Method for determining the inflow profile of fluids of multilayer deposits

Abstract

A method for determining the profile of fluids inflowing into multi-zone reservoirs provides for a temperature measurement in a wellbore during the return of the wellbore to thermal equilibrium after drilling and determining a temperature of the fluids inflowing into the wellbore from each pay zone after perforation at an initial stage of production. Specific flow rate for each pay zone is determined by a rate of change of the measured temperatures.

1 . A method for determining profile of fluid inflow from multi-zone reservoirs into a wellbore comprising:
 measuring a temperature in the wellbore during a wellbore-return-to-thermal-equilibrium time after drilling,   perforating the wellbore,   determining a temperature of the fluids inflowing into the wellbore from each pay zone at an initial stage of production, and   determining a specific flow rate for each pay zone by a rate of change of the measured temperatures.   
     
     
         2 . The method of  claim 1 , wherein the temperature of the fluids inflowing into the wellbore from the pay zones is determined by a direct measurement of temperature of the fluids inflowing into the wellbore from each pay zone, and a specific flow rate of each pay zone is determined by the formula 
       
         
           
             
               
                 
                   Q 
                   i 
                 
                 = 
                 
                   
                     
                       4 
                        
                       π 
                     
                     χ 
                   
                   · 
                   a 
                   · 
                   
                     h 
                     1 
                   
                   · 
                   
                     ( 
                     
                       
                         
                           
                             T 
                             . 
                           
                           
                             in 
                             , 
                             i 
                           
                         
                         
                           
                             T 
                             . 
                           
                           s 
                         
                       
                       - 
                       1 
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where Q i  is a flow rate of the ith pay zone, 
         {dot over (T)} s  is a rate of temperature recovery in the wellbore before perforation, 
         {dot over (T)} in,i  is a rate of temperature variation of the fluid inflowing into the wellbore from the ith pay zone at the initial stage of production, 
         h i  is a thickness of the ith pay zone, 
         a is a thermal diffusivity of the reservoir, 
       
       
         
           
             
               
                 χ 
                 = 
                 
                   
                     
                       c 
                       f 
                     
                     · 
                     
                       ρ 
                       f 
                     
                   
                   
                     
                       ρ 
                       r 
                     
                     · 
                     
                       c 
                       r 
                     
                   
                 
               
               , 
             
           
         
         ρ f c f  is a volumetric heat capacity of the fluid, 
         ρ r c r =φ·ρ f c f +(1−φ)·ρ m c m  is a volumetric heat capacity of the rock saturated with the fluid, 
         ρ m c m  is a volumetric heat capacity of a rock matrix, 
         φ is a porosity of the reservoir. 
       
     
     
         3 . The method of  claim 1 , wherein the wellbore-return-to-thermal-equilibrium time is 5-10 days. 
     
     
         4 . The method of  claim 1 , wherein the temperature of the fluids inflowing into the wellbore from each pay zone at the initial stage of production is measured within 3-5 hours after start of production. 
     
     
         5 . The method of  claim 1 , wherein the temperature of the fluids is determined by sensors installed on a tubing string above each perforated interval, a specific flow rate of a lower pay zone is determined by the formula 
       
         
           
             
               
                 
                   Q 
                   1 
                 
                 = 
                 
                   
                     
                       4 
                        
                       π 
                     
                     χ 
                   
                   · 
                   a 
                   · 
                   
                     h 
                     1 
                   
                   · 
                   
                     ( 
                     
                       
                         
                           
                             T 
                             . 
                           
                           1 
                         
                         
                           
                             T 
                             . 
                           
                           s 
                         
                       
                       - 
                       1 
                     
                     ) 
                   
                 
               
               , 
             
           
         
         where Q 1  is a flow rate of the lower zone, 
         {dot over (T)} s  is a rate of temperature recovery in the wellbore before perforation, 
         {dot over (T)} 1  is a rate of temperature change of the fluid inflowing into the wellbore from the pay zone at the initial stage of production as measured above the lower perforated interval, 
         h 1  is a thickness of the lower pay zone, 
         a is a thermal diffusivity of the reservoir, 
       
       
         
           
             
               
                 χ 
                 = 
                 
                   
                     
                       c 
                       f 
                     
                     · 
                     
                       ρ 
                       f 
                     
                   
                   
                     
                       ρ 
                       r 
                     
                     · 
                     
                       c 
                       r 
                     
                   
                 
               
               , 
             
           
         
         ρ f c f  is a volumetric heat capacity of the fluid, 
         ρ r c r =φ·ρ f c f +(1−φ) ρ m c m  is a volumetric heat capacity of the rock saturated by the fluid, 
         ρ m c m  is a volumetric heat capacity of the rock matrix, 
         φ is a porosity of the reservoir, and a specific flow rate of overlying pay zones is determined by temperatures measured by the sensors installed on the tubing string, using the flow rates determined for the underlying pay zones. 
       
     
     
         6 . The method of  claim 5 , wherein the wellbore-return-to-thermal-equilibrium time is 5-10 days. 
     
     
         7 . The method of  claim 5 , wherein the temperature of the fluids inflowing into the wellbore from each pay zone at the initial stage of production is measured within 3-5 hours after start of production.