Modeling to characterize fractures network in homogeneous petroleum reservoirs

Abstract

Models of complex reservoir systems including fracture networks and faults are provided from pressure transient test data obtained from a well in a region of interest in the reservoir. An analytic solution methodology is provided to interpret well test data signature from the pressure transient test data based on model data formed of simulated flow geometry and pressure data behavior.

What is claimed is: 
     
         1 . A computer implemented method of deter wining a model of a subsurface earth formation, having a well intersecting a complex geological network of a fault and a fracture in the formation, based on a pressure transient test of the formation, the computer implemented method comprising the steps of:
 obtaining a test measure of bottom hole pressure in the well;   obtaining a test pressure derivative of well pressure in the well at sampled instants of measurement during the pressure transient test of the formation;   receiving an estimated reference type-curve set of a plurality of type-curves of well pressures in the well and pressure derivatives for selected test values of fracture conductivity and fault conductivity in the formation;   determining a model well pressure of the formation based on the test measure of well pressure and an estimated value of fracture conductivity and an estimated value of fault conductivity in the formation;   determining a model pressure derivative based on the test measure of well pressure and the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation;   forming a model type-curve of the determined model well pressure of the formation and the model pressure derivative based on the determined model well pressure of the formation;   comparing the model type-curve of the determined model well pressure of the formation and the model pressure derivative with the plurality of type-curves of the estimated reference type-curve set; and   if the model type-curve matches one of the plurality of type-curves of the estimated reference type-curve set within an acceptable limit of accuracy, storing the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation of the matched type-curve of the estimated reference type-curve set as models of the fracture conductivity and the fault conductivity of the formation; and   if not, adjusting one or both of the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation; and   repeating the steps of determining a model well pressure, determining a model pressure derivative, forming a model type-curve and comparing based on the adjusted estimated value of fracture conductivity and fault conductivity of the formation until an acceptable match is achieved.   
     
     
         2 . The computer implemented method of  claim 1 , further including the step of forming a measure of the formation permeability based on the stored models of the fracture conductivity and the fault conductivity of the formation. 
     
     
         3 . The computer implemented method of  claim 1 , further including the step of forming an output display of the stored models of the fracture conductivity and the fault conductivity of the formation. 
     
     
         4 . The computer implemented method of  claim 1 , further including the step of forming an output display of the stored model of the fracture conductivity as dimensional fracture conductivity of the formation. 
     
     
         5 . The computer implemented method of  claim 1 , further including the step of forming an output display of the stored model of the fracture conductivity as dimensionless fracture conductivity of the formation. 
     
     
         6 . The computer implemented method of  claim 1 , further including the step of forming an output display of the stored model of the fault conductivity as dimensional fault conductivity of the formation. 
     
     
         7 . The computer implemented method of  claim 1 , further including the step of forming an output display of the stored model of the fault conductivity as dimensionless fault conductivity of the formation. 
     
     
         8 . A data processing system for determining a model of a subsurface earth formation, having a well intersecting a complex geological network of a fault and a fracture in the formation, based on a pressure transient test of the formation, the data processing system comprising:
 a processor performing the steps of:   obtaining a test measure of bottom-hole pressure in the well;   obtaining a test pressure derivative of well pressure in the well at sampled instants of measurement during the pressure transient test of the formation;   receiving an estimated reference type-curve set of a plurality of type-curves of well pressures in the well and pressure derivatives for selected test values of fracture conductivity and fault conductivity in the formation;   determining a model well pressure of the formation based on the test measure of well pressure and an estimated value of fracture conductivity and an estimated value of fault conductivity in the formation;   determining a model pressure derivative based on the test measure of well pressure and the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation;   forming a model type-curve of the determined model well pressure of the formation and the model pressure derivative based on the determined model well pressure of the formation;   comparing the model type-curve of the determined model well pressure of the formation and the model pressure derivative with the plurality of type-curves of the estimated reference type-curve set; and   if the model type-curve matches one of the plurality of type-curves of the estimated reference type-curve set within an acceptable limit of accuracy, storing the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation of the matched type-curve of the estimated reference type-curve set as models of the fracture conductivity and the fault conductivity of the formation; and   if not, adjusting one or both of the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation; and   repeating the steps of determining a model well pressure, determining a model pressure derivative, forming a model type-curve and comparing based on the adjusted estimated value of fracture conductivity and fault conductivity of the formation until an acceptable match is achieved; and   a memory storing the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation of the matched type-curve of the estimated reference type-curve set as models of the fracture conductivity and the fault conductivity of the formation.   
     
