekly average water production rate for the at least one well from the second zone; and   reducing the weekly average water production rate by at least 20 percent from the peak weekly average water production rate.   
     
     
         12 . The method of  claim 11 , wherein the weekly average water production rate excludes any well shut-in periods. 
     
     
         13 . The method of  claim 2 , wherein the designated level for dewatering means that the first and second zones have been substantially dewatered. 
     
     
         14 . The method of  claim 3 , further comprising:
 completing one or more wells in a third zone within the subsurface formation;   producing formation fluids from the third zone so as to at least partially dewater the third zone;   shutting in the one or more wells completed in the second zone;   injecting gas from the formation fluids from the third zone into the first zone for temporary storage before the gas processing facility is substantially completed.   
     
     
         15 . The method of  claim 14 , further comprising:
 separating water from gas in the formation fluids from the second zone during dewatering of the second zone;   injecting water from the formation fluids from the second zone into the subterranean storage zone;   separating water from gas in the formation fluids from the third zone during dewatering; and   injecting water from the formation fluids from the third zone into the subterranean storage zone.   
     
     
         16 . The method of  claim 15 , wherein co-producing formation fluids further comprises co-producing formation fluids from the third zone with the formation fluids from the first zone, the second zone, and the fourth zone. 
     
     
         17 . The method of  claim 1 , wherein the gas processing facility refrigerates the methane into liquefied natural gas, or introduces the methane into a pipeline. 
     
     
         18 . A method for managing the production of fluids from a low-permeability subsurface formation in a field, the fluids comprising water and gas, and the method comprising:
 completing one or more wells in a first zone within the subsurface formation;   producing formation fluids from the first zone so as to at least partially dewater the first zone;   completing one or more injection wells in a zone in a second subsurface formation having a permeability that is higher than the first zone;   injecting gas produced from the first zone into the zone in the second subsurface formation for temporary storage;   completing one or more wells in a third zone within the low-permeability subsurface formation;   producing formation fluids from the third zone;   substantially completing a gas processing facility when (i) the gas production rate from the field is able to exceed a designated level, or (ii) at least one zone of the subsurface formation has been dewatered to a designated level;   after substantially completing the gas processing facility, co-producing formation fluids from the first zone and the third zone;   substantially separating water in the co-produced formation fluids from the gas in a separator; and   delivering the gas to the substantially completed gas processing facility for processing, the gas comprising greater than about 50 mole percent methane before processing.   
     
     
         19 . The method of  claim 18 , wherein the low-permeability subsurface formation is a coalbed zone, a shale gas zone, or a tight gas zone. 
     
     
         20 . The method of  claim 19 , wherein the zone in the second subsurface formation comprises an aquifer, a salt cavern, or a depleted hydrocarbon reservoir zone. 
     
     
         21 . The method of  claim 20 , wherein the zone in the second subsurface formation is located in subsurface strata that is deeper than the subsurface formation that is undergoing dewatering. 
     
     
         22 . The method of  claim 19 , further comprising:
 completing one or more wells in a second zone within the low-permeability subsurface formation;   producing formation fluids from the second zone so as to at least partially dewater the second zone; and   injecting gas from the formation fluids from the second zone into the zone in the second subsurface formation for temporary storage before substantially completing the gas processing facility.   
     
     
         23 . The method of  claim 19 , further comprising:
 separating water from gas in the formation fluids from the first zone during dewatering;   delivering water from the formation fluids from the first zone to a water disposal location; and   after the gas processing facility is completed, producing gas from the zone in the second subsurface formation and delivering the gas to the separator along with the co-produced formation fluids from the first zone and the third zone.   
     
     
         24 . The method of  claim 23 , wherein:
 the water disposal location is an aquifer, a salt cavern, a depleted hydrocarbon reservoir zone, or a coalbed zone that has been previously substantially dewatered; and   delivering water to the water disposal location comprises injecting the water.   
     
     
         25 . The method of  claim 23 , wherein:
 the water disposal location is a surface watershed; and   delivering water to the water disposal location comprises releasing water to the watershed.   
     
     
         26 . The method of  claim 23 , wherein:
 the subsurface formation is a coalbed zone;   the water disposal location is an extension of the coalbed zone wherein substantial dewatering has previously taken place; and   delivering water to the water disposal location comprises injecting the water into the coalbed zone.   
     
     
         27 . The method of  claim 23 , further comprising:
 completing one or more wells in a second zone within the subsurface formation;   producing formation fluids from the second zone so as to at least partially dewater the second zone;   injecting gas from the formation fluids from the second zone into the zone in the second subsurface formation for temporary storage.   separating water from gas in the formation fluids from the second zone during dewatering of the second zone;   separating water from gas in the formation fluids from the third zone;   delivering separated water from the formation fluids to the water disposal location; and   after the gas processing facility is completed, producing gas from the zone in the second subsurface formation and delivering the gas to the separator along with the co-produced formation fluids from the first zone, the second zone, and the third zone.   
     
     
         28 . The method of  claim 19 , wherein the designated level for the gas production rate from the field is at least 25 percent of the anticipated maximum weekly production rate from the field. 
     
     
         29 . The method of  claim 19 , wherein the designated level for dewatering the at least one zone of the low-permeability subsurface formation is a reduction in the average weekly production rate of water in the first zone to less than 50 percent relative to the beginning water production for the first zone. 
     
     
         30 . The method of  claim 19 , wherein the designated level for dewatering the at least one zone of the low-permeability subsurface formation is calculated by:
 establishing a time period;   calculating a weekly average water production rate for the at least one production well in the at least one zone over the time period;   determining a peak weekly average water production rate for the at least one well from the at least one zone; and   reducing the weekly average water production rate by at least about 20 percent from the peak weekly average water production rate.   
     
     
         31 . The method of  claim 30 , wherein the weekly average water production rate excludes any well shut-in periods. 
     
     
         32 . The method of  claim 19 , wherein the designated level for dewatering means that the first and second zones have been substantially dewatered. 
     
     
         33 . The method of  claim 19 , wherein the gas processing facility refrigerates the methane into liquefied natural gas, or introduces the methane into a pipeline. 
     
     
         34 . A method for managing the production of fluids from a coalbed formation in a field, the fluids comprising water and gas, and the method comprising:
 completing one or more wells in a first production section within the coalbed formation;   producing formation fluids from the first production section so as to at least partially dewater the first section;   completing one or more injection wells in a subterranean storage zone;   separating the formation fluids into a liquid stream comprised substantially of water, and a gas stream comprising at least 50 mole percent methane gas;   injecting the gas from the gas stream into a first subsurface formation for temporary storage;   injecting water from the liquid stream into a second subsurface formation;   completing one or more wells in a subsequent production section within the coalbed formation;   substantially completing a gas processing facility for the field;   after the first production section has been at least partially dewatered and after the gas processing facility is substantially completed, co-producing formation fluids from the first production section, the subsequent production section, and the first subsurface formation;   substantially separating water in the co-produced formation fluids from the gas in a separator; and   delivering the gas to the substantially completed gas processing facility for processing.   
     
     
         35 . The method of  claim 34 , wherein the first subsurface formation is a zone in the coalbed formation. 
     
     
         36 . The method of  claim 34 , wherein the first subsurface formation is an aquifer that is deeper than the coalbed formation.