Estimating petrophysical parameters and invasion profile using joint induction and pressure data inversion approach

Abstract

Methods and related systems are described relating to an inversion approach for interpreting the geophysical electromagnetic data. The inversion can be constrained by using a multiphase fluid flow simulator (incorporating pressure data if available) which simulates the fluid flow process and calculates the spatial distribution of the water saturation and the salt concentration, which are in turn transformed into the formation conductivity using a resistivity-saturation formula. In this way, the inverted invasion profile is consistent with the fluid flow physics and moreover accounts for gravity segregation effects. Jointly with the pressure data, the inversion estimates a parametric one-dimensional distribution of permeability and porosity. The fluid flow volume is directly inverted from the fluid-flow-constrained inversion of the electromagnetic data. The approach is not limited by the traditional interpretation of the formation test, which is based on a single-phase model without taking into account invasion or assuming that the fluid, for example mud-filtrate, has been cleaned up from the formation testing zone. The joint inversion of the electromagnetic and pressure data provides for a more reliable interpretation of formation permeability. One advantage of the approaches described herein, is its possible generalization to three-dimensional geometries, for example dipping beds and highly deviated wells.

What is claimed is: 
     
         1 . A method of estimating porosity for a subterranean formation of interest including one or more geologic beds, the method comprising:
 receiving electromagnetic survey data of the formation of interest;   receiving fluid flow characteristics within the formation of interest; and   estimating porosity within at least a portion of the formation of interest based at least in part on the electromagnetic survey data and the fluid flow characteristics, wherein the estimation has a spatial resolution such that at least two porosity values are estimated for each of the one or more geologic beds.   
     
     
         2 . A method according to  claim 1  wherein the estimated porosity has a spatial resolution such that at least two porosity values are estimated within each predefined depth interval. 
     
     
         3 . A method according to  claim 1  further comprising directly inverting the electromagnetic data and the fluid flow characteristics, wherein the estimated porosity is based at least in part on the direct inversion. 
     
     
         4 . A method according to  claim 3  further comprising estimating a mud filtrate invasion rate based at least in part on the inversion. 
     
     
         5 . A method according to  claim 3  further comprising estimating a well completion fluid invasion rate based at least in part on the inversion. 
     
     
         6 . A method according to  claim 3  further comprising estimating a fluid injection rate based at least in part on the inversion. 
     
     
         7 . A method according to  claim 3  wherein the fluid flow characteristics are generated from a fluid flow simulation. 
     
     
         8 . A method according to  claim 3  wherein the fluid flow characteristics are generated from pressure transient measurements made in the borehole. 
     
     
         9 . A method according to  claim 8  further comprising estimating permeability within the formation based at least in part on the inversion. 
     
     
         10 . A method according to  claim 3  further comprising generating a quantitative predictive formation model for at least part of the formation of interest based at least in part on the inversion. 
     
     
         11 . A method according to  claim 10  further comprising predicting future fluid flow in at least part of the formation of interest, the prediction being based at least in part on the generated quantitative predictive formation model. 
     
     
         12 . A method according to  claim 1  wherein the electromagnetic survey data is obtained using at least a first downhole electromagnetic transceiver deployed in a borehole passing through the formation of interest. 
     
     
         13 . A system of estimating porosity for a subterranean formation of interest including one or more geologic beds, the system comprising a processing system adapted and configured to receive electromagnetic survey data of the formation of interest and fluid flow characteristics within the formation of interest and to estimate porosity within at least a portion of the formation of interest based at least in part on the electromagnetic survey data and the fluid flow characteristics, wherein the estimation has a spatial resolution such that at least two porosity values are estimated for each of the one or more geologic beds. 
     
     
         14 . A system according to  claim 13  wherein the processing system is further adapted and configured to directly invert the electromagnetic data and the fluid flow characteristics, wherein the estimated porosity is based at least in part on the direct inversion. 
     
     
         15 . A system according to  claim 14  wherein the processing system is further adapted and configured to generate a quantitative predictive formation model for at least part of the formation of interest based at least in part on the inversion. 
     
     
         16 . A system according to  claim 13  further comprising a downhole electromagnetic transceiver deployable in a borehole passing through the formation of interest.