Patent ID: 11952869
Assignee: CHINA UNIVERSITY OF PETROLEUM (EAST CHINA)
Field: Civil engineering (Other fields)
Classification: CPC E | IPC E

Claim 1:
2. The high-efficiency yield-increasing exploitation method for the natural gas hydrates according to claim 1, wherein in step (i), an interval among different horizontal wells is determined in the following method:
firstly, based on a Darcy's law, a pressure distribution in the natural gas hydrate reservoirs is as follows:, P
      2
     
     =
     
      
       P
       1
      
      +
      
       
        Q
        ·
        μ
        ·
        L
       
       
        K
        ·
        A
       
      
     
    
   
   
    
     (
     1
     )
    
   
  
 

wherein P1 is a bottom pore pressure of the horizontal wells, MPa; P2 is a pressure in the natural gas hydrate reservoirs, MPa; Q is a flow in pores of the natural gas hydrate reservoirs, m3/s; μ is a fluid viscosity in the reservoirs, mPa·s; L is a seepage radius of a fluid in the reservoirs, m; K is an absolute permeability of the natural gas hydrate reservoirs, mD; A is a sectional area of seepage flow of the natural gas hydrate reservoirs, m2;
then, in order to achieve a decomposition of the natural gas hydrates during an exploitation of the natural gas hydrates under reduced pressure, the pressure P2 in the reservoirs needs to conform to the following criteria:, P
       2
      
      ≤
      
       P
       e
      
     
     =
     
      1
      ⁢
      
       0
       6
      
      ⁢
      
       exp
       ⁡
       (
       
        
         ∑
         
          n
          =
          0
         
         5
        
        
         
          
           a
           n
          
          (
          
           T
           +
           
            Δ
            ⁢
            
             T
             d
            
           
          
          )
         
         n
        
       
       )
      
     
    
   
   
    
     (
     2
     ), wherein, {
     
      
       
        
         
          a
          0
         
         =
         
          
           -
           
            1
            .
            9
           
          
          ⁢
          4
          ⁢
          1
          ⁢
          3
          ⁢
          8
          ⁢
          5
          ⁢
          0
          ⁢
          4
          ⁢
          4
          ⁢
          6
          ⁢
          4
          ⁢
          5
          ⁢
          6
          ⁢
          0
          ×
          1
          ⁢
          
           0
           5
          
         
        
       
      
      
       
        
         
          a
          1
         
         =
         
          
           3
           .
           3
          
          ⁢
          1
          ⁢
          0
          ⁢
          1
          ⁢
          8
          ⁢
          2
          ⁢
          1
          ⁢
          3
          ⁢
          3
          ⁢
          9
          ⁢
          7
          ⁢
          9
          ⁢
          2
          ⁢
          6
          ×
          1
          ⁢
          
           0
           3
          
         
        
       
      
      
       
        
         
          a
          2
         
         =
         
          
           -
           
            2
            .
            2
           
          
          ⁢
          5
          ⁢
          5
          ⁢
          4
          ⁢
          0
          ⁢
          2
          ⁢
          6
          ⁢
          4
          ⁢
          4
          ⁢
          9
          ⁢
          3
          ⁢
          8
          ⁢
          0
          ⁢
          6
          ×
          1
          ⁢
          
           0
           1
          
         
        
       
      
      
       
        
         
          a
          3
         
         =
         
          
           7
           .
           6
          
          ⁢
          7
          ⁢
          5
          ⁢
          5
          ⁢
          9
          ⁢
          1
          ⁢
          1
          ⁢
          7
          ⁢
          7
          ⁢
          8
          ⁢
          7
          ⁢
          0
          ⁢
          5
          ⁢
          9
          ×
          1
          ⁢
          
           0
           
            -
            2
           
          
         
        
       
      
      
       
        
         
          a
          4
         
         =
         
          
           -
           
            1
            .
            3
           
          
          ⁢
          0
          ⁢
          4
          ⁢
          6
          ⁢
          5
          ⁢
          8
          ⁢
          2
          ⁢
          9
          ⁢
          7
          ⁢
          8
          ⁢
          8
          ⁢
          7
          ⁢
          9
          ⁢
          1
          ×
          1
          ⁢
          
           0
           
            -
            4
           
          
         
        
       
      
      
       
        
         
          a
          5
         
         =
         
          
           8
           .
           8
          
          ⁢
          6
          ⁢
          0
          ⁢
          6
          ⁢
          5
          ⁢
          3
          ⁢
          1
          ⁢
          6
          ⁢
          6
          ⁢
          8
          ⁢
          7
          ⁢
          5
          ⁢
          7
          ⁢
          1
          ×
          1
          ⁢
          
           0
           
            -
            8
           
          
         
        
       
      
     
    
   
   
    
     (
     3
     )
    
   
  
 

wherein T is a reservoir temperature, K; ΔTd is a temperature at which a decline in a hydrate equilibrium is caused by a thermodynamic hydrate inhibitor, K;
ΔTd is obtained by the following formula through calculation:, Δ
      ⁢
      
       T
       d
      
     
     =
     
      Δ
      ⁢
      
       T
       
        d
        ,
        r
       
      
      ⁢
      
       
        ln
        ⁡
        (
        
         1
         -
         x
        
        )
       
       
        ln
        ⁡
        (
        
         1
         -
         
          x
          r
         
        
        )
       
      
     
    
   
   
    
     (
     4
     )
    
   
  
 

wherein x is a molar fraction of the thermodynamic hydrate inhibitor in a water phase, which is dimensionless; xr is a reference molar fraction of the thermodynamic hydrate inhibitor in the water phase, which is dimensionless; ΔTd,r is a temperature at which the decline in the hydrate equilibrium is caused under the molar fraction of the thermodynamic hydrate inhibitor as xr, K; and
an interval (L1=L) between every two horizontal wells is solved according to formulas (1)-(4).