Enhanced seismic surveying

Abstract

Embodiments of the present invention help in the processing and interpretation of seismic survey data, by correlating or otherwise comparing or associating seismic data obtained from a seismic survey with flow information obtained from a well or borehole in the surveyed area. In particular, embodiments of the present invention allow for flow data representing a flow profile along a well that is being monitored by a distributed acoustic sensor to be determined, such that regions of higher flow in the well can be determined. For example, in the production zone the well will be perforated to allow oil to enter the well, but it has not previously been possible to determine accurately where in the production zone the oil is entering the well. However, by determining a flow rate profile along the well using the i)AS then this provides information as to where in the perforated production zone oil is entering the well, and hence the location of oil bearing sands. This location can then be combined or otherwise correlated, used, or associated with petroleum reservoir location information obtained from the seismic survey, to improve the confidence and/or accuracy in the determined petroleum reservoir location.

1 . A method for enhancing seismic survey results, comprising:
 receiving seismic data from a seismic survey of an area provided with a well or borehole arranged to tap an underground reservoir;   monitoring the well or borehole with a distributed acoustic sensor (DAS);   determining the fluid flow from the reservoir along one or more parts of the well or borehole using acoustic measurements obtained by the DAS; and   combining, for example by correlation, association or other use, the determined fluid flow data with the seismic data to improve the confidence or accuracy of determined characteristics of the underground reservoir.   
     
     
         2 . A method according to  claim 1 , wherein the characteristics include one or more of the size, depth, extent, volume, and/or pressure of the reservoir. 
     
     
         3 . A method according to  claim 1 , and further comprising acoustically illuminating the well or borehole with a controllable sound source. 
     
     
         4 . A method for hydrocarbons recovery, comprising:
 undertaking fluid injection into an underground hydrocarbons reservoir provided with a production well or borehole; and   monitoring the production well or borehole with a distributed acoustic sensor (DAS) to determine the type of fluid that is being received at one or more parts of the well or borehole.   
     
     
         5 . A method according to  claim 4 , wherein the monitoring comprises determining the speed of sound in received fluid at one or more parts of the well to thereby determine the type of fluid. 
     
     
         6 . A method according to  claim 4 , and further comprising acoustically illuminating the well or borehole with a controllable sound source. 
     
     
         7 . A method according to  claim 4  wherein the injected fluid is any of water, hydraulic fracturing fluid, or steam. 
     
     
         8 . A method according to  claim 4 , wherein the fluid received at one or more parts of the well is recovered hydrocarbons, or injected fluid, depending on location in the well. 
     
     
         9 . A method according to  claim 4 , wherein the fluid injection further comprises water injection. 
     
     
         10 . A method according to  claim 4 , wherein the fluid injection further comprises hydraulic fracturing. 
     
     
         11 . A method according to  claim 4 , wherein the fluid injection further comprises steam assisted gravity drainage (SAGD). 
     
     
         12 . A method according to  claim 4 , wherein the fluid injection further comprises cyclic steam stimulation (CSS) or high pressure CSS (HPCSS).