     
         9 . The data processing system of  claim 8 , further including the processor performing the step of:
 forming a measure of the formation permeability based on the stored models of the fracture conductivity and the fault conductivity of the formation.   
     
     
         10 . The data processing system of  claim 8 , further including:
 an output display forming of the stored models of the fracture conductivity and the fault conductivity of the formation.   
     
     
         11 . The data processing system of  claim 8 , further including:
 the output display forming an output record of the stored model of the fracture conductivity as dimensional fracture conductivity of the formation.   
     
     
         12 . The data processing system of  claim 8 , further including:
 the output display forming an output record of the stored model of the fracture conductivity as dimensionless fracture conductivity of the formation.   
     
     
         13 . The data processing system of  claim 8 , further including:
 the output display forming an output record of the stored model of the fault conductivity as dimensional fault conductivity of the formation.   
     
     
         14 . The data processing system of  claim 8 , further including:
 the output display forming an output record of the stored model of the fault conductivity as dimensionless fault conductivity of the formation.   
     
     
         15 . A data storage device having stored in a non-transitory computer readable medium computer operable instructions for causing a data processing system to determine a model of a subsurface earth formation, having a well intersecting a complex geological network of a fault and a fracture in the formation, based on a pressure transient test of the formation, the instructions stored in the data storage device causing the data processing system to perform the following steps:
 obtaining a test measure of bottom-hole pressure in the well;   obtaining a test pressure derivative of well pressure in the well at sampled instants of measurement during the pressure transient test of the formation;   receiving an estimated reference type-curve set of a plurality of type-curves of well pressures in the well and pressure derivatives for selected test values of fracture conductivity and fault conductivity in the formation;   determining a model well pressure of the formation based on the test measure of well pressure and an estimated value of fracture conductivity and an estimated value of fault conductivity in the formation;   determining a model pressure derivative based on the test measure of well pressure and the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation;   forming a model type-curve of the determined model well pressure of the formation and the model pressure derivative based on the determined model well pressure of the formation;   comparing the model type-curve of the determined model well pressure of the formation and the model pressure derivative with the plurality of type-curves of the estimated reference type-curve set; and   if the model type-curve matches one of the plurality of type-curves of the estimated reference type-curve set within an acceptable limit of accuracy, storing the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation of the matched type-curve of the estimated reference type-curve set as models of the fracture conductivity and the fault conductivity of the formation; and   if not, adjusting one or both of the estimated value of fracture conductivity and the estimated value of fault conductivity in the formation; and   repeating the steps of determining a model well pressure, determining a model pressure derivative, forming a model type-curve and comparing based on the adjusted estimated value of fracture conductivity and fault conductivity of the formation until an acceptable match is achieved.   
     
     
         16 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming a measure of the formation permeability based on the stored models of the fracture conductivity and the fault conductivity of the formation.   
     
     
         17 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming an output display of the stored models of the fracture conductivity and the fault conductivity of the formation.   
     
     
         18 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming an output display of the stored model of the fracture conductivity as dimensional fracture conductivity of the formation.   
     
     
         19 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming an output display of the stored model of the fracture conductivity as dimensionless fracture conductivity of the formation.   
     
     
         20 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming an output display of the stored model of the fault conductivity as dimensional fault conductivity of the formation.   
     
     
         21 . The data storage device of  claim 15 , wherein the instructions cause the data processing system to perform the step of:
 forming an output display of the stored model of the fault conductivity as dimensionless fault conductivity of the formation.